mem_encrypt=on: Activate SME
mem_encrypt=off: Do not activate SME
- Refer to Documentation/virtual/kvm/amd-memory-encryption.rst
+ Refer to Documentation/virt/kvm/amd-memory-encryption.rst
for details on when memory encryption can be activated.
mem_sleep_default= [SUSPEND] Default system suspend mode:
--- /dev/null
+.. SPDX-License-Identifier: GPL-2.0
+
+============================
+Linux Virtualization Support
+============================
+
+.. toctree::
+ :maxdepth: 2
+
+ kvm/index
+ paravirt_ops
+
+.. only:: html and subproject
+
+ Indices
+ =======
+
+ * :ref:`genindex`
--- /dev/null
+======================================
+Secure Encrypted Virtualization (SEV)
+======================================
+
+Overview
+========
+
+Secure Encrypted Virtualization (SEV) is a feature found on AMD processors.
+
+SEV is an extension to the AMD-V architecture which supports running
+virtual machines (VMs) under the control of a hypervisor. When enabled,
+the memory contents of a VM will be transparently encrypted with a key
+unique to that VM.
+
+The hypervisor can determine the SEV support through the CPUID
+instruction. The CPUID function 0x8000001f reports information related
+to SEV::
+
+ 0x8000001f[eax]:
+ Bit[1] indicates support for SEV
+ ...
+ [ecx]:
+ Bits[31:0] Number of encrypted guests supported simultaneously
+
+If support for SEV is present, MSR 0xc001_0010 (MSR_K8_SYSCFG) and MSR 0xc001_0015
+(MSR_K7_HWCR) can be used to determine if it can be enabled::
+
+ 0xc001_0010:
+ Bit[23] 1 = memory encryption can be enabled
+ 0 = memory encryption can not be enabled
+
+ 0xc001_0015:
+ Bit[0] 1 = memory encryption can be enabled
+ 0 = memory encryption can not be enabled
+
+When SEV support is available, it can be enabled in a specific VM by
+setting the SEV bit before executing VMRUN.::
+
+ VMCB[0x90]:
+ Bit[1] 1 = SEV is enabled
+ 0 = SEV is disabled
+
+SEV hardware uses ASIDs to associate a memory encryption key with a VM.
+Hence, the ASID for the SEV-enabled guests must be from 1 to a maximum value
+defined in the CPUID 0x8000001f[ecx] field.
+
+SEV Key Management
+==================
+
+The SEV guest key management is handled by a separate processor called the AMD
+Secure Processor (AMD-SP). Firmware running inside the AMD-SP provides a secure
+key management interface to perform common hypervisor activities such as
+encrypting bootstrap code, snapshot, migrating and debugging the guest. For more
+information, see the SEV Key Management spec [api-spec]_
+
+KVM implements the following commands to support common lifecycle events of SEV
+guests, such as launching, running, snapshotting, migrating and decommissioning.
+
+1. KVM_SEV_INIT
+---------------
+
+The KVM_SEV_INIT command is used by the hypervisor to initialize the SEV platform
+context. In a typical workflow, this command should be the first command issued.
+
+Returns: 0 on success, -negative on error
+
+2. KVM_SEV_LAUNCH_START
+-----------------------
+
+The KVM_SEV_LAUNCH_START command is used for creating the memory encryption
+context. To create the encryption context, user must provide a guest policy,
+the owner's public Diffie-Hellman (PDH) key and session information.
+
+Parameters: struct kvm_sev_launch_start (in/out)
+
+Returns: 0 on success, -negative on error
+
+::
+
+ struct kvm_sev_launch_start {
+ __u32 handle; /* if zero then firmware creates a new handle */
+ __u32 policy; /* guest's policy */
+
+ __u64 dh_uaddr; /* userspace address pointing to the guest owner's PDH key */
+ __u32 dh_len;
+
+ __u64 session_addr; /* userspace address which points to the guest session information */
+ __u32 session_len;
+ };
+
+On success, the 'handle' field contains a new handle and on error, a negative value.
+
+For more details, see SEV spec Section 6.2.
+
+3. KVM_SEV_LAUNCH_UPDATE_DATA
+-----------------------------
+
+The KVM_SEV_LAUNCH_UPDATE_DATA is used for encrypting a memory region. It also
+calculates a measurement of the memory contents. The measurement is a signature
+of the memory contents that can be sent to the guest owner as an attestation
+that the memory was encrypted correctly by the firmware.
+
+Parameters (in): struct kvm_sev_launch_update_data
+
+Returns: 0 on success, -negative on error
+
+::
+
+ struct kvm_sev_launch_update {
+ __u64 uaddr; /* userspace address to be encrypted (must be 16-byte aligned) */
+ __u32 len; /* length of the data to be encrypted (must be 16-byte aligned) */
+ };
+
+For more details, see SEV spec Section 6.3.
+
+4. KVM_SEV_LAUNCH_MEASURE
+-------------------------
+
+The KVM_SEV_LAUNCH_MEASURE command is used to retrieve the measurement of the
+data encrypted by the KVM_SEV_LAUNCH_UPDATE_DATA command. The guest owner may
+wait to provide the guest with confidential information until it can verify the
+measurement. Since the guest owner knows the initial contents of the guest at
+boot, the measurement can be verified by comparing it to what the guest owner
+expects.
+
+Parameters (in): struct kvm_sev_launch_measure
+
+Returns: 0 on success, -negative on error
+
+::
+
+ struct kvm_sev_launch_measure {
+ __u64 uaddr; /* where to copy the measurement */
+ __u32 len; /* length of measurement blob */
+ };
+
+For more details on the measurement verification flow, see SEV spec Section 6.4.
+
+5. KVM_SEV_LAUNCH_FINISH
+------------------------
+
+After completion of the launch flow, the KVM_SEV_LAUNCH_FINISH command can be
+issued to make the guest ready for the execution.
+
+Returns: 0 on success, -negative on error
+
+6. KVM_SEV_GUEST_STATUS
+-----------------------
+
+The KVM_SEV_GUEST_STATUS command is used to retrieve status information about a
+SEV-enabled guest.
+
+Parameters (out): struct kvm_sev_guest_status
+
+Returns: 0 on success, -negative on error
+
+::
+
+ struct kvm_sev_guest_status {
+ __u32 handle; /* guest handle */
+ __u32 policy; /* guest policy */
+ __u8 state; /* guest state (see enum below) */
+ };
+
+SEV guest state:
+
+::
+
+ enum {
+ SEV_STATE_INVALID = 0;
+ SEV_STATE_LAUNCHING, /* guest is currently being launched */
+ SEV_STATE_SECRET, /* guest is being launched and ready to accept the ciphertext data */
+ SEV_STATE_RUNNING, /* guest is fully launched and running */
+ SEV_STATE_RECEIVING, /* guest is being migrated in from another SEV machine */
+ SEV_STATE_SENDING /* guest is getting migrated out to another SEV machine */
+ };
+
+7. KVM_SEV_DBG_DECRYPT
+----------------------
+
+The KVM_SEV_DEBUG_DECRYPT command can be used by the hypervisor to request the
+firmware to decrypt the data at the given memory region.
+
+Parameters (in): struct kvm_sev_dbg
+
+Returns: 0 on success, -negative on error
+
+::
+
+ struct kvm_sev_dbg {
+ __u64 src_uaddr; /* userspace address of data to decrypt */
+ __u64 dst_uaddr; /* userspace address of destination */
+ __u32 len; /* length of memory region to decrypt */
+ };
+
+The command returns an error if the guest policy does not allow debugging.
+
+8. KVM_SEV_DBG_ENCRYPT
+----------------------
+
+The KVM_SEV_DEBUG_ENCRYPT command can be used by the hypervisor to request the
+firmware to encrypt the data at the given memory region.
+
+Parameters (in): struct kvm_sev_dbg
+
+Returns: 0 on success, -negative on error
+
+::
+
+ struct kvm_sev_dbg {
+ __u64 src_uaddr; /* userspace address of data to encrypt */
+ __u64 dst_uaddr; /* userspace address of destination */
+ __u32 len; /* length of memory region to encrypt */
+ };
+
+The command returns an error if the guest policy does not allow debugging.
+
+9. KVM_SEV_LAUNCH_SECRET
+------------------------
+
+The KVM_SEV_LAUNCH_SECRET command can be used by the hypervisor to inject secret
+data after the measurement has been validated by the guest owner.
+
+Parameters (in): struct kvm_sev_launch_secret
+
+Returns: 0 on success, -negative on error
+
+::
+
+ struct kvm_sev_launch_secret {
+ __u64 hdr_uaddr; /* userspace address containing the packet header */
+ __u32 hdr_len;
+
+ __u64 guest_uaddr; /* the guest memory region where the secret should be injected */
+ __u32 guest_len;
+
+ __u64 trans_uaddr; /* the hypervisor memory region which contains the secret */
+ __u32 trans_len;
+ };
+
+References
+==========
+
+
+See [white-paper]_, [api-spec]_, [amd-apm]_ and [kvm-forum]_ for more info.
+
+.. [white-paper] http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2013/12/AMD_Memory_Encryption_Whitepaper_v7-Public.pdf
+.. [api-spec] http://support.amd.com/TechDocs/55766_SEV-KM_API_Specification.pdf
+.. [amd-apm] http://support.amd.com/TechDocs/24593.pdf (section 15.34)
+.. [kvm-forum] http://www.linux-kvm.org/images/7/74/02x08A-Thomas_Lendacky-AMDs_Virtualizatoin_Memory_Encryption_Technology.pdf
--- /dev/null
+The Definitive KVM (Kernel-based Virtual Machine) API Documentation
+===================================================================
+
+1. General description
+----------------------
+
+The kvm API is a set of ioctls that are issued to control various aspects
+of a virtual machine. The ioctls belong to three classes:
+
+ - System ioctls: These query and set global attributes which affect the
+ whole kvm subsystem. In addition a system ioctl is used to create
+ virtual machines.
+
+ - VM ioctls: These query and set attributes that affect an entire virtual
+ machine, for example memory layout. In addition a VM ioctl is used to
+ create virtual cpus (vcpus) and devices.
+
+ VM ioctls must be issued from the same process (address space) that was
+ used to create the VM.
+
+ - vcpu ioctls: These query and set attributes that control the operation
+ of a single virtual cpu.
+
+ vcpu ioctls should be issued from the same thread that was used to create
+ the vcpu, except for asynchronous vcpu ioctl that are marked as such in
+ the documentation. Otherwise, the first ioctl after switching threads
+ could see a performance impact.
+
+ - device ioctls: These query and set attributes that control the operation
+ of a single device.
+
+ device ioctls must be issued from the same process (address space) that
+ was used to create the VM.
+
+2. File descriptors
+-------------------
+
+The kvm API is centered around file descriptors. An initial
+open("/dev/kvm") obtains a handle to the kvm subsystem; this handle
+can be used to issue system ioctls. A KVM_CREATE_VM ioctl on this
+handle will create a VM file descriptor which can be used to issue VM
+ioctls. A KVM_CREATE_VCPU or KVM_CREATE_DEVICE ioctl on a VM fd will
+create a virtual cpu or device and return a file descriptor pointing to
+the new resource. Finally, ioctls on a vcpu or device fd can be used
+to control the vcpu or device. For vcpus, this includes the important
+task of actually running guest code.
+
+In general file descriptors can be migrated among processes by means
+of fork() and the SCM_RIGHTS facility of unix domain socket. These
+kinds of tricks are explicitly not supported by kvm. While they will
+not cause harm to the host, their actual behavior is not guaranteed by
+the API. See "General description" for details on the ioctl usage
+model that is supported by KVM.
+
+It is important to note that althought VM ioctls may only be issued from
+the process that created the VM, a VM's lifecycle is associated with its
+file descriptor, not its creator (process). In other words, the VM and
+its resources, *including the associated address space*, are not freed
+until the last reference to the VM's file descriptor has been released.
+For example, if fork() is issued after ioctl(KVM_CREATE_VM), the VM will
+not be freed until both the parent (original) process and its child have
+put their references to the VM's file descriptor.
+
+Because a VM's resources are not freed until the last reference to its
+file descriptor is released, creating additional references to a VM via
+via fork(), dup(), etc... without careful consideration is strongly
+discouraged and may have unwanted side effects, e.g. memory allocated
+by and on behalf of the VM's process may not be freed/unaccounted when
+the VM is shut down.
+
+
+3. Extensions
+-------------
+
+As of Linux 2.6.22, the KVM ABI has been stabilized: no backward
+incompatible change are allowed. However, there is an extension
+facility that allows backward-compatible extensions to the API to be
+queried and used.
+
+The extension mechanism is not based on the Linux version number.
+Instead, kvm defines extension identifiers and a facility to query
+whether a particular extension identifier is available. If it is, a
+set of ioctls is available for application use.
+
+
+4. API description
+------------------
+
+This section describes ioctls that can be used to control kvm guests.
+For each ioctl, the following information is provided along with a
+description:
+
+ Capability: which KVM extension provides this ioctl. Can be 'basic',
+ which means that is will be provided by any kernel that supports
+ API version 12 (see section 4.1), a KVM_CAP_xyz constant, which
+ means availability needs to be checked with KVM_CHECK_EXTENSION
+ (see section 4.4), or 'none' which means that while not all kernels
+ support this ioctl, there's no capability bit to check its
+ availability: for kernels that don't support the ioctl,
+ the ioctl returns -ENOTTY.
+
+ Architectures: which instruction set architectures provide this ioctl.
+ x86 includes both i386 and x86_64.
+
+ Type: system, vm, or vcpu.
+
+ Parameters: what parameters are accepted by the ioctl.
+
+ Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
+ are not detailed, but errors with specific meanings are.
+
+
+4.1 KVM_GET_API_VERSION
+
+Capability: basic
+Architectures: all
+Type: system ioctl
+Parameters: none
+Returns: the constant KVM_API_VERSION (=12)
+
+This identifies the API version as the stable kvm API. It is not
+expected that this number will change. However, Linux 2.6.20 and
+2.6.21 report earlier versions; these are not documented and not
+supported. Applications should refuse to run if KVM_GET_API_VERSION
+returns a value other than 12. If this check passes, all ioctls
+described as 'basic' will be available.
+
+
+4.2 KVM_CREATE_VM
+
+Capability: basic
+Architectures: all
+Type: system ioctl
+Parameters: machine type identifier (KVM_VM_*)
+Returns: a VM fd that can be used to control the new virtual machine.
+
+The new VM has no virtual cpus and no memory.
+You probably want to use 0 as machine type.
+
+In order to create user controlled virtual machines on S390, check
+KVM_CAP_S390_UCONTROL and use the flag KVM_VM_S390_UCONTROL as
+privileged user (CAP_SYS_ADMIN).
+
+To use hardware assisted virtualization on MIPS (VZ ASE) rather than
+the default trap & emulate implementation (which changes the virtual
+memory layout to fit in user mode), check KVM_CAP_MIPS_VZ and use the
+flag KVM_VM_MIPS_VZ.
+
+
+On arm64, the physical address size for a VM (IPA Size limit) is limited
+to 40bits by default. The limit can be configured if the host supports the
+extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use
+KVM_VM_TYPE_ARM_IPA_SIZE(IPA_Bits) to set the size in the machine type
+identifier, where IPA_Bits is the maximum width of any physical
+address used by the VM. The IPA_Bits is encoded in bits[7-0] of the
+machine type identifier.
+
+e.g, to configure a guest to use 48bit physical address size :
+
+ vm_fd = ioctl(dev_fd, KVM_CREATE_VM, KVM_VM_TYPE_ARM_IPA_SIZE(48));
+
+The requested size (IPA_Bits) must be :
+ 0 - Implies default size, 40bits (for backward compatibility)
+
+ or
+
+ N - Implies N bits, where N is a positive integer such that,
+ 32 <= N <= Host_IPA_Limit
+
+Host_IPA_Limit is the maximum possible value for IPA_Bits on the host and
+is dependent on the CPU capability and the kernel configuration. The limit can
+be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the KVM_CHECK_EXTENSION
+ioctl() at run-time.
+
+Please note that configuring the IPA size does not affect the capability
+exposed by the guest CPUs in ID_AA64MMFR0_EL1[PARange]. It only affects
+size of the address translated by the stage2 level (guest physical to
+host physical address translations).
+
+
+4.3 KVM_GET_MSR_INDEX_LIST, KVM_GET_MSR_FEATURE_INDEX_LIST
+
+Capability: basic, KVM_CAP_GET_MSR_FEATURES for KVM_GET_MSR_FEATURE_INDEX_LIST
+Architectures: x86
+Type: system ioctl
+Parameters: struct kvm_msr_list (in/out)
+Returns: 0 on success; -1 on error
+Errors:
+ EFAULT: the msr index list cannot be read from or written to
+ E2BIG: the msr index list is to be to fit in the array specified by
+ the user.
+
+struct kvm_msr_list {
+ __u32 nmsrs; /* number of msrs in entries */
+ __u32 indices[0];
+};
+
+The user fills in the size of the indices array in nmsrs, and in return
+kvm adjusts nmsrs to reflect the actual number of msrs and fills in the
+indices array with their numbers.
+
+KVM_GET_MSR_INDEX_LIST returns the guest msrs that are supported. The list
+varies by kvm version and host processor, but does not change otherwise.
+
+Note: if kvm indicates supports MCE (KVM_CAP_MCE), then the MCE bank MSRs are
+not returned in the MSR list, as different vcpus can have a different number
+of banks, as set via the KVM_X86_SETUP_MCE ioctl.
+
+KVM_GET_MSR_FEATURE_INDEX_LIST returns the list of MSRs that can be passed
+to the KVM_GET_MSRS system ioctl. This lets userspace probe host capabilities
+and processor features that are exposed via MSRs (e.g., VMX capabilities).
+This list also varies by kvm version and host processor, but does not change
+otherwise.
+
+
+4.4 KVM_CHECK_EXTENSION
+
+Capability: basic, KVM_CAP_CHECK_EXTENSION_VM for vm ioctl
+Architectures: all
+Type: system ioctl, vm ioctl
+Parameters: extension identifier (KVM_CAP_*)
+Returns: 0 if unsupported; 1 (or some other positive integer) if supported
+
+The API allows the application to query about extensions to the core
+kvm API. Userspace passes an extension identifier (an integer) and
+receives an integer that describes the extension availability.
+Generally 0 means no and 1 means yes, but some extensions may report
+additional information in the integer return value.
+
+Based on their initialization different VMs may have different capabilities.
+It is thus encouraged to use the vm ioctl to query for capabilities (available
+with KVM_CAP_CHECK_EXTENSION_VM on the vm fd)
+
+4.5 KVM_GET_VCPU_MMAP_SIZE
+
+Capability: basic
+Architectures: all
+Type: system ioctl
+Parameters: none
+Returns: size of vcpu mmap area, in bytes
+
+The KVM_RUN ioctl (cf.) communicates with userspace via a shared
+memory region. This ioctl returns the size of that region. See the
+KVM_RUN documentation for details.
+
+
+4.6 KVM_SET_MEMORY_REGION
+
+Capability: basic
+Architectures: all
+Type: vm ioctl
+Parameters: struct kvm_memory_region (in)
+Returns: 0 on success, -1 on error
+
+This ioctl is obsolete and has been removed.
+
+
+4.7 KVM_CREATE_VCPU
+
+Capability: basic
+Architectures: all
+Type: vm ioctl
+Parameters: vcpu id (apic id on x86)
+Returns: vcpu fd on success, -1 on error
+
+This API adds a vcpu to a virtual machine. No more than max_vcpus may be added.
+The vcpu id is an integer in the range [0, max_vcpu_id).
+
+The recommended max_vcpus value can be retrieved using the KVM_CAP_NR_VCPUS of
+the KVM_CHECK_EXTENSION ioctl() at run-time.
+The maximum possible value for max_vcpus can be retrieved using the
+KVM_CAP_MAX_VCPUS of the KVM_CHECK_EXTENSION ioctl() at run-time.
+
+If the KVM_CAP_NR_VCPUS does not exist, you should assume that max_vcpus is 4
+cpus max.
+If the KVM_CAP_MAX_VCPUS does not exist, you should assume that max_vcpus is
+same as the value returned from KVM_CAP_NR_VCPUS.
+
+The maximum possible value for max_vcpu_id can be retrieved using the
+KVM_CAP_MAX_VCPU_ID of the KVM_CHECK_EXTENSION ioctl() at run-time.
+
+If the KVM_CAP_MAX_VCPU_ID does not exist, you should assume that max_vcpu_id
+is the same as the value returned from KVM_CAP_MAX_VCPUS.
+
+On powerpc using book3s_hv mode, the vcpus are mapped onto virtual
+threads in one or more virtual CPU cores. (This is because the
+hardware requires all the hardware threads in a CPU core to be in the
+same partition.) The KVM_CAP_PPC_SMT capability indicates the number
+of vcpus per virtual core (vcore). The vcore id is obtained by
+dividing the vcpu id by the number of vcpus per vcore. The vcpus in a
+given vcore will always be in the same physical core as each other
+(though that might be a different physical core from time to time).
+Userspace can control the threading (SMT) mode of the guest by its
+allocation of vcpu ids. For example, if userspace wants
+single-threaded guest vcpus, it should make all vcpu ids be a multiple
+of the number of vcpus per vcore.
+
+For virtual cpus that have been created with S390 user controlled virtual
+machines, the resulting vcpu fd can be memory mapped at page offset
+KVM_S390_SIE_PAGE_OFFSET in order to obtain a memory map of the virtual
+cpu's hardware control block.
+
+
+4.8 KVM_GET_DIRTY_LOG (vm ioctl)
+
+Capability: basic
+Architectures: all
+Type: vm ioctl
+Parameters: struct kvm_dirty_log (in/out)
+Returns: 0 on success, -1 on error
+
+/* for KVM_GET_DIRTY_LOG */
+struct kvm_dirty_log {
+ __u32 slot;
+ __u32 padding;
+ union {
+ void __user *dirty_bitmap; /* one bit per page */
+ __u64 padding;
+ };
+};
+
+Given a memory slot, return a bitmap containing any pages dirtied
+since the last call to this ioctl. Bit 0 is the first page in the
+memory slot. Ensure the entire structure is cleared to avoid padding
+issues.
+
+If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 specifies
+the address space for which you want to return the dirty bitmap.
+They must be less than the value that KVM_CHECK_EXTENSION returns for
+the KVM_CAP_MULTI_ADDRESS_SPACE capability.
+
+The bits in the dirty bitmap are cleared before the ioctl returns, unless
+KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is enabled. For more information,
+see the description of the capability.
+
+4.9 KVM_SET_MEMORY_ALIAS
+
+Capability: basic
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_memory_alias (in)
+Returns: 0 (success), -1 (error)
+
+This ioctl is obsolete and has been removed.
+
+
+4.10 KVM_RUN
+
+Capability: basic
+Architectures: all
+Type: vcpu ioctl
+Parameters: none
+Returns: 0 on success, -1 on error
+Errors:
+ EINTR: an unmasked signal is pending
+
+This ioctl is used to run a guest virtual cpu. While there are no
+explicit parameters, there is an implicit parameter block that can be
+obtained by mmap()ing the vcpu fd at offset 0, with the size given by
+KVM_GET_VCPU_MMAP_SIZE. The parameter block is formatted as a 'struct
+kvm_run' (see below).
+
+
+4.11 KVM_GET_REGS
+
+Capability: basic
+Architectures: all except ARM, arm64
+Type: vcpu ioctl
+Parameters: struct kvm_regs (out)
+Returns: 0 on success, -1 on error
+
+Reads the general purpose registers from the vcpu.
+
+/* x86 */
+struct kvm_regs {
+ /* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
+ __u64 rax, rbx, rcx, rdx;
+ __u64 rsi, rdi, rsp, rbp;
+ __u64 r8, r9, r10, r11;
+ __u64 r12, r13, r14, r15;
+ __u64 rip, rflags;
+};
+
+/* mips */
+struct kvm_regs {
+ /* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
+ __u64 gpr[32];
+ __u64 hi;
+ __u64 lo;
+ __u64 pc;
+};
+
+
+4.12 KVM_SET_REGS
+
+Capability: basic
+Architectures: all except ARM, arm64
+Type: vcpu ioctl
+Parameters: struct kvm_regs (in)
+Returns: 0 on success, -1 on error
+
+Writes the general purpose registers into the vcpu.
+
+See KVM_GET_REGS for the data structure.
+
+
+4.13 KVM_GET_SREGS
+
+Capability: basic
+Architectures: x86, ppc
+Type: vcpu ioctl
+Parameters: struct kvm_sregs (out)
+Returns: 0 on success, -1 on error
+
+Reads special registers from the vcpu.
+
+/* x86 */
+struct kvm_sregs {
+ struct kvm_segment cs, ds, es, fs, gs, ss;
+ struct kvm_segment tr, ldt;
+ struct kvm_dtable gdt, idt;
+ __u64 cr0, cr2, cr3, cr4, cr8;
+ __u64 efer;
+ __u64 apic_base;
+ __u64 interrupt_bitmap[(KVM_NR_INTERRUPTS + 63) / 64];
+};
+
+/* ppc -- see arch/powerpc/include/uapi/asm/kvm.h */
+
+interrupt_bitmap is a bitmap of pending external interrupts. At most
+one bit may be set. This interrupt has been acknowledged by the APIC
+but not yet injected into the cpu core.
+
+
+4.14 KVM_SET_SREGS
+
+Capability: basic
+Architectures: x86, ppc
+Type: vcpu ioctl
+Parameters: struct kvm_sregs (in)
+Returns: 0 on success, -1 on error
+
+Writes special registers into the vcpu. See KVM_GET_SREGS for the
+data structures.
+
+
+4.15 KVM_TRANSLATE
+
+Capability: basic
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_translation (in/out)
+Returns: 0 on success, -1 on error
+
+Translates a virtual address according to the vcpu's current address
+translation mode.
+
+struct kvm_translation {
+ /* in */
+ __u64 linear_address;
+
+ /* out */
+ __u64 physical_address;
+ __u8 valid;
+ __u8 writeable;
+ __u8 usermode;
+ __u8 pad[5];
+};
+
+
+4.16 KVM_INTERRUPT
+
+Capability: basic
+Architectures: x86, ppc, mips
+Type: vcpu ioctl
+Parameters: struct kvm_interrupt (in)
+Returns: 0 on success, negative on failure.
+
+Queues a hardware interrupt vector to be injected.
+
+/* for KVM_INTERRUPT */
+struct kvm_interrupt {
+ /* in */
+ __u32 irq;
+};
+
+X86:
+
+Returns: 0 on success,
+ -EEXIST if an interrupt is already enqueued
+ -EINVAL the the irq number is invalid
+ -ENXIO if the PIC is in the kernel
+ -EFAULT if the pointer is invalid
+
+Note 'irq' is an interrupt vector, not an interrupt pin or line. This
+ioctl is useful if the in-kernel PIC is not used.
+
+PPC:
+
+Queues an external interrupt to be injected. This ioctl is overleaded
+with 3 different irq values:
+
+a) KVM_INTERRUPT_SET
+
+ This injects an edge type external interrupt into the guest once it's ready
+ to receive interrupts. When injected, the interrupt is done.
+
+b) KVM_INTERRUPT_UNSET
+
+ This unsets any pending interrupt.
+
+ Only available with KVM_CAP_PPC_UNSET_IRQ.
+
+c) KVM_INTERRUPT_SET_LEVEL
+
+ This injects a level type external interrupt into the guest context. The
+ interrupt stays pending until a specific ioctl with KVM_INTERRUPT_UNSET
+ is triggered.
+
+ Only available with KVM_CAP_PPC_IRQ_LEVEL.
+
+Note that any value for 'irq' other than the ones stated above is invalid
+and incurs unexpected behavior.
+
+This is an asynchronous vcpu ioctl and can be invoked from any thread.
+
+MIPS:
+
+Queues an external interrupt to be injected into the virtual CPU. A negative
+interrupt number dequeues the interrupt.
+
+This is an asynchronous vcpu ioctl and can be invoked from any thread.
+
+
+4.17 KVM_DEBUG_GUEST
+
+Capability: basic
+Architectures: none
+Type: vcpu ioctl
+Parameters: none)
+Returns: -1 on error
+
+Support for this has been removed. Use KVM_SET_GUEST_DEBUG instead.
+
+
+4.18 KVM_GET_MSRS
+
+Capability: basic (vcpu), KVM_CAP_GET_MSR_FEATURES (system)
+Architectures: x86
+Type: system ioctl, vcpu ioctl
+Parameters: struct kvm_msrs (in/out)
+Returns: number of msrs successfully returned;
+ -1 on error
+
+When used as a system ioctl:
+Reads the values of MSR-based features that are available for the VM. This
+is similar to KVM_GET_SUPPORTED_CPUID, but it returns MSR indices and values.
+The list of msr-based features can be obtained using KVM_GET_MSR_FEATURE_INDEX_LIST
+in a system ioctl.
+
+When used as a vcpu ioctl:
+Reads model-specific registers from the vcpu. Supported msr indices can
+be obtained using KVM_GET_MSR_INDEX_LIST in a system ioctl.
+
+struct kvm_msrs {
+ __u32 nmsrs; /* number of msrs in entries */
+ __u32 pad;
+
+ struct kvm_msr_entry entries[0];
+};
+
+struct kvm_msr_entry {
+ __u32 index;
+ __u32 reserved;
+ __u64 data;
+};
+
+Application code should set the 'nmsrs' member (which indicates the
+size of the entries array) and the 'index' member of each array entry.
+kvm will fill in the 'data' member.
+
+
+4.19 KVM_SET_MSRS
+
+Capability: basic
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_msrs (in)
+Returns: 0 on success, -1 on error
+
+Writes model-specific registers to the vcpu. See KVM_GET_MSRS for the
+data structures.
+
+Application code should set the 'nmsrs' member (which indicates the
+size of the entries array), and the 'index' and 'data' members of each
+array entry.
+
+
+4.20 KVM_SET_CPUID
+
+Capability: basic
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_cpuid (in)
+Returns: 0 on success, -1 on error
+
+Defines the vcpu responses to the cpuid instruction. Applications
+should use the KVM_SET_CPUID2 ioctl if available.
+
+
+struct kvm_cpuid_entry {
+ __u32 function;
+ __u32 eax;
+ __u32 ebx;
+ __u32 ecx;
+ __u32 edx;
+ __u32 padding;
+};
+
+/* for KVM_SET_CPUID */
+struct kvm_cpuid {
+ __u32 nent;
+ __u32 padding;
+ struct kvm_cpuid_entry entries[0];
+};
+
+
+4.21 KVM_SET_SIGNAL_MASK
+
+Capability: basic
+Architectures: all
+Type: vcpu ioctl
+Parameters: struct kvm_signal_mask (in)
+Returns: 0 on success, -1 on error
+
+Defines which signals are blocked during execution of KVM_RUN. This
+signal mask temporarily overrides the threads signal mask. Any
+unblocked signal received (except SIGKILL and SIGSTOP, which retain
+their traditional behaviour) will cause KVM_RUN to return with -EINTR.
+
+Note the signal will only be delivered if not blocked by the original
+signal mask.
+
+/* for KVM_SET_SIGNAL_MASK */
+struct kvm_signal_mask {
+ __u32 len;
+ __u8 sigset[0];
+};
+
+
+4.22 KVM_GET_FPU
+
+Capability: basic
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_fpu (out)
+Returns: 0 on success, -1 on error
+
+Reads the floating point state from the vcpu.
+
+/* for KVM_GET_FPU and KVM_SET_FPU */
+struct kvm_fpu {
+ __u8 fpr[8][16];
+ __u16 fcw;
+ __u16 fsw;
+ __u8 ftwx; /* in fxsave format */
+ __u8 pad1;
+ __u16 last_opcode;
+ __u64 last_ip;
+ __u64 last_dp;
+ __u8 xmm[16][16];
+ __u32 mxcsr;
+ __u32 pad2;
+};
+
+
+4.23 KVM_SET_FPU
+
+Capability: basic
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_fpu (in)
+Returns: 0 on success, -1 on error
+
+Writes the floating point state to the vcpu.
+
+/* for KVM_GET_FPU and KVM_SET_FPU */
+struct kvm_fpu {
+ __u8 fpr[8][16];
+ __u16 fcw;
+ __u16 fsw;
+ __u8 ftwx; /* in fxsave format */
+ __u8 pad1;
+ __u16 last_opcode;
+ __u64 last_ip;
+ __u64 last_dp;
+ __u8 xmm[16][16];
+ __u32 mxcsr;
+ __u32 pad2;
+};
+
+
+4.24 KVM_CREATE_IRQCHIP
+
+Capability: KVM_CAP_IRQCHIP, KVM_CAP_S390_IRQCHIP (s390)
+Architectures: x86, ARM, arm64, s390
+Type: vm ioctl
+Parameters: none
+Returns: 0 on success, -1 on error
+
+Creates an interrupt controller model in the kernel.
+On x86, creates a virtual ioapic, a virtual PIC (two PICs, nested), and sets up
+future vcpus to have a local APIC. IRQ routing for GSIs 0-15 is set to both
+PIC and IOAPIC; GSI 16-23 only go to the IOAPIC.
+On ARM/arm64, a GICv2 is created. Any other GIC versions require the usage of
+KVM_CREATE_DEVICE, which also supports creating a GICv2. Using
+KVM_CREATE_DEVICE is preferred over KVM_CREATE_IRQCHIP for GICv2.
+On s390, a dummy irq routing table is created.
+
+Note that on s390 the KVM_CAP_S390_IRQCHIP vm capability needs to be enabled
+before KVM_CREATE_IRQCHIP can be used.
+
+
+4.25 KVM_IRQ_LINE
+
+Capability: KVM_CAP_IRQCHIP
+Architectures: x86, arm, arm64
+Type: vm ioctl
+Parameters: struct kvm_irq_level
+Returns: 0 on success, -1 on error
+
+Sets the level of a GSI input to the interrupt controller model in the kernel.
+On some architectures it is required that an interrupt controller model has
+been previously created with KVM_CREATE_IRQCHIP. Note that edge-triggered
+interrupts require the level to be set to 1 and then back to 0.
+
+On real hardware, interrupt pins can be active-low or active-high. This
+does not matter for the level field of struct kvm_irq_level: 1 always
+means active (asserted), 0 means inactive (deasserted).
+
+x86 allows the operating system to program the interrupt polarity
+(active-low/active-high) for level-triggered interrupts, and KVM used
+to consider the polarity. However, due to bitrot in the handling of
+active-low interrupts, the above convention is now valid on x86 too.
+This is signaled by KVM_CAP_X86_IOAPIC_POLARITY_IGNORED. Userspace
+should not present interrupts to the guest as active-low unless this
+capability is present (or unless it is not using the in-kernel irqchip,
+of course).
+
+
+ARM/arm64 can signal an interrupt either at the CPU level, or at the
+in-kernel irqchip (GIC), and for in-kernel irqchip can tell the GIC to
+use PPIs designated for specific cpus. The irq field is interpreted
+like this:
+
+ bits: | 31 ... 24 | 23 ... 16 | 15 ... 0 |
+ field: | irq_type | vcpu_index | irq_id |
+
+The irq_type field has the following values:
+- irq_type[0]: out-of-kernel GIC: irq_id 0 is IRQ, irq_id 1 is FIQ
+- irq_type[1]: in-kernel GIC: SPI, irq_id between 32 and 1019 (incl.)
+ (the vcpu_index field is ignored)
+- irq_type[2]: in-kernel GIC: PPI, irq_id between 16 and 31 (incl.)
+
+(The irq_id field thus corresponds nicely to the IRQ ID in the ARM GIC specs)
+
+In both cases, level is used to assert/deassert the line.
+
+struct kvm_irq_level {
+ union {
+ __u32 irq; /* GSI */
+ __s32 status; /* not used for KVM_IRQ_LEVEL */
+ };
+ __u32 level; /* 0 or 1 */
+};
+
+
+4.26 KVM_GET_IRQCHIP
+
+Capability: KVM_CAP_IRQCHIP
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_irqchip (in/out)
+Returns: 0 on success, -1 on error
+
+Reads the state of a kernel interrupt controller created with
+KVM_CREATE_IRQCHIP into a buffer provided by the caller.
+
+struct kvm_irqchip {
+ __u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */
+ __u32 pad;
+ union {
+ char dummy[512]; /* reserving space */
+ struct kvm_pic_state pic;
+ struct kvm_ioapic_state ioapic;
+ } chip;
+};
+
+
+4.27 KVM_SET_IRQCHIP
+
+Capability: KVM_CAP_IRQCHIP
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_irqchip (in)
+Returns: 0 on success, -1 on error
+
+Sets the state of a kernel interrupt controller created with
+KVM_CREATE_IRQCHIP from a buffer provided by the caller.
+
+struct kvm_irqchip {
+ __u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */
+ __u32 pad;
+ union {
+ char dummy[512]; /* reserving space */
+ struct kvm_pic_state pic;
+ struct kvm_ioapic_state ioapic;
+ } chip;
+};
+
+
+4.28 KVM_XEN_HVM_CONFIG
+
+Capability: KVM_CAP_XEN_HVM
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_xen_hvm_config (in)
+Returns: 0 on success, -1 on error
+
+Sets the MSR that the Xen HVM guest uses to initialize its hypercall
+page, and provides the starting address and size of the hypercall
+blobs in userspace. When the guest writes the MSR, kvm copies one
+page of a blob (32- or 64-bit, depending on the vcpu mode) to guest
+memory.
+
+struct kvm_xen_hvm_config {
+ __u32 flags;
+ __u32 msr;
+ __u64 blob_addr_32;
+ __u64 blob_addr_64;
+ __u8 blob_size_32;
+ __u8 blob_size_64;
+ __u8 pad2[30];
+};
+
+
+4.29 KVM_GET_CLOCK
+
+Capability: KVM_CAP_ADJUST_CLOCK
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_clock_data (out)
+Returns: 0 on success, -1 on error
+
+Gets the current timestamp of kvmclock as seen by the current guest. In
+conjunction with KVM_SET_CLOCK, it is used to ensure monotonicity on scenarios
+such as migration.
+
+When KVM_CAP_ADJUST_CLOCK is passed to KVM_CHECK_EXTENSION, it returns the
+set of bits that KVM can return in struct kvm_clock_data's flag member.
+
+The only flag defined now is KVM_CLOCK_TSC_STABLE. If set, the returned
+value is the exact kvmclock value seen by all VCPUs at the instant
+when KVM_GET_CLOCK was called. If clear, the returned value is simply
+CLOCK_MONOTONIC plus a constant offset; the offset can be modified
+with KVM_SET_CLOCK. KVM will try to make all VCPUs follow this clock,
+but the exact value read by each VCPU could differ, because the host
+TSC is not stable.
+
+struct kvm_clock_data {
+ __u64 clock; /* kvmclock current value */
+ __u32 flags;
+ __u32 pad[9];
+};
+
+
+4.30 KVM_SET_CLOCK
+
+Capability: KVM_CAP_ADJUST_CLOCK
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_clock_data (in)
+Returns: 0 on success, -1 on error
+
+Sets the current timestamp of kvmclock to the value specified in its parameter.
+In conjunction with KVM_GET_CLOCK, it is used to ensure monotonicity on scenarios
+such as migration.
+
+struct kvm_clock_data {
+ __u64 clock; /* kvmclock current value */
+ __u32 flags;
+ __u32 pad[9];
+};
+
+
+4.31 KVM_GET_VCPU_EVENTS
+
+Capability: KVM_CAP_VCPU_EVENTS
+Extended by: KVM_CAP_INTR_SHADOW
+Architectures: x86, arm, arm64
+Type: vcpu ioctl
+Parameters: struct kvm_vcpu_event (out)
+Returns: 0 on success, -1 on error
+
+X86:
+
+Gets currently pending exceptions, interrupts, and NMIs as well as related
+states of the vcpu.
+
+struct kvm_vcpu_events {
+ struct {
+ __u8 injected;
+ __u8 nr;
+ __u8 has_error_code;
+ __u8 pending;
+ __u32 error_code;
+ } exception;
+ struct {
+ __u8 injected;
+ __u8 nr;
+ __u8 soft;
+ __u8 shadow;
+ } interrupt;
+ struct {
+ __u8 injected;
+ __u8 pending;
+ __u8 masked;
+ __u8 pad;
+ } nmi;
+ __u32 sipi_vector;
+ __u32 flags;
+ struct {
+ __u8 smm;
+ __u8 pending;
+ __u8 smm_inside_nmi;
+ __u8 latched_init;
+ } smi;
+ __u8 reserved[27];
+ __u8 exception_has_payload;
+ __u64 exception_payload;
+};
+
+The following bits are defined in the flags field:
+
+- KVM_VCPUEVENT_VALID_SHADOW may be set to signal that
+ interrupt.shadow contains a valid state.
+
+- KVM_VCPUEVENT_VALID_SMM may be set to signal that smi contains a
+ valid state.
+
+- KVM_VCPUEVENT_VALID_PAYLOAD may be set to signal that the
+ exception_has_payload, exception_payload, and exception.pending
+ fields contain a valid state. This bit will be set whenever
+ KVM_CAP_EXCEPTION_PAYLOAD is enabled.
+
+ARM/ARM64:
+
+If the guest accesses a device that is being emulated by the host kernel in
+such a way that a real device would generate a physical SError, KVM may make
+a virtual SError pending for that VCPU. This system error interrupt remains
+pending until the guest takes the exception by unmasking PSTATE.A.
+
+Running the VCPU may cause it to take a pending SError, or make an access that
+causes an SError to become pending. The event's description is only valid while
+the VPCU is not running.
+
+This API provides a way to read and write the pending 'event' state that is not
+visible to the guest. To save, restore or migrate a VCPU the struct representing
+the state can be read then written using this GET/SET API, along with the other
+guest-visible registers. It is not possible to 'cancel' an SError that has been
+made pending.
+
+A device being emulated in user-space may also wish to generate an SError. To do
+this the events structure can be populated by user-space. The current state
+should be read first, to ensure no existing SError is pending. If an existing
+SError is pending, the architecture's 'Multiple SError interrupts' rules should
+be followed. (2.5.3 of DDI0587.a "ARM Reliability, Availability, and
+Serviceability (RAS) Specification").
+
+SError exceptions always have an ESR value. Some CPUs have the ability to
+specify what the virtual SError's ESR value should be. These systems will
+advertise KVM_CAP_ARM_INJECT_SERROR_ESR. In this case exception.has_esr will
+always have a non-zero value when read, and the agent making an SError pending
+should specify the ISS field in the lower 24 bits of exception.serror_esr. If
+the system supports KVM_CAP_ARM_INJECT_SERROR_ESR, but user-space sets the events
+with exception.has_esr as zero, KVM will choose an ESR.
+
+Specifying exception.has_esr on a system that does not support it will return
+-EINVAL. Setting anything other than the lower 24bits of exception.serror_esr
+will return -EINVAL.
+
+struct kvm_vcpu_events {
+ struct {
+ __u8 serror_pending;
+ __u8 serror_has_esr;
+ /* Align it to 8 bytes */
+ __u8 pad[6];
+ __u64 serror_esr;
+ } exception;
+ __u32 reserved[12];
+};
+
+4.32 KVM_SET_VCPU_EVENTS
+
+Capability: KVM_CAP_VCPU_EVENTS
+Extended by: KVM_CAP_INTR_SHADOW
+Architectures: x86, arm, arm64
+Type: vcpu ioctl
+Parameters: struct kvm_vcpu_event (in)
+Returns: 0 on success, -1 on error
+
+X86:
+
+Set pending exceptions, interrupts, and NMIs as well as related states of the
+vcpu.
+
+See KVM_GET_VCPU_EVENTS for the data structure.
+
+Fields that may be modified asynchronously by running VCPUs can be excluded
+from the update. These fields are nmi.pending, sipi_vector, smi.smm,
+smi.pending. Keep the corresponding bits in the flags field cleared to
+suppress overwriting the current in-kernel state. The bits are:
+
+KVM_VCPUEVENT_VALID_NMI_PENDING - transfer nmi.pending to the kernel
+KVM_VCPUEVENT_VALID_SIPI_VECTOR - transfer sipi_vector
+KVM_VCPUEVENT_VALID_SMM - transfer the smi sub-struct.
+
+If KVM_CAP_INTR_SHADOW is available, KVM_VCPUEVENT_VALID_SHADOW can be set in
+the flags field to signal that interrupt.shadow contains a valid state and
+shall be written into the VCPU.
+
+KVM_VCPUEVENT_VALID_SMM can only be set if KVM_CAP_X86_SMM is available.
+
+If KVM_CAP_EXCEPTION_PAYLOAD is enabled, KVM_VCPUEVENT_VALID_PAYLOAD
+can be set in the flags field to signal that the
+exception_has_payload, exception_payload, and exception.pending fields
+contain a valid state and shall be written into the VCPU.
+
+ARM/ARM64:
+
+Set the pending SError exception state for this VCPU. It is not possible to
+'cancel' an Serror that has been made pending.
+
+See KVM_GET_VCPU_EVENTS for the data structure.
+
+
+4.33 KVM_GET_DEBUGREGS
+
+Capability: KVM_CAP_DEBUGREGS
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_debugregs (out)
+Returns: 0 on success, -1 on error
+
+Reads debug registers from the vcpu.
+
+struct kvm_debugregs {
+ __u64 db[4];
+ __u64 dr6;
+ __u64 dr7;
+ __u64 flags;
+ __u64 reserved[9];
+};
+
+
+4.34 KVM_SET_DEBUGREGS
+
+Capability: KVM_CAP_DEBUGREGS
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_debugregs (in)
+Returns: 0 on success, -1 on error
+
+Writes debug registers into the vcpu.
+
+See KVM_GET_DEBUGREGS for the data structure. The flags field is unused
+yet and must be cleared on entry.
+
+
+4.35 KVM_SET_USER_MEMORY_REGION
+
+Capability: KVM_CAP_USER_MEMORY
+Architectures: all
+Type: vm ioctl
+Parameters: struct kvm_userspace_memory_region (in)
+Returns: 0 on success, -1 on error
+
+struct kvm_userspace_memory_region {
+ __u32 slot;
+ __u32 flags;
+ __u64 guest_phys_addr;
+ __u64 memory_size; /* bytes */
+ __u64 userspace_addr; /* start of the userspace allocated memory */
+};
+
+/* for kvm_memory_region::flags */
+#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
+#define KVM_MEM_READONLY (1UL << 1)
+
+This ioctl allows the user to create, modify or delete a guest physical
+memory slot. Bits 0-15 of "slot" specify the slot id and this value
+should be less than the maximum number of user memory slots supported per
+VM. The maximum allowed slots can be queried using KVM_CAP_NR_MEMSLOTS.
+Slots may not overlap in guest physical address space.
+
+If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 of "slot"
+specifies the address space which is being modified. They must be
+less than the value that KVM_CHECK_EXTENSION returns for the
+KVM_CAP_MULTI_ADDRESS_SPACE capability. Slots in separate address spaces
+are unrelated; the restriction on overlapping slots only applies within
+each address space.
+
+Deleting a slot is done by passing zero for memory_size. When changing
+an existing slot, it may be moved in the guest physical memory space,
+or its flags may be modified, but it may not be resized.
+
+Memory for the region is taken starting at the address denoted by the
+field userspace_addr, which must point at user addressable memory for
+the entire memory slot size. Any object may back this memory, including
+anonymous memory, ordinary files, and hugetlbfs.
+
+It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr
+be identical. This allows large pages in the guest to be backed by large
+pages in the host.
+
+The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and
+KVM_MEM_READONLY. The former can be set to instruct KVM to keep track of
+writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to
+use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it,
+to make a new slot read-only. In this case, writes to this memory will be
+posted to userspace as KVM_EXIT_MMIO exits.
+
+When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of
+the memory region are automatically reflected into the guest. For example, an
+mmap() that affects the region will be made visible immediately. Another
+example is madvise(MADV_DROP).
+
+It is recommended to use this API instead of the KVM_SET_MEMORY_REGION ioctl.
+The KVM_SET_MEMORY_REGION does not allow fine grained control over memory
+allocation and is deprecated.
+
+
+4.36 KVM_SET_TSS_ADDR
+
+Capability: KVM_CAP_SET_TSS_ADDR
+Architectures: x86
+Type: vm ioctl
+Parameters: unsigned long tss_address (in)
+Returns: 0 on success, -1 on error
+
+This ioctl defines the physical address of a three-page region in the guest
+physical address space. The region must be within the first 4GB of the
+guest physical address space and must not conflict with any memory slot
+or any mmio address. The guest may malfunction if it accesses this memory
+region.
+
+This ioctl is required on Intel-based hosts. This is needed on Intel hardware
+because of a quirk in the virtualization implementation (see the internals
+documentation when it pops into existence).
+
+
+4.37 KVM_ENABLE_CAP
+
+Capability: KVM_CAP_ENABLE_CAP
+Architectures: mips, ppc, s390
+Type: vcpu ioctl
+Parameters: struct kvm_enable_cap (in)
+Returns: 0 on success; -1 on error
+
+Capability: KVM_CAP_ENABLE_CAP_VM
+Architectures: all
+Type: vcpu ioctl
+Parameters: struct kvm_enable_cap (in)
+Returns: 0 on success; -1 on error
+
++Not all extensions are enabled by default. Using this ioctl the application
+can enable an extension, making it available to the guest.
+
+On systems that do not support this ioctl, it always fails. On systems that
+do support it, it only works for extensions that are supported for enablement.
+
+To check if a capability can be enabled, the KVM_CHECK_EXTENSION ioctl should
+be used.
+
+struct kvm_enable_cap {
+ /* in */
+ __u32 cap;
+
+The capability that is supposed to get enabled.
+
+ __u32 flags;
+
+A bitfield indicating future enhancements. Has to be 0 for now.
+
+ __u64 args[4];
+
+Arguments for enabling a feature. If a feature needs initial values to
+function properly, this is the place to put them.
+
+ __u8 pad[64];
+};
+
+The vcpu ioctl should be used for vcpu-specific capabilities, the vm ioctl
+for vm-wide capabilities.
+
+4.38 KVM_GET_MP_STATE
+
+Capability: KVM_CAP_MP_STATE
+Architectures: x86, s390, arm, arm64
+Type: vcpu ioctl
+Parameters: struct kvm_mp_state (out)
+Returns: 0 on success; -1 on error
+
+struct kvm_mp_state {
+ __u32 mp_state;
+};
+
+Returns the vcpu's current "multiprocessing state" (though also valid on
+uniprocessor guests).
+
+Possible values are:
+
+ - KVM_MP_STATE_RUNNABLE: the vcpu is currently running [x86,arm/arm64]
+ - KVM_MP_STATE_UNINITIALIZED: the vcpu is an application processor (AP)
+ which has not yet received an INIT signal [x86]
+ - KVM_MP_STATE_INIT_RECEIVED: the vcpu has received an INIT signal, and is
+ now ready for a SIPI [x86]
+ - KVM_MP_STATE_HALTED: the vcpu has executed a HLT instruction and
+ is waiting for an interrupt [x86]
+ - KVM_MP_STATE_SIPI_RECEIVED: the vcpu has just received a SIPI (vector
+ accessible via KVM_GET_VCPU_EVENTS) [x86]
+ - KVM_MP_STATE_STOPPED: the vcpu is stopped [s390,arm/arm64]
+ - KVM_MP_STATE_CHECK_STOP: the vcpu is in a special error state [s390]
+ - KVM_MP_STATE_OPERATING: the vcpu is operating (running or halted)
+ [s390]
+ - KVM_MP_STATE_LOAD: the vcpu is in a special load/startup state
+ [s390]
+
+On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an
+in-kernel irqchip, the multiprocessing state must be maintained by userspace on
+these architectures.
+
+For arm/arm64:
+
+The only states that are valid are KVM_MP_STATE_STOPPED and
+KVM_MP_STATE_RUNNABLE which reflect if the vcpu is paused or not.
+
+4.39 KVM_SET_MP_STATE
+
+Capability: KVM_CAP_MP_STATE
+Architectures: x86, s390, arm, arm64
+Type: vcpu ioctl
+Parameters: struct kvm_mp_state (in)
+Returns: 0 on success; -1 on error
+
+Sets the vcpu's current "multiprocessing state"; see KVM_GET_MP_STATE for
+arguments.
+
+On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an
+in-kernel irqchip, the multiprocessing state must be maintained by userspace on
+these architectures.
+
+For arm/arm64:
+
+The only states that are valid are KVM_MP_STATE_STOPPED and
+KVM_MP_STATE_RUNNABLE which reflect if the vcpu should be paused or not.
+
+4.40 KVM_SET_IDENTITY_MAP_ADDR
+
+Capability: KVM_CAP_SET_IDENTITY_MAP_ADDR
+Architectures: x86
+Type: vm ioctl
+Parameters: unsigned long identity (in)
+Returns: 0 on success, -1 on error
+
+This ioctl defines the physical address of a one-page region in the guest
+physical address space. The region must be within the first 4GB of the
+guest physical address space and must not conflict with any memory slot
+or any mmio address. The guest may malfunction if it accesses this memory
+region.
+
+Setting the address to 0 will result in resetting the address to its default
+(0xfffbc000).
+
+This ioctl is required on Intel-based hosts. This is needed on Intel hardware
+because of a quirk in the virtualization implementation (see the internals
+documentation when it pops into existence).
+
+Fails if any VCPU has already been created.
+
+4.41 KVM_SET_BOOT_CPU_ID
+
+Capability: KVM_CAP_SET_BOOT_CPU_ID
+Architectures: x86
+Type: vm ioctl
+Parameters: unsigned long vcpu_id
+Returns: 0 on success, -1 on error
+
+Define which vcpu is the Bootstrap Processor (BSP). Values are the same
+as the vcpu id in KVM_CREATE_VCPU. If this ioctl is not called, the default
+is vcpu 0.
+
+
+4.42 KVM_GET_XSAVE
+
+Capability: KVM_CAP_XSAVE
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_xsave (out)
+Returns: 0 on success, -1 on error
+
+struct kvm_xsave {
+ __u32 region[1024];
+};
+
+This ioctl would copy current vcpu's xsave struct to the userspace.
+
+
+4.43 KVM_SET_XSAVE
+
+Capability: KVM_CAP_XSAVE
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_xsave (in)
+Returns: 0 on success, -1 on error
+
+struct kvm_xsave {
+ __u32 region[1024];
+};
+
+This ioctl would copy userspace's xsave struct to the kernel.
+
+
+4.44 KVM_GET_XCRS
+
+Capability: KVM_CAP_XCRS
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_xcrs (out)
+Returns: 0 on success, -1 on error
+
+struct kvm_xcr {
+ __u32 xcr;
+ __u32 reserved;
+ __u64 value;
+};
+
+struct kvm_xcrs {
+ __u32 nr_xcrs;
+ __u32 flags;
+ struct kvm_xcr xcrs[KVM_MAX_XCRS];
+ __u64 padding[16];
+};
+
+This ioctl would copy current vcpu's xcrs to the userspace.
+
+
+4.45 KVM_SET_XCRS
+
+Capability: KVM_CAP_XCRS
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_xcrs (in)
+Returns: 0 on success, -1 on error
+
+struct kvm_xcr {
+ __u32 xcr;
+ __u32 reserved;
+ __u64 value;
+};
+
+struct kvm_xcrs {
+ __u32 nr_xcrs;
+ __u32 flags;
+ struct kvm_xcr xcrs[KVM_MAX_XCRS];
+ __u64 padding[16];
+};
+
+This ioctl would set vcpu's xcr to the value userspace specified.
+
+
+4.46 KVM_GET_SUPPORTED_CPUID
+
+Capability: KVM_CAP_EXT_CPUID
+Architectures: x86
+Type: system ioctl
+Parameters: struct kvm_cpuid2 (in/out)
+Returns: 0 on success, -1 on error
+
+struct kvm_cpuid2 {
+ __u32 nent;
+ __u32 padding;
+ struct kvm_cpuid_entry2 entries[0];
+};
+
+#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0)
+#define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1)
+#define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2)
+
+struct kvm_cpuid_entry2 {
+ __u32 function;
+ __u32 index;
+ __u32 flags;
+ __u32 eax;
+ __u32 ebx;
+ __u32 ecx;
+ __u32 edx;
+ __u32 padding[3];
+};
+
+This ioctl returns x86 cpuid features which are supported by both the
+hardware and kvm in its default configuration. Userspace can use the
+information returned by this ioctl to construct cpuid information (for
+KVM_SET_CPUID2) that is consistent with hardware, kernel, and
+userspace capabilities, and with user requirements (for example, the
+user may wish to constrain cpuid to emulate older hardware, or for
+feature consistency across a cluster).
+
+Note that certain capabilities, such as KVM_CAP_X86_DISABLE_EXITS, may
+expose cpuid features (e.g. MONITOR) which are not supported by kvm in
+its default configuration. If userspace enables such capabilities, it
+is responsible for modifying the results of this ioctl appropriately.
+
+Userspace invokes KVM_GET_SUPPORTED_CPUID by passing a kvm_cpuid2 structure
+with the 'nent' field indicating the number of entries in the variable-size
+array 'entries'. If the number of entries is too low to describe the cpu
+capabilities, an error (E2BIG) is returned. If the number is too high,
+the 'nent' field is adjusted and an error (ENOMEM) is returned. If the
+number is just right, the 'nent' field is adjusted to the number of valid
+entries in the 'entries' array, which is then filled.
+
+The entries returned are the host cpuid as returned by the cpuid instruction,
+with unknown or unsupported features masked out. Some features (for example,
+x2apic), may not be present in the host cpu, but are exposed by kvm if it can
+emulate them efficiently. The fields in each entry are defined as follows:
+
+ function: the eax value used to obtain the entry
+ index: the ecx value used to obtain the entry (for entries that are
+ affected by ecx)
+ flags: an OR of zero or more of the following:
+ KVM_CPUID_FLAG_SIGNIFCANT_INDEX:
+ if the index field is valid
+ KVM_CPUID_FLAG_STATEFUL_FUNC:
+ if cpuid for this function returns different values for successive
+ invocations; there will be several entries with the same function,
+ all with this flag set
+ KVM_CPUID_FLAG_STATE_READ_NEXT:
+ for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is
+ the first entry to be read by a cpu
+ eax, ebx, ecx, edx: the values returned by the cpuid instruction for
+ this function/index combination
+
+The TSC deadline timer feature (CPUID leaf 1, ecx[24]) is always returned
+as false, since the feature depends on KVM_CREATE_IRQCHIP for local APIC
+support. Instead it is reported via
+
+ ioctl(KVM_CHECK_EXTENSION, KVM_CAP_TSC_DEADLINE_TIMER)
+
+if that returns true and you use KVM_CREATE_IRQCHIP, or if you emulate the
+feature in userspace, then you can enable the feature for KVM_SET_CPUID2.
+
+
+4.47 KVM_PPC_GET_PVINFO
+
+Capability: KVM_CAP_PPC_GET_PVINFO
+Architectures: ppc
+Type: vm ioctl
+Parameters: struct kvm_ppc_pvinfo (out)
+Returns: 0 on success, !0 on error
+
+struct kvm_ppc_pvinfo {
+ __u32 flags;
+ __u32 hcall[4];
+ __u8 pad[108];
+};
+
+This ioctl fetches PV specific information that need to be passed to the guest
+using the device tree or other means from vm context.
+
+The hcall array defines 4 instructions that make up a hypercall.
+
+If any additional field gets added to this structure later on, a bit for that
+additional piece of information will be set in the flags bitmap.
+
+The flags bitmap is defined as:
+
+ /* the host supports the ePAPR idle hcall
+ #define KVM_PPC_PVINFO_FLAGS_EV_IDLE (1<<0)
+
+4.52 KVM_SET_GSI_ROUTING
+
+Capability: KVM_CAP_IRQ_ROUTING
+Architectures: x86 s390 arm arm64
+Type: vm ioctl
+Parameters: struct kvm_irq_routing (in)
+Returns: 0 on success, -1 on error
+
+Sets the GSI routing table entries, overwriting any previously set entries.
+
+On arm/arm64, GSI routing has the following limitation:
+- GSI routing does not apply to KVM_IRQ_LINE but only to KVM_IRQFD.
+
+struct kvm_irq_routing {
+ __u32 nr;
+ __u32 flags;
+ struct kvm_irq_routing_entry entries[0];
+};
+
+No flags are specified so far, the corresponding field must be set to zero.
+
+struct kvm_irq_routing_entry {
+ __u32 gsi;
+ __u32 type;
+ __u32 flags;
+ __u32 pad;
+ union {
+ struct kvm_irq_routing_irqchip irqchip;
+ struct kvm_irq_routing_msi msi;
+ struct kvm_irq_routing_s390_adapter adapter;
+ struct kvm_irq_routing_hv_sint hv_sint;
+ __u32 pad[8];
+ } u;
+};
+
+/* gsi routing entry types */
+#define KVM_IRQ_ROUTING_IRQCHIP 1
+#define KVM_IRQ_ROUTING_MSI 2
+#define KVM_IRQ_ROUTING_S390_ADAPTER 3
+#define KVM_IRQ_ROUTING_HV_SINT 4
+
+flags:
+- KVM_MSI_VALID_DEVID: used along with KVM_IRQ_ROUTING_MSI routing entry
+ type, specifies that the devid field contains a valid value. The per-VM
+ KVM_CAP_MSI_DEVID capability advertises the requirement to provide
+ the device ID. If this capability is not available, userspace should
+ never set the KVM_MSI_VALID_DEVID flag as the ioctl might fail.
+- zero otherwise
+
+struct kvm_irq_routing_irqchip {
+ __u32 irqchip;
+ __u32 pin;
+};
+
+struct kvm_irq_routing_msi {
+ __u32 address_lo;
+ __u32 address_hi;
+ __u32 data;
+ union {
+ __u32 pad;
+ __u32 devid;
+ };
+};
+
+If KVM_MSI_VALID_DEVID is set, devid contains a unique device identifier
+for the device that wrote the MSI message. For PCI, this is usually a
+BFD identifier in the lower 16 bits.
+
+On x86, address_hi is ignored unless the KVM_X2APIC_API_USE_32BIT_IDS
+feature of KVM_CAP_X2APIC_API capability is enabled. If it is enabled,
+address_hi bits 31-8 provide bits 31-8 of the destination id. Bits 7-0 of
+address_hi must be zero.
+
+struct kvm_irq_routing_s390_adapter {
+ __u64 ind_addr;
+ __u64 summary_addr;
+ __u64 ind_offset;
+ __u32 summary_offset;
+ __u32 adapter_id;
+};
+
+struct kvm_irq_routing_hv_sint {
+ __u32 vcpu;
+ __u32 sint;
+};
+
+
+4.55 KVM_SET_TSC_KHZ
+
+Capability: KVM_CAP_TSC_CONTROL
+Architectures: x86
+Type: vcpu ioctl
+Parameters: virtual tsc_khz
+Returns: 0 on success, -1 on error
+
+Specifies the tsc frequency for the virtual machine. The unit of the
+frequency is KHz.
+
+
+4.56 KVM_GET_TSC_KHZ
+
+Capability: KVM_CAP_GET_TSC_KHZ
+Architectures: x86
+Type: vcpu ioctl
+Parameters: none
+Returns: virtual tsc-khz on success, negative value on error
+
+Returns the tsc frequency of the guest. The unit of the return value is
+KHz. If the host has unstable tsc this ioctl returns -EIO instead as an
+error.
+
+
+4.57 KVM_GET_LAPIC
+
+Capability: KVM_CAP_IRQCHIP
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_lapic_state (out)
+Returns: 0 on success, -1 on error
+
+#define KVM_APIC_REG_SIZE 0x400
+struct kvm_lapic_state {
+ char regs[KVM_APIC_REG_SIZE];
+};
+
+Reads the Local APIC registers and copies them into the input argument. The
+data format and layout are the same as documented in the architecture manual.
+
+If KVM_X2APIC_API_USE_32BIT_IDS feature of KVM_CAP_X2APIC_API is
+enabled, then the format of APIC_ID register depends on the APIC mode
+(reported by MSR_IA32_APICBASE) of its VCPU. x2APIC stores APIC ID in
+the APIC_ID register (bytes 32-35). xAPIC only allows an 8-bit APIC ID
+which is stored in bits 31-24 of the APIC register, or equivalently in
+byte 35 of struct kvm_lapic_state's regs field. KVM_GET_LAPIC must then
+be called after MSR_IA32_APICBASE has been set with KVM_SET_MSR.
+
+If KVM_X2APIC_API_USE_32BIT_IDS feature is disabled, struct kvm_lapic_state
+always uses xAPIC format.
+
+
+4.58 KVM_SET_LAPIC
+
+Capability: KVM_CAP_IRQCHIP
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_lapic_state (in)
+Returns: 0 on success, -1 on error
+
+#define KVM_APIC_REG_SIZE 0x400
+struct kvm_lapic_state {
+ char regs[KVM_APIC_REG_SIZE];
+};
+
+Copies the input argument into the Local APIC registers. The data format
+and layout are the same as documented in the architecture manual.
+
+The format of the APIC ID register (bytes 32-35 of struct kvm_lapic_state's
+regs field) depends on the state of the KVM_CAP_X2APIC_API capability.
+See the note in KVM_GET_LAPIC.
+
+
+4.59 KVM_IOEVENTFD
+
+Capability: KVM_CAP_IOEVENTFD
+Architectures: all
+Type: vm ioctl
+Parameters: struct kvm_ioeventfd (in)
+Returns: 0 on success, !0 on error
+
+This ioctl attaches or detaches an ioeventfd to a legal pio/mmio address
+within the guest. A guest write in the registered address will signal the
+provided event instead of triggering an exit.
+
+struct kvm_ioeventfd {
+ __u64 datamatch;
+ __u64 addr; /* legal pio/mmio address */
+ __u32 len; /* 0, 1, 2, 4, or 8 bytes */
+ __s32 fd;
+ __u32 flags;
+ __u8 pad[36];
+};
+
+For the special case of virtio-ccw devices on s390, the ioevent is matched
+to a subchannel/virtqueue tuple instead.
+
+The following flags are defined:
+
+#define KVM_IOEVENTFD_FLAG_DATAMATCH (1 << kvm_ioeventfd_flag_nr_datamatch)
+#define KVM_IOEVENTFD_FLAG_PIO (1 << kvm_ioeventfd_flag_nr_pio)
+#define KVM_IOEVENTFD_FLAG_DEASSIGN (1 << kvm_ioeventfd_flag_nr_deassign)
+#define KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY \
+ (1 << kvm_ioeventfd_flag_nr_virtio_ccw_notify)
+
+If datamatch flag is set, the event will be signaled only if the written value
+to the registered address is equal to datamatch in struct kvm_ioeventfd.
+
+For virtio-ccw devices, addr contains the subchannel id and datamatch the
+virtqueue index.
+
+With KVM_CAP_IOEVENTFD_ANY_LENGTH, a zero length ioeventfd is allowed, and
+the kernel will ignore the length of guest write and may get a faster vmexit.
+The speedup may only apply to specific architectures, but the ioeventfd will
+work anyway.
+
+4.60 KVM_DIRTY_TLB
+
+Capability: KVM_CAP_SW_TLB
+Architectures: ppc
+Type: vcpu ioctl
+Parameters: struct kvm_dirty_tlb (in)
+Returns: 0 on success, -1 on error
+
+struct kvm_dirty_tlb {
+ __u64 bitmap;
+ __u32 num_dirty;
+};
+
+This must be called whenever userspace has changed an entry in the shared
+TLB, prior to calling KVM_RUN on the associated vcpu.
+
+The "bitmap" field is the userspace address of an array. This array
+consists of a number of bits, equal to the total number of TLB entries as
+determined by the last successful call to KVM_CONFIG_TLB, rounded up to the
+nearest multiple of 64.
+
+Each bit corresponds to one TLB entry, ordered the same as in the shared TLB
+array.
+
+The array is little-endian: the bit 0 is the least significant bit of the
+first byte, bit 8 is the least significant bit of the second byte, etc.
+This avoids any complications with differing word sizes.
+
+The "num_dirty" field is a performance hint for KVM to determine whether it
+should skip processing the bitmap and just invalidate everything. It must
+be set to the number of set bits in the bitmap.
+
+
+4.62 KVM_CREATE_SPAPR_TCE
+
+Capability: KVM_CAP_SPAPR_TCE
+Architectures: powerpc
+Type: vm ioctl
+Parameters: struct kvm_create_spapr_tce (in)
+Returns: file descriptor for manipulating the created TCE table
+
+This creates a virtual TCE (translation control entry) table, which
+is an IOMMU for PAPR-style virtual I/O. It is used to translate
+logical addresses used in virtual I/O into guest physical addresses,
+and provides a scatter/gather capability for PAPR virtual I/O.
+
+/* for KVM_CAP_SPAPR_TCE */
+struct kvm_create_spapr_tce {
+ __u64 liobn;
+ __u32 window_size;
+};
+
+The liobn field gives the logical IO bus number for which to create a
+TCE table. The window_size field specifies the size of the DMA window
+which this TCE table will translate - the table will contain one 64
+bit TCE entry for every 4kiB of the DMA window.
+
+When the guest issues an H_PUT_TCE hcall on a liobn for which a TCE
+table has been created using this ioctl(), the kernel will handle it
+in real mode, updating the TCE table. H_PUT_TCE calls for other
+liobns will cause a vm exit and must be handled by userspace.
+
+The return value is a file descriptor which can be passed to mmap(2)
+to map the created TCE table into userspace. This lets userspace read
+the entries written by kernel-handled H_PUT_TCE calls, and also lets
+userspace update the TCE table directly which is useful in some
+circumstances.
+
+
+4.63 KVM_ALLOCATE_RMA
+
+Capability: KVM_CAP_PPC_RMA
+Architectures: powerpc
+Type: vm ioctl
+Parameters: struct kvm_allocate_rma (out)
+Returns: file descriptor for mapping the allocated RMA
+
+This allocates a Real Mode Area (RMA) from the pool allocated at boot
+time by the kernel. An RMA is a physically-contiguous, aligned region
+of memory used on older POWER processors to provide the memory which
+will be accessed by real-mode (MMU off) accesses in a KVM guest.
+POWER processors support a set of sizes for the RMA that usually
+includes 64MB, 128MB, 256MB and some larger powers of two.
+
+/* for KVM_ALLOCATE_RMA */
+struct kvm_allocate_rma {
+ __u64 rma_size;
+};
+
+The return value is a file descriptor which can be passed to mmap(2)
+to map the allocated RMA into userspace. The mapped area can then be
+passed to the KVM_SET_USER_MEMORY_REGION ioctl to establish it as the
+RMA for a virtual machine. The size of the RMA in bytes (which is
+fixed at host kernel boot time) is returned in the rma_size field of
+the argument structure.
+
+The KVM_CAP_PPC_RMA capability is 1 or 2 if the KVM_ALLOCATE_RMA ioctl
+is supported; 2 if the processor requires all virtual machines to have
+an RMA, or 1 if the processor can use an RMA but doesn't require it,
+because it supports the Virtual RMA (VRMA) facility.
+
+
+4.64 KVM_NMI
+
+Capability: KVM_CAP_USER_NMI
+Architectures: x86
+Type: vcpu ioctl
+Parameters: none
+Returns: 0 on success, -1 on error
+
+Queues an NMI on the thread's vcpu. Note this is well defined only
+when KVM_CREATE_IRQCHIP has not been called, since this is an interface
+between the virtual cpu core and virtual local APIC. After KVM_CREATE_IRQCHIP
+has been called, this interface is completely emulated within the kernel.
+
+To use this to emulate the LINT1 input with KVM_CREATE_IRQCHIP, use the
+following algorithm:
+
+ - pause the vcpu
+ - read the local APIC's state (KVM_GET_LAPIC)
+ - check whether changing LINT1 will queue an NMI (see the LVT entry for LINT1)
+ - if so, issue KVM_NMI
+ - resume the vcpu
+
+Some guests configure the LINT1 NMI input to cause a panic, aiding in
+debugging.
+
+
+4.65 KVM_S390_UCAS_MAP
+
+Capability: KVM_CAP_S390_UCONTROL
+Architectures: s390
+Type: vcpu ioctl
+Parameters: struct kvm_s390_ucas_mapping (in)
+Returns: 0 in case of success
+
+The parameter is defined like this:
+ struct kvm_s390_ucas_mapping {
+ __u64 user_addr;
+ __u64 vcpu_addr;
+ __u64 length;
+ };
+
+This ioctl maps the memory at "user_addr" with the length "length" to
+the vcpu's address space starting at "vcpu_addr". All parameters need to
+be aligned by 1 megabyte.
+
+
+4.66 KVM_S390_UCAS_UNMAP
+
+Capability: KVM_CAP_S390_UCONTROL
+Architectures: s390
+Type: vcpu ioctl
+Parameters: struct kvm_s390_ucas_mapping (in)
+Returns: 0 in case of success
+
+The parameter is defined like this:
+ struct kvm_s390_ucas_mapping {
+ __u64 user_addr;
+ __u64 vcpu_addr;
+ __u64 length;
+ };
+
+This ioctl unmaps the memory in the vcpu's address space starting at
+"vcpu_addr" with the length "length". The field "user_addr" is ignored.
+All parameters need to be aligned by 1 megabyte.
+
+
+4.67 KVM_S390_VCPU_FAULT
+
+Capability: KVM_CAP_S390_UCONTROL
+Architectures: s390
+Type: vcpu ioctl
+Parameters: vcpu absolute address (in)
+Returns: 0 in case of success
+
+This call creates a page table entry on the virtual cpu's address space
+(for user controlled virtual machines) or the virtual machine's address
+space (for regular virtual machines). This only works for minor faults,
+thus it's recommended to access subject memory page via the user page
+table upfront. This is useful to handle validity intercepts for user
+controlled virtual machines to fault in the virtual cpu's lowcore pages
+prior to calling the KVM_RUN ioctl.
+
+
+4.68 KVM_SET_ONE_REG
+
+Capability: KVM_CAP_ONE_REG
+Architectures: all
+Type: vcpu ioctl
+Parameters: struct kvm_one_reg (in)
+Returns: 0 on success, negative value on failure
+Errors:
+ ENOENT: no such register
+ EINVAL: invalid register ID, or no such register
+ EPERM: (arm64) register access not allowed before vcpu finalization
+(These error codes are indicative only: do not rely on a specific error
+code being returned in a specific situation.)
+
+struct kvm_one_reg {
+ __u64 id;
+ __u64 addr;
+};
+
+Using this ioctl, a single vcpu register can be set to a specific value
+defined by user space with the passed in struct kvm_one_reg, where id
+refers to the register identifier as described below and addr is a pointer
+to a variable with the respective size. There can be architecture agnostic
+and architecture specific registers. Each have their own range of operation
+and their own constants and width. To keep track of the implemented
+registers, find a list below:
+
+ Arch | Register | Width (bits)
+ | |
+ PPC | KVM_REG_PPC_HIOR | 64
+ PPC | KVM_REG_PPC_IAC1 | 64
+ PPC | KVM_REG_PPC_IAC2 | 64
+ PPC | KVM_REG_PPC_IAC3 | 64
+ PPC | KVM_REG_PPC_IAC4 | 64
+ PPC | KVM_REG_PPC_DAC1 | 64
+ PPC | KVM_REG_PPC_DAC2 | 64
+ PPC | KVM_REG_PPC_DABR | 64
+ PPC | KVM_REG_PPC_DSCR | 64
+ PPC | KVM_REG_PPC_PURR | 64
+ PPC | KVM_REG_PPC_SPURR | 64
+ PPC | KVM_REG_PPC_DAR | 64
+ PPC | KVM_REG_PPC_DSISR | 32
+ PPC | KVM_REG_PPC_AMR | 64
+ PPC | KVM_REG_PPC_UAMOR | 64
+ PPC | KVM_REG_PPC_MMCR0 | 64
+ PPC | KVM_REG_PPC_MMCR1 | 64
+ PPC | KVM_REG_PPC_MMCRA | 64
+ PPC | KVM_REG_PPC_MMCR2 | 64
+ PPC | KVM_REG_PPC_MMCRS | 64
+ PPC | KVM_REG_PPC_SIAR | 64
+ PPC | KVM_REG_PPC_SDAR | 64
+ PPC | KVM_REG_PPC_SIER | 64
+ PPC | KVM_REG_PPC_PMC1 | 32
+ PPC | KVM_REG_PPC_PMC2 | 32
+ PPC | KVM_REG_PPC_PMC3 | 32
+ PPC | KVM_REG_PPC_PMC4 | 32
+ PPC | KVM_REG_PPC_PMC5 | 32
+ PPC | KVM_REG_PPC_PMC6 | 32
+ PPC | KVM_REG_PPC_PMC7 | 32
+ PPC | KVM_REG_PPC_PMC8 | 32
+ PPC | KVM_REG_PPC_FPR0 | 64
+ ...
+ PPC | KVM_REG_PPC_FPR31 | 64
+ PPC | KVM_REG_PPC_VR0 | 128
+ ...
+ PPC | KVM_REG_PPC_VR31 | 128
+ PPC | KVM_REG_PPC_VSR0 | 128
+ ...
+ PPC | KVM_REG_PPC_VSR31 | 128
+ PPC | KVM_REG_PPC_FPSCR | 64
+ PPC | KVM_REG_PPC_VSCR | 32
+ PPC | KVM_REG_PPC_VPA_ADDR | 64
+ PPC | KVM_REG_PPC_VPA_SLB | 128
+ PPC | KVM_REG_PPC_VPA_DTL | 128
+ PPC | KVM_REG_PPC_EPCR | 32
+ PPC | KVM_REG_PPC_EPR | 32
+ PPC | KVM_REG_PPC_TCR | 32
+ PPC | KVM_REG_PPC_TSR | 32
+ PPC | KVM_REG_PPC_OR_TSR | 32
+ PPC | KVM_REG_PPC_CLEAR_TSR | 32
+ PPC | KVM_REG_PPC_MAS0 | 32
+ PPC | KVM_REG_PPC_MAS1 | 32
+ PPC | KVM_REG_PPC_MAS2 | 64
+ PPC | KVM_REG_PPC_MAS7_3 | 64
+ PPC | KVM_REG_PPC_MAS4 | 32
+ PPC | KVM_REG_PPC_MAS6 | 32
+ PPC | KVM_REG_PPC_MMUCFG | 32
+ PPC | KVM_REG_PPC_TLB0CFG | 32
+ PPC | KVM_REG_PPC_TLB1CFG | 32
+ PPC | KVM_REG_PPC_TLB2CFG | 32
+ PPC | KVM_REG_PPC_TLB3CFG | 32
+ PPC | KVM_REG_PPC_TLB0PS | 32
+ PPC | KVM_REG_PPC_TLB1PS | 32
+ PPC | KVM_REG_PPC_TLB2PS | 32
+ PPC | KVM_REG_PPC_TLB3PS | 32
+ PPC | KVM_REG_PPC_EPTCFG | 32
+ PPC | KVM_REG_PPC_ICP_STATE | 64
+ PPC | KVM_REG_PPC_VP_STATE | 128
+ PPC | KVM_REG_PPC_TB_OFFSET | 64
+ PPC | KVM_REG_PPC_SPMC1 | 32
+ PPC | KVM_REG_PPC_SPMC2 | 32
+ PPC | KVM_REG_PPC_IAMR | 64
+ PPC | KVM_REG_PPC_TFHAR | 64
+ PPC | KVM_REG_PPC_TFIAR | 64
+ PPC | KVM_REG_PPC_TEXASR | 64
+ PPC | KVM_REG_PPC_FSCR | 64
+ PPC | KVM_REG_PPC_PSPB | 32
+ PPC | KVM_REG_PPC_EBBHR | 64
+ PPC | KVM_REG_PPC_EBBRR | 64
+ PPC | KVM_REG_PPC_BESCR | 64
+ PPC | KVM_REG_PPC_TAR | 64
+ PPC | KVM_REG_PPC_DPDES | 64
+ PPC | KVM_REG_PPC_DAWR | 64
+ PPC | KVM_REG_PPC_DAWRX | 64
+ PPC | KVM_REG_PPC_CIABR | 64
+ PPC | KVM_REG_PPC_IC | 64
+ PPC | KVM_REG_PPC_VTB | 64
+ PPC | KVM_REG_PPC_CSIGR | 64
+ PPC | KVM_REG_PPC_TACR | 64
+ PPC | KVM_REG_PPC_TCSCR | 64
+ PPC | KVM_REG_PPC_PID | 64
+ PPC | KVM_REG_PPC_ACOP | 64
+ PPC | KVM_REG_PPC_VRSAVE | 32
+ PPC | KVM_REG_PPC_LPCR | 32
+ PPC | KVM_REG_PPC_LPCR_64 | 64
+ PPC | KVM_REG_PPC_PPR | 64
+ PPC | KVM_REG_PPC_ARCH_COMPAT | 32
+ PPC | KVM_REG_PPC_DABRX | 32
+ PPC | KVM_REG_PPC_WORT | 64
+ PPC | KVM_REG_PPC_SPRG9 | 64
+ PPC | KVM_REG_PPC_DBSR | 32
+ PPC | KVM_REG_PPC_TIDR | 64
+ PPC | KVM_REG_PPC_PSSCR | 64
+ PPC | KVM_REG_PPC_DEC_EXPIRY | 64
+ PPC | KVM_REG_PPC_PTCR | 64
+ PPC | KVM_REG_PPC_TM_GPR0 | 64
+ ...
+ PPC | KVM_REG_PPC_TM_GPR31 | 64
+ PPC | KVM_REG_PPC_TM_VSR0 | 128
+ ...
+ PPC | KVM_REG_PPC_TM_VSR63 | 128
+ PPC | KVM_REG_PPC_TM_CR | 64
+ PPC | KVM_REG_PPC_TM_LR | 64
+ PPC | KVM_REG_PPC_TM_CTR | 64
+ PPC | KVM_REG_PPC_TM_FPSCR | 64
+ PPC | KVM_REG_PPC_TM_AMR | 64
+ PPC | KVM_REG_PPC_TM_PPR | 64
+ PPC | KVM_REG_PPC_TM_VRSAVE | 64
+ PPC | KVM_REG_PPC_TM_VSCR | 32
+ PPC | KVM_REG_PPC_TM_DSCR | 64
+ PPC | KVM_REG_PPC_TM_TAR | 64
+ PPC | KVM_REG_PPC_TM_XER | 64
+ | |
+ MIPS | KVM_REG_MIPS_R0 | 64
+ ...
+ MIPS | KVM_REG_MIPS_R31 | 64
+ MIPS | KVM_REG_MIPS_HI | 64
+ MIPS | KVM_REG_MIPS_LO | 64
+ MIPS | KVM_REG_MIPS_PC | 64
+ MIPS | KVM_REG_MIPS_CP0_INDEX | 32
+ MIPS | KVM_REG_MIPS_CP0_ENTRYLO0 | 64
+ MIPS | KVM_REG_MIPS_CP0_ENTRYLO1 | 64
+ MIPS | KVM_REG_MIPS_CP0_CONTEXT | 64
+ MIPS | KVM_REG_MIPS_CP0_CONTEXTCONFIG| 32
+ MIPS | KVM_REG_MIPS_CP0_USERLOCAL | 64
+ MIPS | KVM_REG_MIPS_CP0_XCONTEXTCONFIG| 64
+ MIPS | KVM_REG_MIPS_CP0_PAGEMASK | 32
+ MIPS | KVM_REG_MIPS_CP0_PAGEGRAIN | 32
+ MIPS | KVM_REG_MIPS_CP0_SEGCTL0 | 64
+ MIPS | KVM_REG_MIPS_CP0_SEGCTL1 | 64
+ MIPS | KVM_REG_MIPS_CP0_SEGCTL2 | 64
+ MIPS | KVM_REG_MIPS_CP0_PWBASE | 64
+ MIPS | KVM_REG_MIPS_CP0_PWFIELD | 64
+ MIPS | KVM_REG_MIPS_CP0_PWSIZE | 64
+ MIPS | KVM_REG_MIPS_CP0_WIRED | 32
+ MIPS | KVM_REG_MIPS_CP0_PWCTL | 32
+ MIPS | KVM_REG_MIPS_CP0_HWRENA | 32
+ MIPS | KVM_REG_MIPS_CP0_BADVADDR | 64
+ MIPS | KVM_REG_MIPS_CP0_BADINSTR | 32
+ MIPS | KVM_REG_MIPS_CP0_BADINSTRP | 32
+ MIPS | KVM_REG_MIPS_CP0_COUNT | 32
+ MIPS | KVM_REG_MIPS_CP0_ENTRYHI | 64
+ MIPS | KVM_REG_MIPS_CP0_COMPARE | 32
+ MIPS | KVM_REG_MIPS_CP0_STATUS | 32
+ MIPS | KVM_REG_MIPS_CP0_INTCTL | 32
+ MIPS | KVM_REG_MIPS_CP0_CAUSE | 32
+ MIPS | KVM_REG_MIPS_CP0_EPC | 64
+ MIPS | KVM_REG_MIPS_CP0_PRID | 32
+ MIPS | KVM_REG_MIPS_CP0_EBASE | 64
+ MIPS | KVM_REG_MIPS_CP0_CONFIG | 32
+ MIPS | KVM_REG_MIPS_CP0_CONFIG1 | 32
+ MIPS | KVM_REG_MIPS_CP0_CONFIG2 | 32
+ MIPS | KVM_REG_MIPS_CP0_CONFIG3 | 32
+ MIPS | KVM_REG_MIPS_CP0_CONFIG4 | 32
+ MIPS | KVM_REG_MIPS_CP0_CONFIG5 | 32
+ MIPS | KVM_REG_MIPS_CP0_CONFIG7 | 32
+ MIPS | KVM_REG_MIPS_CP0_XCONTEXT | 64
+ MIPS | KVM_REG_MIPS_CP0_ERROREPC | 64
+ MIPS | KVM_REG_MIPS_CP0_KSCRATCH1 | 64
+ MIPS | KVM_REG_MIPS_CP0_KSCRATCH2 | 64
+ MIPS | KVM_REG_MIPS_CP0_KSCRATCH3 | 64
+ MIPS | KVM_REG_MIPS_CP0_KSCRATCH4 | 64
+ MIPS | KVM_REG_MIPS_CP0_KSCRATCH5 | 64
+ MIPS | KVM_REG_MIPS_CP0_KSCRATCH6 | 64
+ MIPS | KVM_REG_MIPS_CP0_MAAR(0..63) | 64
+ MIPS | KVM_REG_MIPS_COUNT_CTL | 64
+ MIPS | KVM_REG_MIPS_COUNT_RESUME | 64
+ MIPS | KVM_REG_MIPS_COUNT_HZ | 64
+ MIPS | KVM_REG_MIPS_FPR_32(0..31) | 32
+ MIPS | KVM_REG_MIPS_FPR_64(0..31) | 64
+ MIPS | KVM_REG_MIPS_VEC_128(0..31) | 128
+ MIPS | KVM_REG_MIPS_FCR_IR | 32
+ MIPS | KVM_REG_MIPS_FCR_CSR | 32
+ MIPS | KVM_REG_MIPS_MSA_IR | 32
+ MIPS | KVM_REG_MIPS_MSA_CSR | 32
+
+ARM registers are mapped using the lower 32 bits. The upper 16 of that
+is the register group type, or coprocessor number:
+
+ARM core registers have the following id bit patterns:
+ 0x4020 0000 0010 <index into the kvm_regs struct:16>
+
+ARM 32-bit CP15 registers have the following id bit patterns:
+ 0x4020 0000 000F <zero:1> <crn:4> <crm:4> <opc1:4> <opc2:3>
+
+ARM 64-bit CP15 registers have the following id bit patterns:
+ 0x4030 0000 000F <zero:1> <zero:4> <crm:4> <opc1:4> <zero:3>
+
+ARM CCSIDR registers are demultiplexed by CSSELR value:
+ 0x4020 0000 0011 00 <csselr:8>
+
+ARM 32-bit VFP control registers have the following id bit patterns:
+ 0x4020 0000 0012 1 <regno:12>
+
+ARM 64-bit FP registers have the following id bit patterns:
+ 0x4030 0000 0012 0 <regno:12>
+
+ARM firmware pseudo-registers have the following bit pattern:
+ 0x4030 0000 0014 <regno:16>
+
+
+arm64 registers are mapped using the lower 32 bits. The upper 16 of
+that is the register group type, or coprocessor number:
+
+arm64 core/FP-SIMD registers have the following id bit patterns. Note
+that the size of the access is variable, as the kvm_regs structure
+contains elements ranging from 32 to 128 bits. The index is a 32bit
+value in the kvm_regs structure seen as a 32bit array.
+ 0x60x0 0000 0010 <index into the kvm_regs struct:16>
+
+Specifically:
+ Encoding Register Bits kvm_regs member
+----------------------------------------------------------------
+ 0x6030 0000 0010 0000 X0 64 regs.regs[0]
+ 0x6030 0000 0010 0002 X1 64 regs.regs[1]
+ ...
+ 0x6030 0000 0010 003c X30 64 regs.regs[30]
+ 0x6030 0000 0010 003e SP 64 regs.sp
+ 0x6030 0000 0010 0040 PC 64 regs.pc
+ 0x6030 0000 0010 0042 PSTATE 64 regs.pstate
+ 0x6030 0000 0010 0044 SP_EL1 64 sp_el1
+ 0x6030 0000 0010 0046 ELR_EL1 64 elr_el1
+ 0x6030 0000 0010 0048 SPSR_EL1 64 spsr[KVM_SPSR_EL1] (alias SPSR_SVC)
+ 0x6030 0000 0010 004a SPSR_ABT 64 spsr[KVM_SPSR_ABT]
+ 0x6030 0000 0010 004c SPSR_UND 64 spsr[KVM_SPSR_UND]
+ 0x6030 0000 0010 004e SPSR_IRQ 64 spsr[KVM_SPSR_IRQ]
+ 0x6060 0000 0010 0050 SPSR_FIQ 64 spsr[KVM_SPSR_FIQ]
+ 0x6040 0000 0010 0054 V0 128 fp_regs.vregs[0] (*)
+ 0x6040 0000 0010 0058 V1 128 fp_regs.vregs[1] (*)
+ ...
+ 0x6040 0000 0010 00d0 V31 128 fp_regs.vregs[31] (*)
+ 0x6020 0000 0010 00d4 FPSR 32 fp_regs.fpsr
+ 0x6020 0000 0010 00d5 FPCR 32 fp_regs.fpcr
+
+(*) These encodings are not accepted for SVE-enabled vcpus. See
+ KVM_ARM_VCPU_INIT.
+
+ The equivalent register content can be accessed via bits [127:0] of
+ the corresponding SVE Zn registers instead for vcpus that have SVE
+ enabled (see below).
+
+arm64 CCSIDR registers are demultiplexed by CSSELR value:
+ 0x6020 0000 0011 00 <csselr:8>
+
+arm64 system registers have the following id bit patterns:
+ 0x6030 0000 0013 <op0:2> <op1:3> <crn:4> <crm:4> <op2:3>
+
+arm64 firmware pseudo-registers have the following bit pattern:
+ 0x6030 0000 0014 <regno:16>
+
+arm64 SVE registers have the following bit patterns:
+ 0x6080 0000 0015 00 <n:5> <slice:5> Zn bits[2048*slice + 2047 : 2048*slice]
+ 0x6050 0000 0015 04 <n:4> <slice:5> Pn bits[256*slice + 255 : 256*slice]
+ 0x6050 0000 0015 060 <slice:5> FFR bits[256*slice + 255 : 256*slice]
+ 0x6060 0000 0015 ffff KVM_REG_ARM64_SVE_VLS pseudo-register
+
+Access to register IDs where 2048 * slice >= 128 * max_vq will fail with
+ENOENT. max_vq is the vcpu's maximum supported vector length in 128-bit
+quadwords: see (**) below.
+
+These registers are only accessible on vcpus for which SVE is enabled.
+See KVM_ARM_VCPU_INIT for details.
+
+In addition, except for KVM_REG_ARM64_SVE_VLS, these registers are not
+accessible until the vcpu's SVE configuration has been finalized
+using KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE). See KVM_ARM_VCPU_INIT
+and KVM_ARM_VCPU_FINALIZE for more information about this procedure.
+
+KVM_REG_ARM64_SVE_VLS is a pseudo-register that allows the set of vector
+lengths supported by the vcpu to be discovered and configured by
+userspace. When transferred to or from user memory via KVM_GET_ONE_REG
+or KVM_SET_ONE_REG, the value of this register is of type
+__u64[KVM_ARM64_SVE_VLS_WORDS], and encodes the set of vector lengths as
+follows:
+
+__u64 vector_lengths[KVM_ARM64_SVE_VLS_WORDS];
+
+if (vq >= SVE_VQ_MIN && vq <= SVE_VQ_MAX &&
+ ((vector_lengths[(vq - KVM_ARM64_SVE_VQ_MIN) / 64] >>
+ ((vq - KVM_ARM64_SVE_VQ_MIN) % 64)) & 1))
+ /* Vector length vq * 16 bytes supported */
+else
+ /* Vector length vq * 16 bytes not supported */
+
+(**) The maximum value vq for which the above condition is true is
+max_vq. This is the maximum vector length available to the guest on
+this vcpu, and determines which register slices are visible through
+this ioctl interface.
+
+(See Documentation/arm64/sve.rst for an explanation of the "vq"
+nomenclature.)
+
+KVM_REG_ARM64_SVE_VLS is only accessible after KVM_ARM_VCPU_INIT.
+KVM_ARM_VCPU_INIT initialises it to the best set of vector lengths that
+the host supports.
+
+Userspace may subsequently modify it if desired until the vcpu's SVE
+configuration is finalized using KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE).
+
+Apart from simply removing all vector lengths from the host set that
+exceed some value, support for arbitrarily chosen sets of vector lengths
+is hardware-dependent and may not be available. Attempting to configure
+an invalid set of vector lengths via KVM_SET_ONE_REG will fail with
+EINVAL.
+
+After the vcpu's SVE configuration is finalized, further attempts to
+write this register will fail with EPERM.
+
+
+MIPS registers are mapped using the lower 32 bits. The upper 16 of that is
+the register group type:
+
+MIPS core registers (see above) have the following id bit patterns:
+ 0x7030 0000 0000 <reg:16>
+
+MIPS CP0 registers (see KVM_REG_MIPS_CP0_* above) have the following id bit
+patterns depending on whether they're 32-bit or 64-bit registers:
+ 0x7020 0000 0001 00 <reg:5> <sel:3> (32-bit)
+ 0x7030 0000 0001 00 <reg:5> <sel:3> (64-bit)
+
+Note: KVM_REG_MIPS_CP0_ENTRYLO0 and KVM_REG_MIPS_CP0_ENTRYLO1 are the MIPS64
+versions of the EntryLo registers regardless of the word size of the host
+hardware, host kernel, guest, and whether XPA is present in the guest, i.e.
+with the RI and XI bits (if they exist) in bits 63 and 62 respectively, and
+the PFNX field starting at bit 30.
+
+MIPS MAARs (see KVM_REG_MIPS_CP0_MAAR(*) above) have the following id bit
+patterns:
+ 0x7030 0000 0001 01 <reg:8>
+
+MIPS KVM control registers (see above) have the following id bit patterns:
+ 0x7030 0000 0002 <reg:16>
+
+MIPS FPU registers (see KVM_REG_MIPS_FPR_{32,64}() above) have the following
+id bit patterns depending on the size of the register being accessed. They are
+always accessed according to the current guest FPU mode (Status.FR and
+Config5.FRE), i.e. as the guest would see them, and they become unpredictable
+if the guest FPU mode is changed. MIPS SIMD Architecture (MSA) vector
+registers (see KVM_REG_MIPS_VEC_128() above) have similar patterns as they
+overlap the FPU registers:
+ 0x7020 0000 0003 00 <0:3> <reg:5> (32-bit FPU registers)
+ 0x7030 0000 0003 00 <0:3> <reg:5> (64-bit FPU registers)
+ 0x7040 0000 0003 00 <0:3> <reg:5> (128-bit MSA vector registers)
+
+MIPS FPU control registers (see KVM_REG_MIPS_FCR_{IR,CSR} above) have the
+following id bit patterns:
+ 0x7020 0000 0003 01 <0:3> <reg:5>
+
+MIPS MSA control registers (see KVM_REG_MIPS_MSA_{IR,CSR} above) have the
+following id bit patterns:
+ 0x7020 0000 0003 02 <0:3> <reg:5>
+
+
+4.69 KVM_GET_ONE_REG
+
+Capability: KVM_CAP_ONE_REG
+Architectures: all
+Type: vcpu ioctl
+Parameters: struct kvm_one_reg (in and out)
+Returns: 0 on success, negative value on failure
+Errors include:
+ ENOENT: no such register
+ EINVAL: invalid register ID, or no such register
+ EPERM: (arm64) register access not allowed before vcpu finalization
+(These error codes are indicative only: do not rely on a specific error
+code being returned in a specific situation.)
+
+This ioctl allows to receive the value of a single register implemented
+in a vcpu. The register to read is indicated by the "id" field of the
+kvm_one_reg struct passed in. On success, the register value can be found
+at the memory location pointed to by "addr".
+
+The list of registers accessible using this interface is identical to the
+list in 4.68.
+
+
+4.70 KVM_KVMCLOCK_CTRL
+
+Capability: KVM_CAP_KVMCLOCK_CTRL
+Architectures: Any that implement pvclocks (currently x86 only)
+Type: vcpu ioctl
+Parameters: None
+Returns: 0 on success, -1 on error
+
+This signals to the host kernel that the specified guest is being paused by
+userspace. The host will set a flag in the pvclock structure that is checked
+from the soft lockup watchdog. The flag is part of the pvclock structure that
+is shared between guest and host, specifically the second bit of the flags
+field of the pvclock_vcpu_time_info structure. It will be set exclusively by
+the host and read/cleared exclusively by the guest. The guest operation of
+checking and clearing the flag must an atomic operation so
+load-link/store-conditional, or equivalent must be used. There are two cases
+where the guest will clear the flag: when the soft lockup watchdog timer resets
+itself or when a soft lockup is detected. This ioctl can be called any time
+after pausing the vcpu, but before it is resumed.
+
+
+4.71 KVM_SIGNAL_MSI
+
+Capability: KVM_CAP_SIGNAL_MSI
+Architectures: x86 arm arm64
+Type: vm ioctl
+Parameters: struct kvm_msi (in)
+Returns: >0 on delivery, 0 if guest blocked the MSI, and -1 on error
+
+Directly inject a MSI message. Only valid with in-kernel irqchip that handles
+MSI messages.
+
+struct kvm_msi {
+ __u32 address_lo;
+ __u32 address_hi;
+ __u32 data;
+ __u32 flags;
+ __u32 devid;
+ __u8 pad[12];
+};
+
+flags: KVM_MSI_VALID_DEVID: devid contains a valid value. The per-VM
+ KVM_CAP_MSI_DEVID capability advertises the requirement to provide
+ the device ID. If this capability is not available, userspace
+ should never set the KVM_MSI_VALID_DEVID flag as the ioctl might fail.
+
+If KVM_MSI_VALID_DEVID is set, devid contains a unique device identifier
+for the device that wrote the MSI message. For PCI, this is usually a
+BFD identifier in the lower 16 bits.
+
+On x86, address_hi is ignored unless the KVM_X2APIC_API_USE_32BIT_IDS
+feature of KVM_CAP_X2APIC_API capability is enabled. If it is enabled,
+address_hi bits 31-8 provide bits 31-8 of the destination id. Bits 7-0 of
+address_hi must be zero.
+
+
+4.71 KVM_CREATE_PIT2
+
+Capability: KVM_CAP_PIT2
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_pit_config (in)
+Returns: 0 on success, -1 on error
+
+Creates an in-kernel device model for the i8254 PIT. This call is only valid
+after enabling in-kernel irqchip support via KVM_CREATE_IRQCHIP. The following
+parameters have to be passed:
+
+struct kvm_pit_config {
+ __u32 flags;
+ __u32 pad[15];
+};
+
+Valid flags are:
+
+#define KVM_PIT_SPEAKER_DUMMY 1 /* emulate speaker port stub */
+
+PIT timer interrupts may use a per-VM kernel thread for injection. If it
+exists, this thread will have a name of the following pattern:
+
+kvm-pit/<owner-process-pid>
+
+When running a guest with elevated priorities, the scheduling parameters of
+this thread may have to be adjusted accordingly.
+
+This IOCTL replaces the obsolete KVM_CREATE_PIT.
+
+
+4.72 KVM_GET_PIT2
+
+Capability: KVM_CAP_PIT_STATE2
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_pit_state2 (out)
+Returns: 0 on success, -1 on error
+
+Retrieves the state of the in-kernel PIT model. Only valid after
+KVM_CREATE_PIT2. The state is returned in the following structure:
+
+struct kvm_pit_state2 {
+ struct kvm_pit_channel_state channels[3];
+ __u32 flags;
+ __u32 reserved[9];
+};
+
+Valid flags are:
+
+/* disable PIT in HPET legacy mode */
+#define KVM_PIT_FLAGS_HPET_LEGACY 0x00000001
+
+This IOCTL replaces the obsolete KVM_GET_PIT.
+
+
+4.73 KVM_SET_PIT2
+
+Capability: KVM_CAP_PIT_STATE2
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_pit_state2 (in)
+Returns: 0 on success, -1 on error
+
+Sets the state of the in-kernel PIT model. Only valid after KVM_CREATE_PIT2.
+See KVM_GET_PIT2 for details on struct kvm_pit_state2.
+
+This IOCTL replaces the obsolete KVM_SET_PIT.
+
+
+4.74 KVM_PPC_GET_SMMU_INFO
+
+Capability: KVM_CAP_PPC_GET_SMMU_INFO
+Architectures: powerpc
+Type: vm ioctl
+Parameters: None
+Returns: 0 on success, -1 on error
+
+This populates and returns a structure describing the features of
+the "Server" class MMU emulation supported by KVM.
+This can in turn be used by userspace to generate the appropriate
+device-tree properties for the guest operating system.
+
+The structure contains some global information, followed by an
+array of supported segment page sizes:
+
+ struct kvm_ppc_smmu_info {
+ __u64 flags;
+ __u32 slb_size;
+ __u32 pad;
+ struct kvm_ppc_one_seg_page_size sps[KVM_PPC_PAGE_SIZES_MAX_SZ];
+ };
+
+The supported flags are:
+
+ - KVM_PPC_PAGE_SIZES_REAL:
+ When that flag is set, guest page sizes must "fit" the backing
+ store page sizes. When not set, any page size in the list can
+ be used regardless of how they are backed by userspace.
+
+ - KVM_PPC_1T_SEGMENTS
+ The emulated MMU supports 1T segments in addition to the
+ standard 256M ones.
+
+ - KVM_PPC_NO_HASH
+ This flag indicates that HPT guests are not supported by KVM,
+ thus all guests must use radix MMU mode.
+
+The "slb_size" field indicates how many SLB entries are supported
+
+The "sps" array contains 8 entries indicating the supported base
+page sizes for a segment in increasing order. Each entry is defined
+as follow:
+
+ struct kvm_ppc_one_seg_page_size {
+ __u32 page_shift; /* Base page shift of segment (or 0) */
+ __u32 slb_enc; /* SLB encoding for BookS */
+ struct kvm_ppc_one_page_size enc[KVM_PPC_PAGE_SIZES_MAX_SZ];
+ };
+
+An entry with a "page_shift" of 0 is unused. Because the array is
+organized in increasing order, a lookup can stop when encoutering
+such an entry.
+
+The "slb_enc" field provides the encoding to use in the SLB for the
+page size. The bits are in positions such as the value can directly
+be OR'ed into the "vsid" argument of the slbmte instruction.
+
+The "enc" array is a list which for each of those segment base page
+size provides the list of supported actual page sizes (which can be
+only larger or equal to the base page size), along with the
+corresponding encoding in the hash PTE. Similarly, the array is
+8 entries sorted by increasing sizes and an entry with a "0" shift
+is an empty entry and a terminator:
+
+ struct kvm_ppc_one_page_size {
+ __u32 page_shift; /* Page shift (or 0) */
+ __u32 pte_enc; /* Encoding in the HPTE (>>12) */
+ };
+
+The "pte_enc" field provides a value that can OR'ed into the hash
+PTE's RPN field (ie, it needs to be shifted left by 12 to OR it
+into the hash PTE second double word).
+
+4.75 KVM_IRQFD
+
+Capability: KVM_CAP_IRQFD
+Architectures: x86 s390 arm arm64
+Type: vm ioctl
+Parameters: struct kvm_irqfd (in)
+Returns: 0 on success, -1 on error
+
+Allows setting an eventfd to directly trigger a guest interrupt.
+kvm_irqfd.fd specifies the file descriptor to use as the eventfd and
+kvm_irqfd.gsi specifies the irqchip pin toggled by this event. When
+an event is triggered on the eventfd, an interrupt is injected into
+the guest using the specified gsi pin. The irqfd is removed using
+the KVM_IRQFD_FLAG_DEASSIGN flag, specifying both kvm_irqfd.fd
+and kvm_irqfd.gsi.
+
+With KVM_CAP_IRQFD_RESAMPLE, KVM_IRQFD supports a de-assert and notify
+mechanism allowing emulation of level-triggered, irqfd-based
+interrupts. When KVM_IRQFD_FLAG_RESAMPLE is set the user must pass an
+additional eventfd in the kvm_irqfd.resamplefd field. When operating
+in resample mode, posting of an interrupt through kvm_irq.fd asserts
+the specified gsi in the irqchip. When the irqchip is resampled, such
+as from an EOI, the gsi is de-asserted and the user is notified via
+kvm_irqfd.resamplefd. It is the user's responsibility to re-queue
+the interrupt if the device making use of it still requires service.
+Note that closing the resamplefd is not sufficient to disable the
+irqfd. The KVM_IRQFD_FLAG_RESAMPLE is only necessary on assignment
+and need not be specified with KVM_IRQFD_FLAG_DEASSIGN.
+
+On arm/arm64, gsi routing being supported, the following can happen:
+- in case no routing entry is associated to this gsi, injection fails
+- in case the gsi is associated to an irqchip routing entry,
+ irqchip.pin + 32 corresponds to the injected SPI ID.
+- in case the gsi is associated to an MSI routing entry, the MSI
+ message and device ID are translated into an LPI (support restricted
+ to GICv3 ITS in-kernel emulation).
+
+4.76 KVM_PPC_ALLOCATE_HTAB
+
+Capability: KVM_CAP_PPC_ALLOC_HTAB
+Architectures: powerpc
+Type: vm ioctl
+Parameters: Pointer to u32 containing hash table order (in/out)
+Returns: 0 on success, -1 on error
+
+This requests the host kernel to allocate an MMU hash table for a
+guest using the PAPR paravirtualization interface. This only does
+anything if the kernel is configured to use the Book 3S HV style of
+virtualization. Otherwise the capability doesn't exist and the ioctl
+returns an ENOTTY error. The rest of this description assumes Book 3S
+HV.
+
+There must be no vcpus running when this ioctl is called; if there
+are, it will do nothing and return an EBUSY error.
+
+The parameter is a pointer to a 32-bit unsigned integer variable
+containing the order (log base 2) of the desired size of the hash
+table, which must be between 18 and 46. On successful return from the
+ioctl, the value will not be changed by the kernel.
+
+If no hash table has been allocated when any vcpu is asked to run
+(with the KVM_RUN ioctl), the host kernel will allocate a
+default-sized hash table (16 MB).
+
+If this ioctl is called when a hash table has already been allocated,
+with a different order from the existing hash table, the existing hash
+table will be freed and a new one allocated. If this is ioctl is
+called when a hash table has already been allocated of the same order
+as specified, the kernel will clear out the existing hash table (zero
+all HPTEs). In either case, if the guest is using the virtualized
+real-mode area (VRMA) facility, the kernel will re-create the VMRA
+HPTEs on the next KVM_RUN of any vcpu.
+
+4.77 KVM_S390_INTERRUPT
+
+Capability: basic
+Architectures: s390
+Type: vm ioctl, vcpu ioctl
+Parameters: struct kvm_s390_interrupt (in)
+Returns: 0 on success, -1 on error
+
+Allows to inject an interrupt to the guest. Interrupts can be floating
+(vm ioctl) or per cpu (vcpu ioctl), depending on the interrupt type.
+
+Interrupt parameters are passed via kvm_s390_interrupt:
+
+struct kvm_s390_interrupt {
+ __u32 type;
+ __u32 parm;
+ __u64 parm64;
+};
+
+type can be one of the following:
+
+KVM_S390_SIGP_STOP (vcpu) - sigp stop; optional flags in parm
+KVM_S390_PROGRAM_INT (vcpu) - program check; code in parm
+KVM_S390_SIGP_SET_PREFIX (vcpu) - sigp set prefix; prefix address in parm
+KVM_S390_RESTART (vcpu) - restart
+KVM_S390_INT_CLOCK_COMP (vcpu) - clock comparator interrupt
+KVM_S390_INT_CPU_TIMER (vcpu) - CPU timer interrupt
+KVM_S390_INT_VIRTIO (vm) - virtio external interrupt; external interrupt
+ parameters in parm and parm64
+KVM_S390_INT_SERVICE (vm) - sclp external interrupt; sclp parameter in parm
+KVM_S390_INT_EMERGENCY (vcpu) - sigp emergency; source cpu in parm
+KVM_S390_INT_EXTERNAL_CALL (vcpu) - sigp external call; source cpu in parm
+KVM_S390_INT_IO(ai,cssid,ssid,schid) (vm) - compound value to indicate an
+ I/O interrupt (ai - adapter interrupt; cssid,ssid,schid - subchannel);
+ I/O interruption parameters in parm (subchannel) and parm64 (intparm,
+ interruption subclass)
+KVM_S390_MCHK (vm, vcpu) - machine check interrupt; cr 14 bits in parm,
+ machine check interrupt code in parm64 (note that
+ machine checks needing further payload are not
+ supported by this ioctl)
+
+This is an asynchronous vcpu ioctl and can be invoked from any thread.
+
+4.78 KVM_PPC_GET_HTAB_FD
+
+Capability: KVM_CAP_PPC_HTAB_FD
+Architectures: powerpc
+Type: vm ioctl
+Parameters: Pointer to struct kvm_get_htab_fd (in)
+Returns: file descriptor number (>= 0) on success, -1 on error
+
+This returns a file descriptor that can be used either to read out the
+entries in the guest's hashed page table (HPT), or to write entries to
+initialize the HPT. The returned fd can only be written to if the
+KVM_GET_HTAB_WRITE bit is set in the flags field of the argument, and
+can only be read if that bit is clear. The argument struct looks like
+this:
+
+/* For KVM_PPC_GET_HTAB_FD */
+struct kvm_get_htab_fd {
+ __u64 flags;
+ __u64 start_index;
+ __u64 reserved[2];
+};
+
+/* Values for kvm_get_htab_fd.flags */
+#define KVM_GET_HTAB_BOLTED_ONLY ((__u64)0x1)
+#define KVM_GET_HTAB_WRITE ((__u64)0x2)
+
+The `start_index' field gives the index in the HPT of the entry at
+which to start reading. It is ignored when writing.
+
+Reads on the fd will initially supply information about all
+"interesting" HPT entries. Interesting entries are those with the
+bolted bit set, if the KVM_GET_HTAB_BOLTED_ONLY bit is set, otherwise
+all entries. When the end of the HPT is reached, the read() will
+return. If read() is called again on the fd, it will start again from
+the beginning of the HPT, but will only return HPT entries that have
+changed since they were last read.
+
+Data read or written is structured as a header (8 bytes) followed by a
+series of valid HPT entries (16 bytes) each. The header indicates how
+many valid HPT entries there are and how many invalid entries follow
+the valid entries. The invalid entries are not represented explicitly
+in the stream. The header format is:
+
+struct kvm_get_htab_header {
+ __u32 index;
+ __u16 n_valid;
+ __u16 n_invalid;
+};
+
+Writes to the fd create HPT entries starting at the index given in the
+header; first `n_valid' valid entries with contents from the data
+written, then `n_invalid' invalid entries, invalidating any previously
+valid entries found.
+
+4.79 KVM_CREATE_DEVICE
+
+Capability: KVM_CAP_DEVICE_CTRL
+Type: vm ioctl
+Parameters: struct kvm_create_device (in/out)
+Returns: 0 on success, -1 on error
+Errors:
+ ENODEV: The device type is unknown or unsupported
+ EEXIST: Device already created, and this type of device may not
+ be instantiated multiple times
+
+ Other error conditions may be defined by individual device types or
+ have their standard meanings.
+
+Creates an emulated device in the kernel. The file descriptor returned
+in fd can be used with KVM_SET/GET/HAS_DEVICE_ATTR.
+
+If the KVM_CREATE_DEVICE_TEST flag is set, only test whether the
+device type is supported (not necessarily whether it can be created
+in the current vm).
+
+Individual devices should not define flags. Attributes should be used
+for specifying any behavior that is not implied by the device type
+number.
+
+struct kvm_create_device {
+ __u32 type; /* in: KVM_DEV_TYPE_xxx */
+ __u32 fd; /* out: device handle */
+ __u32 flags; /* in: KVM_CREATE_DEVICE_xxx */
+};
+
+4.80 KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR
+
+Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device,
+ KVM_CAP_VCPU_ATTRIBUTES for vcpu device
+Type: device ioctl, vm ioctl, vcpu ioctl
+Parameters: struct kvm_device_attr
+Returns: 0 on success, -1 on error
+Errors:
+ ENXIO: The group or attribute is unknown/unsupported for this device
+ or hardware support is missing.
+ EPERM: The attribute cannot (currently) be accessed this way
+ (e.g. read-only attribute, or attribute that only makes
+ sense when the device is in a different state)
+
+ Other error conditions may be defined by individual device types.
+
+Gets/sets a specified piece of device configuration and/or state. The
+semantics are device-specific. See individual device documentation in
+the "devices" directory. As with ONE_REG, the size of the data
+transferred is defined by the particular attribute.
+
+struct kvm_device_attr {
+ __u32 flags; /* no flags currently defined */
+ __u32 group; /* device-defined */
+ __u64 attr; /* group-defined */
+ __u64 addr; /* userspace address of attr data */
+};
+
+4.81 KVM_HAS_DEVICE_ATTR
+
+Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device,
+ KVM_CAP_VCPU_ATTRIBUTES for vcpu device
+Type: device ioctl, vm ioctl, vcpu ioctl
+Parameters: struct kvm_device_attr
+Returns: 0 on success, -1 on error
+Errors:
+ ENXIO: The group or attribute is unknown/unsupported for this device
+ or hardware support is missing.
+
+Tests whether a device supports a particular attribute. A successful
+return indicates the attribute is implemented. It does not necessarily
+indicate that the attribute can be read or written in the device's
+current state. "addr" is ignored.
+
+4.82 KVM_ARM_VCPU_INIT
+
+Capability: basic
+Architectures: arm, arm64
+Type: vcpu ioctl
+Parameters: struct kvm_vcpu_init (in)
+Returns: 0 on success; -1 on error
+Errors:
+ EINVAL: the target is unknown, or the combination of features is invalid.
+ ENOENT: a features bit specified is unknown.
+
+This tells KVM what type of CPU to present to the guest, and what
+optional features it should have. This will cause a reset of the cpu
+registers to their initial values. If this is not called, KVM_RUN will
+return ENOEXEC for that vcpu.
+
+Note that because some registers reflect machine topology, all vcpus
+should be created before this ioctl is invoked.
+
+Userspace can call this function multiple times for a given vcpu, including
+after the vcpu has been run. This will reset the vcpu to its initial
+state. All calls to this function after the initial call must use the same
+target and same set of feature flags, otherwise EINVAL will be returned.
+
+Possible features:
+ - KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state.
+ Depends on KVM_CAP_ARM_PSCI. If not set, the CPU will be powered on
+ and execute guest code when KVM_RUN is called.
+ - KVM_ARM_VCPU_EL1_32BIT: Starts the CPU in a 32bit mode.
+ Depends on KVM_CAP_ARM_EL1_32BIT (arm64 only).
+ - KVM_ARM_VCPU_PSCI_0_2: Emulate PSCI v0.2 (or a future revision
+ backward compatible with v0.2) for the CPU.
+ Depends on KVM_CAP_ARM_PSCI_0_2.
+ - KVM_ARM_VCPU_PMU_V3: Emulate PMUv3 for the CPU.
+ Depends on KVM_CAP_ARM_PMU_V3.
+
+ - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication
+ for arm64 only.
+ Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS.
+ If KVM_CAP_ARM_PTRAUTH_ADDRESS and KVM_CAP_ARM_PTRAUTH_GENERIC are
+ both present, then both KVM_ARM_VCPU_PTRAUTH_ADDRESS and
+ KVM_ARM_VCPU_PTRAUTH_GENERIC must be requested or neither must be
+ requested.
+
+ - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication
+ for arm64 only.
+ Depends on KVM_CAP_ARM_PTRAUTH_GENERIC.
+ If KVM_CAP_ARM_PTRAUTH_ADDRESS and KVM_CAP_ARM_PTRAUTH_GENERIC are
+ both present, then both KVM_ARM_VCPU_PTRAUTH_ADDRESS and
+ KVM_ARM_VCPU_PTRAUTH_GENERIC must be requested or neither must be
+ requested.
+
+ - KVM_ARM_VCPU_SVE: Enables SVE for the CPU (arm64 only).
+ Depends on KVM_CAP_ARM_SVE.
+ Requires KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE):
+
+ * After KVM_ARM_VCPU_INIT:
+
+ - KVM_REG_ARM64_SVE_VLS may be read using KVM_GET_ONE_REG: the
+ initial value of this pseudo-register indicates the best set of
+ vector lengths possible for a vcpu on this host.
+
+ * Before KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE):
+
+ - KVM_RUN and KVM_GET_REG_LIST are not available;
+
+ - KVM_GET_ONE_REG and KVM_SET_ONE_REG cannot be used to access
+ the scalable archietctural SVE registers
+ KVM_REG_ARM64_SVE_ZREG(), KVM_REG_ARM64_SVE_PREG() or
+ KVM_REG_ARM64_SVE_FFR;
+
+ - KVM_REG_ARM64_SVE_VLS may optionally be written using
+ KVM_SET_ONE_REG, to modify the set of vector lengths available
+ for the vcpu.
+
+ * After KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE):
+
+ - the KVM_REG_ARM64_SVE_VLS pseudo-register is immutable, and can
+ no longer be written using KVM_SET_ONE_REG.
+
+4.83 KVM_ARM_PREFERRED_TARGET
+
+Capability: basic
+Architectures: arm, arm64
+Type: vm ioctl
+Parameters: struct struct kvm_vcpu_init (out)
+Returns: 0 on success; -1 on error
+Errors:
+ ENODEV: no preferred target available for the host
+
+This queries KVM for preferred CPU target type which can be emulated
+by KVM on underlying host.
+
+The ioctl returns struct kvm_vcpu_init instance containing information
+about preferred CPU target type and recommended features for it. The
+kvm_vcpu_init->features bitmap returned will have feature bits set if
+the preferred target recommends setting these features, but this is
+not mandatory.
+
+The information returned by this ioctl can be used to prepare an instance
+of struct kvm_vcpu_init for KVM_ARM_VCPU_INIT ioctl which will result in
+in VCPU matching underlying host.
+
+
+4.84 KVM_GET_REG_LIST
+
+Capability: basic
+Architectures: arm, arm64, mips
+Type: vcpu ioctl
+Parameters: struct kvm_reg_list (in/out)
+Returns: 0 on success; -1 on error
+Errors:
+ E2BIG: the reg index list is too big to fit in the array specified by
+ the user (the number required will be written into n).
+
+struct kvm_reg_list {
+ __u64 n; /* number of registers in reg[] */
+ __u64 reg[0];
+};
+
+This ioctl returns the guest registers that are supported for the
+KVM_GET_ONE_REG/KVM_SET_ONE_REG calls.
+
+
+4.85 KVM_ARM_SET_DEVICE_ADDR (deprecated)
+
+Capability: KVM_CAP_ARM_SET_DEVICE_ADDR
+Architectures: arm, arm64
+Type: vm ioctl
+Parameters: struct kvm_arm_device_address (in)
+Returns: 0 on success, -1 on error
+Errors:
+ ENODEV: The device id is unknown
+ ENXIO: Device not supported on current system
+ EEXIST: Address already set
+ E2BIG: Address outside guest physical address space
+ EBUSY: Address overlaps with other device range
+
+struct kvm_arm_device_addr {
+ __u64 id;
+ __u64 addr;
+};
+
+Specify a device address in the guest's physical address space where guests
+can access emulated or directly exposed devices, which the host kernel needs
+to know about. The id field is an architecture specific identifier for a
+specific device.
+
+ARM/arm64 divides the id field into two parts, a device id and an
+address type id specific to the individual device.
+
+ bits: | 63 ... 32 | 31 ... 16 | 15 ... 0 |
+ field: | 0x00000000 | device id | addr type id |
+
+ARM/arm64 currently only require this when using the in-kernel GIC
+support for the hardware VGIC features, using KVM_ARM_DEVICE_VGIC_V2
+as the device id. When setting the base address for the guest's
+mapping of the VGIC virtual CPU and distributor interface, the ioctl
+must be called after calling KVM_CREATE_IRQCHIP, but before calling
+KVM_RUN on any of the VCPUs. Calling this ioctl twice for any of the
+base addresses will return -EEXIST.
+
+Note, this IOCTL is deprecated and the more flexible SET/GET_DEVICE_ATTR API
+should be used instead.
+
+
+4.86 KVM_PPC_RTAS_DEFINE_TOKEN
+
+Capability: KVM_CAP_PPC_RTAS
+Architectures: ppc
+Type: vm ioctl
+Parameters: struct kvm_rtas_token_args
+Returns: 0 on success, -1 on error
+
+Defines a token value for a RTAS (Run Time Abstraction Services)
+service in order to allow it to be handled in the kernel. The
+argument struct gives the name of the service, which must be the name
+of a service that has a kernel-side implementation. If the token
+value is non-zero, it will be associated with that service, and
+subsequent RTAS calls by the guest specifying that token will be
+handled by the kernel. If the token value is 0, then any token
+associated with the service will be forgotten, and subsequent RTAS
+calls by the guest for that service will be passed to userspace to be
+handled.
+
+4.87 KVM_SET_GUEST_DEBUG
+
+Capability: KVM_CAP_SET_GUEST_DEBUG
+Architectures: x86, s390, ppc, arm64
+Type: vcpu ioctl
+Parameters: struct kvm_guest_debug (in)
+Returns: 0 on success; -1 on error
+
+struct kvm_guest_debug {
+ __u32 control;
+ __u32 pad;
+ struct kvm_guest_debug_arch arch;
+};
+
+Set up the processor specific debug registers and configure vcpu for
+handling guest debug events. There are two parts to the structure, the
+first a control bitfield indicates the type of debug events to handle
+when running. Common control bits are:
+
+ - KVM_GUESTDBG_ENABLE: guest debugging is enabled
+ - KVM_GUESTDBG_SINGLESTEP: the next run should single-step
+
+The top 16 bits of the control field are architecture specific control
+flags which can include the following:
+
+ - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64]
+ - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390, arm64]
+ - KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86]
+ - KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86]
+ - KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s390]
+
+For example KVM_GUESTDBG_USE_SW_BP indicates that software breakpoints
+are enabled in memory so we need to ensure breakpoint exceptions are
+correctly trapped and the KVM run loop exits at the breakpoint and not
+running off into the normal guest vector. For KVM_GUESTDBG_USE_HW_BP
+we need to ensure the guest vCPUs architecture specific registers are
+updated to the correct (supplied) values.
+
+The second part of the structure is architecture specific and
+typically contains a set of debug registers.
+
+For arm64 the number of debug registers is implementation defined and
+can be determined by querying the KVM_CAP_GUEST_DEBUG_HW_BPS and
+KVM_CAP_GUEST_DEBUG_HW_WPS capabilities which return a positive number
+indicating the number of supported registers.
+
+When debug events exit the main run loop with the reason
+KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run
+structure containing architecture specific debug information.
+
+4.88 KVM_GET_EMULATED_CPUID
+
+Capability: KVM_CAP_EXT_EMUL_CPUID
+Architectures: x86
+Type: system ioctl
+Parameters: struct kvm_cpuid2 (in/out)
+Returns: 0 on success, -1 on error
+
+struct kvm_cpuid2 {
+ __u32 nent;
+ __u32 flags;
+ struct kvm_cpuid_entry2 entries[0];
+};
+
+The member 'flags' is used for passing flags from userspace.
+
+#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0)
+#define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1)
+#define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2)
+
+struct kvm_cpuid_entry2 {
+ __u32 function;
+ __u32 index;
+ __u32 flags;
+ __u32 eax;
+ __u32 ebx;
+ __u32 ecx;
+ __u32 edx;
+ __u32 padding[3];
+};
+
+This ioctl returns x86 cpuid features which are emulated by
+kvm.Userspace can use the information returned by this ioctl to query
+which features are emulated by kvm instead of being present natively.
+
+Userspace invokes KVM_GET_EMULATED_CPUID by passing a kvm_cpuid2
+structure with the 'nent' field indicating the number of entries in
+the variable-size array 'entries'. If the number of entries is too low
+to describe the cpu capabilities, an error (E2BIG) is returned. If the
+number is too high, the 'nent' field is adjusted and an error (ENOMEM)
+is returned. If the number is just right, the 'nent' field is adjusted
+to the number of valid entries in the 'entries' array, which is then
+filled.
+
+The entries returned are the set CPUID bits of the respective features
+which kvm emulates, as returned by the CPUID instruction, with unknown
+or unsupported feature bits cleared.
+
+Features like x2apic, for example, may not be present in the host cpu
+but are exposed by kvm in KVM_GET_SUPPORTED_CPUID because they can be
+emulated efficiently and thus not included here.
+
+The fields in each entry are defined as follows:
+
+ function: the eax value used to obtain the entry
+ index: the ecx value used to obtain the entry (for entries that are
+ affected by ecx)
+ flags: an OR of zero or more of the following:
+ KVM_CPUID_FLAG_SIGNIFCANT_INDEX:
+ if the index field is valid
+ KVM_CPUID_FLAG_STATEFUL_FUNC:
+ if cpuid for this function returns different values for successive
+ invocations; there will be several entries with the same function,
+ all with this flag set
+ KVM_CPUID_FLAG_STATE_READ_NEXT:
+ for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is
+ the first entry to be read by a cpu
+ eax, ebx, ecx, edx: the values returned by the cpuid instruction for
+ this function/index combination
+
+4.89 KVM_S390_MEM_OP
+
+Capability: KVM_CAP_S390_MEM_OP
+Architectures: s390
+Type: vcpu ioctl
+Parameters: struct kvm_s390_mem_op (in)
+Returns: = 0 on success,
+ < 0 on generic error (e.g. -EFAULT or -ENOMEM),
+ > 0 if an exception occurred while walking the page tables
+
+Read or write data from/to the logical (virtual) memory of a VCPU.
+
+Parameters are specified via the following structure:
+
+struct kvm_s390_mem_op {
+ __u64 gaddr; /* the guest address */
+ __u64 flags; /* flags */
+ __u32 size; /* amount of bytes */
+ __u32 op; /* type of operation */
+ __u64 buf; /* buffer in userspace */
+ __u8 ar; /* the access register number */
+ __u8 reserved[31]; /* should be set to 0 */
+};
+
+The type of operation is specified in the "op" field. It is either
+KVM_S390_MEMOP_LOGICAL_READ for reading from logical memory space or
+KVM_S390_MEMOP_LOGICAL_WRITE for writing to logical memory space. The
+KVM_S390_MEMOP_F_CHECK_ONLY flag can be set in the "flags" field to check
+whether the corresponding memory access would create an access exception
+(without touching the data in the memory at the destination). In case an
+access exception occurred while walking the MMU tables of the guest, the
+ioctl returns a positive error number to indicate the type of exception.
+This exception is also raised directly at the corresponding VCPU if the
+flag KVM_S390_MEMOP_F_INJECT_EXCEPTION is set in the "flags" field.
+
+The start address of the memory region has to be specified in the "gaddr"
+field, and the length of the region in the "size" field. "buf" is the buffer
+supplied by the userspace application where the read data should be written
+to for KVM_S390_MEMOP_LOGICAL_READ, or where the data that should be written
+is stored for a KVM_S390_MEMOP_LOGICAL_WRITE. "buf" is unused and can be NULL
+when KVM_S390_MEMOP_F_CHECK_ONLY is specified. "ar" designates the access
+register number to be used.
+
+The "reserved" field is meant for future extensions. It is not used by
+KVM with the currently defined set of flags.
+
+4.90 KVM_S390_GET_SKEYS
+
+Capability: KVM_CAP_S390_SKEYS
+Architectures: s390
+Type: vm ioctl
+Parameters: struct kvm_s390_skeys
+Returns: 0 on success, KVM_S390_GET_KEYS_NONE if guest is not using storage
+ keys, negative value on error
+
+This ioctl is used to get guest storage key values on the s390
+architecture. The ioctl takes parameters via the kvm_s390_skeys struct.
+
+struct kvm_s390_skeys {
+ __u64 start_gfn;
+ __u64 count;
+ __u64 skeydata_addr;
+ __u32 flags;
+ __u32 reserved[9];
+};
+
+The start_gfn field is the number of the first guest frame whose storage keys
+you want to get.
+
+The count field is the number of consecutive frames (starting from start_gfn)
+whose storage keys to get. The count field must be at least 1 and the maximum
+allowed value is defined as KVM_S390_SKEYS_ALLOC_MAX. Values outside this range
+will cause the ioctl to return -EINVAL.
+
+The skeydata_addr field is the address to a buffer large enough to hold count
+bytes. This buffer will be filled with storage key data by the ioctl.
+
+4.91 KVM_S390_SET_SKEYS
+
+Capability: KVM_CAP_S390_SKEYS
+Architectures: s390
+Type: vm ioctl
+Parameters: struct kvm_s390_skeys
+Returns: 0 on success, negative value on error
+
+This ioctl is used to set guest storage key values on the s390
+architecture. The ioctl takes parameters via the kvm_s390_skeys struct.
+See section on KVM_S390_GET_SKEYS for struct definition.
+
+The start_gfn field is the number of the first guest frame whose storage keys
+you want to set.
+
+The count field is the number of consecutive frames (starting from start_gfn)
+whose storage keys to get. The count field must be at least 1 and the maximum
+allowed value is defined as KVM_S390_SKEYS_ALLOC_MAX. Values outside this range
+will cause the ioctl to return -EINVAL.
+
+The skeydata_addr field is the address to a buffer containing count bytes of
+storage keys. Each byte in the buffer will be set as the storage key for a
+single frame starting at start_gfn for count frames.
+
+Note: If any architecturally invalid key value is found in the given data then
+the ioctl will return -EINVAL.
+
+4.92 KVM_S390_IRQ
+
+Capability: KVM_CAP_S390_INJECT_IRQ
+Architectures: s390
+Type: vcpu ioctl
+Parameters: struct kvm_s390_irq (in)
+Returns: 0 on success, -1 on error
+Errors:
+ EINVAL: interrupt type is invalid
+ type is KVM_S390_SIGP_STOP and flag parameter is invalid value
+ type is KVM_S390_INT_EXTERNAL_CALL and code is bigger
+ than the maximum of VCPUs
+ EBUSY: type is KVM_S390_SIGP_SET_PREFIX and vcpu is not stopped
+ type is KVM_S390_SIGP_STOP and a stop irq is already pending
+ type is KVM_S390_INT_EXTERNAL_CALL and an external call interrupt
+ is already pending
+
+Allows to inject an interrupt to the guest.
+
+Using struct kvm_s390_irq as a parameter allows
+to inject additional payload which is not
+possible via KVM_S390_INTERRUPT.
+
+Interrupt parameters are passed via kvm_s390_irq:
+
+struct kvm_s390_irq {
+ __u64 type;
+ union {
+ struct kvm_s390_io_info io;
+ struct kvm_s390_ext_info ext;
+ struct kvm_s390_pgm_info pgm;
+ struct kvm_s390_emerg_info emerg;
+ struct kvm_s390_extcall_info extcall;
+ struct kvm_s390_prefix_info prefix;
+ struct kvm_s390_stop_info stop;
+ struct kvm_s390_mchk_info mchk;
+ char reserved[64];
+ } u;
+};
+
+type can be one of the following:
+
+KVM_S390_SIGP_STOP - sigp stop; parameter in .stop
+KVM_S390_PROGRAM_INT - program check; parameters in .pgm
+KVM_S390_SIGP_SET_PREFIX - sigp set prefix; parameters in .prefix
+KVM_S390_RESTART - restart; no parameters
+KVM_S390_INT_CLOCK_COMP - clock comparator interrupt; no parameters
+KVM_S390_INT_CPU_TIMER - CPU timer interrupt; no parameters
+KVM_S390_INT_EMERGENCY - sigp emergency; parameters in .emerg
+KVM_S390_INT_EXTERNAL_CALL - sigp external call; parameters in .extcall
+KVM_S390_MCHK - machine check interrupt; parameters in .mchk
+
+This is an asynchronous vcpu ioctl and can be invoked from any thread.
+
+4.94 KVM_S390_GET_IRQ_STATE
+
+Capability: KVM_CAP_S390_IRQ_STATE
+Architectures: s390
+Type: vcpu ioctl
+Parameters: struct kvm_s390_irq_state (out)
+Returns: >= number of bytes copied into buffer,
+ -EINVAL if buffer size is 0,
+ -ENOBUFS if buffer size is too small to fit all pending interrupts,
+ -EFAULT if the buffer address was invalid
+
+This ioctl allows userspace to retrieve the complete state of all currently
+pending interrupts in a single buffer. Use cases include migration
+and introspection. The parameter structure contains the address of a
+userspace buffer and its length:
+
+struct kvm_s390_irq_state {
+ __u64 buf;
+ __u32 flags; /* will stay unused for compatibility reasons */
+ __u32 len;
+ __u32 reserved[4]; /* will stay unused for compatibility reasons */
+};
+
+Userspace passes in the above struct and for each pending interrupt a
+struct kvm_s390_irq is copied to the provided buffer.
+
+The structure contains a flags and a reserved field for future extensions. As
+the kernel never checked for flags == 0 and QEMU never pre-zeroed flags and
+reserved, these fields can not be used in the future without breaking
+compatibility.
+
+If -ENOBUFS is returned the buffer provided was too small and userspace
+may retry with a bigger buffer.
+
+4.95 KVM_S390_SET_IRQ_STATE
+
+Capability: KVM_CAP_S390_IRQ_STATE
+Architectures: s390
+Type: vcpu ioctl
+Parameters: struct kvm_s390_irq_state (in)
+Returns: 0 on success,
+ -EFAULT if the buffer address was invalid,
+ -EINVAL for an invalid buffer length (see below),
+ -EBUSY if there were already interrupts pending,
+ errors occurring when actually injecting the
+ interrupt. See KVM_S390_IRQ.
+
+This ioctl allows userspace to set the complete state of all cpu-local
+interrupts currently pending for the vcpu. It is intended for restoring
+interrupt state after a migration. The input parameter is a userspace buffer
+containing a struct kvm_s390_irq_state:
+
+struct kvm_s390_irq_state {
+ __u64 buf;
+ __u32 flags; /* will stay unused for compatibility reasons */
+ __u32 len;
+ __u32 reserved[4]; /* will stay unused for compatibility reasons */
+};
+
+The restrictions for flags and reserved apply as well.
+(see KVM_S390_GET_IRQ_STATE)
+
+The userspace memory referenced by buf contains a struct kvm_s390_irq
+for each interrupt to be injected into the guest.
+If one of the interrupts could not be injected for some reason the
+ioctl aborts.
+
+len must be a multiple of sizeof(struct kvm_s390_irq). It must be > 0
+and it must not exceed (max_vcpus + 32) * sizeof(struct kvm_s390_irq),
+which is the maximum number of possibly pending cpu-local interrupts.
+
+4.96 KVM_SMI
+
+Capability: KVM_CAP_X86_SMM
+Architectures: x86
+Type: vcpu ioctl
+Parameters: none
+Returns: 0 on success, -1 on error
+
+Queues an SMI on the thread's vcpu.
+
+4.97 KVM_CAP_PPC_MULTITCE
+
+Capability: KVM_CAP_PPC_MULTITCE
+Architectures: ppc
+Type: vm
+
+This capability means the kernel is capable of handling hypercalls
+H_PUT_TCE_INDIRECT and H_STUFF_TCE without passing those into the user
+space. This significantly accelerates DMA operations for PPC KVM guests.
+User space should expect that its handlers for these hypercalls
+are not going to be called if user space previously registered LIOBN
+in KVM (via KVM_CREATE_SPAPR_TCE or similar calls).
+
+In order to enable H_PUT_TCE_INDIRECT and H_STUFF_TCE use in the guest,
+user space might have to advertise it for the guest. For example,
+IBM pSeries (sPAPR) guest starts using them if "hcall-multi-tce" is
+present in the "ibm,hypertas-functions" device-tree property.
+
+The hypercalls mentioned above may or may not be processed successfully
+in the kernel based fast path. If they can not be handled by the kernel,
+they will get passed on to user space. So user space still has to have
+an implementation for these despite the in kernel acceleration.
+
+This capability is always enabled.
+
+4.98 KVM_CREATE_SPAPR_TCE_64
+
+Capability: KVM_CAP_SPAPR_TCE_64
+Architectures: powerpc
+Type: vm ioctl
+Parameters: struct kvm_create_spapr_tce_64 (in)
+Returns: file descriptor for manipulating the created TCE table
+
+This is an extension for KVM_CAP_SPAPR_TCE which only supports 32bit
+windows, described in 4.62 KVM_CREATE_SPAPR_TCE
+
+This capability uses extended struct in ioctl interface:
+
+/* for KVM_CAP_SPAPR_TCE_64 */
+struct kvm_create_spapr_tce_64 {
+ __u64 liobn;
+ __u32 page_shift;
+ __u32 flags;
+ __u64 offset; /* in pages */
+ __u64 size; /* in pages */
+};
+
+The aim of extension is to support an additional bigger DMA window with
+a variable page size.
+KVM_CREATE_SPAPR_TCE_64 receives a 64bit window size, an IOMMU page shift and
+a bus offset of the corresponding DMA window, @size and @offset are numbers
+of IOMMU pages.
+
+@flags are not used at the moment.
+
+The rest of functionality is identical to KVM_CREATE_SPAPR_TCE.
+
+4.99 KVM_REINJECT_CONTROL
+
+Capability: KVM_CAP_REINJECT_CONTROL
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_reinject_control (in)
+Returns: 0 on success,
+ -EFAULT if struct kvm_reinject_control cannot be read,
+ -ENXIO if KVM_CREATE_PIT or KVM_CREATE_PIT2 didn't succeed earlier.
+
+i8254 (PIT) has two modes, reinject and !reinject. The default is reinject,
+where KVM queues elapsed i8254 ticks and monitors completion of interrupt from
+vector(s) that i8254 injects. Reinject mode dequeues a tick and injects its
+interrupt whenever there isn't a pending interrupt from i8254.
+!reinject mode injects an interrupt as soon as a tick arrives.
+
+struct kvm_reinject_control {
+ __u8 pit_reinject;
+ __u8 reserved[31];
+};
+
+pit_reinject = 0 (!reinject mode) is recommended, unless running an old
+operating system that uses the PIT for timing (e.g. Linux 2.4.x).
+
+4.100 KVM_PPC_CONFIGURE_V3_MMU
+
+Capability: KVM_CAP_PPC_RADIX_MMU or KVM_CAP_PPC_HASH_MMU_V3
+Architectures: ppc
+Type: vm ioctl
+Parameters: struct kvm_ppc_mmuv3_cfg (in)
+Returns: 0 on success,
+ -EFAULT if struct kvm_ppc_mmuv3_cfg cannot be read,
+ -EINVAL if the configuration is invalid
+
+This ioctl controls whether the guest will use radix or HPT (hashed
+page table) translation, and sets the pointer to the process table for
+the guest.
+
+struct kvm_ppc_mmuv3_cfg {
+ __u64 flags;
+ __u64 process_table;
+};
+
+There are two bits that can be set in flags; KVM_PPC_MMUV3_RADIX and
+KVM_PPC_MMUV3_GTSE. KVM_PPC_MMUV3_RADIX, if set, configures the guest
+to use radix tree translation, and if clear, to use HPT translation.
+KVM_PPC_MMUV3_GTSE, if set and if KVM permits it, configures the guest
+to be able to use the global TLB and SLB invalidation instructions;
+if clear, the guest may not use these instructions.
+
+The process_table field specifies the address and size of the guest
+process table, which is in the guest's space. This field is formatted
+as the second doubleword of the partition table entry, as defined in
+the Power ISA V3.00, Book III section 5.7.6.1.
+
+4.101 KVM_PPC_GET_RMMU_INFO
+
+Capability: KVM_CAP_PPC_RADIX_MMU
+Architectures: ppc
+Type: vm ioctl
+Parameters: struct kvm_ppc_rmmu_info (out)
+Returns: 0 on success,
+ -EFAULT if struct kvm_ppc_rmmu_info cannot be written,
+ -EINVAL if no useful information can be returned
+
+This ioctl returns a structure containing two things: (a) a list
+containing supported radix tree geometries, and (b) a list that maps
+page sizes to put in the "AP" (actual page size) field for the tlbie
+(TLB invalidate entry) instruction.
+
+struct kvm_ppc_rmmu_info {
+ struct kvm_ppc_radix_geom {
+ __u8 page_shift;
+ __u8 level_bits[4];
+ __u8 pad[3];
+ } geometries[8];
+ __u32 ap_encodings[8];
+};
+
+The geometries[] field gives up to 8 supported geometries for the
+radix page table, in terms of the log base 2 of the smallest page
+size, and the number of bits indexed at each level of the tree, from
+the PTE level up to the PGD level in that order. Any unused entries
+will have 0 in the page_shift field.
+
+The ap_encodings gives the supported page sizes and their AP field
+encodings, encoded with the AP value in the top 3 bits and the log
+base 2 of the page size in the bottom 6 bits.
+
+4.102 KVM_PPC_RESIZE_HPT_PREPARE
+
+Capability: KVM_CAP_SPAPR_RESIZE_HPT
+Architectures: powerpc
+Type: vm ioctl
+Parameters: struct kvm_ppc_resize_hpt (in)
+Returns: 0 on successful completion,
+ >0 if a new HPT is being prepared, the value is an estimated
+ number of milliseconds until preparation is complete
+ -EFAULT if struct kvm_reinject_control cannot be read,
+ -EINVAL if the supplied shift or flags are invalid
+ -ENOMEM if unable to allocate the new HPT
+ -ENOSPC if there was a hash collision when moving existing
+ HPT entries to the new HPT
+ -EIO on other error conditions
+
+Used to implement the PAPR extension for runtime resizing of a guest's
+Hashed Page Table (HPT). Specifically this starts, stops or monitors
+the preparation of a new potential HPT for the guest, essentially
+implementing the H_RESIZE_HPT_PREPARE hypercall.
+
+If called with shift > 0 when there is no pending HPT for the guest,
+this begins preparation of a new pending HPT of size 2^(shift) bytes.
+It then returns a positive integer with the estimated number of
+milliseconds until preparation is complete.
+
+If called when there is a pending HPT whose size does not match that
+requested in the parameters, discards the existing pending HPT and
+creates a new one as above.
+
+If called when there is a pending HPT of the size requested, will:
+ * If preparation of the pending HPT is already complete, return 0
+ * If preparation of the pending HPT has failed, return an error
+ code, then discard the pending HPT.
+ * If preparation of the pending HPT is still in progress, return an
+ estimated number of milliseconds until preparation is complete.
+
+If called with shift == 0, discards any currently pending HPT and
+returns 0 (i.e. cancels any in-progress preparation).
+
+flags is reserved for future expansion, currently setting any bits in
+flags will result in an -EINVAL.
+
+Normally this will be called repeatedly with the same parameters until
+it returns <= 0. The first call will initiate preparation, subsequent
+ones will monitor preparation until it completes or fails.
+
+struct kvm_ppc_resize_hpt {
+ __u64 flags;
+ __u32 shift;
+ __u32 pad;
+};
+
+4.103 KVM_PPC_RESIZE_HPT_COMMIT
+
+Capability: KVM_CAP_SPAPR_RESIZE_HPT
+Architectures: powerpc
+Type: vm ioctl
+Parameters: struct kvm_ppc_resize_hpt (in)
+Returns: 0 on successful completion,
+ -EFAULT if struct kvm_reinject_control cannot be read,
+ -EINVAL if the supplied shift or flags are invalid
+ -ENXIO is there is no pending HPT, or the pending HPT doesn't
+ have the requested size
+ -EBUSY if the pending HPT is not fully prepared
+ -ENOSPC if there was a hash collision when moving existing
+ HPT entries to the new HPT
+ -EIO on other error conditions
+
+Used to implement the PAPR extension for runtime resizing of a guest's
+Hashed Page Table (HPT). Specifically this requests that the guest be
+transferred to working with the new HPT, essentially implementing the
+H_RESIZE_HPT_COMMIT hypercall.
+
+This should only be called after KVM_PPC_RESIZE_HPT_PREPARE has
+returned 0 with the same parameters. In other cases
+KVM_PPC_RESIZE_HPT_COMMIT will return an error (usually -ENXIO or
+-EBUSY, though others may be possible if the preparation was started,
+but failed).
+
+This will have undefined effects on the guest if it has not already
+placed itself in a quiescent state where no vcpu will make MMU enabled
+memory accesses.
+
+On succsful completion, the pending HPT will become the guest's active
+HPT and the previous HPT will be discarded.
+
+On failure, the guest will still be operating on its previous HPT.
+
+struct kvm_ppc_resize_hpt {
+ __u64 flags;
+ __u32 shift;
+ __u32 pad;
+};
+
+4.104 KVM_X86_GET_MCE_CAP_SUPPORTED
+
+Capability: KVM_CAP_MCE
+Architectures: x86
+Type: system ioctl
+Parameters: u64 mce_cap (out)
+Returns: 0 on success, -1 on error
+
+Returns supported MCE capabilities. The u64 mce_cap parameter
+has the same format as the MSR_IA32_MCG_CAP register. Supported
+capabilities will have the corresponding bits set.
+
+4.105 KVM_X86_SETUP_MCE
+
+Capability: KVM_CAP_MCE
+Architectures: x86
+Type: vcpu ioctl
+Parameters: u64 mcg_cap (in)
+Returns: 0 on success,
+ -EFAULT if u64 mcg_cap cannot be read,
+ -EINVAL if the requested number of banks is invalid,
+ -EINVAL if requested MCE capability is not supported.
+
+Initializes MCE support for use. The u64 mcg_cap parameter
+has the same format as the MSR_IA32_MCG_CAP register and
+specifies which capabilities should be enabled. The maximum
+supported number of error-reporting banks can be retrieved when
+checking for KVM_CAP_MCE. The supported capabilities can be
+retrieved with KVM_X86_GET_MCE_CAP_SUPPORTED.
+
+4.106 KVM_X86_SET_MCE
+
+Capability: KVM_CAP_MCE
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_x86_mce (in)
+Returns: 0 on success,
+ -EFAULT if struct kvm_x86_mce cannot be read,
+ -EINVAL if the bank number is invalid,
+ -EINVAL if VAL bit is not set in status field.
+
+Inject a machine check error (MCE) into the guest. The input
+parameter is:
+
+struct kvm_x86_mce {
+ __u64 status;
+ __u64 addr;
+ __u64 misc;
+ __u64 mcg_status;
+ __u8 bank;
+ __u8 pad1[7];
+ __u64 pad2[3];
+};
+
+If the MCE being reported is an uncorrected error, KVM will
+inject it as an MCE exception into the guest. If the guest
+MCG_STATUS register reports that an MCE is in progress, KVM
+causes an KVM_EXIT_SHUTDOWN vmexit.
+
+Otherwise, if the MCE is a corrected error, KVM will just
+store it in the corresponding bank (provided this bank is
+not holding a previously reported uncorrected error).
+
+4.107 KVM_S390_GET_CMMA_BITS
+
+Capability: KVM_CAP_S390_CMMA_MIGRATION
+Architectures: s390
+Type: vm ioctl
+Parameters: struct kvm_s390_cmma_log (in, out)
+Returns: 0 on success, a negative value on error
+
+This ioctl is used to get the values of the CMMA bits on the s390
+architecture. It is meant to be used in two scenarios:
+- During live migration to save the CMMA values. Live migration needs
+ to be enabled via the KVM_REQ_START_MIGRATION VM property.
+- To non-destructively peek at the CMMA values, with the flag
+ KVM_S390_CMMA_PEEK set.
+
+The ioctl takes parameters via the kvm_s390_cmma_log struct. The desired
+values are written to a buffer whose location is indicated via the "values"
+member in the kvm_s390_cmma_log struct. The values in the input struct are
+also updated as needed.
+Each CMMA value takes up one byte.
+
+struct kvm_s390_cmma_log {
+ __u64 start_gfn;
+ __u32 count;
+ __u32 flags;
+ union {
+ __u64 remaining;
+ __u64 mask;
+ };
+ __u64 values;
+};
+
+start_gfn is the number of the first guest frame whose CMMA values are
+to be retrieved,
+
+count is the length of the buffer in bytes,
+
+values points to the buffer where the result will be written to.
+
+If count is greater than KVM_S390_SKEYS_MAX, then it is considered to be
+KVM_S390_SKEYS_MAX. KVM_S390_SKEYS_MAX is re-used for consistency with
+other ioctls.
+
+The result is written in the buffer pointed to by the field values, and
+the values of the input parameter are updated as follows.
+
+Depending on the flags, different actions are performed. The only
+supported flag so far is KVM_S390_CMMA_PEEK.
+
+The default behaviour if KVM_S390_CMMA_PEEK is not set is:
+start_gfn will indicate the first page frame whose CMMA bits were dirty.
+It is not necessarily the same as the one passed as input, as clean pages
+are skipped.
+
+count will indicate the number of bytes actually written in the buffer.
+It can (and very often will) be smaller than the input value, since the
+buffer is only filled until 16 bytes of clean values are found (which
+are then not copied in the buffer). Since a CMMA migration block needs
+the base address and the length, for a total of 16 bytes, we will send
+back some clean data if there is some dirty data afterwards, as long as
+the size of the clean data does not exceed the size of the header. This
+allows to minimize the amount of data to be saved or transferred over
+the network at the expense of more roundtrips to userspace. The next
+invocation of the ioctl will skip over all the clean values, saving
+potentially more than just the 16 bytes we found.
+
+If KVM_S390_CMMA_PEEK is set:
+the existing storage attributes are read even when not in migration
+mode, and no other action is performed;
+
+the output start_gfn will be equal to the input start_gfn,
+
+the output count will be equal to the input count, except if the end of
+memory has been reached.
+
+In both cases:
+the field "remaining" will indicate the total number of dirty CMMA values
+still remaining, or 0 if KVM_S390_CMMA_PEEK is set and migration mode is
+not enabled.
+
+mask is unused.
+
+values points to the userspace buffer where the result will be stored.
+
+This ioctl can fail with -ENOMEM if not enough memory can be allocated to
+complete the task, with -ENXIO if CMMA is not enabled, with -EINVAL if
+KVM_S390_CMMA_PEEK is not set but migration mode was not enabled, with
+-EFAULT if the userspace address is invalid or if no page table is
+present for the addresses (e.g. when using hugepages).
+
+4.108 KVM_S390_SET_CMMA_BITS
+
+Capability: KVM_CAP_S390_CMMA_MIGRATION
+Architectures: s390
+Type: vm ioctl
+Parameters: struct kvm_s390_cmma_log (in)
+Returns: 0 on success, a negative value on error
+
+This ioctl is used to set the values of the CMMA bits on the s390
+architecture. It is meant to be used during live migration to restore
+the CMMA values, but there are no restrictions on its use.
+The ioctl takes parameters via the kvm_s390_cmma_values struct.
+Each CMMA value takes up one byte.
+
+struct kvm_s390_cmma_log {
+ __u64 start_gfn;
+ __u32 count;
+ __u32 flags;
+ union {
+ __u64 remaining;
+ __u64 mask;
+ };
+ __u64 values;
+};
+
+start_gfn indicates the starting guest frame number,
+
+count indicates how many values are to be considered in the buffer,
+
+flags is not used and must be 0.
+
+mask indicates which PGSTE bits are to be considered.
+
+remaining is not used.
+
+values points to the buffer in userspace where to store the values.
+
+This ioctl can fail with -ENOMEM if not enough memory can be allocated to
+complete the task, with -ENXIO if CMMA is not enabled, with -EINVAL if
+the count field is too large (e.g. more than KVM_S390_CMMA_SIZE_MAX) or
+if the flags field was not 0, with -EFAULT if the userspace address is
+invalid, if invalid pages are written to (e.g. after the end of memory)
+or if no page table is present for the addresses (e.g. when using
+hugepages).
+
+4.109 KVM_PPC_GET_CPU_CHAR
+
+Capability: KVM_CAP_PPC_GET_CPU_CHAR
+Architectures: powerpc
+Type: vm ioctl
+Parameters: struct kvm_ppc_cpu_char (out)
+Returns: 0 on successful completion
+ -EFAULT if struct kvm_ppc_cpu_char cannot be written
+
+This ioctl gives userspace information about certain characteristics
+of the CPU relating to speculative execution of instructions and
+possible information leakage resulting from speculative execution (see
+CVE-2017-5715, CVE-2017-5753 and CVE-2017-5754). The information is
+returned in struct kvm_ppc_cpu_char, which looks like this:
+
+struct kvm_ppc_cpu_char {
+ __u64 character; /* characteristics of the CPU */
+ __u64 behaviour; /* recommended software behaviour */
+ __u64 character_mask; /* valid bits in character */
+ __u64 behaviour_mask; /* valid bits in behaviour */
+};
+
+For extensibility, the character_mask and behaviour_mask fields
+indicate which bits of character and behaviour have been filled in by
+the kernel. If the set of defined bits is extended in future then
+userspace will be able to tell whether it is running on a kernel that
+knows about the new bits.
+
+The character field describes attributes of the CPU which can help
+with preventing inadvertent information disclosure - specifically,
+whether there is an instruction to flash-invalidate the L1 data cache
+(ori 30,30,0 or mtspr SPRN_TRIG2,rN), whether the L1 data cache is set
+to a mode where entries can only be used by the thread that created
+them, whether the bcctr[l] instruction prevents speculation, and
+whether a speculation barrier instruction (ori 31,31,0) is provided.
+
+The behaviour field describes actions that software should take to
+prevent inadvertent information disclosure, and thus describes which
+vulnerabilities the hardware is subject to; specifically whether the
+L1 data cache should be flushed when returning to user mode from the
+kernel, and whether a speculation barrier should be placed between an
+array bounds check and the array access.
+
+These fields use the same bit definitions as the new
+H_GET_CPU_CHARACTERISTICS hypercall.
+
+4.110 KVM_MEMORY_ENCRYPT_OP
+
+Capability: basic
+Architectures: x86
+Type: system
+Parameters: an opaque platform specific structure (in/out)
+Returns: 0 on success; -1 on error
+
+If the platform supports creating encrypted VMs then this ioctl can be used
+for issuing platform-specific memory encryption commands to manage those
+encrypted VMs.
+
+Currently, this ioctl is used for issuing Secure Encrypted Virtualization
+(SEV) commands on AMD Processors. The SEV commands are defined in
+Documentation/virt/kvm/amd-memory-encryption.rst.
+
+4.111 KVM_MEMORY_ENCRYPT_REG_REGION
+
+Capability: basic
+Architectures: x86
+Type: system
+Parameters: struct kvm_enc_region (in)
+Returns: 0 on success; -1 on error
+
+This ioctl can be used to register a guest memory region which may
+contain encrypted data (e.g. guest RAM, SMRAM etc).
+
+It is used in the SEV-enabled guest. When encryption is enabled, a guest
+memory region may contain encrypted data. The SEV memory encryption
+engine uses a tweak such that two identical plaintext pages, each at
+different locations will have differing ciphertexts. So swapping or
+moving ciphertext of those pages will not result in plaintext being
+swapped. So relocating (or migrating) physical backing pages for the SEV
+guest will require some additional steps.
+
+Note: The current SEV key management spec does not provide commands to
+swap or migrate (move) ciphertext pages. Hence, for now we pin the guest
+memory region registered with the ioctl.
+
+4.112 KVM_MEMORY_ENCRYPT_UNREG_REGION
+
+Capability: basic
+Architectures: x86
+Type: system
+Parameters: struct kvm_enc_region (in)
+Returns: 0 on success; -1 on error
+
+This ioctl can be used to unregister the guest memory region registered
+with KVM_MEMORY_ENCRYPT_REG_REGION ioctl above.
+
+4.113 KVM_HYPERV_EVENTFD
+
+Capability: KVM_CAP_HYPERV_EVENTFD
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_hyperv_eventfd (in)
+
+This ioctl (un)registers an eventfd to receive notifications from the guest on
+the specified Hyper-V connection id through the SIGNAL_EVENT hypercall, without
+causing a user exit. SIGNAL_EVENT hypercall with non-zero event flag number
+(bits 24-31) still triggers a KVM_EXIT_HYPERV_HCALL user exit.
+
+struct kvm_hyperv_eventfd {
+ __u32 conn_id;
+ __s32 fd;
+ __u32 flags;
+ __u32 padding[3];
+};
+
+The conn_id field should fit within 24 bits:
+
+#define KVM_HYPERV_CONN_ID_MASK 0x00ffffff
+
+The acceptable values for the flags field are:
+
+#define KVM_HYPERV_EVENTFD_DEASSIGN (1 << 0)
+
+Returns: 0 on success,
+ -EINVAL if conn_id or flags is outside the allowed range
+ -ENOENT on deassign if the conn_id isn't registered
+ -EEXIST on assign if the conn_id is already registered
+
+4.114 KVM_GET_NESTED_STATE
+
+Capability: KVM_CAP_NESTED_STATE
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_nested_state (in/out)
+Returns: 0 on success, -1 on error
+Errors:
+ E2BIG: the total state size exceeds the value of 'size' specified by
+ the user; the size required will be written into size.
+
+struct kvm_nested_state {
+ __u16 flags;
+ __u16 format;
+ __u32 size;
+
+ union {
+ struct kvm_vmx_nested_state_hdr vmx;
+ struct kvm_svm_nested_state_hdr svm;
+
+ /* Pad the header to 128 bytes. */
+ __u8 pad[120];
+ } hdr;
+
+ union {
+ struct kvm_vmx_nested_state_data vmx[0];
+ struct kvm_svm_nested_state_data svm[0];
+ } data;
+};
+
+#define KVM_STATE_NESTED_GUEST_MODE 0x00000001
+#define KVM_STATE_NESTED_RUN_PENDING 0x00000002
+#define KVM_STATE_NESTED_EVMCS 0x00000004
+
+#define KVM_STATE_NESTED_FORMAT_VMX 0
+#define KVM_STATE_NESTED_FORMAT_SVM 1
+
+#define KVM_STATE_NESTED_VMX_VMCS_SIZE 0x1000
+
+#define KVM_STATE_NESTED_VMX_SMM_GUEST_MODE 0x00000001
+#define KVM_STATE_NESTED_VMX_SMM_VMXON 0x00000002
+
+struct kvm_vmx_nested_state_hdr {
+ __u64 vmxon_pa;
+ __u64 vmcs12_pa;
+
+ struct {
+ __u16 flags;
+ } smm;
+};
+
+struct kvm_vmx_nested_state_data {
+ __u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
+ __u8 shadow_vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
+};
+
+This ioctl copies the vcpu's nested virtualization state from the kernel to
+userspace.
+
+The maximum size of the state can be retrieved by passing KVM_CAP_NESTED_STATE
+to the KVM_CHECK_EXTENSION ioctl().
+
+4.115 KVM_SET_NESTED_STATE
+
+Capability: KVM_CAP_NESTED_STATE
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_nested_state (in)
+Returns: 0 on success, -1 on error
+
+This copies the vcpu's kvm_nested_state struct from userspace to the kernel.
+For the definition of struct kvm_nested_state, see KVM_GET_NESTED_STATE.
+
+4.116 KVM_(UN)REGISTER_COALESCED_MMIO
+
+Capability: KVM_CAP_COALESCED_MMIO (for coalesced mmio)
+ KVM_CAP_COALESCED_PIO (for coalesced pio)
+Architectures: all
+Type: vm ioctl
+Parameters: struct kvm_coalesced_mmio_zone
+Returns: 0 on success, < 0 on error
+
+Coalesced I/O is a performance optimization that defers hardware
+register write emulation so that userspace exits are avoided. It is
+typically used to reduce the overhead of emulating frequently accessed
+hardware registers.
+
+When a hardware register is configured for coalesced I/O, write accesses
+do not exit to userspace and their value is recorded in a ring buffer
+that is shared between kernel and userspace.
+
+Coalesced I/O is used if one or more write accesses to a hardware
+register can be deferred until a read or a write to another hardware
+register on the same device. This last access will cause a vmexit and
+userspace will process accesses from the ring buffer before emulating
+it. That will avoid exiting to userspace on repeated writes.
+
+Coalesced pio is based on coalesced mmio. There is little difference
+between coalesced mmio and pio except that coalesced pio records accesses
+to I/O ports.
+
+4.117 KVM_CLEAR_DIRTY_LOG (vm ioctl)
+
+Capability: KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
+Architectures: x86, arm, arm64, mips
+Type: vm ioctl
+Parameters: struct kvm_dirty_log (in)
+Returns: 0 on success, -1 on error
+
+/* for KVM_CLEAR_DIRTY_LOG */
+struct kvm_clear_dirty_log {
+ __u32 slot;
+ __u32 num_pages;
+ __u64 first_page;
+ union {
+ void __user *dirty_bitmap; /* one bit per page */
+ __u64 padding;
+ };
+};
+
+The ioctl clears the dirty status of pages in a memory slot, according to
+the bitmap that is passed in struct kvm_clear_dirty_log's dirty_bitmap
+field. Bit 0 of the bitmap corresponds to page "first_page" in the
+memory slot, and num_pages is the size in bits of the input bitmap.
+first_page must be a multiple of 64; num_pages must also be a multiple of
+64 unless first_page + num_pages is the size of the memory slot. For each
+bit that is set in the input bitmap, the corresponding page is marked "clean"
+in KVM's dirty bitmap, and dirty tracking is re-enabled for that page
+(for example via write-protection, or by clearing the dirty bit in
+a page table entry).
+
+If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 specifies
+the address space for which you want to return the dirty bitmap.
+They must be less than the value that KVM_CHECK_EXTENSION returns for
+the KVM_CAP_MULTI_ADDRESS_SPACE capability.
+
+This ioctl is mostly useful when KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
+is enabled; for more information, see the description of the capability.
+However, it can always be used as long as KVM_CHECK_EXTENSION confirms
+that KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is present.
+
+4.118 KVM_GET_SUPPORTED_HV_CPUID
+
+Capability: KVM_CAP_HYPERV_CPUID
+Architectures: x86
+Type: vcpu ioctl
+Parameters: struct kvm_cpuid2 (in/out)
+Returns: 0 on success, -1 on error
+
+struct kvm_cpuid2 {
+ __u32 nent;
+ __u32 padding;
+ struct kvm_cpuid_entry2 entries[0];
+};
+
+struct kvm_cpuid_entry2 {
+ __u32 function;
+ __u32 index;
+ __u32 flags;
+ __u32 eax;
+ __u32 ebx;
+ __u32 ecx;
+ __u32 edx;
+ __u32 padding[3];
+};
+
+This ioctl returns x86 cpuid features leaves related to Hyper-V emulation in
+KVM. Userspace can use the information returned by this ioctl to construct
+cpuid information presented to guests consuming Hyper-V enlightenments (e.g.
+Windows or Hyper-V guests).
+
+CPUID feature leaves returned by this ioctl are defined by Hyper-V Top Level
+Functional Specification (TLFS). These leaves can't be obtained with
+KVM_GET_SUPPORTED_CPUID ioctl because some of them intersect with KVM feature
+leaves (0x40000000, 0x40000001).
+
+Currently, the following list of CPUID leaves are returned:
+ HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS
+ HYPERV_CPUID_INTERFACE
+ HYPERV_CPUID_VERSION
+ HYPERV_CPUID_FEATURES
+ HYPERV_CPUID_ENLIGHTMENT_INFO
+ HYPERV_CPUID_IMPLEMENT_LIMITS
+ HYPERV_CPUID_NESTED_FEATURES
+
+HYPERV_CPUID_NESTED_FEATURES leaf is only exposed when Enlightened VMCS was
+enabled on the corresponding vCPU (KVM_CAP_HYPERV_ENLIGHTENED_VMCS).
+
+Userspace invokes KVM_GET_SUPPORTED_CPUID by passing a kvm_cpuid2 structure
+with the 'nent' field indicating the number of entries in the variable-size
+array 'entries'. If the number of entries is too low to describe all Hyper-V
+feature leaves, an error (E2BIG) is returned. If the number is more or equal
+to the number of Hyper-V feature leaves, the 'nent' field is adjusted to the
+number of valid entries in the 'entries' array, which is then filled.
+
+'index' and 'flags' fields in 'struct kvm_cpuid_entry2' are currently reserved,
+userspace should not expect to get any particular value there.
+
+4.119 KVM_ARM_VCPU_FINALIZE
+
+Architectures: arm, arm64
+Type: vcpu ioctl
+Parameters: int feature (in)
+Returns: 0 on success, -1 on error
+Errors:
+ EPERM: feature not enabled, needs configuration, or already finalized
+ EINVAL: feature unknown or not present
+
+Recognised values for feature:
+ arm64 KVM_ARM_VCPU_SVE (requires KVM_CAP_ARM_SVE)
+
+Finalizes the configuration of the specified vcpu feature.
+
+The vcpu must already have been initialised, enabling the affected feature, by
+means of a successful KVM_ARM_VCPU_INIT call with the appropriate flag set in
+features[].
+
+For affected vcpu features, this is a mandatory step that must be performed
+before the vcpu is fully usable.
+
+Between KVM_ARM_VCPU_INIT and KVM_ARM_VCPU_FINALIZE, the feature may be
+configured by use of ioctls such as KVM_SET_ONE_REG. The exact configuration
+that should be performaned and how to do it are feature-dependent.
+
+Other calls that depend on a particular feature being finalized, such as
+KVM_RUN, KVM_GET_REG_LIST, KVM_GET_ONE_REG and KVM_SET_ONE_REG, will fail with
+-EPERM unless the feature has already been finalized by means of a
+KVM_ARM_VCPU_FINALIZE call.
+
+See KVM_ARM_VCPU_INIT for details of vcpu features that require finalization
+using this ioctl.
+
+4.120 KVM_SET_PMU_EVENT_FILTER
+
+Capability: KVM_CAP_PMU_EVENT_FILTER
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_pmu_event_filter (in)
+Returns: 0 on success, -1 on error
+
+struct kvm_pmu_event_filter {
+ __u32 action;
+ __u32 nevents;
+ __u32 fixed_counter_bitmap;
+ __u32 flags;
+ __u32 pad[4];
+ __u64 events[0];
+};
+
+This ioctl restricts the set of PMU events that the guest can program.
+The argument holds a list of events which will be allowed or denied.
+The eventsel+umask of each event the guest attempts to program is compared
+against the events field to determine whether the guest should have access.
+The events field only controls general purpose counters; fixed purpose
+counters are controlled by the fixed_counter_bitmap.
+
+No flags are defined yet, the field must be zero.
+
+Valid values for 'action':
+#define KVM_PMU_EVENT_ALLOW 0
+#define KVM_PMU_EVENT_DENY 1
+
+
+5. The kvm_run structure
+------------------------
+
+Application code obtains a pointer to the kvm_run structure by
+mmap()ing a vcpu fd. From that point, application code can control
+execution by changing fields in kvm_run prior to calling the KVM_RUN
+ioctl, and obtain information about the reason KVM_RUN returned by
+looking up structure members.
+
+struct kvm_run {
+ /* in */
+ __u8 request_interrupt_window;
+
+Request that KVM_RUN return when it becomes possible to inject external
+interrupts into the guest. Useful in conjunction with KVM_INTERRUPT.
+
+ __u8 immediate_exit;
+
+This field is polled once when KVM_RUN starts; if non-zero, KVM_RUN
+exits immediately, returning -EINTR. In the common scenario where a
+signal is used to "kick" a VCPU out of KVM_RUN, this field can be used
+to avoid usage of KVM_SET_SIGNAL_MASK, which has worse scalability.
+Rather than blocking the signal outside KVM_RUN, userspace can set up
+a signal handler that sets run->immediate_exit to a non-zero value.
+
+This field is ignored if KVM_CAP_IMMEDIATE_EXIT is not available.
+
+ __u8 padding1[6];
+
+ /* out */
+ __u32 exit_reason;
+
+When KVM_RUN has returned successfully (return value 0), this informs
+application code why KVM_RUN has returned. Allowable values for this
+field are detailed below.
+
+ __u8 ready_for_interrupt_injection;
+
+If request_interrupt_window has been specified, this field indicates
+an interrupt can be injected now with KVM_INTERRUPT.
+
+ __u8 if_flag;
+
+The value of the current interrupt flag. Only valid if in-kernel
+local APIC is not used.
+
+ __u16 flags;
+
+More architecture-specific flags detailing state of the VCPU that may
+affect the device's behavior. The only currently defined flag is
+KVM_RUN_X86_SMM, which is valid on x86 machines and is set if the
+VCPU is in system management mode.
+
+ /* in (pre_kvm_run), out (post_kvm_run) */
+ __u64 cr8;
+
+The value of the cr8 register. Only valid if in-kernel local APIC is
+not used. Both input and output.
+
+ __u64 apic_base;
+
+The value of the APIC BASE msr. Only valid if in-kernel local
+APIC is not used. Both input and output.
+
+ union {
+ /* KVM_EXIT_UNKNOWN */
+ struct {
+ __u64 hardware_exit_reason;
+ } hw;
+
+If exit_reason is KVM_EXIT_UNKNOWN, the vcpu has exited due to unknown
+reasons. Further architecture-specific information is available in
+hardware_exit_reason.
+
+ /* KVM_EXIT_FAIL_ENTRY */
+ struct {
+ __u64 hardware_entry_failure_reason;
+ } fail_entry;
+
+If exit_reason is KVM_EXIT_FAIL_ENTRY, the vcpu could not be run due
+to unknown reasons. Further architecture-specific information is
+available in hardware_entry_failure_reason.
+
+ /* KVM_EXIT_EXCEPTION */
+ struct {
+ __u32 exception;
+ __u32 error_code;
+ } ex;
+
+Unused.
+
+ /* KVM_EXIT_IO */
+ struct {
+#define KVM_EXIT_IO_IN 0
+#define KVM_EXIT_IO_OUT 1
+ __u8 direction;
+ __u8 size; /* bytes */
+ __u16 port;
+ __u32 count;
+ __u64 data_offset; /* relative to kvm_run start */
+ } io;
+
+If exit_reason is KVM_EXIT_IO, then the vcpu has
+executed a port I/O instruction which could not be satisfied by kvm.
+data_offset describes where the data is located (KVM_EXIT_IO_OUT) or
+where kvm expects application code to place the data for the next
+KVM_RUN invocation (KVM_EXIT_IO_IN). Data format is a packed array.
+
+ /* KVM_EXIT_DEBUG */
+ struct {
+ struct kvm_debug_exit_arch arch;
+ } debug;
+
+If the exit_reason is KVM_EXIT_DEBUG, then a vcpu is processing a debug event
+for which architecture specific information is returned.
+
+ /* KVM_EXIT_MMIO */
+ struct {
+ __u64 phys_addr;
+ __u8 data[8];
+ __u32 len;
+ __u8 is_write;
+ } mmio;
+
+If exit_reason is KVM_EXIT_MMIO, then the vcpu has
+executed a memory-mapped I/O instruction which could not be satisfied
+by kvm. The 'data' member contains the written data if 'is_write' is
+true, and should be filled by application code otherwise.
+
+The 'data' member contains, in its first 'len' bytes, the value as it would
+appear if the VCPU performed a load or store of the appropriate width directly
+to the byte array.
+
+NOTE: For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR and
+ KVM_EXIT_EPR the corresponding
+operations are complete (and guest state is consistent) only after userspace
+has re-entered the kernel with KVM_RUN. The kernel side will first finish
+incomplete operations and then check for pending signals. Userspace
+can re-enter the guest with an unmasked signal pending to complete
+pending operations.
+
+ /* KVM_EXIT_HYPERCALL */
+ struct {
+ __u64 nr;
+ __u64 args[6];
+ __u64 ret;
+ __u32 longmode;
+ __u32 pad;
+ } hypercall;
+
+Unused. This was once used for 'hypercall to userspace'. To implement
+such functionality, use KVM_EXIT_IO (x86) or KVM_EXIT_MMIO (all except s390).
+Note KVM_EXIT_IO is significantly faster than KVM_EXIT_MMIO.
+
+ /* KVM_EXIT_TPR_ACCESS */
+ struct {
+ __u64 rip;
+ __u32 is_write;
+ __u32 pad;
+ } tpr_access;
+
+To be documented (KVM_TPR_ACCESS_REPORTING).
+
+ /* KVM_EXIT_S390_SIEIC */
+ struct {
+ __u8 icptcode;
+ __u64 mask; /* psw upper half */
+ __u64 addr; /* psw lower half */
+ __u16 ipa;
+ __u32 ipb;
+ } s390_sieic;
+
+s390 specific.
+
+ /* KVM_EXIT_S390_RESET */
+#define KVM_S390_RESET_POR 1
+#define KVM_S390_RESET_CLEAR 2
+#define KVM_S390_RESET_SUBSYSTEM 4
+#define KVM_S390_RESET_CPU_INIT 8
+#define KVM_S390_RESET_IPL 16
+ __u64 s390_reset_flags;
+
+s390 specific.
+
+ /* KVM_EXIT_S390_UCONTROL */
+ struct {
+ __u64 trans_exc_code;
+ __u32 pgm_code;
+ } s390_ucontrol;
+
+s390 specific. A page fault has occurred for a user controlled virtual
+machine (KVM_VM_S390_UNCONTROL) on it's host page table that cannot be
+resolved by the kernel.
+The program code and the translation exception code that were placed
+in the cpu's lowcore are presented here as defined by the z Architecture
+Principles of Operation Book in the Chapter for Dynamic Address Translation
+(DAT)
+
+ /* KVM_EXIT_DCR */
+ struct {
+ __u32 dcrn;
+ __u32 data;
+ __u8 is_write;
+ } dcr;
+
+Deprecated - was used for 440 KVM.
+
+ /* KVM_EXIT_OSI */
+ struct {
+ __u64 gprs[32];
+ } osi;
+
+MOL uses a special hypercall interface it calls 'OSI'. To enable it, we catch
+hypercalls and exit with this exit struct that contains all the guest gprs.
+
+If exit_reason is KVM_EXIT_OSI, then the vcpu has triggered such a hypercall.
+Userspace can now handle the hypercall and when it's done modify the gprs as
+necessary. Upon guest entry all guest GPRs will then be replaced by the values
+in this struct.
+
+ /* KVM_EXIT_PAPR_HCALL */
+ struct {
+ __u64 nr;
+ __u64 ret;
+ __u64 args[9];
+ } papr_hcall;
+
+This is used on 64-bit PowerPC when emulating a pSeries partition,
+e.g. with the 'pseries' machine type in qemu. It occurs when the
+guest does a hypercall using the 'sc 1' instruction. The 'nr' field
+contains the hypercall number (from the guest R3), and 'args' contains
+the arguments (from the guest R4 - R12). Userspace should put the
+return code in 'ret' and any extra returned values in args[].
+The possible hypercalls are defined in the Power Architecture Platform
+Requirements (PAPR) document available from www.power.org (free
+developer registration required to access it).
+
+ /* KVM_EXIT_S390_TSCH */
+ struct {
+ __u16 subchannel_id;
+ __u16 subchannel_nr;
+ __u32 io_int_parm;
+ __u32 io_int_word;
+ __u32 ipb;
+ __u8 dequeued;
+ } s390_tsch;
+
+s390 specific. This exit occurs when KVM_CAP_S390_CSS_SUPPORT has been enabled
+and TEST SUBCHANNEL was intercepted. If dequeued is set, a pending I/O
+interrupt for the target subchannel has been dequeued and subchannel_id,
+subchannel_nr, io_int_parm and io_int_word contain the parameters for that
+interrupt. ipb is needed for instruction parameter decoding.
+
+ /* KVM_EXIT_EPR */
+ struct {
+ __u32 epr;
+ } epr;
+
+On FSL BookE PowerPC chips, the interrupt controller has a fast patch
+interrupt acknowledge path to the core. When the core successfully
+delivers an interrupt, it automatically populates the EPR register with
+the interrupt vector number and acknowledges the interrupt inside
+the interrupt controller.
+
+In case the interrupt controller lives in user space, we need to do
+the interrupt acknowledge cycle through it to fetch the next to be
+delivered interrupt vector using this exit.
+
+It gets triggered whenever both KVM_CAP_PPC_EPR are enabled and an
+external interrupt has just been delivered into the guest. User space
+should put the acknowledged interrupt vector into the 'epr' field.
+
+ /* KVM_EXIT_SYSTEM_EVENT */
+ struct {
+#define KVM_SYSTEM_EVENT_SHUTDOWN 1
+#define KVM_SYSTEM_EVENT_RESET 2
+#define KVM_SYSTEM_EVENT_CRASH 3
+ __u32 type;
+ __u64 flags;
+ } system_event;
+
+If exit_reason is KVM_EXIT_SYSTEM_EVENT then the vcpu has triggered
+a system-level event using some architecture specific mechanism (hypercall
+or some special instruction). In case of ARM/ARM64, this is triggered using
+HVC instruction based PSCI call from the vcpu. The 'type' field describes
+the system-level event type. The 'flags' field describes architecture
+specific flags for the system-level event.
+
+Valid values for 'type' are:
+ KVM_SYSTEM_EVENT_SHUTDOWN -- the guest has requested a shutdown of the
+ VM. Userspace is not obliged to honour this, and if it does honour
+ this does not need to destroy the VM synchronously (ie it may call
+ KVM_RUN again before shutdown finally occurs).
+ KVM_SYSTEM_EVENT_RESET -- the guest has requested a reset of the VM.
+ As with SHUTDOWN, userspace can choose to ignore the request, or
+ to schedule the reset to occur in the future and may call KVM_RUN again.
+ KVM_SYSTEM_EVENT_CRASH -- the guest crash occurred and the guest
+ has requested a crash condition maintenance. Userspace can choose
+ to ignore the request, or to gather VM memory core dump and/or
+ reset/shutdown of the VM.
+
+ /* KVM_EXIT_IOAPIC_EOI */
+ struct {
+ __u8 vector;
+ } eoi;
+
+Indicates that the VCPU's in-kernel local APIC received an EOI for a
+level-triggered IOAPIC interrupt. This exit only triggers when the
+IOAPIC is implemented in userspace (i.e. KVM_CAP_SPLIT_IRQCHIP is enabled);
+the userspace IOAPIC should process the EOI and retrigger the interrupt if
+it is still asserted. Vector is the LAPIC interrupt vector for which the
+EOI was received.
+
+ struct kvm_hyperv_exit {
+#define KVM_EXIT_HYPERV_SYNIC 1
+#define KVM_EXIT_HYPERV_HCALL 2
+ __u32 type;
+ union {
+ struct {
+ __u32 msr;
+ __u64 control;
+ __u64 evt_page;
+ __u64 msg_page;
+ } synic;
+ struct {
+ __u64 input;
+ __u64 result;
+ __u64 params[2];
+ } hcall;
+ } u;
+ };
+ /* KVM_EXIT_HYPERV */
+ struct kvm_hyperv_exit hyperv;
+Indicates that the VCPU exits into userspace to process some tasks
+related to Hyper-V emulation.
+Valid values for 'type' are:
+ KVM_EXIT_HYPERV_SYNIC -- synchronously notify user-space about
+Hyper-V SynIC state change. Notification is used to remap SynIC
+event/message pages and to enable/disable SynIC messages/events processing
+in userspace.
+
+ /* Fix the size of the union. */
+ char padding[256];
+ };
+
+ /*
+ * shared registers between kvm and userspace.
+ * kvm_valid_regs specifies the register classes set by the host
+ * kvm_dirty_regs specified the register classes dirtied by userspace
+ * struct kvm_sync_regs is architecture specific, as well as the
+ * bits for kvm_valid_regs and kvm_dirty_regs
+ */
+ __u64 kvm_valid_regs;
+ __u64 kvm_dirty_regs;
+ union {
+ struct kvm_sync_regs regs;
+ char padding[SYNC_REGS_SIZE_BYTES];
+ } s;
+
+If KVM_CAP_SYNC_REGS is defined, these fields allow userspace to access
+certain guest registers without having to call SET/GET_*REGS. Thus we can
+avoid some system call overhead if userspace has to handle the exit.
+Userspace can query the validity of the structure by checking
+kvm_valid_regs for specific bits. These bits are architecture specific
+and usually define the validity of a groups of registers. (e.g. one bit
+ for general purpose registers)
+
+Please note that the kernel is allowed to use the kvm_run structure as the
+primary storage for certain register types. Therefore, the kernel may use the
+values in kvm_run even if the corresponding bit in kvm_dirty_regs is not set.
+
+};
+
+
+
+6. Capabilities that can be enabled on vCPUs
+--------------------------------------------
+
+There are certain capabilities that change the behavior of the virtual CPU or
+the virtual machine when enabled. To enable them, please see section 4.37.
+Below you can find a list of capabilities and what their effect on the vCPU or
+the virtual machine is when enabling them.
+
+The following information is provided along with the description:
+
+ Architectures: which instruction set architectures provide this ioctl.
+ x86 includes both i386 and x86_64.
+
+ Target: whether this is a per-vcpu or per-vm capability.
+
+ Parameters: what parameters are accepted by the capability.
+
+ Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
+ are not detailed, but errors with specific meanings are.
+
+
+6.1 KVM_CAP_PPC_OSI
+
+Architectures: ppc
+Target: vcpu
+Parameters: none
+Returns: 0 on success; -1 on error
+
+This capability enables interception of OSI hypercalls that otherwise would
+be treated as normal system calls to be injected into the guest. OSI hypercalls
+were invented by Mac-on-Linux to have a standardized communication mechanism
+between the guest and the host.
+
+When this capability is enabled, KVM_EXIT_OSI can occur.
+
+
+6.2 KVM_CAP_PPC_PAPR
+
+Architectures: ppc
+Target: vcpu
+Parameters: none
+Returns: 0 on success; -1 on error
+
+This capability enables interception of PAPR hypercalls. PAPR hypercalls are
+done using the hypercall instruction "sc 1".
+
+It also sets the guest privilege level to "supervisor" mode. Usually the guest
+runs in "hypervisor" privilege mode with a few missing features.
+
+In addition to the above, it changes the semantics of SDR1. In this mode, the
+HTAB address part of SDR1 contains an HVA instead of a GPA, as PAPR keeps the
+HTAB invisible to the guest.
+
+When this capability is enabled, KVM_EXIT_PAPR_HCALL can occur.
+
+
+6.3 KVM_CAP_SW_TLB
+
+Architectures: ppc
+Target: vcpu
+Parameters: args[0] is the address of a struct kvm_config_tlb
+Returns: 0 on success; -1 on error
+
+struct kvm_config_tlb {
+ __u64 params;
+ __u64 array;
+ __u32 mmu_type;
+ __u32 array_len;
+};
+
+Configures the virtual CPU's TLB array, establishing a shared memory area
+between userspace and KVM. The "params" and "array" fields are userspace
+addresses of mmu-type-specific data structures. The "array_len" field is an
+safety mechanism, and should be set to the size in bytes of the memory that
+userspace has reserved for the array. It must be at least the size dictated
+by "mmu_type" and "params".
+
+While KVM_RUN is active, the shared region is under control of KVM. Its
+contents are undefined, and any modification by userspace results in
+boundedly undefined behavior.
+
+On return from KVM_RUN, the shared region will reflect the current state of
+the guest's TLB. If userspace makes any changes, it must call KVM_DIRTY_TLB
+to tell KVM which entries have been changed, prior to calling KVM_RUN again
+on this vcpu.
+
+For mmu types KVM_MMU_FSL_BOOKE_NOHV and KVM_MMU_FSL_BOOKE_HV:
+ - The "params" field is of type "struct kvm_book3e_206_tlb_params".
+ - The "array" field points to an array of type "struct
+ kvm_book3e_206_tlb_entry".
+ - The array consists of all entries in the first TLB, followed by all
+ entries in the second TLB.
+ - Within a TLB, entries are ordered first by increasing set number. Within a
+ set, entries are ordered by way (increasing ESEL).
+ - The hash for determining set number in TLB0 is: (MAS2 >> 12) & (num_sets - 1)
+ where "num_sets" is the tlb_sizes[] value divided by the tlb_ways[] value.
+ - The tsize field of mas1 shall be set to 4K on TLB0, even though the
+ hardware ignores this value for TLB0.
+
+6.4 KVM_CAP_S390_CSS_SUPPORT
+
+Architectures: s390
+Target: vcpu
+Parameters: none
+Returns: 0 on success; -1 on error
+
+This capability enables support for handling of channel I/O instructions.
+
+TEST PENDING INTERRUPTION and the interrupt portion of TEST SUBCHANNEL are
+handled in-kernel, while the other I/O instructions are passed to userspace.
+
+When this capability is enabled, KVM_EXIT_S390_TSCH will occur on TEST
+SUBCHANNEL intercepts.
+
+Note that even though this capability is enabled per-vcpu, the complete
+virtual machine is affected.
+
+6.5 KVM_CAP_PPC_EPR
+
+Architectures: ppc
+Target: vcpu
+Parameters: args[0] defines whether the proxy facility is active
+Returns: 0 on success; -1 on error
+
+This capability enables or disables the delivery of interrupts through the
+external proxy facility.
+
+When enabled (args[0] != 0), every time the guest gets an external interrupt
+delivered, it automatically exits into user space with a KVM_EXIT_EPR exit
+to receive the topmost interrupt vector.
+
+When disabled (args[0] == 0), behavior is as if this facility is unsupported.
+
+When this capability is enabled, KVM_EXIT_EPR can occur.
+
+6.6 KVM_CAP_IRQ_MPIC
+
+Architectures: ppc
+Parameters: args[0] is the MPIC device fd
+ args[1] is the MPIC CPU number for this vcpu
+
+This capability connects the vcpu to an in-kernel MPIC device.
+
+6.7 KVM_CAP_IRQ_XICS
+
+Architectures: ppc
+Target: vcpu
+Parameters: args[0] is the XICS device fd
+ args[1] is the XICS CPU number (server ID) for this vcpu
+
+This capability connects the vcpu to an in-kernel XICS device.
+
+6.8 KVM_CAP_S390_IRQCHIP
+
+Architectures: s390
+Target: vm
+Parameters: none
+
+This capability enables the in-kernel irqchip for s390. Please refer to
+"4.24 KVM_CREATE_IRQCHIP" for details.
+
+6.9 KVM_CAP_MIPS_FPU
+
+Architectures: mips
+Target: vcpu
+Parameters: args[0] is reserved for future use (should be 0).
+
+This capability allows the use of the host Floating Point Unit by the guest. It
+allows the Config1.FP bit to be set to enable the FPU in the guest. Once this is
+done the KVM_REG_MIPS_FPR_* and KVM_REG_MIPS_FCR_* registers can be accessed
+(depending on the current guest FPU register mode), and the Status.FR,
+Config5.FRE bits are accessible via the KVM API and also from the guest,
+depending on them being supported by the FPU.
+
+6.10 KVM_CAP_MIPS_MSA
+
+Architectures: mips
+Target: vcpu
+Parameters: args[0] is reserved for future use (should be 0).
+
+This capability allows the use of the MIPS SIMD Architecture (MSA) by the guest.
+It allows the Config3.MSAP bit to be set to enable the use of MSA by the guest.
+Once this is done the KVM_REG_MIPS_VEC_* and KVM_REG_MIPS_MSA_* registers can be
+accessed, and the Config5.MSAEn bit is accessible via the KVM API and also from
+the guest.
+
+6.74 KVM_CAP_SYNC_REGS
+Architectures: s390, x86
+Target: s390: always enabled, x86: vcpu
+Parameters: none
+Returns: x86: KVM_CHECK_EXTENSION returns a bit-array indicating which register
+sets are supported (bitfields defined in arch/x86/include/uapi/asm/kvm.h).
+
+As described above in the kvm_sync_regs struct info in section 5 (kvm_run):
+KVM_CAP_SYNC_REGS "allow[s] userspace to access certain guest registers
+without having to call SET/GET_*REGS". This reduces overhead by eliminating
+repeated ioctl calls for setting and/or getting register values. This is
+particularly important when userspace is making synchronous guest state
+modifications, e.g. when emulating and/or intercepting instructions in
+userspace.
+
+For s390 specifics, please refer to the source code.
+
+For x86:
+- the register sets to be copied out to kvm_run are selectable
+ by userspace (rather that all sets being copied out for every exit).
+- vcpu_events are available in addition to regs and sregs.
+
+For x86, the 'kvm_valid_regs' field of struct kvm_run is overloaded to
+function as an input bit-array field set by userspace to indicate the
+specific register sets to be copied out on the next exit.
+
+To indicate when userspace has modified values that should be copied into
+the vCPU, the all architecture bitarray field, 'kvm_dirty_regs' must be set.
+This is done using the same bitflags as for the 'kvm_valid_regs' field.
+If the dirty bit is not set, then the register set values will not be copied
+into the vCPU even if they've been modified.
+
+Unused bitfields in the bitarrays must be set to zero.
+
+struct kvm_sync_regs {
+ struct kvm_regs regs;
+ struct kvm_sregs sregs;
+ struct kvm_vcpu_events events;
+};
+
+6.75 KVM_CAP_PPC_IRQ_XIVE
+
+Architectures: ppc
+Target: vcpu
+Parameters: args[0] is the XIVE device fd
+ args[1] is the XIVE CPU number (server ID) for this vcpu
+
+This capability connects the vcpu to an in-kernel XIVE device.
+
+7. Capabilities that can be enabled on VMs
+------------------------------------------
+
+There are certain capabilities that change the behavior of the virtual
+machine when enabled. To enable them, please see section 4.37. Below
+you can find a list of capabilities and what their effect on the VM
+is when enabling them.
+
+The following information is provided along with the description:
+
+ Architectures: which instruction set architectures provide this ioctl.
+ x86 includes both i386 and x86_64.
+
+ Parameters: what parameters are accepted by the capability.
+
+ Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
+ are not detailed, but errors with specific meanings are.
+
+
+7.1 KVM_CAP_PPC_ENABLE_HCALL
+
+Architectures: ppc
+Parameters: args[0] is the sPAPR hcall number
+ args[1] is 0 to disable, 1 to enable in-kernel handling
+
+This capability controls whether individual sPAPR hypercalls (hcalls)
+get handled by the kernel or not. Enabling or disabling in-kernel
+handling of an hcall is effective across the VM. On creation, an
+initial set of hcalls are enabled for in-kernel handling, which
+consists of those hcalls for which in-kernel handlers were implemented
+before this capability was implemented. If disabled, the kernel will
+not to attempt to handle the hcall, but will always exit to userspace
+to handle it. Note that it may not make sense to enable some and
+disable others of a group of related hcalls, but KVM does not prevent
+userspace from doing that.
+
+If the hcall number specified is not one that has an in-kernel
+implementation, the KVM_ENABLE_CAP ioctl will fail with an EINVAL
+error.
+
+7.2 KVM_CAP_S390_USER_SIGP
+
+Architectures: s390
+Parameters: none
+
+This capability controls which SIGP orders will be handled completely in user
+space. With this capability enabled, all fast orders will be handled completely
+in the kernel:
+- SENSE
+- SENSE RUNNING
+- EXTERNAL CALL
+- EMERGENCY SIGNAL
+- CONDITIONAL EMERGENCY SIGNAL
+
+All other orders will be handled completely in user space.
+
+Only privileged operation exceptions will be checked for in the kernel (or even
+in the hardware prior to interception). If this capability is not enabled, the
+old way of handling SIGP orders is used (partially in kernel and user space).
+
+7.3 KVM_CAP_S390_VECTOR_REGISTERS
+
+Architectures: s390
+Parameters: none
+Returns: 0 on success, negative value on error
+
+Allows use of the vector registers introduced with z13 processor, and
+provides for the synchronization between host and user space. Will
+return -EINVAL if the machine does not support vectors.
+
+7.4 KVM_CAP_S390_USER_STSI
+
+Architectures: s390
+Parameters: none
+
+This capability allows post-handlers for the STSI instruction. After
+initial handling in the kernel, KVM exits to user space with
+KVM_EXIT_S390_STSI to allow user space to insert further data.
+
+Before exiting to userspace, kvm handlers should fill in s390_stsi field of
+vcpu->run:
+struct {
+ __u64 addr;
+ __u8 ar;
+ __u8 reserved;
+ __u8 fc;
+ __u8 sel1;
+ __u16 sel2;
+} s390_stsi;
+
+@addr - guest address of STSI SYSIB
+@fc - function code
+@sel1 - selector 1
+@sel2 - selector 2
+@ar - access register number
+
+KVM handlers should exit to userspace with rc = -EREMOTE.
+
+7.5 KVM_CAP_SPLIT_IRQCHIP
+
+Architectures: x86
+Parameters: args[0] - number of routes reserved for userspace IOAPICs
+Returns: 0 on success, -1 on error
+
+Create a local apic for each processor in the kernel. This can be used
+instead of KVM_CREATE_IRQCHIP if the userspace VMM wishes to emulate the
+IOAPIC and PIC (and also the PIT, even though this has to be enabled
+separately).
+
+This capability also enables in kernel routing of interrupt requests;
+when KVM_CAP_SPLIT_IRQCHIP only routes of KVM_IRQ_ROUTING_MSI type are
+used in the IRQ routing table. The first args[0] MSI routes are reserved
+for the IOAPIC pins. Whenever the LAPIC receives an EOI for these routes,
+a KVM_EXIT_IOAPIC_EOI vmexit will be reported to userspace.
+
+Fails if VCPU has already been created, or if the irqchip is already in the
+kernel (i.e. KVM_CREATE_IRQCHIP has already been called).
+
+7.6 KVM_CAP_S390_RI
+
+Architectures: s390
+Parameters: none
+
+Allows use of runtime-instrumentation introduced with zEC12 processor.
+Will return -EINVAL if the machine does not support runtime-instrumentation.
+Will return -EBUSY if a VCPU has already been created.
+
+7.7 KVM_CAP_X2APIC_API
+
+Architectures: x86
+Parameters: args[0] - features that should be enabled
+Returns: 0 on success, -EINVAL when args[0] contains invalid features
+
+Valid feature flags in args[0] are
+
+#define KVM_X2APIC_API_USE_32BIT_IDS (1ULL << 0)
+#define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK (1ULL << 1)
+
+Enabling KVM_X2APIC_API_USE_32BIT_IDS changes the behavior of
+KVM_SET_GSI_ROUTING, KVM_SIGNAL_MSI, KVM_SET_LAPIC, and KVM_GET_LAPIC,
+allowing the use of 32-bit APIC IDs. See KVM_CAP_X2APIC_API in their
+respective sections.
+
+KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK must be enabled for x2APIC to work
+in logical mode or with more than 255 VCPUs. Otherwise, KVM treats 0xff
+as a broadcast even in x2APIC mode in order to support physical x2APIC
+without interrupt remapping. This is undesirable in logical mode,
+where 0xff represents CPUs 0-7 in cluster 0.
+
+7.8 KVM_CAP_S390_USER_INSTR0
+
+Architectures: s390
+Parameters: none
+
+With this capability enabled, all illegal instructions 0x0000 (2 bytes) will
+be intercepted and forwarded to user space. User space can use this
+mechanism e.g. to realize 2-byte software breakpoints. The kernel will
+not inject an operating exception for these instructions, user space has
+to take care of that.
+
+This capability can be enabled dynamically even if VCPUs were already
+created and are running.
+
+7.9 KVM_CAP_S390_GS
+
+Architectures: s390
+Parameters: none
+Returns: 0 on success; -EINVAL if the machine does not support
+ guarded storage; -EBUSY if a VCPU has already been created.
+
+Allows use of guarded storage for the KVM guest.
+
+7.10 KVM_CAP_S390_AIS
+
+Architectures: s390
+Parameters: none
+
+Allow use of adapter-interruption suppression.
+Returns: 0 on success; -EBUSY if a VCPU has already been created.
+
+7.11 KVM_CAP_PPC_SMT
+
+Architectures: ppc
+Parameters: vsmt_mode, flags
+
+Enabling this capability on a VM provides userspace with a way to set
+the desired virtual SMT mode (i.e. the number of virtual CPUs per
+virtual core). The virtual SMT mode, vsmt_mode, must be a power of 2
+between 1 and 8. On POWER8, vsmt_mode must also be no greater than
+the number of threads per subcore for the host. Currently flags must
+be 0. A successful call to enable this capability will result in
+vsmt_mode being returned when the KVM_CAP_PPC_SMT capability is
+subsequently queried for the VM. This capability is only supported by
+HV KVM, and can only be set before any VCPUs have been created.
+The KVM_CAP_PPC_SMT_POSSIBLE capability indicates which virtual SMT
+modes are available.
+
+7.12 KVM_CAP_PPC_FWNMI
+
+Architectures: ppc
+Parameters: none
+
+With this capability a machine check exception in the guest address
+space will cause KVM to exit the guest with NMI exit reason. This
+enables QEMU to build error log and branch to guest kernel registered
+machine check handling routine. Without this capability KVM will
+branch to guests' 0x200 interrupt vector.
+
+7.13 KVM_CAP_X86_DISABLE_EXITS
+
+Architectures: x86
+Parameters: args[0] defines which exits are disabled
+Returns: 0 on success, -EINVAL when args[0] contains invalid exits
+
+Valid bits in args[0] are
+
+#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
+#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
+#define KVM_X86_DISABLE_EXITS_PAUSE (1 << 2)
+#define KVM_X86_DISABLE_EXITS_CSTATE (1 << 3)
+
+Enabling this capability on a VM provides userspace with a way to no
+longer intercept some instructions for improved latency in some
+workloads, and is suggested when vCPUs are associated to dedicated
+physical CPUs. More bits can be added in the future; userspace can
+just pass the KVM_CHECK_EXTENSION result to KVM_ENABLE_CAP to disable
+all such vmexits.
+
+Do not enable KVM_FEATURE_PV_UNHALT if you disable HLT exits.
+
+7.14 KVM_CAP_S390_HPAGE_1M
+
+Architectures: s390
+Parameters: none
+Returns: 0 on success, -EINVAL if hpage module parameter was not set
+ or cmma is enabled, or the VM has the KVM_VM_S390_UCONTROL
+ flag set
+
+With this capability the KVM support for memory backing with 1m pages
+through hugetlbfs can be enabled for a VM. After the capability is
+enabled, cmma can't be enabled anymore and pfmfi and the storage key
+interpretation are disabled. If cmma has already been enabled or the
+hpage module parameter is not set to 1, -EINVAL is returned.
+
+While it is generally possible to create a huge page backed VM without
+this capability, the VM will not be able to run.
+
+7.15 KVM_CAP_MSR_PLATFORM_INFO
+
+Architectures: x86
+Parameters: args[0] whether feature should be enabled or not
+
+With this capability, a guest may read the MSR_PLATFORM_INFO MSR. Otherwise,
+a #GP would be raised when the guest tries to access. Currently, this
+capability does not enable write permissions of this MSR for the guest.
+
+7.16 KVM_CAP_PPC_NESTED_HV
+
+Architectures: ppc
+Parameters: none
+Returns: 0 on success, -EINVAL when the implementation doesn't support
+ nested-HV virtualization.
+
+HV-KVM on POWER9 and later systems allows for "nested-HV"
+virtualization, which provides a way for a guest VM to run guests that
+can run using the CPU's supervisor mode (privileged non-hypervisor
+state). Enabling this capability on a VM depends on the CPU having
+the necessary functionality and on the facility being enabled with a
+kvm-hv module parameter.
+
+7.17 KVM_CAP_EXCEPTION_PAYLOAD
+
+Architectures: x86
+Parameters: args[0] whether feature should be enabled or not
+
+With this capability enabled, CR2 will not be modified prior to the
+emulated VM-exit when L1 intercepts a #PF exception that occurs in
+L2. Similarly, for kvm-intel only, DR6 will not be modified prior to
+the emulated VM-exit when L1 intercepts a #DB exception that occurs in
+L2. As a result, when KVM_GET_VCPU_EVENTS reports a pending #PF (or
+#DB) exception for L2, exception.has_payload will be set and the
+faulting address (or the new DR6 bits*) will be reported in the
+exception_payload field. Similarly, when userspace injects a #PF (or
+#DB) into L2 using KVM_SET_VCPU_EVENTS, it is expected to set
+exception.has_payload and to put the faulting address (or the new DR6
+bits*) in the exception_payload field.
+
+This capability also enables exception.pending in struct
+kvm_vcpu_events, which allows userspace to distinguish between pending
+and injected exceptions.
+
+
+* For the new DR6 bits, note that bit 16 is set iff the #DB exception
+ will clear DR6.RTM.
+
+7.18 KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
+
+Architectures: x86, arm, arm64, mips
+Parameters: args[0] whether feature should be enabled or not
+
+With this capability enabled, KVM_GET_DIRTY_LOG will not automatically
+clear and write-protect all pages that are returned as dirty.
+Rather, userspace will have to do this operation separately using
+KVM_CLEAR_DIRTY_LOG.
+
+At the cost of a slightly more complicated operation, this provides better
+scalability and responsiveness for two reasons. First,
+KVM_CLEAR_DIRTY_LOG ioctl can operate on a 64-page granularity rather
+than requiring to sync a full memslot; this ensures that KVM does not
+take spinlocks for an extended period of time. Second, in some cases a
+large amount of time can pass between a call to KVM_GET_DIRTY_LOG and
+userspace actually using the data in the page. Pages can be modified
+during this time, which is inefficint for both the guest and userspace:
+the guest will incur a higher penalty due to write protection faults,
+while userspace can see false reports of dirty pages. Manual reprotection
+helps reducing this time, improving guest performance and reducing the
+number of dirty log false positives.
+
+KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 was previously available under the name
+KVM_CAP_MANUAL_DIRTY_LOG_PROTECT, but the implementation had bugs that make
+it hard or impossible to use it correctly. The availability of
+KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 signals that those bugs are fixed.
+Userspace should not try to use KVM_CAP_MANUAL_DIRTY_LOG_PROTECT.
+
+8. Other capabilities.
+----------------------
+
+This section lists capabilities that give information about other
+features of the KVM implementation.
+
+8.1 KVM_CAP_PPC_HWRNG
+
+Architectures: ppc
+
+This capability, if KVM_CHECK_EXTENSION indicates that it is
+available, means that that the kernel has an implementation of the
+H_RANDOM hypercall backed by a hardware random-number generator.
+If present, the kernel H_RANDOM handler can be enabled for guest use
+with the KVM_CAP_PPC_ENABLE_HCALL capability.
+
+8.2 KVM_CAP_HYPERV_SYNIC
+
+Architectures: x86
+This capability, if KVM_CHECK_EXTENSION indicates that it is
+available, means that that the kernel has an implementation of the
+Hyper-V Synthetic interrupt controller(SynIC). Hyper-V SynIC is
+used to support Windows Hyper-V based guest paravirt drivers(VMBus).
+
+In order to use SynIC, it has to be activated by setting this
+capability via KVM_ENABLE_CAP ioctl on the vcpu fd. Note that this
+will disable the use of APIC hardware virtualization even if supported
+by the CPU, as it's incompatible with SynIC auto-EOI behavior.
+
+8.3 KVM_CAP_PPC_RADIX_MMU
+
+Architectures: ppc
+
+This capability, if KVM_CHECK_EXTENSION indicates that it is
+available, means that that the kernel can support guests using the
+radix MMU defined in Power ISA V3.00 (as implemented in the POWER9
+processor).
+
+8.4 KVM_CAP_PPC_HASH_MMU_V3
+
+Architectures: ppc
+
+This capability, if KVM_CHECK_EXTENSION indicates that it is
+available, means that that the kernel can support guests using the
+hashed page table MMU defined in Power ISA V3.00 (as implemented in
+the POWER9 processor), including in-memory segment tables.
+
+8.5 KVM_CAP_MIPS_VZ
+
+Architectures: mips
+
+This capability, if KVM_CHECK_EXTENSION on the main kvm handle indicates that
+it is available, means that full hardware assisted virtualization capabilities
+of the hardware are available for use through KVM. An appropriate
+KVM_VM_MIPS_* type must be passed to KVM_CREATE_VM to create a VM which
+utilises it.
+
+If KVM_CHECK_EXTENSION on a kvm VM handle indicates that this capability is
+available, it means that the VM is using full hardware assisted virtualization
+capabilities of the hardware. This is useful to check after creating a VM with
+KVM_VM_MIPS_DEFAULT.
+
+The value returned by KVM_CHECK_EXTENSION should be compared against known
+values (see below). All other values are reserved. This is to allow for the
+possibility of other hardware assisted virtualization implementations which
+may be incompatible with the MIPS VZ ASE.
+
+ 0: The trap & emulate implementation is in use to run guest code in user
+ mode. Guest virtual memory segments are rearranged to fit the guest in the
+ user mode address space.
+
+ 1: The MIPS VZ ASE is in use, providing full hardware assisted
+ virtualization, including standard guest virtual memory segments.
+
+8.6 KVM_CAP_MIPS_TE
+
+Architectures: mips
+
+This capability, if KVM_CHECK_EXTENSION on the main kvm handle indicates that
+it is available, means that the trap & emulate implementation is available to
+run guest code in user mode, even if KVM_CAP_MIPS_VZ indicates that hardware
+assisted virtualisation is also available. KVM_VM_MIPS_TE (0) must be passed
+to KVM_CREATE_VM to create a VM which utilises it.
+
+If KVM_CHECK_EXTENSION on a kvm VM handle indicates that this capability is
+available, it means that the VM is using trap & emulate.
+
+8.7 KVM_CAP_MIPS_64BIT
+
+Architectures: mips
+
+This capability indicates the supported architecture type of the guest, i.e. the
+supported register and address width.
+
+The values returned when this capability is checked by KVM_CHECK_EXTENSION on a
+kvm VM handle correspond roughly to the CP0_Config.AT register field, and should
+be checked specifically against known values (see below). All other values are
+reserved.
+
+ 0: MIPS32 or microMIPS32.
+ Both registers and addresses are 32-bits wide.
+ It will only be possible to run 32-bit guest code.
+
+ 1: MIPS64 or microMIPS64 with access only to 32-bit compatibility segments.
+ Registers are 64-bits wide, but addresses are 32-bits wide.
+ 64-bit guest code may run but cannot access MIPS64 memory segments.
+ It will also be possible to run 32-bit guest code.
+
+ 2: MIPS64 or microMIPS64 with access to all address segments.
+ Both registers and addresses are 64-bits wide.
+ It will be possible to run 64-bit or 32-bit guest code.
+
+8.9 KVM_CAP_ARM_USER_IRQ
+
+Architectures: arm, arm64
+This capability, if KVM_CHECK_EXTENSION indicates that it is available, means
+that if userspace creates a VM without an in-kernel interrupt controller, it
+will be notified of changes to the output level of in-kernel emulated devices,
+which can generate virtual interrupts, presented to the VM.
+For such VMs, on every return to userspace, the kernel
+updates the vcpu's run->s.regs.device_irq_level field to represent the actual
+output level of the device.
+
+Whenever kvm detects a change in the device output level, kvm guarantees at
+least one return to userspace before running the VM. This exit could either
+be a KVM_EXIT_INTR or any other exit event, like KVM_EXIT_MMIO. This way,
+userspace can always sample the device output level and re-compute the state of
+the userspace interrupt controller. Userspace should always check the state
+of run->s.regs.device_irq_level on every kvm exit.
+The value in run->s.regs.device_irq_level can represent both level and edge
+triggered interrupt signals, depending on the device. Edge triggered interrupt
+signals will exit to userspace with the bit in run->s.regs.device_irq_level
+set exactly once per edge signal.
+
+The field run->s.regs.device_irq_level is available independent of
+run->kvm_valid_regs or run->kvm_dirty_regs bits.
+
+If KVM_CAP_ARM_USER_IRQ is supported, the KVM_CHECK_EXTENSION ioctl returns a
+number larger than 0 indicating the version of this capability is implemented
+and thereby which bits in in run->s.regs.device_irq_level can signal values.
+
+Currently the following bits are defined for the device_irq_level bitmap:
+
+ KVM_CAP_ARM_USER_IRQ >= 1:
+
+ KVM_ARM_DEV_EL1_VTIMER - EL1 virtual timer
+ KVM_ARM_DEV_EL1_PTIMER - EL1 physical timer
+ KVM_ARM_DEV_PMU - ARM PMU overflow interrupt signal
+
+Future versions of kvm may implement additional events. These will get
+indicated by returning a higher number from KVM_CHECK_EXTENSION and will be
+listed above.
+
+8.10 KVM_CAP_PPC_SMT_POSSIBLE
+
+Architectures: ppc
+
+Querying this capability returns a bitmap indicating the possible
+virtual SMT modes that can be set using KVM_CAP_PPC_SMT. If bit N
+(counting from the right) is set, then a virtual SMT mode of 2^N is
+available.
+
+8.11 KVM_CAP_HYPERV_SYNIC2
+
+Architectures: x86
+
+This capability enables a newer version of Hyper-V Synthetic interrupt
+controller (SynIC). The only difference with KVM_CAP_HYPERV_SYNIC is that KVM
+doesn't clear SynIC message and event flags pages when they are enabled by
+writing to the respective MSRs.
+
+8.12 KVM_CAP_HYPERV_VP_INDEX
+
+Architectures: x86
+
+This capability indicates that userspace can load HV_X64_MSR_VP_INDEX msr. Its
+value is used to denote the target vcpu for a SynIC interrupt. For
+compatibilty, KVM initializes this msr to KVM's internal vcpu index. When this
+capability is absent, userspace can still query this msr's value.
+
+8.13 KVM_CAP_S390_AIS_MIGRATION
+
+Architectures: s390
+Parameters: none
+
+This capability indicates if the flic device will be able to get/set the
+AIS states for migration via the KVM_DEV_FLIC_AISM_ALL attribute and allows
+to discover this without having to create a flic device.
+
+8.14 KVM_CAP_S390_PSW
+
+Architectures: s390
+
+This capability indicates that the PSW is exposed via the kvm_run structure.
+
+8.15 KVM_CAP_S390_GMAP
+
+Architectures: s390
+
+This capability indicates that the user space memory used as guest mapping can
+be anywhere in the user memory address space, as long as the memory slots are
+aligned and sized to a segment (1MB) boundary.
+
+8.16 KVM_CAP_S390_COW
+
+Architectures: s390
+
+This capability indicates that the user space memory used as guest mapping can
+use copy-on-write semantics as well as dirty pages tracking via read-only page
+tables.
+
+8.17 KVM_CAP_S390_BPB
+
+Architectures: s390
+
+This capability indicates that kvm will implement the interfaces to handle
+reset, migration and nested KVM for branch prediction blocking. The stfle
+facility 82 should not be provided to the guest without this capability.
+
+8.18 KVM_CAP_HYPERV_TLBFLUSH
+
+Architectures: x86
+
+This capability indicates that KVM supports paravirtualized Hyper-V TLB Flush
+hypercalls:
+HvFlushVirtualAddressSpace, HvFlushVirtualAddressSpaceEx,
+HvFlushVirtualAddressList, HvFlushVirtualAddressListEx.
+
+8.19 KVM_CAP_ARM_INJECT_SERROR_ESR
+
+Architectures: arm, arm64
+
+This capability indicates that userspace can specify (via the
+KVM_SET_VCPU_EVENTS ioctl) the syndrome value reported to the guest when it
+takes a virtual SError interrupt exception.
+If KVM advertises this capability, userspace can only specify the ISS field for
+the ESR syndrome. Other parts of the ESR, such as the EC are generated by the
+CPU when the exception is taken. If this virtual SError is taken to EL1 using
+AArch64, this value will be reported in the ISS field of ESR_ELx.
+
+See KVM_CAP_VCPU_EVENTS for more details.
+8.20 KVM_CAP_HYPERV_SEND_IPI
+
+Architectures: x86
+
+This capability indicates that KVM supports paravirtualized Hyper-V IPI send
+hypercalls:
+HvCallSendSyntheticClusterIpi, HvCallSendSyntheticClusterIpiEx.
--- /dev/null
+* Internal ABI between the kernel and HYP
+
+This file documents the interaction between the Linux kernel and the
+hypervisor layer when running Linux as a hypervisor (for example
+KVM). It doesn't cover the interaction of the kernel with the
+hypervisor when running as a guest (under Xen, KVM or any other
+hypervisor), or any hypervisor-specific interaction when the kernel is
+used as a host.
+
+On arm and arm64 (without VHE), the kernel doesn't run in hypervisor
+mode, but still needs to interact with it, allowing a built-in
+hypervisor to be either installed or torn down.
+
+In order to achieve this, the kernel must be booted at HYP (arm) or
+EL2 (arm64), allowing it to install a set of stubs before dropping to
+SVC/EL1. These stubs are accessible by using a 'hvc #0' instruction,
+and only act on individual CPUs.
+
+Unless specified otherwise, any built-in hypervisor must implement
+these functions (see arch/arm{,64}/include/asm/virt.h):
+
+* r0/x0 = HVC_SET_VECTORS
+ r1/x1 = vectors
+
+ Set HVBAR/VBAR_EL2 to 'vectors' to enable a hypervisor. 'vectors'
+ must be a physical address, and respect the alignment requirements
+ of the architecture. Only implemented by the initial stubs, not by
+ Linux hypervisors.
+
+* r0/x0 = HVC_RESET_VECTORS
+
+ Turn HYP/EL2 MMU off, and reset HVBAR/VBAR_EL2 to the initials
+ stubs' exception vector value. This effectively disables an existing
+ hypervisor.
+
+* r0/x0 = HVC_SOFT_RESTART
+ r1/x1 = restart address
+ x2 = x0's value when entering the next payload (arm64)
+ x3 = x1's value when entering the next payload (arm64)
+ x4 = x2's value when entering the next payload (arm64)
+
+ Mask all exceptions, disable the MMU, move the arguments into place
+ (arm64 only), and jump to the restart address while at HYP/EL2. This
+ hypercall is not expected to return to its caller.
+
+Any other value of r0/x0 triggers a hypervisor-specific handling,
+which is not documented here.
+
+The return value of a stub hypercall is held by r0/x0, and is 0 on
+success, and HVC_STUB_ERR on error. A stub hypercall is allowed to
+clobber any of the caller-saved registers (x0-x18 on arm64, r0-r3 and
+ip on arm). It is thus recommended to use a function call to perform
+the hypercall.
--- /dev/null
+KVM implements the PSCI (Power State Coordination Interface)
+specification in order to provide services such as CPU on/off, reset
+and power-off to the guest.
+
+The PSCI specification is regularly updated to provide new features,
+and KVM implements these updates if they make sense from a virtualization
+point of view.
+
+This means that a guest booted on two different versions of KVM can
+observe two different "firmware" revisions. This could cause issues if
+a given guest is tied to a particular PSCI revision (unlikely), or if
+a migration causes a different PSCI version to be exposed out of the
+blue to an unsuspecting guest.
+
+In order to remedy this situation, KVM exposes a set of "firmware
+pseudo-registers" that can be manipulated using the GET/SET_ONE_REG
+interface. These registers can be saved/restored by userspace, and set
+to a convenient value if required.
+
+The following register is defined:
+
+* KVM_REG_ARM_PSCI_VERSION:
+
+ - Only valid if the vcpu has the KVM_ARM_VCPU_PSCI_0_2 feature set
+ (and thus has already been initialized)
+ - Returns the current PSCI version on GET_ONE_REG (defaulting to the
+ highest PSCI version implemented by KVM and compatible with v0.2)
+ - Allows any PSCI version implemented by KVM and compatible with
+ v0.2 to be set with SET_ONE_REG
+ - Affects the whole VM (even if the register view is per-vcpu)
+
+* KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
+ Holds the state of the firmware support to mitigate CVE-2017-5715, as
+ offered by KVM to the guest via a HVC call. The workaround is described
+ under SMCCC_ARCH_WORKAROUND_1 in [1].
+ Accepted values are:
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL: KVM does not offer
+ firmware support for the workaround. The mitigation status for the
+ guest is unknown.
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL: The workaround HVC call is
+ available to the guest and required for the mitigation.
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED: The workaround HVC call
+ is available to the guest, but it is not needed on this VCPU.
+
+* KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
+ Holds the state of the firmware support to mitigate CVE-2018-3639, as
+ offered by KVM to the guest via a HVC call. The workaround is described
+ under SMCCC_ARCH_WORKAROUND_2 in [1].
+ Accepted values are:
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL: A workaround is not
+ available. KVM does not offer firmware support for the workaround.
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN: The workaround state is
+ unknown. KVM does not offer firmware support for the workaround.
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL: The workaround is available,
+ and can be disabled by a vCPU. If
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED is set, it is active for
+ this vCPU.
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED: The workaround is
+ always active on this vCPU or it is not needed.
+
+[1] https://developer.arm.com/-/media/developer/pdf/ARM_DEN_0070A_Firmware_interfaces_for_mitigating_CVE-2017-5715.pdf
--- /dev/null
+.. SPDX-License-Identifier: GPL-2.0
+
+==============
+KVM CPUID bits
+==============
+
+:Author: Glauber Costa <glommer@gmail.com>
+
+A guest running on a kvm host, can check some of its features using
+cpuid. This is not always guaranteed to work, since userspace can
+mask-out some, or even all KVM-related cpuid features before launching
+a guest.
+
+KVM cpuid functions are:
+
+function: KVM_CPUID_SIGNATURE (0x40000000)
+
+returns::
+
+ eax = 0x40000001
+ ebx = 0x4b4d564b
+ ecx = 0x564b4d56
+ edx = 0x4d
+
+Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM".
+The value in eax corresponds to the maximum cpuid function present in this leaf,
+and will be updated if more functions are added in the future.
+Note also that old hosts set eax value to 0x0. This should
+be interpreted as if the value was 0x40000001.
+This function queries the presence of KVM cpuid leafs.
+
+function: define KVM_CPUID_FEATURES (0x40000001)
+
+returns::
+
+ ebx, ecx
+ eax = an OR'ed group of (1 << flag)
+
+where ``flag`` is defined as below:
+
+================================= =========== ================================
+flag value meaning
+================================= =========== ================================
+KVM_FEATURE_CLOCKSOURCE 0 kvmclock available at msrs
+ 0x11 and 0x12
+
+KVM_FEATURE_NOP_IO_DELAY 1 not necessary to perform delays
+ on PIO operations
+
+KVM_FEATURE_MMU_OP 2 deprecated
+
+KVM_FEATURE_CLOCKSOURCE2 3 kvmclock available at msrs
+
+ 0x4b564d00 and 0x4b564d01
+KVM_FEATURE_ASYNC_PF 4 async pf can be enabled by
+ writing to msr 0x4b564d02
+
+KVM_FEATURE_STEAL_TIME 5 steal time can be enabled by
+ writing to msr 0x4b564d03
+
+KVM_FEATURE_PV_EOI 6 paravirtualized end of interrupt
+ handler can be enabled by
+ writing to msr 0x4b564d04
+
+KVM_FEATURE_PV_UNHAULT 7 guest checks this feature bit
+ before enabling paravirtualized
+ spinlock support
+
+KVM_FEATURE_PV_TLB_FLUSH 9 guest checks this feature bit
+ before enabling paravirtualized
+ tlb flush
+
+KVM_FEATURE_ASYNC_PF_VMEXIT 10 paravirtualized async PF VM EXIT
+ can be enabled by setting bit 2
+ when writing to msr 0x4b564d02
+
+KVM_FEATURE_PV_SEND_IPI 11 guest checks this feature bit
+ before enabling paravirtualized
+ sebd IPIs
+
+KVM_FEATURE_PV_POLL_CONTROL 12 host-side polling on HLT can
+ be disabled by writing
+ to msr 0x4b564d05.
+
+KVM_FEATURE_PV_SCHED_YIELD 13 guest checks this feature bit
+ before using paravirtualized
+ sched yield.
+
+KVM_FEATURE_CLOCSOURCE_STABLE_BIT 24 host will warn if no guest-side
+ per-cpu warps are expeced in
+ kvmclock
+================================= =========== ================================
+
+::
+
+ edx = an OR'ed group of (1 << flag)
+
+Where ``flag`` here is defined as below:
+
+================== ============ =================================
+flag value meaning
+================== ============ =================================
+KVM_HINTS_REALTIME 0 guest checks this feature bit to
+ determine that vCPUs are never
+ preempted for an unlimited time
+ allowing optimizations
+================== ============ =================================
--- /dev/null
+This directory contains specific device bindings for KVM_CAP_DEVICE_CTRL.
--- /dev/null
+ARM Virtual Interrupt Translation Service (ITS)
+===============================================
+
+Device types supported:
+ KVM_DEV_TYPE_ARM_VGIC_ITS ARM Interrupt Translation Service Controller
+
+The ITS allows MSI(-X) interrupts to be injected into guests. This extension is
+optional. Creating a virtual ITS controller also requires a host GICv3 (see
+arm-vgic-v3.txt), but does not depend on having physical ITS controllers.
+
+There can be multiple ITS controllers per guest, each of them has to have
+a separate, non-overlapping MMIO region.
+
+
+Groups:
+ KVM_DEV_ARM_VGIC_GRP_ADDR
+ Attributes:
+ KVM_VGIC_ITS_ADDR_TYPE (rw, 64-bit)
+ Base address in the guest physical address space of the GICv3 ITS
+ control register frame.
+ This address needs to be 64K aligned and the region covers 128K.
+ Errors:
+ -E2BIG: Address outside of addressable IPA range
+ -EINVAL: Incorrectly aligned address
+ -EEXIST: Address already configured
+ -EFAULT: Invalid user pointer for attr->addr.
+ -ENODEV: Incorrect attribute or the ITS is not supported.
+
+
+ KVM_DEV_ARM_VGIC_GRP_CTRL
+ Attributes:
+ KVM_DEV_ARM_VGIC_CTRL_INIT
+ request the initialization of the ITS, no additional parameter in
+ kvm_device_attr.addr.
+
+ KVM_DEV_ARM_ITS_CTRL_RESET
+ reset the ITS, no additional parameter in kvm_device_attr.addr.
+ See "ITS Reset State" section.
+
+ KVM_DEV_ARM_ITS_SAVE_TABLES
+ save the ITS table data into guest RAM, at the location provisioned
+ by the guest in corresponding registers/table entries.
+
+ The layout of the tables in guest memory defines an ABI. The entries
+ are laid out in little endian format as described in the last paragraph.
+
+ KVM_DEV_ARM_ITS_RESTORE_TABLES
+ restore the ITS tables from guest RAM to ITS internal structures.
+
+ The GICV3 must be restored before the ITS and all ITS registers but
+ the GITS_CTLR must be restored before restoring the ITS tables.
+
+ The GITS_IIDR read-only register must also be restored before
+ calling KVM_DEV_ARM_ITS_RESTORE_TABLES as the IIDR revision field
+ encodes the ABI revision.
+
+ The expected ordering when restoring the GICv3/ITS is described in section
+ "ITS Restore Sequence".
+
+ Errors:
+ -ENXIO: ITS not properly configured as required prior to setting
+ this attribute
+ -ENOMEM: Memory shortage when allocating ITS internal data
+ -EINVAL: Inconsistent restored data
+ -EFAULT: Invalid guest ram access
+ -EBUSY: One or more VCPUS are running
+ -EACCES: The virtual ITS is backed by a physical GICv4 ITS, and the
+ state is not available
+
+ KVM_DEV_ARM_VGIC_GRP_ITS_REGS
+ Attributes:
+ The attr field of kvm_device_attr encodes the offset of the
+ ITS register, relative to the ITS control frame base address
+ (ITS_base).
+
+ kvm_device_attr.addr points to a __u64 value whatever the width
+ of the addressed register (32/64 bits). 64 bit registers can only
+ be accessed with full length.
+
+ Writes to read-only registers are ignored by the kernel except for:
+ - GITS_CREADR. It must be restored otherwise commands in the queue
+ will be re-executed after restoring CWRITER. GITS_CREADR must be
+ restored before restoring the GITS_CTLR which is likely to enable the
+ ITS. Also it must be restored after GITS_CBASER since a write to
+ GITS_CBASER resets GITS_CREADR.
+ - GITS_IIDR. The Revision field encodes the table layout ABI revision.
+ In the future we might implement direct injection of virtual LPIs.
+ This will require an upgrade of the table layout and an evolution of
+ the ABI. GITS_IIDR must be restored before calling
+ KVM_DEV_ARM_ITS_RESTORE_TABLES.
+
+ For other registers, getting or setting a register has the same
+ effect as reading/writing the register on real hardware.
+ Errors:
+ -ENXIO: Offset does not correspond to any supported register
+ -EFAULT: Invalid user pointer for attr->addr
+ -EINVAL: Offset is not 64-bit aligned
+ -EBUSY: one or more VCPUS are running
+
+ ITS Restore Sequence:
+ -------------------------
+
+The following ordering must be followed when restoring the GIC and the ITS:
+a) restore all guest memory and create vcpus
+b) restore all redistributors
+c) provide the ITS base address
+ (KVM_DEV_ARM_VGIC_GRP_ADDR)
+d) restore the ITS in the following order:
+ 1. Restore GITS_CBASER
+ 2. Restore all other GITS_ registers, except GITS_CTLR!
+ 3. Load the ITS table data (KVM_DEV_ARM_ITS_RESTORE_TABLES)
+ 4. Restore GITS_CTLR
+
+Then vcpus can be started.
+
+ ITS Table ABI REV0:
+ -------------------
+
+ Revision 0 of the ABI only supports the features of a virtual GICv3, and does
+ not support a virtual GICv4 with support for direct injection of virtual
+ interrupts for nested hypervisors.
+
+ The device table and ITT are indexed by the DeviceID and EventID,
+ respectively. The collection table is not indexed by CollectionID, and the
+ entries in the collection are listed in no particular order.
+ All entries are 8 bytes.
+
+ Device Table Entry (DTE):
+
+ bits: | 63| 62 ... 49 | 48 ... 5 | 4 ... 0 |
+ values: | V | next | ITT_addr | Size |
+
+ where;
+ - V indicates whether the entry is valid. If not, other fields
+ are not meaningful.
+ - next: equals to 0 if this entry is the last one; otherwise it
+ corresponds to the DeviceID offset to the next DTE, capped by
+ 2^14 -1.
+ - ITT_addr matches bits [51:8] of the ITT address (256 Byte aligned).
+ - Size specifies the supported number of bits for the EventID,
+ minus one
+
+ Collection Table Entry (CTE):
+
+ bits: | 63| 62 .. 52 | 51 ... 16 | 15 ... 0 |
+ values: | V | RES0 | RDBase | ICID |
+
+ where:
+ - V indicates whether the entry is valid. If not, other fields are
+ not meaningful.
+ - RES0: reserved field with Should-Be-Zero-or-Preserved behavior.
+ - RDBase is the PE number (GICR_TYPER.Processor_Number semantic),
+ - ICID is the collection ID
+
+ Interrupt Translation Entry (ITE):
+
+ bits: | 63 ... 48 | 47 ... 16 | 15 ... 0 |
+ values: | next | pINTID | ICID |
+
+ where:
+ - next: equals to 0 if this entry is the last one; otherwise it corresponds
+ to the EventID offset to the next ITE capped by 2^16 -1.
+ - pINTID is the physical LPI ID; if zero, it means the entry is not valid
+ and other fields are not meaningful.
+ - ICID is the collection ID
+
+ ITS Reset State:
+ ----------------
+
+RESET returns the ITS to the same state that it was when first created and
+initialized. When the RESET command returns, the following things are
+guaranteed:
+
+- The ITS is not enabled and quiescent
+ GITS_CTLR.Enabled = 0 .Quiescent=1
+- There is no internally cached state
+- No collection or device table are used
+ GITS_BASER<n>.Valid = 0
+- GITS_CBASER = 0, GITS_CREADR = 0, GITS_CWRITER = 0
+- The ABI version is unchanged and remains the one set when the ITS
+ device was first created.
--- /dev/null
+ARM Virtual Generic Interrupt Controller v3 and later (VGICv3)
+==============================================================
+
+
+Device types supported:
+ KVM_DEV_TYPE_ARM_VGIC_V3 ARM Generic Interrupt Controller v3.0
+
+Only one VGIC instance may be instantiated through this API. The created VGIC
+will act as the VM interrupt controller, requiring emulated user-space devices
+to inject interrupts to the VGIC instead of directly to CPUs. It is not
+possible to create both a GICv3 and GICv2 on the same VM.
+
+Creating a guest GICv3 device requires a host GICv3 as well.
+
+
+Groups:
+ KVM_DEV_ARM_VGIC_GRP_ADDR
+ Attributes:
+ KVM_VGIC_V3_ADDR_TYPE_DIST (rw, 64-bit)
+ Base address in the guest physical address space of the GICv3 distributor
+ register mappings. Only valid for KVM_DEV_TYPE_ARM_VGIC_V3.
+ This address needs to be 64K aligned and the region covers 64 KByte.
+
+ KVM_VGIC_V3_ADDR_TYPE_REDIST (rw, 64-bit)
+ Base address in the guest physical address space of the GICv3
+ redistributor register mappings. There are two 64K pages for each
+ VCPU and all of the redistributor pages are contiguous.
+ Only valid for KVM_DEV_TYPE_ARM_VGIC_V3.
+ This address needs to be 64K aligned.
+
+ KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION (rw, 64-bit)
+ The attribute data pointed to by kvm_device_attr.addr is a __u64 value:
+ bits: | 63 .... 52 | 51 .... 16 | 15 - 12 |11 - 0
+ values: | count | base | flags | index
+ - index encodes the unique redistributor region index
+ - flags: reserved for future use, currently 0
+ - base field encodes bits [51:16] of the guest physical base address
+ of the first redistributor in the region.
+ - count encodes the number of redistributors in the region. Must be
+ greater than 0.
+ There are two 64K pages for each redistributor in the region and
+ redistributors are laid out contiguously within the region. Regions
+ are filled with redistributors in the index order. The sum of all
+ region count fields must be greater than or equal to the number of
+ VCPUs. Redistributor regions must be registered in the incremental
+ index order, starting from index 0.
+ The characteristics of a specific redistributor region can be read
+ by presetting the index field in the attr data.
+ Only valid for KVM_DEV_TYPE_ARM_VGIC_V3.
+
+ It is invalid to mix calls with KVM_VGIC_V3_ADDR_TYPE_REDIST and
+ KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION attributes.
+
+ Errors:
+ -E2BIG: Address outside of addressable IPA range
+ -EINVAL: Incorrectly aligned address, bad redistributor region
+ count/index, mixed redistributor region attribute usage
+ -EEXIST: Address already configured
+ -ENOENT: Attempt to read the characteristics of a non existing
+ redistributor region
+ -ENXIO: The group or attribute is unknown/unsupported for this device
+ or hardware support is missing.
+ -EFAULT: Invalid user pointer for attr->addr.
+
+
+ KVM_DEV_ARM_VGIC_GRP_DIST_REGS
+ KVM_DEV_ARM_VGIC_GRP_REDIST_REGS
+ Attributes:
+ The attr field of kvm_device_attr encodes two values:
+ bits: | 63 .... 32 | 31 .... 0 |
+ values: | mpidr | offset |
+
+ All distributor regs are (rw, 32-bit) and kvm_device_attr.addr points to a
+ __u32 value. 64-bit registers must be accessed by separately accessing the
+ lower and higher word.
+
+ Writes to read-only registers are ignored by the kernel.
+
+ KVM_DEV_ARM_VGIC_GRP_DIST_REGS accesses the main distributor registers.
+ KVM_DEV_ARM_VGIC_GRP_REDIST_REGS accesses the redistributor of the CPU
+ specified by the mpidr.
+
+ The offset is relative to the "[Re]Distributor base address" as defined
+ in the GICv3/4 specs. Getting or setting such a register has the same
+ effect as reading or writing the register on real hardware, except for the
+ following registers: GICD_STATUSR, GICR_STATUSR, GICD_ISPENDR,
+ GICR_ISPENDR0, GICD_ICPENDR, and GICR_ICPENDR0. These registers behave
+ differently when accessed via this interface compared to their
+ architecturally defined behavior to allow software a full view of the
+ VGIC's internal state.
+
+ The mpidr field is used to specify which
+ redistributor is accessed. The mpidr is ignored for the distributor.
+
+ The mpidr encoding is based on the affinity information in the
+ architecture defined MPIDR, and the field is encoded as follows:
+ | 63 .... 56 | 55 .... 48 | 47 .... 40 | 39 .... 32 |
+ | Aff3 | Aff2 | Aff1 | Aff0 |
+
+ Note that distributor fields are not banked, but return the same value
+ regardless of the mpidr used to access the register.
+
+ GICD_IIDR.Revision is updated when the KVM implementation is changed in a
+ way directly observable by the guest or userspace. Userspace should read
+ GICD_IIDR from KVM and write back the read value to confirm its expected
+ behavior is aligned with the KVM implementation. Userspace should set
+ GICD_IIDR before setting any other registers to ensure the expected
+ behavior.
+
+
+ The GICD_STATUSR and GICR_STATUSR registers are architecturally defined such
+ that a write of a clear bit has no effect, whereas a write with a set bit
+ clears that value. To allow userspace to freely set the values of these two
+ registers, setting the attributes with the register offsets for these two
+ registers simply sets the non-reserved bits to the value written.
+
+
+ Accesses (reads and writes) to the GICD_ISPENDR register region and
+ GICR_ISPENDR0 registers get/set the value of the latched pending state for
+ the interrupts.
+
+ This is identical to the value returned by a guest read from ISPENDR for an
+ edge triggered interrupt, but may differ for level triggered interrupts.
+ For edge triggered interrupts, once an interrupt becomes pending (whether
+ because of an edge detected on the input line or because of a guest write
+ to ISPENDR) this state is "latched", and only cleared when either the
+ interrupt is activated or when the guest writes to ICPENDR. A level
+ triggered interrupt may be pending either because the level input is held
+ high by a device, or because of a guest write to the ISPENDR register. Only
+ ISPENDR writes are latched; if the device lowers the line level then the
+ interrupt is no longer pending unless the guest also wrote to ISPENDR, and
+ conversely writes to ICPENDR or activations of the interrupt do not clear
+ the pending status if the line level is still being held high. (These
+ rules are documented in the GICv3 specification descriptions of the ICPENDR
+ and ISPENDR registers.) For a level triggered interrupt the value accessed
+ here is that of the latch which is set by ISPENDR and cleared by ICPENDR or
+ interrupt activation, whereas the value returned by a guest read from
+ ISPENDR is the logical OR of the latch value and the input line level.
+
+ Raw access to the latch state is provided to userspace so that it can save
+ and restore the entire GIC internal state (which is defined by the
+ combination of the current input line level and the latch state, and cannot
+ be deduced from purely the line level and the value of the ISPENDR
+ registers).
+
+ Accesses to GICD_ICPENDR register region and GICR_ICPENDR0 registers have
+ RAZ/WI semantics, meaning that reads always return 0 and writes are always
+ ignored.
+
+ Errors:
+ -ENXIO: Getting or setting this register is not yet supported
+ -EBUSY: One or more VCPUs are running
+
+
+ KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS
+ Attributes:
+ The attr field of kvm_device_attr encodes two values:
+ bits: | 63 .... 32 | 31 .... 16 | 15 .... 0 |
+ values: | mpidr | RES | instr |
+
+ The mpidr field encodes the CPU ID based on the affinity information in the
+ architecture defined MPIDR, and the field is encoded as follows:
+ | 63 .... 56 | 55 .... 48 | 47 .... 40 | 39 .... 32 |
+ | Aff3 | Aff2 | Aff1 | Aff0 |
+
+ The instr field encodes the system register to access based on the fields
+ defined in the A64 instruction set encoding for system register access
+ (RES means the bits are reserved for future use and should be zero):
+
+ | 15 ... 14 | 13 ... 11 | 10 ... 7 | 6 ... 3 | 2 ... 0 |
+ | Op 0 | Op1 | CRn | CRm | Op2 |
+
+ All system regs accessed through this API are (rw, 64-bit) and
+ kvm_device_attr.addr points to a __u64 value.
+
+ KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS accesses the CPU interface registers for the
+ CPU specified by the mpidr field.
+
+ CPU interface registers access is not implemented for AArch32 mode.
+ Error -ENXIO is returned when accessed in AArch32 mode.
+ Errors:
+ -ENXIO: Getting or setting this register is not yet supported
+ -EBUSY: VCPU is running
+ -EINVAL: Invalid mpidr or register value supplied
+
+
+ KVM_DEV_ARM_VGIC_GRP_NR_IRQS
+ Attributes:
+ A value describing the number of interrupts (SGI, PPI and SPI) for
+ this GIC instance, ranging from 64 to 1024, in increments of 32.
+
+ kvm_device_attr.addr points to a __u32 value.
+
+ Errors:
+ -EINVAL: Value set is out of the expected range
+ -EBUSY: Value has already be set.
+
+
+ KVM_DEV_ARM_VGIC_GRP_CTRL
+ Attributes:
+ KVM_DEV_ARM_VGIC_CTRL_INIT
+ request the initialization of the VGIC, no additional parameter in
+ kvm_device_attr.addr.
+ KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES
+ save all LPI pending bits into guest RAM pending tables.
+
+ The first kB of the pending table is not altered by this operation.
+ Errors:
+ -ENXIO: VGIC not properly configured as required prior to calling
+ this attribute
+ -ENODEV: no online VCPU
+ -ENOMEM: memory shortage when allocating vgic internal data
+ -EFAULT: Invalid guest ram access
+ -EBUSY: One or more VCPUS are running
+
+
+ KVM_DEV_ARM_VGIC_GRP_LEVEL_INFO
+ Attributes:
+ The attr field of kvm_device_attr encodes the following values:
+ bits: | 63 .... 32 | 31 .... 10 | 9 .... 0 |
+ values: | mpidr | info | vINTID |
+
+ The vINTID specifies which set of IRQs is reported on.
+
+ The info field specifies which information userspace wants to get or set
+ using this interface. Currently we support the following info values:
+
+ VGIC_LEVEL_INFO_LINE_LEVEL:
+ Get/Set the input level of the IRQ line for a set of 32 contiguously
+ numbered interrupts.
+ vINTID must be a multiple of 32.
+
+ kvm_device_attr.addr points to a __u32 value which will contain a
+ bitmap where a set bit means the interrupt level is asserted.
+
+ Bit[n] indicates the status for interrupt vINTID + n.
+
+ SGIs and any interrupt with a higher ID than the number of interrupts
+ supported, will be RAZ/WI. LPIs are always edge-triggered and are
+ therefore not supported by this interface.
+
+ PPIs are reported per VCPU as specified in the mpidr field, and SPIs are
+ reported with the same value regardless of the mpidr specified.
+
+ The mpidr field encodes the CPU ID based on the affinity information in the
+ architecture defined MPIDR, and the field is encoded as follows:
+ | 63 .... 56 | 55 .... 48 | 47 .... 40 | 39 .... 32 |
+ | Aff3 | Aff2 | Aff1 | Aff0 |
+ Errors:
+ -EINVAL: vINTID is not multiple of 32 or
+ info field is not VGIC_LEVEL_INFO_LINE_LEVEL
--- /dev/null
+ARM Virtual Generic Interrupt Controller v2 (VGIC)
+==================================================
+
+Device types supported:
+ KVM_DEV_TYPE_ARM_VGIC_V2 ARM Generic Interrupt Controller v2.0
+
+Only one VGIC instance may be instantiated through either this API or the
+legacy KVM_CREATE_IRQCHIP API. The created VGIC will act as the VM interrupt
+controller, requiring emulated user-space devices to inject interrupts to the
+VGIC instead of directly to CPUs.
+
+GICv3 implementations with hardware compatibility support allow creating a
+guest GICv2 through this interface. For information on creating a guest GICv3
+device and guest ITS devices, see arm-vgic-v3.txt. It is not possible to
+create both a GICv3 and GICv2 device on the same VM.
+
+
+Groups:
+ KVM_DEV_ARM_VGIC_GRP_ADDR
+ Attributes:
+ KVM_VGIC_V2_ADDR_TYPE_DIST (rw, 64-bit)
+ Base address in the guest physical address space of the GIC distributor
+ register mappings. Only valid for KVM_DEV_TYPE_ARM_VGIC_V2.
+ This address needs to be 4K aligned and the region covers 4 KByte.
+
+ KVM_VGIC_V2_ADDR_TYPE_CPU (rw, 64-bit)
+ Base address in the guest physical address space of the GIC virtual cpu
+ interface register mappings. Only valid for KVM_DEV_TYPE_ARM_VGIC_V2.
+ This address needs to be 4K aligned and the region covers 4 KByte.
+ Errors:
+ -E2BIG: Address outside of addressable IPA range
+ -EINVAL: Incorrectly aligned address
+ -EEXIST: Address already configured
+ -ENXIO: The group or attribute is unknown/unsupported for this device
+ or hardware support is missing.
+ -EFAULT: Invalid user pointer for attr->addr.
+
+ KVM_DEV_ARM_VGIC_GRP_DIST_REGS
+ Attributes:
+ The attr field of kvm_device_attr encodes two values:
+ bits: | 63 .... 40 | 39 .. 32 | 31 .... 0 |
+ values: | reserved | vcpu_index | offset |
+
+ All distributor regs are (rw, 32-bit)
+
+ The offset is relative to the "Distributor base address" as defined in the
+ GICv2 specs. Getting or setting such a register has the same effect as
+ reading or writing the register on the actual hardware from the cpu whose
+ index is specified with the vcpu_index field. Note that most distributor
+ fields are not banked, but return the same value regardless of the
+ vcpu_index used to access the register.
+
+ GICD_IIDR.Revision is updated when the KVM implementation of an emulated
+ GICv2 is changed in a way directly observable by the guest or userspace.
+ Userspace should read GICD_IIDR from KVM and write back the read value to
+ confirm its expected behavior is aligned with the KVM implementation.
+ Userspace should set GICD_IIDR before setting any other registers (both
+ KVM_DEV_ARM_VGIC_GRP_DIST_REGS and KVM_DEV_ARM_VGIC_GRP_CPU_REGS) to ensure
+ the expected behavior. Unless GICD_IIDR has been set from userspace, writes
+ to the interrupt group registers (GICD_IGROUPR) are ignored.
+ Errors:
+ -ENXIO: Getting or setting this register is not yet supported
+ -EBUSY: One or more VCPUs are running
+ -EINVAL: Invalid vcpu_index supplied
+
+ KVM_DEV_ARM_VGIC_GRP_CPU_REGS
+ Attributes:
+ The attr field of kvm_device_attr encodes two values:
+ bits: | 63 .... 40 | 39 .. 32 | 31 .... 0 |
+ values: | reserved | vcpu_index | offset |
+
+ All CPU interface regs are (rw, 32-bit)
+
+ The offset specifies the offset from the "CPU interface base address" as
+ defined in the GICv2 specs. Getting or setting such a register has the
+ same effect as reading or writing the register on the actual hardware.
+
+ The Active Priorities Registers APRn are implementation defined, so we set a
+ fixed format for our implementation that fits with the model of a "GICv2
+ implementation without the security extensions" which we present to the
+ guest. This interface always exposes four register APR[0-3] describing the
+ maximum possible 128 preemption levels. The semantics of the register
+ indicate if any interrupts in a given preemption level are in the active
+ state by setting the corresponding bit.
+
+ Thus, preemption level X has one or more active interrupts if and only if:
+
+ APRn[X mod 32] == 0b1, where n = X / 32
+
+ Bits for undefined preemption levels are RAZ/WI.
+
+ Note that this differs from a CPU's view of the APRs on hardware in which
+ a GIC without the security extensions expose group 0 and group 1 active
+ priorities in separate register groups, whereas we show a combined view
+ similar to GICv2's GICH_APR.
+
+ For historical reasons and to provide ABI compatibility with userspace we
+ export the GICC_PMR register in the format of the GICH_VMCR.VMPriMask
+ field in the lower 5 bits of a word, meaning that userspace must always
+ use the lower 5 bits to communicate with the KVM device and must shift the
+ value left by 3 places to obtain the actual priority mask level.
+
+ Errors:
+ -ENXIO: Getting or setting this register is not yet supported
+ -EBUSY: One or more VCPUs are running
+ -EINVAL: Invalid vcpu_index supplied
+
+ KVM_DEV_ARM_VGIC_GRP_NR_IRQS
+ Attributes:
+ A value describing the number of interrupts (SGI, PPI and SPI) for
+ this GIC instance, ranging from 64 to 1024, in increments of 32.
+
+ Errors:
+ -EINVAL: Value set is out of the expected range
+ -EBUSY: Value has already be set, or GIC has already been initialized
+ with default values.
+
+ KVM_DEV_ARM_VGIC_GRP_CTRL
+ Attributes:
+ KVM_DEV_ARM_VGIC_CTRL_INIT
+ request the initialization of the VGIC or ITS, no additional parameter
+ in kvm_device_attr.addr.
+ Errors:
+ -ENXIO: VGIC not properly configured as required prior to calling
+ this attribute
+ -ENODEV: no online VCPU
+ -ENOMEM: memory shortage when allocating vgic internal data
--- /dev/null
+MPIC interrupt controller
+=========================
+
+Device types supported:
+ KVM_DEV_TYPE_FSL_MPIC_20 Freescale MPIC v2.0
+ KVM_DEV_TYPE_FSL_MPIC_42 Freescale MPIC v4.2
+
+Only one MPIC instance, of any type, may be instantiated. The created
+MPIC will act as the system interrupt controller, connecting to each
+vcpu's interrupt inputs.
+
+Groups:
+ KVM_DEV_MPIC_GRP_MISC
+ Attributes:
+ KVM_DEV_MPIC_BASE_ADDR (rw, 64-bit)
+ Base address of the 256 KiB MPIC register space. Must be
+ naturally aligned. A value of zero disables the mapping.
+ Reset value is zero.
+
+ KVM_DEV_MPIC_GRP_REGISTER (rw, 32-bit)
+ Access an MPIC register, as if the access were made from the guest.
+ "attr" is the byte offset into the MPIC register space. Accesses
+ must be 4-byte aligned.
+
+ MSIs may be signaled by using this attribute group to write
+ to the relevant MSIIR.
+
+ KVM_DEV_MPIC_GRP_IRQ_ACTIVE (rw, 32-bit)
+ IRQ input line for each standard openpic source. 0 is inactive and 1
+ is active, regardless of interrupt sense.
+
+ For edge-triggered interrupts: Writing 1 is considered an activating
+ edge, and writing 0 is ignored. Reading returns 1 if a previously
+ signaled edge has not been acknowledged, and 0 otherwise.
+
+ "attr" is the IRQ number. IRQ numbers for standard sources are the
+ byte offset of the relevant IVPR from EIVPR0, divided by 32.
+
+IRQ Routing:
+
+ The MPIC emulation supports IRQ routing. Only a single MPIC device can
+ be instantiated. Once that device has been created, it's available as
+ irqchip id 0.
+
+ This irqchip 0 has 256 interrupt pins, which expose the interrupts in
+ the main array of interrupt sources (a.k.a. "SRC" interrupts).
+
+ The numbering is the same as the MPIC device tree binding -- based on
+ the register offset from the beginning of the sources array, without
+ regard to any subdivisions in chip documentation such as "internal"
+ or "external" interrupts.
+
+ Access to non-SRC interrupts is not implemented through IRQ routing mechanisms.
--- /dev/null
+FLIC (floating interrupt controller)
+====================================
+
+FLIC handles floating (non per-cpu) interrupts, i.e. I/O, service and some
+machine check interruptions. All interrupts are stored in a per-vm list of
+pending interrupts. FLIC performs operations on this list.
+
+Only one FLIC instance may be instantiated.
+
+FLIC provides support to
+- add interrupts (KVM_DEV_FLIC_ENQUEUE)
+- inspect currently pending interrupts (KVM_FLIC_GET_ALL_IRQS)
+- purge all pending floating interrupts (KVM_DEV_FLIC_CLEAR_IRQS)
+- purge one pending floating I/O interrupt (KVM_DEV_FLIC_CLEAR_IO_IRQ)
+- enable/disable for the guest transparent async page faults
+- register and modify adapter interrupt sources (KVM_DEV_FLIC_ADAPTER_*)
+- modify AIS (adapter-interruption-suppression) mode state (KVM_DEV_FLIC_AISM)
+- inject adapter interrupts on a specified adapter (KVM_DEV_FLIC_AIRQ_INJECT)
+- get/set all AIS mode states (KVM_DEV_FLIC_AISM_ALL)
+
+Groups:
+ KVM_DEV_FLIC_ENQUEUE
+ Passes a buffer and length into the kernel which are then injected into
+ the list of pending interrupts.
+ attr->addr contains the pointer to the buffer and attr->attr contains
+ the length of the buffer.
+ The format of the data structure kvm_s390_irq as it is copied from userspace
+ is defined in usr/include/linux/kvm.h.
+
+ KVM_DEV_FLIC_GET_ALL_IRQS
+ Copies all floating interrupts into a buffer provided by userspace.
+ When the buffer is too small it returns -ENOMEM, which is the indication
+ for userspace to try again with a bigger buffer.
+ -ENOBUFS is returned when the allocation of a kernelspace buffer has
+ failed.
+ -EFAULT is returned when copying data to userspace failed.
+ All interrupts remain pending, i.e. are not deleted from the list of
+ currently pending interrupts.
+ attr->addr contains the userspace address of the buffer into which all
+ interrupt data will be copied.
+ attr->attr contains the size of the buffer in bytes.
+
+ KVM_DEV_FLIC_CLEAR_IRQS
+ Simply deletes all elements from the list of currently pending floating
+ interrupts. No interrupts are injected into the guest.
+
+ KVM_DEV_FLIC_CLEAR_IO_IRQ
+ Deletes one (if any) I/O interrupt for a subchannel identified by the
+ subsystem identification word passed via the buffer specified by
+ attr->addr (address) and attr->attr (length).
+
+ KVM_DEV_FLIC_APF_ENABLE
+ Enables async page faults for the guest. So in case of a major page fault
+ the host is allowed to handle this async and continues the guest.
+
+ KVM_DEV_FLIC_APF_DISABLE_WAIT
+ Disables async page faults for the guest and waits until already pending
+ async page faults are done. This is necessary to trigger a completion interrupt
+ for every init interrupt before migrating the interrupt list.
+
+ KVM_DEV_FLIC_ADAPTER_REGISTER
+ Register an I/O adapter interrupt source. Takes a kvm_s390_io_adapter
+ describing the adapter to register:
+
+struct kvm_s390_io_adapter {
+ __u32 id;
+ __u8 isc;
+ __u8 maskable;
+ __u8 swap;
+ __u8 flags;
+};
+
+ id contains the unique id for the adapter, isc the I/O interruption subclass
+ to use, maskable whether this adapter may be masked (interrupts turned off),
+ swap whether the indicators need to be byte swapped, and flags contains
+ further characteristics of the adapter.
+ Currently defined values for 'flags' are:
+ - KVM_S390_ADAPTER_SUPPRESSIBLE: adapter is subject to AIS
+ (adapter-interrupt-suppression) facility. This flag only has an effect if
+ the AIS capability is enabled.
+ Unknown flag values are ignored.
+
+
+ KVM_DEV_FLIC_ADAPTER_MODIFY
+ Modifies attributes of an existing I/O adapter interrupt source. Takes
+ a kvm_s390_io_adapter_req specifying the adapter and the operation:
+
+struct kvm_s390_io_adapter_req {
+ __u32 id;
+ __u8 type;
+ __u8 mask;
+ __u16 pad0;
+ __u64 addr;
+};
+
+ id specifies the adapter and type the operation. The supported operations
+ are:
+
+ KVM_S390_IO_ADAPTER_MASK
+ mask or unmask the adapter, as specified in mask
+
+ KVM_S390_IO_ADAPTER_MAP
+ perform a gmap translation for the guest address provided in addr,
+ pin a userspace page for the translated address and add it to the
+ list of mappings
+ Note: A new mapping will be created unconditionally; therefore,
+ the calling code should avoid making duplicate mappings.
+
+ KVM_S390_IO_ADAPTER_UNMAP
+ release a userspace page for the translated address specified in addr
+ from the list of mappings
+
+ KVM_DEV_FLIC_AISM
+ modify the adapter-interruption-suppression mode for a given isc if the
+ AIS capability is enabled. Takes a kvm_s390_ais_req describing:
+
+struct kvm_s390_ais_req {
+ __u8 isc;
+ __u16 mode;
+};
+
+ isc contains the target I/O interruption subclass, mode the target
+ adapter-interruption-suppression mode. The following modes are
+ currently supported:
+ - KVM_S390_AIS_MODE_ALL: ALL-Interruptions Mode, i.e. airq injection
+ is always allowed;
+ - KVM_S390_AIS_MODE_SINGLE: SINGLE-Interruption Mode, i.e. airq
+ injection is only allowed once and the following adapter interrupts
+ will be suppressed until the mode is set again to ALL-Interruptions
+ or SINGLE-Interruption mode.
+
+ KVM_DEV_FLIC_AIRQ_INJECT
+ Inject adapter interrupts on a specified adapter.
+ attr->attr contains the unique id for the adapter, which allows for
+ adapter-specific checks and actions.
+ For adapters subject to AIS, handle the airq injection suppression for
+ an isc according to the adapter-interruption-suppression mode on condition
+ that the AIS capability is enabled.
+
+ KVM_DEV_FLIC_AISM_ALL
+ Gets or sets the adapter-interruption-suppression mode for all ISCs. Takes
+ a kvm_s390_ais_all describing:
+
+struct kvm_s390_ais_all {
+ __u8 simm; /* Single-Interruption-Mode mask */
+ __u8 nimm; /* No-Interruption-Mode mask *
+};
+
+ simm contains Single-Interruption-Mode mask for all ISCs, nimm contains
+ No-Interruption-Mode mask for all ISCs. Each bit in simm and nimm corresponds
+ to an ISC (MSB0 bit 0 to ISC 0 and so on). The combination of simm bit and
+ nimm bit presents AIS mode for a ISC.
+
+ KVM_DEV_FLIC_AISM_ALL is indicated by KVM_CAP_S390_AIS_MIGRATION.
+
+Note: The KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR device ioctls executed on
+FLIC with an unknown group or attribute gives the error code EINVAL (instead of
+ENXIO, as specified in the API documentation). It is not possible to conclude
+that a FLIC operation is unavailable based on the error code resulting from a
+usage attempt.
+
+Note: The KVM_DEV_FLIC_CLEAR_IO_IRQ ioctl will return EINVAL in case a zero
+schid is specified.
--- /dev/null
+Generic vcpu interface
+====================================
+
+The virtual cpu "device" also accepts the ioctls KVM_SET_DEVICE_ATTR,
+KVM_GET_DEVICE_ATTR, and KVM_HAS_DEVICE_ATTR. The interface uses the same struct
+kvm_device_attr as other devices, but targets VCPU-wide settings and controls.
+
+The groups and attributes per virtual cpu, if any, are architecture specific.
+
+1. GROUP: KVM_ARM_VCPU_PMU_V3_CTRL
+Architectures: ARM64
+
+1.1. ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_IRQ
+Parameters: in kvm_device_attr.addr the address for PMU overflow interrupt is a
+ pointer to an int
+Returns: -EBUSY: The PMU overflow interrupt is already set
+ -ENXIO: The overflow interrupt not set when attempting to get it
+ -ENODEV: PMUv3 not supported
+ -EINVAL: Invalid PMU overflow interrupt number supplied or
+ trying to set the IRQ number without using an in-kernel
+ irqchip.
+
+A value describing the PMUv3 (Performance Monitor Unit v3) overflow interrupt
+number for this vcpu. This interrupt could be a PPI or SPI, but the interrupt
+type must be same for each vcpu. As a PPI, the interrupt number is the same for
+all vcpus, while as an SPI it must be a separate number per vcpu.
+
+1.2 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_INIT
+Parameters: no additional parameter in kvm_device_attr.addr
+Returns: -ENODEV: PMUv3 not supported or GIC not initialized
+ -ENXIO: PMUv3 not properly configured or in-kernel irqchip not
+ configured as required prior to calling this attribute
+ -EBUSY: PMUv3 already initialized
+
+Request the initialization of the PMUv3. If using the PMUv3 with an in-kernel
+virtual GIC implementation, this must be done after initializing the in-kernel
+irqchip.
+
+
+2. GROUP: KVM_ARM_VCPU_TIMER_CTRL
+Architectures: ARM,ARM64
+
+2.1. ATTRIBUTE: KVM_ARM_VCPU_TIMER_IRQ_VTIMER
+2.2. ATTRIBUTE: KVM_ARM_VCPU_TIMER_IRQ_PTIMER
+Parameters: in kvm_device_attr.addr the address for the timer interrupt is a
+ pointer to an int
+Returns: -EINVAL: Invalid timer interrupt number
+ -EBUSY: One or more VCPUs has already run
+
+A value describing the architected timer interrupt number when connected to an
+in-kernel virtual GIC. These must be a PPI (16 <= intid < 32). Setting the
+attribute overrides the default values (see below).
+
+KVM_ARM_VCPU_TIMER_IRQ_VTIMER: The EL1 virtual timer intid (default: 27)
+KVM_ARM_VCPU_TIMER_IRQ_PTIMER: The EL1 physical timer intid (default: 30)
+
+Setting the same PPI for different timers will prevent the VCPUs from running.
+Setting the interrupt number on a VCPU configures all VCPUs created at that
+time to use the number provided for a given timer, overwriting any previously
+configured values on other VCPUs. Userspace should configure the interrupt
+numbers on at least one VCPU after creating all VCPUs and before running any
+VCPUs.
--- /dev/null
+VFIO virtual device
+===================
+
+Device types supported:
+ KVM_DEV_TYPE_VFIO
+
+Only one VFIO instance may be created per VM. The created device
+tracks VFIO groups in use by the VM and features of those groups
+important to the correctness and acceleration of the VM. As groups
+are enabled and disabled for use by the VM, KVM should be updated
+about their presence. When registered with KVM, a reference to the
+VFIO-group is held by KVM.
+
+Groups:
+ KVM_DEV_VFIO_GROUP
+
+KVM_DEV_VFIO_GROUP attributes:
+ KVM_DEV_VFIO_GROUP_ADD: Add a VFIO group to VFIO-KVM device tracking
+ kvm_device_attr.addr points to an int32_t file descriptor
+ for the VFIO group.
+ KVM_DEV_VFIO_GROUP_DEL: Remove a VFIO group from VFIO-KVM device tracking
+ kvm_device_attr.addr points to an int32_t file descriptor
+ for the VFIO group.
+ KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table
+ allocated by sPAPR KVM.
+ kvm_device_attr.addr points to a struct:
+
+ struct kvm_vfio_spapr_tce {
+ __s32 groupfd;
+ __s32 tablefd;
+ };
+
+ where
+ @groupfd is a file descriptor for a VFIO group;
+ @tablefd is a file descriptor for a TCE table allocated via
+ KVM_CREATE_SPAPR_TCE.
--- /dev/null
+Generic vm interface
+====================================
+
+The virtual machine "device" also accepts the ioctls KVM_SET_DEVICE_ATTR,
+KVM_GET_DEVICE_ATTR, and KVM_HAS_DEVICE_ATTR. The interface uses the same
+struct kvm_device_attr as other devices, but targets VM-wide settings
+and controls.
+
+The groups and attributes per virtual machine, if any, are architecture
+specific.
+
+1. GROUP: KVM_S390_VM_MEM_CTRL
+Architectures: s390
+
+1.1. ATTRIBUTE: KVM_S390_VM_MEM_ENABLE_CMMA
+Parameters: none
+Returns: -EBUSY if a vcpu is already defined, otherwise 0
+
+Enables Collaborative Memory Management Assist (CMMA) for the virtual machine.
+
+1.2. ATTRIBUTE: KVM_S390_VM_MEM_CLR_CMMA
+Parameters: none
+Returns: -EINVAL if CMMA was not enabled
+ 0 otherwise
+
+Clear the CMMA status for all guest pages, so any pages the guest marked
+as unused are again used any may not be reclaimed by the host.
+
+1.3. ATTRIBUTE KVM_S390_VM_MEM_LIMIT_SIZE
+Parameters: in attr->addr the address for the new limit of guest memory
+Returns: -EFAULT if the given address is not accessible
+ -EINVAL if the virtual machine is of type UCONTROL
+ -E2BIG if the given guest memory is to big for that machine
+ -EBUSY if a vcpu is already defined
+ -ENOMEM if not enough memory is available for a new shadow guest mapping
+ 0 otherwise
+
+Allows userspace to query the actual limit and set a new limit for
+the maximum guest memory size. The limit will be rounded up to
+2048 MB, 4096 GB, 8192 TB respectively, as this limit is governed by
+the number of page table levels. In the case that there is no limit we will set
+the limit to KVM_S390_NO_MEM_LIMIT (U64_MAX).
+
+2. GROUP: KVM_S390_VM_CPU_MODEL
+Architectures: s390
+
+2.1. ATTRIBUTE: KVM_S390_VM_CPU_MACHINE (r/o)
+
+Allows user space to retrieve machine and kvm specific cpu related information:
+
+struct kvm_s390_vm_cpu_machine {
+ __u64 cpuid; # CPUID of host
+ __u32 ibc; # IBC level range offered by host
+ __u8 pad[4];
+ __u64 fac_mask[256]; # set of cpu facilities enabled by KVM
+ __u64 fac_list[256]; # set of cpu facilities offered by host
+}
+
+Parameters: address of buffer to store the machine related cpu data
+ of type struct kvm_s390_vm_cpu_machine*
+Returns: -EFAULT if the given address is not accessible from kernel space
+ -ENOMEM if not enough memory is available to process the ioctl
+ 0 in case of success
+
+2.2. ATTRIBUTE: KVM_S390_VM_CPU_PROCESSOR (r/w)
+
+Allows user space to retrieve or request to change cpu related information for a vcpu:
+
+struct kvm_s390_vm_cpu_processor {
+ __u64 cpuid; # CPUID currently (to be) used by this vcpu
+ __u16 ibc; # IBC level currently (to be) used by this vcpu
+ __u8 pad[6];
+ __u64 fac_list[256]; # set of cpu facilities currently (to be) used
+ # by this vcpu
+}
+
+KVM does not enforce or limit the cpu model data in any form. Take the information
+retrieved by means of KVM_S390_VM_CPU_MACHINE as hint for reasonable configuration
+setups. Instruction interceptions triggered by additionally set facility bits that
+are not handled by KVM need to by imlemented in the VM driver code.
+
+Parameters: address of buffer to store/set the processor related cpu
+ data of type struct kvm_s390_vm_cpu_processor*.
+Returns: -EBUSY in case 1 or more vcpus are already activated (only in write case)
+ -EFAULT if the given address is not accessible from kernel space
+ -ENOMEM if not enough memory is available to process the ioctl
+ 0 in case of success
+
+2.3. ATTRIBUTE: KVM_S390_VM_CPU_MACHINE_FEAT (r/o)
+
+Allows user space to retrieve available cpu features. A feature is available if
+provided by the hardware and supported by kvm. In theory, cpu features could
+even be completely emulated by kvm.
+
+struct kvm_s390_vm_cpu_feat {
+ __u64 feat[16]; # Bitmap (1 = feature available), MSB 0 bit numbering
+};
+
+Parameters: address of a buffer to load the feature list from.
+Returns: -EFAULT if the given address is not accessible from kernel space.
+ 0 in case of success.
+
+2.4. ATTRIBUTE: KVM_S390_VM_CPU_PROCESSOR_FEAT (r/w)
+
+Allows user space to retrieve or change enabled cpu features for all VCPUs of a
+VM. Features that are not available cannot be enabled.
+
+See 2.3. for a description of the parameter struct.
+
+Parameters: address of a buffer to store/load the feature list from.
+Returns: -EFAULT if the given address is not accessible from kernel space.
+ -EINVAL if a cpu feature that is not available is to be enabled.
+ -EBUSY if at least one VCPU has already been defined.
+ 0 in case of success.
+
+2.5. ATTRIBUTE: KVM_S390_VM_CPU_MACHINE_SUBFUNC (r/o)
+
+Allows user space to retrieve available cpu subfunctions without any filtering
+done by a set IBC. These subfunctions are indicated to the guest VCPU via
+query or "test bit" subfunctions and used e.g. by cpacf functions, plo and ptff.
+
+A subfunction block is only valid if KVM_S390_VM_CPU_MACHINE contains the
+STFL(E) bit introducing the affected instruction. If the affected instruction
+indicates subfunctions via a "query subfunction", the response block is
+contained in the returned struct. If the affected instruction
+indicates subfunctions via a "test bit" mechanism, the subfunction codes are
+contained in the returned struct in MSB 0 bit numbering.
+
+struct kvm_s390_vm_cpu_subfunc {
+ u8 plo[32]; # always valid (ESA/390 feature)
+ u8 ptff[16]; # valid with TOD-clock steering
+ u8 kmac[16]; # valid with Message-Security-Assist
+ u8 kmc[16]; # valid with Message-Security-Assist
+ u8 km[16]; # valid with Message-Security-Assist
+ u8 kimd[16]; # valid with Message-Security-Assist
+ u8 klmd[16]; # valid with Message-Security-Assist
+ u8 pckmo[16]; # valid with Message-Security-Assist-Extension 3
+ u8 kmctr[16]; # valid with Message-Security-Assist-Extension 4
+ u8 kmf[16]; # valid with Message-Security-Assist-Extension 4
+ u8 kmo[16]; # valid with Message-Security-Assist-Extension 4
+ u8 pcc[16]; # valid with Message-Security-Assist-Extension 4
+ u8 ppno[16]; # valid with Message-Security-Assist-Extension 5
+ u8 kma[16]; # valid with Message-Security-Assist-Extension 8
+ u8 kdsa[16]; # valid with Message-Security-Assist-Extension 9
+ u8 reserved[1792]; # reserved for future instructions
+};
+
+Parameters: address of a buffer to load the subfunction blocks from.
+Returns: -EFAULT if the given address is not accessible from kernel space.
+ 0 in case of success.
+
+2.6. ATTRIBUTE: KVM_S390_VM_CPU_PROCESSOR_SUBFUNC (r/w)
+
+Allows user space to retrieve or change cpu subfunctions to be indicated for
+all VCPUs of a VM. This attribute will only be available if kernel and
+hardware support are in place.
+
+The kernel uses the configured subfunction blocks for indication to
+the guest. A subfunction block will only be used if the associated STFL(E) bit
+has not been disabled by user space (so the instruction to be queried is
+actually available for the guest).
+
+As long as no data has been written, a read will fail. The IBC will be used
+to determine available subfunctions in this case, this will guarantee backward
+compatibility.
+
+See 2.5. for a description of the parameter struct.
+
+Parameters: address of a buffer to store/load the subfunction blocks from.
+Returns: -EFAULT if the given address is not accessible from kernel space.
+ -EINVAL when reading, if there was no write yet.
+ -EBUSY if at least one VCPU has already been defined.
+ 0 in case of success.
+
+3. GROUP: KVM_S390_VM_TOD
+Architectures: s390
+
+3.1. ATTRIBUTE: KVM_S390_VM_TOD_HIGH
+
+Allows user space to set/get the TOD clock extension (u8) (superseded by
+KVM_S390_VM_TOD_EXT).
+
+Parameters: address of a buffer in user space to store the data (u8) to
+Returns: -EFAULT if the given address is not accessible from kernel space
+ -EINVAL if setting the TOD clock extension to != 0 is not supported
+
+3.2. ATTRIBUTE: KVM_S390_VM_TOD_LOW
+
+Allows user space to set/get bits 0-63 of the TOD clock register as defined in
+the POP (u64).
+
+Parameters: address of a buffer in user space to store the data (u64) to
+Returns: -EFAULT if the given address is not accessible from kernel space
+
+3.3. ATTRIBUTE: KVM_S390_VM_TOD_EXT
+Allows user space to set/get bits 0-63 of the TOD clock register as defined in
+the POP (u64). If the guest CPU model supports the TOD clock extension (u8), it
+also allows user space to get/set it. If the guest CPU model does not support
+it, it is stored as 0 and not allowed to be set to a value != 0.
+
+Parameters: address of a buffer in user space to store the data
+ (kvm_s390_vm_tod_clock) to
+Returns: -EFAULT if the given address is not accessible from kernel space
+ -EINVAL if setting the TOD clock extension to != 0 is not supported
+
+4. GROUP: KVM_S390_VM_CRYPTO
+Architectures: s390
+
+4.1. ATTRIBUTE: KVM_S390_VM_CRYPTO_ENABLE_AES_KW (w/o)
+
+Allows user space to enable aes key wrapping, including generating a new
+wrapping key.
+
+Parameters: none
+Returns: 0
+
+4.2. ATTRIBUTE: KVM_S390_VM_CRYPTO_ENABLE_DEA_KW (w/o)
+
+Allows user space to enable dea key wrapping, including generating a new
+wrapping key.
+
+Parameters: none
+Returns: 0
+
+4.3. ATTRIBUTE: KVM_S390_VM_CRYPTO_DISABLE_AES_KW (w/o)
+
+Allows user space to disable aes key wrapping, clearing the wrapping key.
+
+Parameters: none
+Returns: 0
+
+4.4. ATTRIBUTE: KVM_S390_VM_CRYPTO_DISABLE_DEA_KW (w/o)
+
+Allows user space to disable dea key wrapping, clearing the wrapping key.
+
+Parameters: none
+Returns: 0
+
+5. GROUP: KVM_S390_VM_MIGRATION
+Architectures: s390
+
+5.1. ATTRIBUTE: KVM_S390_VM_MIGRATION_STOP (w/o)
+
+Allows userspace to stop migration mode, needed for PGSTE migration.
+Setting this attribute when migration mode is not active will have no
+effects.
+
+Parameters: none
+Returns: 0
+
+5.2. ATTRIBUTE: KVM_S390_VM_MIGRATION_START (w/o)
+
+Allows userspace to start migration mode, needed for PGSTE migration.
+Setting this attribute when migration mode is already active will have
+no effects.
+
+Parameters: none
+Returns: -ENOMEM if there is not enough free memory to start migration mode
+ -EINVAL if the state of the VM is invalid (e.g. no memory defined)
+ 0 in case of success.
+
+5.3. ATTRIBUTE: KVM_S390_VM_MIGRATION_STATUS (r/o)
+
+Allows userspace to query the status of migration mode.
+
+Parameters: address of a buffer in user space to store the data (u64) to;
+ the data itself is either 0 if migration mode is disabled or 1
+ if it is enabled
+Returns: -EFAULT if the given address is not accessible from kernel space
+ 0 in case of success.
--- /dev/null
+XICS interrupt controller
+
+Device type supported: KVM_DEV_TYPE_XICS
+
+Groups:
+ KVM_DEV_XICS_SOURCES
+ Attributes: One per interrupt source, indexed by the source number.
+
+This device emulates the XICS (eXternal Interrupt Controller
+Specification) defined in PAPR. The XICS has a set of interrupt
+sources, each identified by a 20-bit source number, and a set of
+Interrupt Control Presentation (ICP) entities, also called "servers",
+each associated with a virtual CPU.
+
+The ICP entities are created by enabling the KVM_CAP_IRQ_ARCH
+capability for each vcpu, specifying KVM_CAP_IRQ_XICS in args[0] and
+the interrupt server number (i.e. the vcpu number from the XICS's
+point of view) in args[1] of the kvm_enable_cap struct. Each ICP has
+64 bits of state which can be read and written using the
+KVM_GET_ONE_REG and KVM_SET_ONE_REG ioctls on the vcpu. The 64 bit
+state word has the following bitfields, starting at the
+least-significant end of the word:
+
+* Unused, 16 bits
+
+* Pending interrupt priority, 8 bits
+ Zero is the highest priority, 255 means no interrupt is pending.
+
+* Pending IPI (inter-processor interrupt) priority, 8 bits
+ Zero is the highest priority, 255 means no IPI is pending.
+
+* Pending interrupt source number, 24 bits
+ Zero means no interrupt pending, 2 means an IPI is pending
+
+* Current processor priority, 8 bits
+ Zero is the highest priority, meaning no interrupts can be
+ delivered, and 255 is the lowest priority.
+
+Each source has 64 bits of state that can be read and written using
+the KVM_GET_DEVICE_ATTR and KVM_SET_DEVICE_ATTR ioctls, specifying the
+KVM_DEV_XICS_SOURCES attribute group, with the attribute number being
+the interrupt source number. The 64 bit state word has the following
+bitfields, starting from the least-significant end of the word:
+
+* Destination (server number), 32 bits
+ This specifies where the interrupt should be sent, and is the
+ interrupt server number specified for the destination vcpu.
+
+* Priority, 8 bits
+ This is the priority specified for this interrupt source, where 0 is
+ the highest priority and 255 is the lowest. An interrupt with a
+ priority of 255 will never be delivered.
+
+* Level sensitive flag, 1 bit
+ This bit is 1 for a level-sensitive interrupt source, or 0 for
+ edge-sensitive (or MSI).
+
+* Masked flag, 1 bit
+ This bit is set to 1 if the interrupt is masked (cannot be delivered
+ regardless of its priority), for example by the ibm,int-off RTAS
+ call, or 0 if it is not masked.
+
+* Pending flag, 1 bit
+ This bit is 1 if the source has a pending interrupt, otherwise 0.
+
+Only one XICS instance may be created per VM.
--- /dev/null
+POWER9 eXternal Interrupt Virtualization Engine (XIVE Gen1)
+==========================================================
+
+Device types supported:
+ KVM_DEV_TYPE_XIVE POWER9 XIVE Interrupt Controller generation 1
+
+This device acts as a VM interrupt controller. It provides the KVM
+interface to configure the interrupt sources of a VM in the underlying
+POWER9 XIVE interrupt controller.
+
+Only one XIVE instance may be instantiated. A guest XIVE device
+requires a POWER9 host and the guest OS should have support for the
+XIVE native exploitation interrupt mode. If not, it should run using
+the legacy interrupt mode, referred as XICS (POWER7/8).
+
+* Device Mappings
+
+ The KVM device exposes different MMIO ranges of the XIVE HW which
+ are required for interrupt management. These are exposed to the
+ guest in VMAs populated with a custom VM fault handler.
+
+ 1. Thread Interrupt Management Area (TIMA)
+
+ Each thread has an associated Thread Interrupt Management context
+ composed of a set of registers. These registers let the thread
+ handle priority management and interrupt acknowledgment. The most
+ important are :
+
+ - Interrupt Pending Buffer (IPB)
+ - Current Processor Priority (CPPR)
+ - Notification Source Register (NSR)
+
+ They are exposed to software in four different pages each proposing
+ a view with a different privilege. The first page is for the
+ physical thread context and the second for the hypervisor. Only the
+ third (operating system) and the fourth (user level) are exposed the
+ guest.
+
+ 2. Event State Buffer (ESB)
+
+ Each source is associated with an Event State Buffer (ESB) with
+ either a pair of even/odd pair of pages which provides commands to
+ manage the source: to trigger, to EOI, to turn off the source for
+ instance.
+
+ 3. Device pass-through
+
+ When a device is passed-through into the guest, the source
+ interrupts are from a different HW controller (PHB4) and the ESB
+ pages exposed to the guest should accommadate this change.
+
+ The passthru_irq helpers, kvmppc_xive_set_mapped() and
+ kvmppc_xive_clr_mapped() are called when the device HW irqs are
+ mapped into or unmapped from the guest IRQ number space. The KVM
+ device extends these helpers to clear the ESB pages of the guest IRQ
+ number being mapped and then lets the VM fault handler repopulate.
+ The handler will insert the ESB page corresponding to the HW
+ interrupt of the device being passed-through or the initial IPI ESB
+ page if the device has being removed.
+
+ The ESB remapping is fully transparent to the guest and the OS
+ device driver. All handling is done within VFIO and the above
+ helpers in KVM-PPC.
+
+* Groups:
+
+ 1. KVM_DEV_XIVE_GRP_CTRL
+ Provides global controls on the device
+ Attributes:
+ 1.1 KVM_DEV_XIVE_RESET (write only)
+ Resets the interrupt controller configuration for sources and event
+ queues. To be used by kexec and kdump.
+ Errors: none
+
+ 1.2 KVM_DEV_XIVE_EQ_SYNC (write only)
+ Sync all the sources and queues and mark the EQ pages dirty. This
+ to make sure that a consistent memory state is captured when
+ migrating the VM.
+ Errors: none
+
+ 2. KVM_DEV_XIVE_GRP_SOURCE (write only)
+ Initializes a new source in the XIVE device and mask it.
+ Attributes:
+ Interrupt source number (64-bit)
+ The kvm_device_attr.addr points to a __u64 value:
+ bits: | 63 .... 2 | 1 | 0
+ values: | unused | level | type
+ - type: 0:MSI 1:LSI
+ - level: assertion level in case of an LSI.
+ Errors:
+ -E2BIG: Interrupt source number is out of range
+ -ENOMEM: Could not create a new source block
+ -EFAULT: Invalid user pointer for attr->addr.
+ -ENXIO: Could not allocate underlying HW interrupt
+
+ 3. KVM_DEV_XIVE_GRP_SOURCE_CONFIG (write only)
+ Configures source targeting
+ Attributes:
+ Interrupt source number (64-bit)
+ The kvm_device_attr.addr points to a __u64 value:
+ bits: | 63 .... 33 | 32 | 31 .. 3 | 2 .. 0
+ values: | eisn | mask | server | priority
+ - priority: 0-7 interrupt priority level
+ - server: CPU number chosen to handle the interrupt
+ - mask: mask flag (unused)
+ - eisn: Effective Interrupt Source Number
+ Errors:
+ -ENOENT: Unknown source number
+ -EINVAL: Not initialized source number
+ -EINVAL: Invalid priority
+ -EINVAL: Invalid CPU number.
+ -EFAULT: Invalid user pointer for attr->addr.
+ -ENXIO: CPU event queues not configured or configuration of the
+ underlying HW interrupt failed
+ -EBUSY: No CPU available to serve interrupt
+
+ 4. KVM_DEV_XIVE_GRP_EQ_CONFIG (read-write)
+ Configures an event queue of a CPU
+ Attributes:
+ EQ descriptor identifier (64-bit)
+ The EQ descriptor identifier is a tuple (server, priority) :
+ bits: | 63 .... 32 | 31 .. 3 | 2 .. 0
+ values: | unused | server | priority
+ The kvm_device_attr.addr points to :
+ struct kvm_ppc_xive_eq {
+ __u32 flags;
+ __u32 qshift;
+ __u64 qaddr;
+ __u32 qtoggle;
+ __u32 qindex;
+ __u8 pad[40];
+ };
+ - flags: queue flags
+ KVM_XIVE_EQ_ALWAYS_NOTIFY (required)
+ forces notification without using the coalescing mechanism
+ provided by the XIVE END ESBs.
+ - qshift: queue size (power of 2)
+ - qaddr: real address of queue
+ - qtoggle: current queue toggle bit
+ - qindex: current queue index
+ - pad: reserved for future use
+ Errors:
+ -ENOENT: Invalid CPU number
+ -EINVAL: Invalid priority
+ -EINVAL: Invalid flags
+ -EINVAL: Invalid queue size
+ -EINVAL: Invalid queue address
+ -EFAULT: Invalid user pointer for attr->addr.
+ -EIO: Configuration of the underlying HW failed
+
+ 5. KVM_DEV_XIVE_GRP_SOURCE_SYNC (write only)
+ Synchronize the source to flush event notifications
+ Attributes:
+ Interrupt source number (64-bit)
+ Errors:
+ -ENOENT: Unknown source number
+ -EINVAL: Not initialized source number
+
+* VCPU state
+
+ The XIVE IC maintains VP interrupt state in an internal structure
+ called the NVT. When a VP is not dispatched on a HW processor
+ thread, this structure can be updated by HW if the VP is the target
+ of an event notification.
+
+ It is important for migration to capture the cached IPB from the NVT
+ as it synthesizes the priorities of the pending interrupts. We
+ capture a bit more to report debug information.
+
+ KVM_REG_PPC_VP_STATE (2 * 64bits)
+ bits: | 63 .... 32 | 31 .... 0 |
+ values: | TIMA word0 | TIMA word1 |
+ bits: | 127 .......... 64 |
+ values: | unused |
+
+* Migration:
+
+ Saving the state of a VM using the XIVE native exploitation mode
+ should follow a specific sequence. When the VM is stopped :
+
+ 1. Mask all sources (PQ=01) to stop the flow of events.
+
+ 2. Sync the XIVE device with the KVM control KVM_DEV_XIVE_EQ_SYNC to
+ flush any in-flight event notification and to stabilize the EQs. At
+ this stage, the EQ pages are marked dirty to make sure they are
+ transferred in the migration sequence.
+
+ 3. Capture the state of the source targeting, the EQs configuration
+ and the state of thread interrupt context registers.
+
+ Restore is similar :
+
+ 1. Restore the EQ configuration. As targeting depends on it.
+ 2. Restore targeting
+ 3. Restore the thread interrupt contexts
+ 4. Restore the source states
+ 5. Let the vCPU run
--- /dev/null
+The KVM halt polling system
+===========================
+
+The KVM halt polling system provides a feature within KVM whereby the latency
+of a guest can, under some circumstances, be reduced by polling in the host
+for some time period after the guest has elected to no longer run by cedeing.
+That is, when a guest vcpu has ceded, or in the case of powerpc when all of the
+vcpus of a single vcore have ceded, the host kernel polls for wakeup conditions
+before giving up the cpu to the scheduler in order to let something else run.
+
+Polling provides a latency advantage in cases where the guest can be run again
+very quickly by at least saving us a trip through the scheduler, normally on
+the order of a few micro-seconds, although performance benefits are workload
+dependant. In the event that no wakeup source arrives during the polling
+interval or some other task on the runqueue is runnable the scheduler is
+invoked. Thus halt polling is especially useful on workloads with very short
+wakeup periods where the time spent halt polling is minimised and the time
+savings of not invoking the scheduler are distinguishable.
+
+The generic halt polling code is implemented in:
+
+ virt/kvm/kvm_main.c: kvm_vcpu_block()
+
+The powerpc kvm-hv specific case is implemented in:
+
+ arch/powerpc/kvm/book3s_hv.c: kvmppc_vcore_blocked()
+
+Halt Polling Interval
+=====================
+
+The maximum time for which to poll before invoking the scheduler, referred to
+as the halt polling interval, is increased and decreased based on the perceived
+effectiveness of the polling in an attempt to limit pointless polling.
+This value is stored in either the vcpu struct:
+
+ kvm_vcpu->halt_poll_ns
+
+or in the case of powerpc kvm-hv, in the vcore struct:
+
+ kvmppc_vcore->halt_poll_ns
+
+Thus this is a per vcpu (or vcore) value.
+
+During polling if a wakeup source is received within the halt polling interval,
+the interval is left unchanged. In the event that a wakeup source isn't
+received during the polling interval (and thus schedule is invoked) there are
+two options, either the polling interval and total block time[0] were less than
+the global max polling interval (see module params below), or the total block
+time was greater than the global max polling interval.
+
+In the event that both the polling interval and total block time were less than
+the global max polling interval then the polling interval can be increased in
+the hope that next time during the longer polling interval the wake up source
+will be received while the host is polling and the latency benefits will be
+received. The polling interval is grown in the function grow_halt_poll_ns() and
+is multiplied by the module parameters halt_poll_ns_grow and
+halt_poll_ns_grow_start.
+
+In the event that the total block time was greater than the global max polling
+interval then the host will never poll for long enough (limited by the global
+max) to wakeup during the polling interval so it may as well be shrunk in order
+to avoid pointless polling. The polling interval is shrunk in the function
+shrink_halt_poll_ns() and is divided by the module parameter
+halt_poll_ns_shrink, or set to 0 iff halt_poll_ns_shrink == 0.
+
+It is worth noting that this adjustment process attempts to hone in on some
+steady state polling interval but will only really do a good job for wakeups
+which come at an approximately constant rate, otherwise there will be constant
+adjustment of the polling interval.
+
+[0] total block time: the time between when the halt polling function is
+ invoked and a wakeup source received (irrespective of
+ whether the scheduler is invoked within that function).
+
+Module Parameters
+=================
+
+The kvm module has 3 tuneable module parameters to adjust the global max
+polling interval as well as the rate at which the polling interval is grown and
+shrunk. These variables are defined in include/linux/kvm_host.h and as module
+parameters in virt/kvm/kvm_main.c, or arch/powerpc/kvm/book3s_hv.c in the
+powerpc kvm-hv case.
+
+Module Parameter | Description | Default Value
+--------------------------------------------------------------------------------
+halt_poll_ns | The global max polling | KVM_HALT_POLL_NS_DEFAULT
+ | interval which defines |
+ | the ceiling value of the |
+ | polling interval for | (per arch value)
+ | each vcpu. |
+--------------------------------------------------------------------------------
+halt_poll_ns_grow | The value by which the | 2
+ | halt polling interval is |
+ | multiplied in the |
+ | grow_halt_poll_ns() |
+ | function. |
+--------------------------------------------------------------------------------
+halt_poll_ns_grow_start | The initial value to grow | 10000
+ | to from zero in the |
+ | grow_halt_poll_ns() |
+ | function. |
+--------------------------------------------------------------------------------
+halt_poll_ns_shrink | The value by which the | 0
+ | halt polling interval is |
+ | divided in the |
+ | shrink_halt_poll_ns() |
+ | function. |
+--------------------------------------------------------------------------------
+
+These module parameters can be set from the debugfs files in:
+
+ /sys/module/kvm/parameters/
+
+Note: that these module parameters are system wide values and are not able to
+ be tuned on a per vm basis.
+
+Further Notes
+=============
+
+- Care should be taken when setting the halt_poll_ns module parameter as a
+large value has the potential to drive the cpu usage to 100% on a machine which
+would be almost entirely idle otherwise. This is because even if a guest has
+wakeups during which very little work is done and which are quite far apart, if
+the period is shorter than the global max polling interval (halt_poll_ns) then
+the host will always poll for the entire block time and thus cpu utilisation
+will go to 100%.
+
+- Halt polling essentially presents a trade off between power usage and latency
+and the module parameters should be used to tune the affinity for this. Idle
+cpu time is essentially converted to host kernel time with the aim of decreasing
+latency when entering the guest.
+
+- Halt polling will only be conducted by the host when no other tasks are
+runnable on that cpu, otherwise the polling will cease immediately and
+schedule will be invoked to allow that other task to run. Thus this doesn't
+allow a guest to denial of service the cpu.
--- /dev/null
+Linux KVM Hypercall:
+===================
+X86:
+ KVM Hypercalls have a three-byte sequence of either the vmcall or the vmmcall
+ instruction. The hypervisor can replace it with instructions that are
+ guaranteed to be supported.
+
+ Up to four arguments may be passed in rbx, rcx, rdx, and rsi respectively.
+ The hypercall number should be placed in rax and the return value will be
+ placed in rax. No other registers will be clobbered unless explicitly stated
+ by the particular hypercall.
+
+S390:
+ R2-R7 are used for parameters 1-6. In addition, R1 is used for hypercall
+ number. The return value is written to R2.
+
+ S390 uses diagnose instruction as hypercall (0x500) along with hypercall
+ number in R1.
+
+ For further information on the S390 diagnose call as supported by KVM,
+ refer to Documentation/virt/kvm/s390-diag.txt.
+
+ PowerPC:
+ It uses R3-R10 and hypercall number in R11. R4-R11 are used as output registers.
+ Return value is placed in R3.
+
+ KVM hypercalls uses 4 byte opcode, that are patched with 'hypercall-instructions'
+ property inside the device tree's /hypervisor node.
+ For more information refer to Documentation/virt/kvm/ppc-pv.txt
+
+MIPS:
+ KVM hypercalls use the HYPCALL instruction with code 0 and the hypercall
+ number in $2 (v0). Up to four arguments may be placed in $4-$7 (a0-a3) and
+ the return value is placed in $2 (v0).
+
+KVM Hypercalls Documentation
+===========================
+The template for each hypercall is:
+1. Hypercall name.
+2. Architecture(s)
+3. Status (deprecated, obsolete, active)
+4. Purpose
+
+1. KVM_HC_VAPIC_POLL_IRQ
+------------------------
+Architecture: x86
+Status: active
+Purpose: Trigger guest exit so that the host can check for pending
+interrupts on reentry.
+
+2. KVM_HC_MMU_OP
+------------------------
+Architecture: x86
+Status: deprecated.
+Purpose: Support MMU operations such as writing to PTE,
+flushing TLB, release PT.
+
+3. KVM_HC_FEATURES
+------------------------
+Architecture: PPC
+Status: active
+Purpose: Expose hypercall availability to the guest. On x86 platforms, cpuid
+used to enumerate which hypercalls are available. On PPC, either device tree
+based lookup ( which is also what EPAPR dictates) OR KVM specific enumeration
+mechanism (which is this hypercall) can be used.
+
+4. KVM_HC_PPC_MAP_MAGIC_PAGE
+------------------------
+Architecture: PPC
+Status: active
+Purpose: To enable communication between the hypervisor and guest there is a
+shared page that contains parts of supervisor visible register state.
+The guest can map this shared page to access its supervisor register through
+memory using this hypercall.
+
+5. KVM_HC_KICK_CPU
+------------------------
+Architecture: x86
+Status: active
+Purpose: Hypercall used to wakeup a vcpu from HLT state
+Usage example : A vcpu of a paravirtualized guest that is busywaiting in guest
+kernel mode for an event to occur (ex: a spinlock to become available) can
+execute HLT instruction once it has busy-waited for more than a threshold
+time-interval. Execution of HLT instruction would cause the hypervisor to put
+the vcpu to sleep until occurrence of an appropriate event. Another vcpu of the
+same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
+specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
+is used in the hypercall for future use.
+
+
+6. KVM_HC_CLOCK_PAIRING
+------------------------
+Architecture: x86
+Status: active
+Purpose: Hypercall used to synchronize host and guest clocks.
+Usage:
+
+a0: guest physical address where host copies
+"struct kvm_clock_offset" structure.
+
+a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
+is supported (corresponding to the host's CLOCK_REALTIME clock).
+
+ struct kvm_clock_pairing {
+ __s64 sec;
+ __s64 nsec;
+ __u64 tsc;
+ __u32 flags;
+ __u32 pad[9];
+ };
+
+ Where:
+ * sec: seconds from clock_type clock.
+ * nsec: nanoseconds from clock_type clock.
+ * tsc: guest TSC value used to calculate sec/nsec pair
+ * flags: flags, unused (0) at the moment.
+
+The hypercall lets a guest compute a precise timestamp across
+host and guest. The guest can use the returned TSC value to
+compute the CLOCK_REALTIME for its clock, at the same instant.
+
+Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
+or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
+
+6. KVM_HC_SEND_IPI
+------------------------
+Architecture: x86
+Status: active
+Purpose: Send IPIs to multiple vCPUs.
+
+a0: lower part of the bitmap of destination APIC IDs
+a1: higher part of the bitmap of destination APIC IDs
+a2: the lowest APIC ID in bitmap
+a3: APIC ICR
+
+The hypercall lets a guest send multicast IPIs, with at most 128
+128 destinations per hypercall in 64-bit mode and 64 vCPUs per
+hypercall in 32-bit mode. The destinations are represented by a
+bitmap contained in the first two arguments (a0 and a1). Bit 0 of
+a0 corresponds to the APIC ID in the third argument (a2), bit 1
+corresponds to the APIC ID a2+1, and so on.
+
+Returns the number of CPUs to which the IPIs were delivered successfully.
+
+7. KVM_HC_SCHED_YIELD
+------------------------
+Architecture: x86
+Status: active
+Purpose: Hypercall used to yield if the IPI target vCPU is preempted
+
+a0: destination APIC ID
+
+Usage example: When sending a call-function IPI-many to vCPUs, yield if
+any of the IPI target vCPUs was preempted.
--- /dev/null
+.. SPDX-License-Identifier: GPL-2.0
+
+===
+KVM
+===
+
+.. toctree::
+ :maxdepth: 2
+
+ amd-memory-encryption
+ cpuid
--- /dev/null
+KVM Lock Overview
+=================
+
+1. Acquisition Orders
+---------------------
+
+The acquisition orders for mutexes are as follows:
+
+- kvm->lock is taken outside vcpu->mutex
+
+- kvm->lock is taken outside kvm->slots_lock and kvm->irq_lock
+
+- kvm->slots_lock is taken outside kvm->irq_lock, though acquiring
+ them together is quite rare.
+
+On x86, vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock.
+
+Everything else is a leaf: no other lock is taken inside the critical
+sections.
+
+2: Exception
+------------
+
+Fast page fault:
+
+Fast page fault is the fast path which fixes the guest page fault out of
+the mmu-lock on x86. Currently, the page fault can be fast in one of the
+following two cases:
+
+1. Access Tracking: The SPTE is not present, but it is marked for access
+tracking i.e. the SPTE_SPECIAL_MASK is set. That means we need to
+restore the saved R/X bits. This is described in more detail later below.
+
+2. Write-Protection: The SPTE is present and the fault is
+caused by write-protect. That means we just need to change the W bit of the
+spte.
+
+What we use to avoid all the race is the SPTE_HOST_WRITEABLE bit and
+SPTE_MMU_WRITEABLE bit on the spte:
+- SPTE_HOST_WRITEABLE means the gfn is writable on host.
+- SPTE_MMU_WRITEABLE means the gfn is writable on mmu. The bit is set when
+ the gfn is writable on guest mmu and it is not write-protected by shadow
+ page write-protection.
+
+On fast page fault path, we will use cmpxchg to atomically set the spte W
+bit if spte.SPTE_HOST_WRITEABLE = 1 and spte.SPTE_WRITE_PROTECT = 1, or
+restore the saved R/X bits if VMX_EPT_TRACK_ACCESS mask is set, or both. This
+is safe because whenever changing these bits can be detected by cmpxchg.
+
+But we need carefully check these cases:
+1): The mapping from gfn to pfn
+The mapping from gfn to pfn may be changed since we can only ensure the pfn
+is not changed during cmpxchg. This is a ABA problem, for example, below case
+will happen:
+
+At the beginning:
+gpte = gfn1
+gfn1 is mapped to pfn1 on host
+spte is the shadow page table entry corresponding with gpte and
+spte = pfn1
+
+ VCPU 0 VCPU0
+on fast page fault path:
+
+ old_spte = *spte;
+ pfn1 is swapped out:
+ spte = 0;
+
+ pfn1 is re-alloced for gfn2.
+
+ gpte is changed to point to
+ gfn2 by the guest:
+ spte = pfn1;
+
+ if (cmpxchg(spte, old_spte, old_spte+W)
+ mark_page_dirty(vcpu->kvm, gfn1)
+ OOPS!!!
+
+We dirty-log for gfn1, that means gfn2 is lost in dirty-bitmap.
+
+For direct sp, we can easily avoid it since the spte of direct sp is fixed
+to gfn. For indirect sp, before we do cmpxchg, we call gfn_to_pfn_atomic()
+to pin gfn to pfn, because after gfn_to_pfn_atomic():
+- We have held the refcount of pfn that means the pfn can not be freed and
+ be reused for another gfn.
+- The pfn is writable that means it can not be shared between different gfns
+ by KSM.
+
+Then, we can ensure the dirty bitmaps is correctly set for a gfn.
+
+Currently, to simplify the whole things, we disable fast page fault for
+indirect shadow page.
+
+2): Dirty bit tracking
+In the origin code, the spte can be fast updated (non-atomically) if the
+spte is read-only and the Accessed bit has already been set since the
+Accessed bit and Dirty bit can not be lost.
+
+But it is not true after fast page fault since the spte can be marked
+writable between reading spte and updating spte. Like below case:
+
+At the beginning:
+spte.W = 0
+spte.Accessed = 1
+
+ VCPU 0 VCPU0
+In mmu_spte_clear_track_bits():
+
+ old_spte = *spte;
+
+ /* 'if' condition is satisfied. */
+ if (old_spte.Accessed == 1 &&
+ old_spte.W == 0)
+ spte = 0ull;
+ on fast page fault path:
+ spte.W = 1
+ memory write on the spte:
+ spte.Dirty = 1
+
+
+ else
+ old_spte = xchg(spte, 0ull)
+
+
+ if (old_spte.Accessed == 1)
+ kvm_set_pfn_accessed(spte.pfn);
+ if (old_spte.Dirty == 1)
+ kvm_set_pfn_dirty(spte.pfn);
+ OOPS!!!
+
+The Dirty bit is lost in this case.
+
+In order to avoid this kind of issue, we always treat the spte as "volatile"
+if it can be updated out of mmu-lock, see spte_has_volatile_bits(), it means,
+the spte is always atomically updated in this case.
+
+3): flush tlbs due to spte updated
+If the spte is updated from writable to readonly, we should flush all TLBs,
+otherwise rmap_write_protect will find a read-only spte, even though the
+writable spte might be cached on a CPU's TLB.
+
+As mentioned before, the spte can be updated to writable out of mmu-lock on
+fast page fault path, in order to easily audit the path, we see if TLBs need
+be flushed caused by this reason in mmu_spte_update() since this is a common
+function to update spte (present -> present).
+
+Since the spte is "volatile" if it can be updated out of mmu-lock, we always
+atomically update the spte, the race caused by fast page fault can be avoided,
+See the comments in spte_has_volatile_bits() and mmu_spte_update().
+
+Lockless Access Tracking:
+
+This is used for Intel CPUs that are using EPT but do not support the EPT A/D
+bits. In this case, when the KVM MMU notifier is called to track accesses to a
+page (via kvm_mmu_notifier_clear_flush_young), it marks the PTE as not-present
+by clearing the RWX bits in the PTE and storing the original R & X bits in
+some unused/ignored bits. In addition, the SPTE_SPECIAL_MASK is also set on the
+PTE (using the ignored bit 62). When the VM tries to access the page later on,
+a fault is generated and the fast page fault mechanism described above is used
+to atomically restore the PTE to a Present state. The W bit is not saved when
+the PTE is marked for access tracking and during restoration to the Present
+state, the W bit is set depending on whether or not it was a write access. If
+it wasn't, then the W bit will remain clear until a write access happens, at
+which time it will be set using the Dirty tracking mechanism described above.
+
+3. Reference
+------------
+
+Name: kvm_lock
+Type: mutex
+Arch: any
+Protects: - vm_list
+
+Name: kvm_count_lock
+Type: raw_spinlock_t
+Arch: any
+Protects: - hardware virtualization enable/disable
+Comment: 'raw' because hardware enabling/disabling must be atomic /wrt
+ migration.
+
+Name: kvm_arch::tsc_write_lock
+Type: raw_spinlock
+Arch: x86
+Protects: - kvm_arch::{last_tsc_write,last_tsc_nsec,last_tsc_offset}
+ - tsc offset in vmcb
+Comment: 'raw' because updating the tsc offsets must not be preempted.
+
+Name: kvm->mmu_lock
+Type: spinlock_t
+Arch: any
+Protects: -shadow page/shadow tlb entry
+Comment: it is a spinlock since it is used in mmu notifier.
+
+Name: kvm->srcu
+Type: srcu lock
+Arch: any
+Protects: - kvm->memslots
+ - kvm->buses
+Comment: The srcu read lock must be held while accessing memslots (e.g.
+ when using gfn_to_* functions) and while accessing in-kernel
+ MMIO/PIO address->device structure mapping (kvm->buses).
+ The srcu index can be stored in kvm_vcpu->srcu_idx per vcpu
+ if it is needed by multiple functions.
+
+Name: blocked_vcpu_on_cpu_lock
+Type: spinlock_t
+Arch: x86
+Protects: blocked_vcpu_on_cpu
+Comment: This is a per-CPU lock and it is used for VT-d posted-interrupts.
+ When VT-d posted-interrupts is supported and the VM has assigned
+ devices, we put the blocked vCPU on the list blocked_vcpu_on_cpu
+ protected by blocked_vcpu_on_cpu_lock, when VT-d hardware issues
+ wakeup notification event since external interrupts from the
+ assigned devices happens, we will find the vCPU on the list to
+ wakeup.
--- /dev/null
+The x86 kvm shadow mmu
+======================
+
+The mmu (in arch/x86/kvm, files mmu.[ch] and paging_tmpl.h) is responsible
+for presenting a standard x86 mmu to the guest, while translating guest
+physical addresses to host physical addresses.
+
+The mmu code attempts to satisfy the following requirements:
+
+- correctness: the guest should not be able to determine that it is running
+ on an emulated mmu except for timing (we attempt to comply
+ with the specification, not emulate the characteristics of
+ a particular implementation such as tlb size)
+- security: the guest must not be able to touch host memory not assigned
+ to it
+- performance: minimize the performance penalty imposed by the mmu
+- scaling: need to scale to large memory and large vcpu guests
+- hardware: support the full range of x86 virtualization hardware
+- integration: Linux memory management code must be in control of guest memory
+ so that swapping, page migration, page merging, transparent
+ hugepages, and similar features work without change
+- dirty tracking: report writes to guest memory to enable live migration
+ and framebuffer-based displays
+- footprint: keep the amount of pinned kernel memory low (most memory
+ should be shrinkable)
+- reliability: avoid multipage or GFP_ATOMIC allocations
+
+Acronyms
+========
+
+pfn host page frame number
+hpa host physical address
+hva host virtual address
+gfn guest frame number
+gpa guest physical address
+gva guest virtual address
+ngpa nested guest physical address
+ngva nested guest virtual address
+pte page table entry (used also to refer generically to paging structure
+ entries)
+gpte guest pte (referring to gfns)
+spte shadow pte (referring to pfns)
+tdp two dimensional paging (vendor neutral term for NPT and EPT)
+
+Virtual and real hardware supported
+===================================
+
+The mmu supports first-generation mmu hardware, which allows an atomic switch
+of the current paging mode and cr3 during guest entry, as well as
+two-dimensional paging (AMD's NPT and Intel's EPT). The emulated hardware
+it exposes is the traditional 2/3/4 level x86 mmu, with support for global
+pages, pae, pse, pse36, cr0.wp, and 1GB pages. Emulated hardware also
+able to expose NPT capable hardware on NPT capable hosts.
+
+Translation
+===========
+
+The primary job of the mmu is to program the processor's mmu to translate
+addresses for the guest. Different translations are required at different
+times:
+
+- when guest paging is disabled, we translate guest physical addresses to
+ host physical addresses (gpa->hpa)
+- when guest paging is enabled, we translate guest virtual addresses, to
+ guest physical addresses, to host physical addresses (gva->gpa->hpa)
+- when the guest launches a guest of its own, we translate nested guest
+ virtual addresses, to nested guest physical addresses, to guest physical
+ addresses, to host physical addresses (ngva->ngpa->gpa->hpa)
+
+The primary challenge is to encode between 1 and 3 translations into hardware
+that support only 1 (traditional) and 2 (tdp) translations. When the
+number of required translations matches the hardware, the mmu operates in
+direct mode; otherwise it operates in shadow mode (see below).
+
+Memory
+======
+
+Guest memory (gpa) is part of the user address space of the process that is
+using kvm. Userspace defines the translation between guest addresses and user
+addresses (gpa->hva); note that two gpas may alias to the same hva, but not
+vice versa.
+
+These hvas may be backed using any method available to the host: anonymous
+memory, file backed memory, and device memory. Memory might be paged by the
+host at any time.
+
+Events
+======
+
+The mmu is driven by events, some from the guest, some from the host.
+
+Guest generated events:
+- writes to control registers (especially cr3)
+- invlpg/invlpga instruction execution
+- access to missing or protected translations
+
+Host generated events:
+- changes in the gpa->hpa translation (either through gpa->hva changes or
+ through hva->hpa changes)
+- memory pressure (the shrinker)
+
+Shadow pages
+============
+
+The principal data structure is the shadow page, 'struct kvm_mmu_page'. A
+shadow page contains 512 sptes, which can be either leaf or nonleaf sptes. A
+shadow page may contain a mix of leaf and nonleaf sptes.
+
+A nonleaf spte allows the hardware mmu to reach the leaf pages and
+is not related to a translation directly. It points to other shadow pages.
+
+A leaf spte corresponds to either one or two translations encoded into
+one paging structure entry. These are always the lowest level of the
+translation stack, with optional higher level translations left to NPT/EPT.
+Leaf ptes point at guest pages.
+
+The following table shows translations encoded by leaf ptes, with higher-level
+translations in parentheses:
+
+ Non-nested guests:
+ nonpaging: gpa->hpa
+ paging: gva->gpa->hpa
+ paging, tdp: (gva->)gpa->hpa
+ Nested guests:
+ non-tdp: ngva->gpa->hpa (*)
+ tdp: (ngva->)ngpa->gpa->hpa
+
+(*) the guest hypervisor will encode the ngva->gpa translation into its page
+ tables if npt is not present
+
+Shadow pages contain the following information:
+ role.level:
+ The level in the shadow paging hierarchy that this shadow page belongs to.
+ 1=4k sptes, 2=2M sptes, 3=1G sptes, etc.
+ role.direct:
+ If set, leaf sptes reachable from this page are for a linear range.
+ Examples include real mode translation, large guest pages backed by small
+ host pages, and gpa->hpa translations when NPT or EPT is active.
+ The linear range starts at (gfn << PAGE_SHIFT) and its size is determined
+ by role.level (2MB for first level, 1GB for second level, 0.5TB for third
+ level, 256TB for fourth level)
+ If clear, this page corresponds to a guest page table denoted by the gfn
+ field.
+ role.quadrant:
+ When role.gpte_is_8_bytes=0, the guest uses 32-bit gptes while the host uses 64-bit
+ sptes. That means a guest page table contains more ptes than the host,
+ so multiple shadow pages are needed to shadow one guest page.
+ For first-level shadow pages, role.quadrant can be 0 or 1 and denotes the
+ first or second 512-gpte block in the guest page table. For second-level
+ page tables, each 32-bit gpte is converted to two 64-bit sptes
+ (since each first-level guest page is shadowed by two first-level
+ shadow pages) so role.quadrant takes values in the range 0..3. Each
+ quadrant maps 1GB virtual address space.
+ role.access:
+ Inherited guest access permissions in the form uwx. Note execute
+ permission is positive, not negative.
+ role.invalid:
+ The page is invalid and should not be used. It is a root page that is
+ currently pinned (by a cpu hardware register pointing to it); once it is
+ unpinned it will be destroyed.
+ role.gpte_is_8_bytes:
+ Reflects the size of the guest PTE for which the page is valid, i.e. '1'
+ if 64-bit gptes are in use, '0' if 32-bit gptes are in use.
+ role.nxe:
+ Contains the value of efer.nxe for which the page is valid.
+ role.cr0_wp:
+ Contains the value of cr0.wp for which the page is valid.
+ role.smep_andnot_wp:
+ Contains the value of cr4.smep && !cr0.wp for which the page is valid
+ (pages for which this is true are different from other pages; see the
+ treatment of cr0.wp=0 below).
+ role.smap_andnot_wp:
+ Contains the value of cr4.smap && !cr0.wp for which the page is valid
+ (pages for which this is true are different from other pages; see the
+ treatment of cr0.wp=0 below).
+ role.ept_sp:
+ This is a virtual flag to denote a shadowed nested EPT page. ept_sp
+ is true if "cr0_wp && smap_andnot_wp", an otherwise invalid combination.
+ role.smm:
+ Is 1 if the page is valid in system management mode. This field
+ determines which of the kvm_memslots array was used to build this
+ shadow page; it is also used to go back from a struct kvm_mmu_page
+ to a memslot, through the kvm_memslots_for_spte_role macro and
+ __gfn_to_memslot.
+ role.ad_disabled:
+ Is 1 if the MMU instance cannot use A/D bits. EPT did not have A/D
+ bits before Haswell; shadow EPT page tables also cannot use A/D bits
+ if the L1 hypervisor does not enable them.
+ gfn:
+ Either the guest page table containing the translations shadowed by this
+ page, or the base page frame for linear translations. See role.direct.
+ spt:
+ A pageful of 64-bit sptes containing the translations for this page.
+ Accessed by both kvm and hardware.
+ The page pointed to by spt will have its page->private pointing back
+ at the shadow page structure.
+ sptes in spt point either at guest pages, or at lower-level shadow pages.
+ Specifically, if sp1 and sp2 are shadow pages, then sp1->spt[n] may point
+ at __pa(sp2->spt). sp2 will point back at sp1 through parent_pte.
+ The spt array forms a DAG structure with the shadow page as a node, and
+ guest pages as leaves.
+ gfns:
+ An array of 512 guest frame numbers, one for each present pte. Used to
+ perform a reverse map from a pte to a gfn. When role.direct is set, any
+ element of this array can be calculated from the gfn field when used, in
+ this case, the array of gfns is not allocated. See role.direct and gfn.
+ root_count:
+ A counter keeping track of how many hardware registers (guest cr3 or
+ pdptrs) are now pointing at the page. While this counter is nonzero, the
+ page cannot be destroyed. See role.invalid.
+ parent_ptes:
+ The reverse mapping for the pte/ptes pointing at this page's spt. If
+ parent_ptes bit 0 is zero, only one spte points at this page and
+ parent_ptes points at this single spte, otherwise, there exists multiple
+ sptes pointing at this page and (parent_ptes & ~0x1) points at a data
+ structure with a list of parent sptes.
+ unsync:
+ If true, then the translations in this page may not match the guest's
+ translation. This is equivalent to the state of the tlb when a pte is
+ changed but before the tlb entry is flushed. Accordingly, unsync ptes
+ are synchronized when the guest executes invlpg or flushes its tlb by
+ other means. Valid for leaf pages.
+ unsync_children:
+ How many sptes in the page point at pages that are unsync (or have
+ unsynchronized children).
+ unsync_child_bitmap:
+ A bitmap indicating which sptes in spt point (directly or indirectly) at
+ pages that may be unsynchronized. Used to quickly locate all unsychronized
+ pages reachable from a given page.
+ clear_spte_count:
+ Only present on 32-bit hosts, where a 64-bit spte cannot be written
+ atomically. The reader uses this while running out of the MMU lock
+ to detect in-progress updates and retry them until the writer has
+ finished the write.
+ write_flooding_count:
+ A guest may write to a page table many times, causing a lot of
+ emulations if the page needs to be write-protected (see "Synchronized
+ and unsynchronized pages" below). Leaf pages can be unsynchronized
+ so that they do not trigger frequent emulation, but this is not
+ possible for non-leafs. This field counts the number of emulations
+ since the last time the page table was actually used; if emulation
+ is triggered too frequently on this page, KVM will unmap the page
+ to avoid emulation in the future.
+
+Reverse map
+===========
+
+The mmu maintains a reverse mapping whereby all ptes mapping a page can be
+reached given its gfn. This is used, for example, when swapping out a page.
+
+Synchronized and unsynchronized pages
+=====================================
+
+The guest uses two events to synchronize its tlb and page tables: tlb flushes
+and page invalidations (invlpg).
+
+A tlb flush means that we need to synchronize all sptes reachable from the
+guest's cr3. This is expensive, so we keep all guest page tables write
+protected, and synchronize sptes to gptes when a gpte is written.
+
+A special case is when a guest page table is reachable from the current
+guest cr3. In this case, the guest is obliged to issue an invlpg instruction
+before using the translation. We take advantage of that by removing write
+protection from the guest page, and allowing the guest to modify it freely.
+We synchronize modified gptes when the guest invokes invlpg. This reduces
+the amount of emulation we have to do when the guest modifies multiple gptes,
+or when the a guest page is no longer used as a page table and is used for
+random guest data.
+
+As a side effect we have to resynchronize all reachable unsynchronized shadow
+pages on a tlb flush.
+
+
+Reaction to events
+==================
+
+- guest page fault (or npt page fault, or ept violation)
+
+This is the most complicated event. The cause of a page fault can be:
+
+ - a true guest fault (the guest translation won't allow the access) (*)
+ - access to a missing translation
+ - access to a protected translation
+ - when logging dirty pages, memory is write protected
+ - synchronized shadow pages are write protected (*)
+ - access to untranslatable memory (mmio)
+
+ (*) not applicable in direct mode
+
+Handling a page fault is performed as follows:
+
+ - if the RSV bit of the error code is set, the page fault is caused by guest
+ accessing MMIO and cached MMIO information is available.
+ - walk shadow page table
+ - check for valid generation number in the spte (see "Fast invalidation of
+ MMIO sptes" below)
+ - cache the information to vcpu->arch.mmio_gva, vcpu->arch.access and
+ vcpu->arch.mmio_gfn, and call the emulator
+ - If both P bit and R/W bit of error code are set, this could possibly
+ be handled as a "fast page fault" (fixed without taking the MMU lock). See
+ the description in Documentation/virt/kvm/locking.txt.
+ - if needed, walk the guest page tables to determine the guest translation
+ (gva->gpa or ngpa->gpa)
+ - if permissions are insufficient, reflect the fault back to the guest
+ - determine the host page
+ - if this is an mmio request, there is no host page; cache the info to
+ vcpu->arch.mmio_gva, vcpu->arch.access and vcpu->arch.mmio_gfn
+ - walk the shadow page table to find the spte for the translation,
+ instantiating missing intermediate page tables as necessary
+ - If this is an mmio request, cache the mmio info to the spte and set some
+ reserved bit on the spte (see callers of kvm_mmu_set_mmio_spte_mask)
+ - try to unsynchronize the page
+ - if successful, we can let the guest continue and modify the gpte
+ - emulate the instruction
+ - if failed, unshadow the page and let the guest continue
+ - update any translations that were modified by the instruction
+
+invlpg handling:
+
+ - walk the shadow page hierarchy and drop affected translations
+ - try to reinstantiate the indicated translation in the hope that the
+ guest will use it in the near future
+
+Guest control register updates:
+
+- mov to cr3
+ - look up new shadow roots
+ - synchronize newly reachable shadow pages
+
+- mov to cr0/cr4/efer
+ - set up mmu context for new paging mode
+ - look up new shadow roots
+ - synchronize newly reachable shadow pages
+
+Host translation updates:
+
+ - mmu notifier called with updated hva
+ - look up affected sptes through reverse map
+ - drop (or update) translations
+
+Emulating cr0.wp
+================
+
+If tdp is not enabled, the host must keep cr0.wp=1 so page write protection
+works for the guest kernel, not guest guest userspace. When the guest
+cr0.wp=1, this does not present a problem. However when the guest cr0.wp=0,
+we cannot map the permissions for gpte.u=1, gpte.w=0 to any spte (the
+semantics require allowing any guest kernel access plus user read access).
+
+We handle this by mapping the permissions to two possible sptes, depending
+on fault type:
+
+- kernel write fault: spte.u=0, spte.w=1 (allows full kernel access,
+ disallows user access)
+- read fault: spte.u=1, spte.w=0 (allows full read access, disallows kernel
+ write access)
+
+(user write faults generate a #PF)
+
+In the first case there are two additional complications:
+- if CR4.SMEP is enabled: since we've turned the page into a kernel page,
+ the kernel may now execute it. We handle this by also setting spte.nx.
+ If we get a user fetch or read fault, we'll change spte.u=1 and
+ spte.nx=gpte.nx back. For this to work, KVM forces EFER.NX to 1 when
+ shadow paging is in use.
+- if CR4.SMAP is disabled: since the page has been changed to a kernel
+ page, it can not be reused when CR4.SMAP is enabled. We set
+ CR4.SMAP && !CR0.WP into shadow page's role to avoid this case. Note,
+ here we do not care the case that CR4.SMAP is enabled since KVM will
+ directly inject #PF to guest due to failed permission check.
+
+To prevent an spte that was converted into a kernel page with cr0.wp=0
+from being written by the kernel after cr0.wp has changed to 1, we make
+the value of cr0.wp part of the page role. This means that an spte created
+with one value of cr0.wp cannot be used when cr0.wp has a different value -
+it will simply be missed by the shadow page lookup code. A similar issue
+exists when an spte created with cr0.wp=0 and cr4.smep=0 is used after
+changing cr4.smep to 1. To avoid this, the value of !cr0.wp && cr4.smep
+is also made a part of the page role.
+
+Large pages
+===========
+
+The mmu supports all combinations of large and small guest and host pages.
+Supported page sizes include 4k, 2M, 4M, and 1G. 4M pages are treated as
+two separate 2M pages, on both guest and host, since the mmu always uses PAE
+paging.
+
+To instantiate a large spte, four constraints must be satisfied:
+
+- the spte must point to a large host page
+- the guest pte must be a large pte of at least equivalent size (if tdp is
+ enabled, there is no guest pte and this condition is satisfied)
+- if the spte will be writeable, the large page frame may not overlap any
+ write-protected pages
+- the guest page must be wholly contained by a single memory slot
+
+To check the last two conditions, the mmu maintains a ->disallow_lpage set of
+arrays for each memory slot and large page size. Every write protected page
+causes its disallow_lpage to be incremented, thus preventing instantiation of
+a large spte. The frames at the end of an unaligned memory slot have
+artificially inflated ->disallow_lpages so they can never be instantiated.
+
+Fast invalidation of MMIO sptes
+===============================
+
+As mentioned in "Reaction to events" above, kvm will cache MMIO
+information in leaf sptes. When a new memslot is added or an existing
+memslot is changed, this information may become stale and needs to be
+invalidated. This also needs to hold the MMU lock while walking all
+shadow pages, and is made more scalable with a similar technique.
+
+MMIO sptes have a few spare bits, which are used to store a
+generation number. The global generation number is stored in
+kvm_memslots(kvm)->generation, and increased whenever guest memory info
+changes.
+
+When KVM finds an MMIO spte, it checks the generation number of the spte.
+If the generation number of the spte does not equal the global generation
+number, it will ignore the cached MMIO information and handle the page
+fault through the slow path.
+
+Since only 19 bits are used to store generation-number on mmio spte, all
+pages are zapped when there is an overflow.
+
+Unfortunately, a single memory access might access kvm_memslots(kvm) multiple
+times, the last one happening when the generation number is retrieved and
+stored into the MMIO spte. Thus, the MMIO spte might be created based on
+out-of-date information, but with an up-to-date generation number.
+
+To avoid this, the generation number is incremented again after synchronize_srcu
+returns; thus, bit 63 of kvm_memslots(kvm)->generation set to 1 only during a
+memslot update, while some SRCU readers might be using the old copy. We do not
+want to use an MMIO sptes created with an odd generation number, and we can do
+this without losing a bit in the MMIO spte. The "update in-progress" bit of the
+generation is not stored in MMIO spte, and is so is implicitly zero when the
+generation is extracted out of the spte. If KVM is unlucky and creates an MMIO
+spte while an update is in-progress, the next access to the spte will always be
+a cache miss. For example, a subsequent access during the update window will
+miss due to the in-progress flag diverging, while an access after the update
+window closes will have a higher generation number (as compared to the spte).
+
+
+Further reading
+===============
+
+- NPT presentation from KVM Forum 2008
+ http://www.linux-kvm.org/images/c/c8/KvmForum2008%24kdf2008_21.pdf
+
--- /dev/null
+KVM-specific MSRs.
+Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010
+=====================================================
+
+KVM makes use of some custom MSRs to service some requests.
+
+Custom MSRs have a range reserved for them, that goes from
+0x4b564d00 to 0x4b564dff. There are MSRs outside this area,
+but they are deprecated and their use is discouraged.
+
+Custom MSR list
+--------
+
+The current supported Custom MSR list is:
+
+MSR_KVM_WALL_CLOCK_NEW: 0x4b564d00
+
+ data: 4-byte alignment physical address of a memory area which must be
+ in guest RAM. This memory is expected to hold a copy of the following
+ structure:
+
+ struct pvclock_wall_clock {
+ u32 version;
+ u32 sec;
+ u32 nsec;
+ } __attribute__((__packed__));
+
+ whose data will be filled in by the hypervisor. The hypervisor is only
+ guaranteed to update this data at the moment of MSR write.
+ Users that want to reliably query this information more than once have
+ to write more than once to this MSR. Fields have the following meanings:
+
+ version: guest has to check version before and after grabbing
+ time information and check that they are both equal and even.
+ An odd version indicates an in-progress update.
+
+ sec: number of seconds for wallclock at time of boot.
+
+ nsec: number of nanoseconds for wallclock at time of boot.
+
+ In order to get the current wallclock time, the system_time from
+ MSR_KVM_SYSTEM_TIME_NEW needs to be added.
+
+ Note that although MSRs are per-CPU entities, the effect of this
+ particular MSR is global.
+
+ Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
+ leaf prior to usage.
+
+MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
+
+ data: 4-byte aligned physical address of a memory area which must be in
+ guest RAM, plus an enable bit in bit 0. This memory is expected to hold
+ a copy of the following structure:
+
+ struct pvclock_vcpu_time_info {
+ u32 version;
+ u32 pad0;
+ u64 tsc_timestamp;
+ u64 system_time;
+ u32 tsc_to_system_mul;
+ s8 tsc_shift;
+ u8 flags;
+ u8 pad[2];
+ } __attribute__((__packed__)); /* 32 bytes */
+
+ whose data will be filled in by the hypervisor periodically. Only one
+ write, or registration, is needed for each VCPU. The interval between
+ updates of this structure is arbitrary and implementation-dependent.
+ The hypervisor may update this structure at any time it sees fit until
+ anything with bit0 == 0 is written to it.
+
+ Fields have the following meanings:
+
+ version: guest has to check version before and after grabbing
+ time information and check that they are both equal and even.
+ An odd version indicates an in-progress update.
+
+ tsc_timestamp: the tsc value at the current VCPU at the time
+ of the update of this structure. Guests can subtract this value
+ from current tsc to derive a notion of elapsed time since the
+ structure update.
+
+ system_time: a host notion of monotonic time, including sleep
+ time at the time this structure was last updated. Unit is
+ nanoseconds.
+
+ tsc_to_system_mul: multiplier to be used when converting
+ tsc-related quantity to nanoseconds
+
+ tsc_shift: shift to be used when converting tsc-related
+ quantity to nanoseconds. This shift will ensure that
+ multiplication with tsc_to_system_mul does not overflow.
+ A positive value denotes a left shift, a negative value
+ a right shift.
+
+ The conversion from tsc to nanoseconds involves an additional
+ right shift by 32 bits. With this information, guests can
+ derive per-CPU time by doing:
+
+ time = (current_tsc - tsc_timestamp)
+ if (tsc_shift >= 0)
+ time <<= tsc_shift;
+ else
+ time >>= -tsc_shift;
+ time = (time * tsc_to_system_mul) >> 32
+ time = time + system_time
+
+ flags: bits in this field indicate extended capabilities
+ coordinated between the guest and the hypervisor. Availability
+ of specific flags has to be checked in 0x40000001 cpuid leaf.
+ Current flags are:
+
+ flag bit | cpuid bit | meaning
+ -------------------------------------------------------------
+ | | time measures taken across
+ 0 | 24 | multiple cpus are guaranteed to
+ | | be monotonic
+ -------------------------------------------------------------
+ | | guest vcpu has been paused by
+ 1 | N/A | the host
+ | | See 4.70 in api.txt
+ -------------------------------------------------------------
+
+ Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
+ leaf prior to usage.
+
+
+MSR_KVM_WALL_CLOCK: 0x11
+
+ data and functioning: same as MSR_KVM_WALL_CLOCK_NEW. Use that instead.
+
+ This MSR falls outside the reserved KVM range and may be removed in the
+ future. Its usage is deprecated.
+
+ Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
+ leaf prior to usage.
+
+MSR_KVM_SYSTEM_TIME: 0x12
+
+ data and functioning: same as MSR_KVM_SYSTEM_TIME_NEW. Use that instead.
+
+ This MSR falls outside the reserved KVM range and may be removed in the
+ future. Its usage is deprecated.
+
+ Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
+ leaf prior to usage.
+
+ The suggested algorithm for detecting kvmclock presence is then:
+
+ if (!kvm_para_available()) /* refer to cpuid.txt */
+ return NON_PRESENT;
+
+ flags = cpuid_eax(0x40000001);
+ if (flags & 3) {
+ msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
+ msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
+ return PRESENT;
+ } else if (flags & 0) {
+ msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
+ msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
+ return PRESENT;
+ } else
+ return NON_PRESENT;
+
+MSR_KVM_ASYNC_PF_EN: 0x4b564d02
+ data: Bits 63-6 hold 64-byte aligned physical address of a
+ 64 byte memory area which must be in guest RAM and must be
+ zeroed. Bits 5-3 are reserved and should be zero. Bit 0 is 1
+ when asynchronous page faults are enabled on the vcpu 0 when
+ disabled. Bit 1 is 1 if asynchronous page faults can be injected
+ when vcpu is in cpl == 0. Bit 2 is 1 if asynchronous page faults
+ are delivered to L1 as #PF vmexits. Bit 2 can be set only if
+ KVM_FEATURE_ASYNC_PF_VMEXIT is present in CPUID.
+
+ First 4 byte of 64 byte memory location will be written to by
+ the hypervisor at the time of asynchronous page fault (APF)
+ injection to indicate type of asynchronous page fault. Value
+ of 1 means that the page referred to by the page fault is not
+ present. Value 2 means that the page is now available. Disabling
+ interrupt inhibits APFs. Guest must not enable interrupt
+ before the reason is read, or it may be overwritten by another
+ APF. Since APF uses the same exception vector as regular page
+ fault guest must reset the reason to 0 before it does
+ something that can generate normal page fault. If during page
+ fault APF reason is 0 it means that this is regular page
+ fault.
+
+ During delivery of type 1 APF cr2 contains a token that will
+ be used to notify a guest when missing page becomes
+ available. When page becomes available type 2 APF is sent with
+ cr2 set to the token associated with the page. There is special
+ kind of token 0xffffffff which tells vcpu that it should wake
+ up all processes waiting for APFs and no individual type 2 APFs
+ will be sent.
+
+ If APF is disabled while there are outstanding APFs, they will
+ not be delivered.
+
+ Currently type 2 APF will be always delivered on the same vcpu as
+ type 1 was, but guest should not rely on that.
+
+MSR_KVM_STEAL_TIME: 0x4b564d03
+
+ data: 64-byte alignment physical address of a memory area which must be
+ in guest RAM, plus an enable bit in bit 0. This memory is expected to
+ hold a copy of the following structure:
+
+ struct kvm_steal_time {
+ __u64 steal;
+ __u32 version;
+ __u32 flags;
+ __u8 preempted;
+ __u8 u8_pad[3];
+ __u32 pad[11];
+ }
+
+ whose data will be filled in by the hypervisor periodically. Only one
+ write, or registration, is needed for each VCPU. The interval between
+ updates of this structure is arbitrary and implementation-dependent.
+ The hypervisor may update this structure at any time it sees fit until
+ anything with bit0 == 0 is written to it. Guest is required to make sure
+ this structure is initialized to zero.
+
+ Fields have the following meanings:
+
+ version: a sequence counter. In other words, guest has to check
+ this field before and after grabbing time information and make
+ sure they are both equal and even. An odd version indicates an
+ in-progress update.
+
+ flags: At this point, always zero. May be used to indicate
+ changes in this structure in the future.
+
+ steal: the amount of time in which this vCPU did not run, in
+ nanoseconds. Time during which the vcpu is idle, will not be
+ reported as steal time.
+
+ preempted: indicate the vCPU who owns this struct is running or
+ not. Non-zero values mean the vCPU has been preempted. Zero
+ means the vCPU is not preempted. NOTE, it is always zero if the
+ the hypervisor doesn't support this field.
+
+MSR_KVM_EOI_EN: 0x4b564d04
+ data: Bit 0 is 1 when PV end of interrupt is enabled on the vcpu; 0
+ when disabled. Bit 1 is reserved and must be zero. When PV end of
+ interrupt is enabled (bit 0 set), bits 63-2 hold a 4-byte aligned
+ physical address of a 4 byte memory area which must be in guest RAM and
+ must be zeroed.
+
+ The first, least significant bit of 4 byte memory location will be
+ written to by the hypervisor, typically at the time of interrupt
+ injection. Value of 1 means that guest can skip writing EOI to the apic
+ (using MSR or MMIO write); instead, it is sufficient to signal
+ EOI by clearing the bit in guest memory - this location will
+ later be polled by the hypervisor.
+ Value of 0 means that the EOI write is required.
+
+ It is always safe for the guest to ignore the optimization and perform
+ the APIC EOI write anyway.
+
+ Hypervisor is guaranteed to only modify this least
+ significant bit while in the current VCPU context, this means that
+ guest does not need to use either lock prefix or memory ordering
+ primitives to synchronise with the hypervisor.
+
+ However, hypervisor can set and clear this memory bit at any time:
+ therefore to make sure hypervisor does not interrupt the
+ guest and clear the least significant bit in the memory area
+ in the window between guest testing it to detect
+ whether it can skip EOI apic write and between guest
+ clearing it to signal EOI to the hypervisor,
+ guest must both read the least significant bit in the memory area and
+ clear it using a single CPU instruction, such as test and clear, or
+ compare and exchange.
+
+MSR_KVM_POLL_CONTROL: 0x4b564d05
+ Control host-side polling.
+
+ data: Bit 0 enables (1) or disables (0) host-side HLT polling logic.
+
+ KVM guests can request the host not to poll on HLT, for example if
+ they are performing polling themselves.
+
--- /dev/null
+Nested VMX
+==========
+
+Overview
+---------
+
+On Intel processors, KVM uses Intel's VMX (Virtual-Machine eXtensions)
+to easily and efficiently run guest operating systems. Normally, these guests
+*cannot* themselves be hypervisors running their own guests, because in VMX,
+guests cannot use VMX instructions.
+
+The "Nested VMX" feature adds this missing capability - of running guest
+hypervisors (which use VMX) with their own nested guests. It does so by
+allowing a guest to use VMX instructions, and correctly and efficiently
+emulating them using the single level of VMX available in the hardware.
+
+We describe in much greater detail the theory behind the nested VMX feature,
+its implementation and its performance characteristics, in the OSDI 2010 paper
+"The Turtles Project: Design and Implementation of Nested Virtualization",
+available at:
+
+ http://www.usenix.org/events/osdi10/tech/full_papers/Ben-Yehuda.pdf
+
+
+Terminology
+-----------
+
+Single-level virtualization has two levels - the host (KVM) and the guests.
+In nested virtualization, we have three levels: The host (KVM), which we call
+L0, the guest hypervisor, which we call L1, and its nested guest, which we
+call L2.
+
+
+Running nested VMX
+------------------
+
+The nested VMX feature is disabled by default. It can be enabled by giving
+the "nested=1" option to the kvm-intel module.
+
+No modifications are required to user space (qemu). However, qemu's default
+emulated CPU type (qemu64) does not list the "VMX" CPU feature, so it must be
+explicitly enabled, by giving qemu one of the following options:
+
+ -cpu host (emulated CPU has all features of the real CPU)
+
+ -cpu qemu64,+vmx (add just the vmx feature to a named CPU type)
+
+
+ABIs
+----
+
+Nested VMX aims to present a standard and (eventually) fully-functional VMX
+implementation for the a guest hypervisor to use. As such, the official
+specification of the ABI that it provides is Intel's VMX specification,
+namely volume 3B of their "Intel 64 and IA-32 Architectures Software
+Developer's Manual". Not all of VMX's features are currently fully supported,
+but the goal is to eventually support them all, starting with the VMX features
+which are used in practice by popular hypervisors (KVM and others).
+
+As a VMX implementation, nested VMX presents a VMCS structure to L1.
+As mandated by the spec, other than the two fields revision_id and abort,
+this structure is *opaque* to its user, who is not supposed to know or care
+about its internal structure. Rather, the structure is accessed through the
+VMREAD and VMWRITE instructions.
+Still, for debugging purposes, KVM developers might be interested to know the
+internals of this structure; This is struct vmcs12 from arch/x86/kvm/vmx.c.
+
+The name "vmcs12" refers to the VMCS that L1 builds for L2. In the code we
+also have "vmcs01", the VMCS that L0 built for L1, and "vmcs02" is the VMCS
+which L0 builds to actually run L2 - how this is done is explained in the
+aforementioned paper.
+
+For convenience, we repeat the content of struct vmcs12 here. If the internals
+of this structure changes, this can break live migration across KVM versions.
+VMCS12_REVISION (from vmx.c) should be changed if struct vmcs12 or its inner
+struct shadow_vmcs is ever changed.
+
+ typedef u64 natural_width;
+ struct __packed vmcs12 {
+ /* According to the Intel spec, a VMCS region must start with
+ * these two user-visible fields */
+ u32 revision_id;
+ u32 abort;
+
+ u32 launch_state; /* set to 0 by VMCLEAR, to 1 by VMLAUNCH */
+ u32 padding[7]; /* room for future expansion */
+
+ u64 io_bitmap_a;
+ u64 io_bitmap_b;
+ u64 msr_bitmap;
+ u64 vm_exit_msr_store_addr;
+ u64 vm_exit_msr_load_addr;
+ u64 vm_entry_msr_load_addr;
+ u64 tsc_offset;
+ u64 virtual_apic_page_addr;
+ u64 apic_access_addr;
+ u64 ept_pointer;
+ u64 guest_physical_address;
+ u64 vmcs_link_pointer;
+ u64 guest_ia32_debugctl;
+ u64 guest_ia32_pat;
+ u64 guest_ia32_efer;
+ u64 guest_pdptr0;
+ u64 guest_pdptr1;
+ u64 guest_pdptr2;
+ u64 guest_pdptr3;
+ u64 host_ia32_pat;
+ u64 host_ia32_efer;
+ u64 padding64[8]; /* room for future expansion */
+ natural_width cr0_guest_host_mask;
+ natural_width cr4_guest_host_mask;
+ natural_width cr0_read_shadow;
+ natural_width cr4_read_shadow;
+ natural_width cr3_target_value0;
+ natural_width cr3_target_value1;
+ natural_width cr3_target_value2;
+ natural_width cr3_target_value3;
+ natural_width exit_qualification;
+ natural_width guest_linear_address;
+ natural_width guest_cr0;
+ natural_width guest_cr3;
+ natural_width guest_cr4;
+ natural_width guest_es_base;
+ natural_width guest_cs_base;
+ natural_width guest_ss_base;
+ natural_width guest_ds_base;
+ natural_width guest_fs_base;
+ natural_width guest_gs_base;
+ natural_width guest_ldtr_base;
+ natural_width guest_tr_base;
+ natural_width guest_gdtr_base;
+ natural_width guest_idtr_base;
+ natural_width guest_dr7;
+ natural_width guest_rsp;
+ natural_width guest_rip;
+ natural_width guest_rflags;
+ natural_width guest_pending_dbg_exceptions;
+ natural_width guest_sysenter_esp;
+ natural_width guest_sysenter_eip;
+ natural_width host_cr0;
+ natural_width host_cr3;
+ natural_width host_cr4;
+ natural_width host_fs_base;
+ natural_width host_gs_base;
+ natural_width host_tr_base;
+ natural_width host_gdtr_base;
+ natural_width host_idtr_base;
+ natural_width host_ia32_sysenter_esp;
+ natural_width host_ia32_sysenter_eip;
+ natural_width host_rsp;
+ natural_width host_rip;
+ natural_width paddingl[8]; /* room for future expansion */
+ u32 pin_based_vm_exec_control;
+ u32 cpu_based_vm_exec_control;
+ u32 exception_bitmap;
+ u32 page_fault_error_code_mask;
+ u32 page_fault_error_code_match;
+ u32 cr3_target_count;
+ u32 vm_exit_controls;
+ u32 vm_exit_msr_store_count;
+ u32 vm_exit_msr_load_count;
+ u32 vm_entry_controls;
+ u32 vm_entry_msr_load_count;
+ u32 vm_entry_intr_info_field;
+ u32 vm_entry_exception_error_code;
+ u32 vm_entry_instruction_len;
+ u32 tpr_threshold;
+ u32 secondary_vm_exec_control;
+ u32 vm_instruction_error;
+ u32 vm_exit_reason;
+ u32 vm_exit_intr_info;
+ u32 vm_exit_intr_error_code;
+ u32 idt_vectoring_info_field;
+ u32 idt_vectoring_error_code;
+ u32 vm_exit_instruction_len;
+ u32 vmx_instruction_info;
+ u32 guest_es_limit;
+ u32 guest_cs_limit;
+ u32 guest_ss_limit;
+ u32 guest_ds_limit;
+ u32 guest_fs_limit;
+ u32 guest_gs_limit;
+ u32 guest_ldtr_limit;
+ u32 guest_tr_limit;
+ u32 guest_gdtr_limit;
+ u32 guest_idtr_limit;
+ u32 guest_es_ar_bytes;
+ u32 guest_cs_ar_bytes;
+ u32 guest_ss_ar_bytes;
+ u32 guest_ds_ar_bytes;
+ u32 guest_fs_ar_bytes;
+ u32 guest_gs_ar_bytes;
+ u32 guest_ldtr_ar_bytes;
+ u32 guest_tr_ar_bytes;
+ u32 guest_interruptibility_info;
+ u32 guest_activity_state;
+ u32 guest_sysenter_cs;
+ u32 host_ia32_sysenter_cs;
+ u32 padding32[8]; /* room for future expansion */
+ u16 virtual_processor_id;
+ u16 guest_es_selector;
+ u16 guest_cs_selector;
+ u16 guest_ss_selector;
+ u16 guest_ds_selector;
+ u16 guest_fs_selector;
+ u16 guest_gs_selector;
+ u16 guest_ldtr_selector;
+ u16 guest_tr_selector;
+ u16 host_es_selector;
+ u16 host_cs_selector;
+ u16 host_ss_selector;
+ u16 host_ds_selector;
+ u16 host_fs_selector;
+ u16 host_gs_selector;
+ u16 host_tr_selector;
+ };
+
+
+Authors
+-------
+
+These patches were written by:
+ Abel Gordon, abelg <at> il.ibm.com
+ Nadav Har'El, nyh <at> il.ibm.com
+ Orit Wasserman, oritw <at> il.ibm.com
+ Ben-Ami Yassor, benami <at> il.ibm.com
+ Muli Ben-Yehuda, muli <at> il.ibm.com
+
+With contributions by:
+ Anthony Liguori, aliguori <at> us.ibm.com
+ Mike Day, mdday <at> us.ibm.com
+ Michael Factor, factor <at> il.ibm.com
+ Zvi Dubitzky, dubi <at> il.ibm.com
+
+And valuable reviews by:
+ Avi Kivity, avi <at> redhat.com
+ Gleb Natapov, gleb <at> redhat.com
+ Marcelo Tosatti, mtosatti <at> redhat.com
+ Kevin Tian, kevin.tian <at> intel.com
+ and others.
--- /dev/null
+The PPC KVM paravirtual interface
+=================================
+
+The basic execution principle by which KVM on PowerPC works is to run all kernel
+space code in PR=1 which is user space. This way we trap all privileged
+instructions and can emulate them accordingly.
+
+Unfortunately that is also the downfall. There are quite some privileged
+instructions that needlessly return us to the hypervisor even though they
+could be handled differently.
+
+This is what the PPC PV interface helps with. It takes privileged instructions
+and transforms them into unprivileged ones with some help from the hypervisor.
+This cuts down virtualization costs by about 50% on some of my benchmarks.
+
+The code for that interface can be found in arch/powerpc/kernel/kvm*
+
+Querying for existence
+======================
+
+To find out if we're running on KVM or not, we leverage the device tree. When
+Linux is running on KVM, a node /hypervisor exists. That node contains a
+compatible property with the value "linux,kvm".
+
+Once you determined you're running under a PV capable KVM, you can now use
+hypercalls as described below.
+
+KVM hypercalls
+==============
+
+Inside the device tree's /hypervisor node there's a property called
+'hypercall-instructions'. This property contains at most 4 opcodes that make
+up the hypercall. To call a hypercall, just call these instructions.
+
+The parameters are as follows:
+
+ Register IN OUT
+
+ r0 - volatile
+ r3 1st parameter Return code
+ r4 2nd parameter 1st output value
+ r5 3rd parameter 2nd output value
+ r6 4th parameter 3rd output value
+ r7 5th parameter 4th output value
+ r8 6th parameter 5th output value
+ r9 7th parameter 6th output value
+ r10 8th parameter 7th output value
+ r11 hypercall number 8th output value
+ r12 - volatile
+
+Hypercall definitions are shared in generic code, so the same hypercall numbers
+apply for x86 and powerpc alike with the exception that each KVM hypercall
+also needs to be ORed with the KVM vendor code which is (42 << 16).
+
+Return codes can be as follows:
+
+ Code Meaning
+
+ 0 Success
+ 12 Hypercall not implemented
+ <0 Error
+
+The magic page
+==============
+
+To enable communication between the hypervisor and guest there is a new shared
+page that contains parts of supervisor visible register state. The guest can
+map this shared page using the KVM hypercall KVM_HC_PPC_MAP_MAGIC_PAGE.
+
+With this hypercall issued the guest always gets the magic page mapped at the
+desired location. The first parameter indicates the effective address when the
+MMU is enabled. The second parameter indicates the address in real mode, if
+applicable to the target. For now, we always map the page to -4096. This way we
+can access it using absolute load and store functions. The following
+instruction reads the first field of the magic page:
+
+ ld rX, -4096(0)
+
+The interface is designed to be extensible should there be need later to add
+additional registers to the magic page. If you add fields to the magic page,
+also define a new hypercall feature to indicate that the host can give you more
+registers. Only if the host supports the additional features, make use of them.
+
+The magic page layout is described by struct kvm_vcpu_arch_shared
+in arch/powerpc/include/asm/kvm_para.h.
+
+Magic page features
+===================
+
+When mapping the magic page using the KVM hypercall KVM_HC_PPC_MAP_MAGIC_PAGE,
+a second return value is passed to the guest. This second return value contains
+a bitmap of available features inside the magic page.
+
+The following enhancements to the magic page are currently available:
+
+ KVM_MAGIC_FEAT_SR Maps SR registers r/w in the magic page
+ KVM_MAGIC_FEAT_MAS0_TO_SPRG7 Maps MASn, ESR, PIR and high SPRGs
+
+For enhanced features in the magic page, please check for the existence of the
+feature before using them!
+
+Magic page flags
+================
+
+In addition to features that indicate whether a host is capable of a particular
+feature we also have a channel for a guest to tell the guest whether it's capable
+of something. This is what we call "flags".
+
+Flags are passed to the host in the low 12 bits of the Effective Address.
+
+The following flags are currently available for a guest to expose:
+
+ MAGIC_PAGE_FLAG_NOT_MAPPED_NX Guest handles NX bits correctly wrt magic page
+
+MSR bits
+========
+
+The MSR contains bits that require hypervisor intervention and bits that do
+not require direct hypervisor intervention because they only get interpreted
+when entering the guest or don't have any impact on the hypervisor's behavior.
+
+The following bits are safe to be set inside the guest:
+
+ MSR_EE
+ MSR_RI
+
+If any other bit changes in the MSR, please still use mtmsr(d).
+
+Patched instructions
+====================
+
+The "ld" and "std" instructions are transformed to "lwz" and "stw" instructions
+respectively on 32 bit systems with an added offset of 4 to accommodate for big
+endianness.
+
+The following is a list of mapping the Linux kernel performs when running as
+guest. Implementing any of those mappings is optional, as the instruction traps
+also act on the shared page. So calling privileged instructions still works as
+before.
+
+From To
+==== ==
+
+mfmsr rX ld rX, magic_page->msr
+mfsprg rX, 0 ld rX, magic_page->sprg0
+mfsprg rX, 1 ld rX, magic_page->sprg1
+mfsprg rX, 2 ld rX, magic_page->sprg2
+mfsprg rX, 3 ld rX, magic_page->sprg3
+mfsrr0 rX ld rX, magic_page->srr0
+mfsrr1 rX ld rX, magic_page->srr1
+mfdar rX ld rX, magic_page->dar
+mfdsisr rX lwz rX, magic_page->dsisr
+
+mtmsr rX std rX, magic_page->msr
+mtsprg 0, rX std rX, magic_page->sprg0
+mtsprg 1, rX std rX, magic_page->sprg1
+mtsprg 2, rX std rX, magic_page->sprg2
+mtsprg 3, rX std rX, magic_page->sprg3
+mtsrr0 rX std rX, magic_page->srr0
+mtsrr1 rX std rX, magic_page->srr1
+mtdar rX std rX, magic_page->dar
+mtdsisr rX stw rX, magic_page->dsisr
+
+tlbsync nop
+
+mtmsrd rX, 0 b <special mtmsr section>
+mtmsr rX b <special mtmsr section>
+
+mtmsrd rX, 1 b <special mtmsrd section>
+
+[Book3S only]
+mtsrin rX, rY b <special mtsrin section>
+
+[BookE only]
+wrteei [0|1] b <special wrteei section>
+
+
+Some instructions require more logic to determine what's going on than a load
+or store instruction can deliver. To enable patching of those, we keep some
+RAM around where we can live translate instructions to. What happens is the
+following:
+
+ 1) copy emulation code to memory
+ 2) patch that code to fit the emulated instruction
+ 3) patch that code to return to the original pc + 4
+ 4) patch the original instruction to branch to the new code
+
+That way we can inject an arbitrary amount of code as replacement for a single
+instruction. This allows us to check for pending interrupts when setting EE=1
+for example.
+
+Hypercall ABIs in KVM on PowerPC
+=================================
+1) KVM hypercalls (ePAPR)
+
+These are ePAPR compliant hypercall implementation (mentioned above). Even
+generic hypercalls are implemented here, like the ePAPR idle hcall. These are
+available on all targets.
+
+2) PAPR hypercalls
+
+PAPR hypercalls are needed to run server PowerPC PAPR guests (-M pseries in QEMU).
+These are the same hypercalls that pHyp, the POWER hypervisor implements. Some of
+them are handled in the kernel, some are handled in user space. This is only
+available on book3s_64.
+
+3) OSI hypercalls
+
+Mac-on-Linux is another user of KVM on PowerPC, which has its own hypercall (long
+before KVM). This is supported to maintain compatibility. All these hypercalls get
+forwarded to user space. This is only useful on book3s_32, but can be used with
+book3s_64 as well.
--- /dev/null
+Review checklist for kvm patches
+================================
+
+1. The patch must follow Documentation/process/coding-style.rst and
+ Documentation/process/submitting-patches.rst.
+
+2. Patches should be against kvm.git master branch.
+
+3. If the patch introduces or modifies a new userspace API:
+ - the API must be documented in Documentation/virt/kvm/api.txt
+ - the API must be discoverable using KVM_CHECK_EXTENSION
+
+4. New state must include support for save/restore.
+
+5. New features must default to off (userspace should explicitly request them).
+ Performance improvements can and should default to on.
+
+6. New cpu features should be exposed via KVM_GET_SUPPORTED_CPUID2
+
+7. Emulator changes should be accompanied by unit tests for qemu-kvm.git
+ kvm/test directory.
+
+8. Changes should be vendor neutral when possible. Changes to common code
+ are better than duplicating changes to vendor code.
+
+9. Similarly, prefer changes to arch independent code than to arch dependent
+ code.
+
+10. User/kernel interfaces and guest/host interfaces must be 64-bit clean
+ (all variables and sizes naturally aligned on 64-bit; use specific types
+ only - u64 rather than ulong).
+
+11. New guest visible features must either be documented in a hardware manual
+ or be accompanied by documentation.
+
+12. Features must be robust against reset and kexec - for example, shared
+ host/guest memory must be unshared to prevent the host from writing to
+ guest memory that the guest has not reserved for this purpose.
--- /dev/null
+The s390 DIAGNOSE call on KVM
+=============================
+
+KVM on s390 supports the DIAGNOSE call for making hypercalls, both for
+native hypercalls and for selected hypercalls found on other s390
+hypervisors.
+
+Note that bits are numbered as by the usual s390 convention (most significant
+bit on the left).
+
+
+General remarks
+---------------
+
+DIAGNOSE calls by the guest cause a mandatory intercept. This implies
+all supported DIAGNOSE calls need to be handled by either KVM or its
+userspace.
+
+All DIAGNOSE calls supported by KVM use the RS-a format:
+
+--------------------------------------
+| '83' | R1 | R3 | B2 | D2 |
+--------------------------------------
+0 8 12 16 20 31
+
+The second-operand address (obtained by the base/displacement calculation)
+is not used to address data. Instead, bits 48-63 of this address specify
+the function code, and bits 0-47 are ignored.
+
+The supported DIAGNOSE function codes vary by the userspace used. For
+DIAGNOSE function codes not specific to KVM, please refer to the
+documentation for the s390 hypervisors defining them.
+
+
+DIAGNOSE function code 'X'500' - KVM virtio functions
+-----------------------------------------------------
+
+If the function code specifies 0x500, various virtio-related functions
+are performed.
+
+General register 1 contains the virtio subfunction code. Supported
+virtio subfunctions depend on KVM's userspace. Generally, userspace
+provides either s390-virtio (subcodes 0-2) or virtio-ccw (subcode 3).
+
+Upon completion of the DIAGNOSE instruction, general register 2 contains
+the function's return code, which is either a return code or a subcode
+specific value.
+
+Subcode 0 - s390-virtio notification and early console printk
+ Handled by userspace.
+
+Subcode 1 - s390-virtio reset
+ Handled by userspace.
+
+Subcode 2 - s390-virtio set status
+ Handled by userspace.
+
+Subcode 3 - virtio-ccw notification
+ Handled by either userspace or KVM (ioeventfd case).
+
+ General register 2 contains a subchannel-identification word denoting
+ the subchannel of the virtio-ccw proxy device to be notified.
+
+ General register 3 contains the number of the virtqueue to be notified.
+
+ General register 4 contains a 64bit identifier for KVM usage (the
+ kvm_io_bus cookie). If general register 4 does not contain a valid
+ identifier, it is ignored.
+
+ After completion of the DIAGNOSE call, general register 2 may contain
+ a 64bit identifier (in the kvm_io_bus cookie case), or a negative
+ error value, if an internal error occurred.
+
+ See also the virtio standard for a discussion of this hypercall.
+
+
+DIAGNOSE function code 'X'501 - KVM breakpoint
+----------------------------------------------
+
+If the function code specifies 0x501, breakpoint functions may be performed.
+This function code is handled by userspace.
+
+This diagnose function code has no subfunctions and uses no parameters.
--- /dev/null
+
+ Timekeeping Virtualization for X86-Based Architectures
+
+ Zachary Amsden <zamsden@redhat.com>
+ Copyright (c) 2010, Red Hat. All rights reserved.
+
+1) Overview
+2) Timing Devices
+3) TSC Hardware
+4) Virtualization Problems
+
+=========================================================================
+
+1) Overview
+
+One of the most complicated parts of the X86 platform, and specifically,
+the virtualization of this platform is the plethora of timing devices available
+and the complexity of emulating those devices. In addition, virtualization of
+time introduces a new set of challenges because it introduces a multiplexed
+division of time beyond the control of the guest CPU.
+
+First, we will describe the various timekeeping hardware available, then
+present some of the problems which arise and solutions available, giving
+specific recommendations for certain classes of KVM guests.
+
+The purpose of this document is to collect data and information relevant to
+timekeeping which may be difficult to find elsewhere, specifically,
+information relevant to KVM and hardware-based virtualization.
+
+=========================================================================
+
+2) Timing Devices
+
+First we discuss the basic hardware devices available. TSC and the related
+KVM clock are special enough to warrant a full exposition and are described in
+the following section.
+
+2.1) i8254 - PIT
+
+One of the first timer devices available is the programmable interrupt timer,
+or PIT. The PIT has a fixed frequency 1.193182 MHz base clock and three
+channels which can be programmed to deliver periodic or one-shot interrupts.
+These three channels can be configured in different modes and have individual
+counters. Channel 1 and 2 were not available for general use in the original
+IBM PC, and historically were connected to control RAM refresh and the PC
+speaker. Now the PIT is typically integrated as part of an emulated chipset
+and a separate physical PIT is not used.
+
+The PIT uses I/O ports 0x40 - 0x43. Access to the 16-bit counters is done
+using single or multiple byte access to the I/O ports. There are 6 modes
+available, but not all modes are available to all timers, as only timer 2
+has a connected gate input, required for modes 1 and 5. The gate line is
+controlled by port 61h, bit 0, as illustrated in the following diagram.
+
+ -------------- ----------------
+| | | |
+| 1.1932 MHz |---------->| CLOCK OUT | ---------> IRQ 0
+| Clock | | | |
+ -------------- | +->| GATE TIMER 0 |
+ | ----------------
+ |
+ | ----------------
+ | | |
+ |------>| CLOCK OUT | ---------> 66.3 KHZ DRAM
+ | | | (aka /dev/null)
+ | +->| GATE TIMER 1 |
+ | ----------------
+ |
+ | ----------------
+ | | |
+ |------>| CLOCK OUT | ---------> Port 61h, bit 5
+ | | |
+Port 61h, bit 0 ---------->| GATE TIMER 2 | \_.---- ____
+ ---------------- _| )--|LPF|---Speaker
+ / *---- \___/
+Port 61h, bit 1 -----------------------------------/
+
+The timer modes are now described.
+
+Mode 0: Single Timeout. This is a one-shot software timeout that counts down
+ when the gate is high (always true for timers 0 and 1). When the count
+ reaches zero, the output goes high.
+
+Mode 1: Triggered One-shot. The output is initially set high. When the gate
+ line is set high, a countdown is initiated (which does not stop if the gate is
+ lowered), during which the output is set low. When the count reaches zero,
+ the output goes high.
+
+Mode 2: Rate Generator. The output is initially set high. When the countdown
+ reaches 1, the output goes low for one count and then returns high. The value
+ is reloaded and the countdown automatically resumes. If the gate line goes
+ low, the count is halted. If the output is low when the gate is lowered, the
+ output automatically goes high (this only affects timer 2).
+
+Mode 3: Square Wave. This generates a high / low square wave. The count
+ determines the length of the pulse, which alternates between high and low
+ when zero is reached. The count only proceeds when gate is high and is
+ automatically reloaded on reaching zero. The count is decremented twice at
+ each clock to generate a full high / low cycle at the full periodic rate.
+ If the count is even, the clock remains high for N/2 counts and low for N/2
+ counts; if the clock is odd, the clock is high for (N+1)/2 counts and low
+ for (N-1)/2 counts. Only even values are latched by the counter, so odd
+ values are not observed when reading. This is the intended mode for timer 2,
+ which generates sine-like tones by low-pass filtering the square wave output.
+
+Mode 4: Software Strobe. After programming this mode and loading the counter,
+ the output remains high until the counter reaches zero. Then the output
+ goes low for 1 clock cycle and returns high. The counter is not reloaded.
+ Counting only occurs when gate is high.
+
+Mode 5: Hardware Strobe. After programming and loading the counter, the
+ output remains high. When the gate is raised, a countdown is initiated
+ (which does not stop if the gate is lowered). When the counter reaches zero,
+ the output goes low for 1 clock cycle and then returns high. The counter is
+ not reloaded.
+
+In addition to normal binary counting, the PIT supports BCD counting. The
+command port, 0x43 is used to set the counter and mode for each of the three
+timers.
+
+PIT commands, issued to port 0x43, using the following bit encoding:
+
+Bit 7-4: Command (See table below)
+Bit 3-1: Mode (000 = Mode 0, 101 = Mode 5, 11X = undefined)
+Bit 0 : Binary (0) / BCD (1)
+
+Command table:
+
+0000 - Latch Timer 0 count for port 0x40
+ sample and hold the count to be read in port 0x40;
+ additional commands ignored until counter is read;
+ mode bits ignored.
+
+0001 - Set Timer 0 LSB mode for port 0x40
+ set timer to read LSB only and force MSB to zero;
+ mode bits set timer mode
+
+0010 - Set Timer 0 MSB mode for port 0x40
+ set timer to read MSB only and force LSB to zero;
+ mode bits set timer mode
+
+0011 - Set Timer 0 16-bit mode for port 0x40
+ set timer to read / write LSB first, then MSB;
+ mode bits set timer mode
+
+0100 - Latch Timer 1 count for port 0x41 - as described above
+0101 - Set Timer 1 LSB mode for port 0x41 - as described above
+0110 - Set Timer 1 MSB mode for port 0x41 - as described above
+0111 - Set Timer 1 16-bit mode for port 0x41 - as described above
+
+1000 - Latch Timer 2 count for port 0x42 - as described above
+1001 - Set Timer 2 LSB mode for port 0x42 - as described above
+1010 - Set Timer 2 MSB mode for port 0x42 - as described above
+1011 - Set Timer 2 16-bit mode for port 0x42 as described above
+
+1101 - General counter latch
+ Latch combination of counters into corresponding ports
+ Bit 3 = Counter 2
+ Bit 2 = Counter 1
+ Bit 1 = Counter 0
+ Bit 0 = Unused
+
+1110 - Latch timer status
+ Latch combination of counter mode into corresponding ports
+ Bit 3 = Counter 2
+ Bit 2 = Counter 1
+ Bit 1 = Counter 0
+
+ The output of ports 0x40-0x42 following this command will be:
+
+ Bit 7 = Output pin
+ Bit 6 = Count loaded (0 if timer has expired)
+ Bit 5-4 = Read / Write mode
+ 01 = MSB only
+ 10 = LSB only
+ 11 = LSB / MSB (16-bit)
+ Bit 3-1 = Mode
+ Bit 0 = Binary (0) / BCD mode (1)
+
+2.2) RTC
+
+The second device which was available in the original PC was the MC146818 real
+time clock. The original device is now obsolete, and usually emulated by the
+system chipset, sometimes by an HPET and some frankenstein IRQ routing.
+
+The RTC is accessed through CMOS variables, which uses an index register to
+control which bytes are read. Since there is only one index register, read
+of the CMOS and read of the RTC require lock protection (in addition, it is
+dangerous to allow userspace utilities such as hwclock to have direct RTC
+access, as they could corrupt kernel reads and writes of CMOS memory).
+
+The RTC generates an interrupt which is usually routed to IRQ 8. The interrupt
+can function as a periodic timer, an additional once a day alarm, and can issue
+interrupts after an update of the CMOS registers by the MC146818 is complete.
+The type of interrupt is signalled in the RTC status registers.
+
+The RTC will update the current time fields by battery power even while the
+system is off. The current time fields should not be read while an update is
+in progress, as indicated in the status register.
+
+The clock uses a 32.768kHz crystal, so bits 6-4 of register A should be
+programmed to a 32kHz divider if the RTC is to count seconds.
+
+This is the RAM map originally used for the RTC/CMOS:
+
+Location Size Description
+------------------------------------------
+00h byte Current second (BCD)
+01h byte Seconds alarm (BCD)
+02h byte Current minute (BCD)
+03h byte Minutes alarm (BCD)
+04h byte Current hour (BCD)
+05h byte Hours alarm (BCD)
+06h byte Current day of week (BCD)
+07h byte Current day of month (BCD)
+08h byte Current month (BCD)
+09h byte Current year (BCD)
+0Ah byte Register A
+ bit 7 = Update in progress
+ bit 6-4 = Divider for clock
+ 000 = 4.194 MHz
+ 001 = 1.049 MHz
+ 010 = 32 kHz
+ 10X = test modes
+ 110 = reset / disable
+ 111 = reset / disable
+ bit 3-0 = Rate selection for periodic interrupt
+ 000 = periodic timer disabled
+ 001 = 3.90625 uS
+ 010 = 7.8125 uS
+ 011 = .122070 mS
+ 100 = .244141 mS
+ ...
+ 1101 = 125 mS
+ 1110 = 250 mS
+ 1111 = 500 mS
+0Bh byte Register B
+ bit 7 = Run (0) / Halt (1)
+ bit 6 = Periodic interrupt enable
+ bit 5 = Alarm interrupt enable
+ bit 4 = Update-ended interrupt enable
+ bit 3 = Square wave interrupt enable
+ bit 2 = BCD calendar (0) / Binary (1)
+ bit 1 = 12-hour mode (0) / 24-hour mode (1)
+ bit 0 = 0 (DST off) / 1 (DST enabled)
+OCh byte Register C (read only)
+ bit 7 = interrupt request flag (IRQF)
+ bit 6 = periodic interrupt flag (PF)
+ bit 5 = alarm interrupt flag (AF)
+ bit 4 = update interrupt flag (UF)
+ bit 3-0 = reserved
+ODh byte Register D (read only)
+ bit 7 = RTC has power
+ bit 6-0 = reserved
+32h byte Current century BCD (*)
+ (*) location vendor specific and now determined from ACPI global tables
+
+2.3) APIC
+
+On Pentium and later processors, an on-board timer is available to each CPU
+as part of the Advanced Programmable Interrupt Controller. The APIC is
+accessed through memory-mapped registers and provides interrupt service to each
+CPU, used for IPIs and local timer interrupts.
+
+Although in theory the APIC is a safe and stable source for local interrupts,
+in practice, many bugs and glitches have occurred due to the special nature of
+the APIC CPU-local memory-mapped hardware. Beware that CPU errata may affect
+the use of the APIC and that workarounds may be required. In addition, some of
+these workarounds pose unique constraints for virtualization - requiring either
+extra overhead incurred from extra reads of memory-mapped I/O or additional
+functionality that may be more computationally expensive to implement.
+
+Since the APIC is documented quite well in the Intel and AMD manuals, we will
+avoid repetition of the detail here. It should be pointed out that the APIC
+timer is programmed through the LVT (local vector timer) register, is capable
+of one-shot or periodic operation, and is based on the bus clock divided down
+by the programmable divider register.
+
+2.4) HPET
+
+HPET is quite complex, and was originally intended to replace the PIT / RTC
+support of the X86 PC. It remains to be seen whether that will be the case, as
+the de facto standard of PC hardware is to emulate these older devices. Some
+systems designated as legacy free may support only the HPET as a hardware timer
+device.
+
+The HPET spec is rather loose and vague, requiring at least 3 hardware timers,
+but allowing implementation freedom to support many more. It also imposes no
+fixed rate on the timer frequency, but does impose some extremal values on
+frequency, error and slew.
+
+In general, the HPET is recommended as a high precision (compared to PIT /RTC)
+time source which is independent of local variation (as there is only one HPET
+in any given system). The HPET is also memory-mapped, and its presence is
+indicated through ACPI tables by the BIOS.
+
+Detailed specification of the HPET is beyond the current scope of this
+document, as it is also very well documented elsewhere.
+
+2.5) Offboard Timers
+
+Several cards, both proprietary (watchdog boards) and commonplace (e1000) have
+timing chips built into the cards which may have registers which are accessible
+to kernel or user drivers. To the author's knowledge, using these to generate
+a clocksource for a Linux or other kernel has not yet been attempted and is in
+general frowned upon as not playing by the agreed rules of the game. Such a
+timer device would require additional support to be virtualized properly and is
+not considered important at this time as no known operating system does this.
+
+=========================================================================
+
+3) TSC Hardware
+
+The TSC or time stamp counter is relatively simple in theory; it counts
+instruction cycles issued by the processor, which can be used as a measure of
+time. In practice, due to a number of problems, it is the most complicated
+timekeeping device to use.
+
+The TSC is represented internally as a 64-bit MSR which can be read with the
+RDMSR, RDTSC, or RDTSCP (when available) instructions. In the past, hardware
+limitations made it possible to write the TSC, but generally on old hardware it
+was only possible to write the low 32-bits of the 64-bit counter, and the upper
+32-bits of the counter were cleared. Now, however, on Intel processors family
+0Fh, for models 3, 4 and 6, and family 06h, models e and f, this restriction
+has been lifted and all 64-bits are writable. On AMD systems, the ability to
+write the TSC MSR is not an architectural guarantee.
+
+The TSC is accessible from CPL-0 and conditionally, for CPL > 0 software by
+means of the CR4.TSD bit, which when enabled, disables CPL > 0 TSC access.
+
+Some vendors have implemented an additional instruction, RDTSCP, which returns
+atomically not just the TSC, but an indicator which corresponds to the
+processor number. This can be used to index into an array of TSC variables to
+determine offset information in SMP systems where TSCs are not synchronized.
+The presence of this instruction must be determined by consulting CPUID feature
+bits.
+
+Both VMX and SVM provide extension fields in the virtualization hardware which
+allows the guest visible TSC to be offset by a constant. Newer implementations
+promise to allow the TSC to additionally be scaled, but this hardware is not
+yet widely available.
+
+3.1) TSC synchronization
+
+The TSC is a CPU-local clock in most implementations. This means, on SMP
+platforms, the TSCs of different CPUs may start at different times depending
+on when the CPUs are powered on. Generally, CPUs on the same die will share
+the same clock, however, this is not always the case.
+
+The BIOS may attempt to resynchronize the TSCs during the poweron process and
+the operating system or other system software may attempt to do this as well.
+Several hardware limitations make the problem worse - if it is not possible to
+write the full 64-bits of the TSC, it may be impossible to match the TSC in
+newly arriving CPUs to that of the rest of the system, resulting in
+unsynchronized TSCs. This may be done by BIOS or system software, but in
+practice, getting a perfectly synchronized TSC will not be possible unless all
+values are read from the same clock, which generally only is possible on single
+socket systems or those with special hardware support.
+
+3.2) TSC and CPU hotplug
+
+As touched on already, CPUs which arrive later than the boot time of the system
+may not have a TSC value that is synchronized with the rest of the system.
+Either system software, BIOS, or SMM code may actually try to establish the TSC
+to a value matching the rest of the system, but a perfect match is usually not
+a guarantee. This can have the effect of bringing a system from a state where
+TSC is synchronized back to a state where TSC synchronization flaws, however
+small, may be exposed to the OS and any virtualization environment.
+
+3.3) TSC and multi-socket / NUMA
+
+Multi-socket systems, especially large multi-socket systems are likely to have
+individual clocksources rather than a single, universally distributed clock.
+Since these clocks are driven by different crystals, they will not have
+perfectly matched frequency, and temperature and electrical variations will
+cause the CPU clocks, and thus the TSCs to drift over time. Depending on the
+exact clock and bus design, the drift may or may not be fixed in absolute
+error, and may accumulate over time.
+
+In addition, very large systems may deliberately slew the clocks of individual
+cores. This technique, known as spread-spectrum clocking, reduces EMI at the
+clock frequency and harmonics of it, which may be required to pass FCC
+standards for telecommunications and computer equipment.
+
+It is recommended not to trust the TSCs to remain synchronized on NUMA or
+multiple socket systems for these reasons.
+
+3.4) TSC and C-states
+
+C-states, or idling states of the processor, especially C1E and deeper sleep
+states may be problematic for TSC as well. The TSC may stop advancing in such
+a state, resulting in a TSC which is behind that of other CPUs when execution
+is resumed. Such CPUs must be detected and flagged by the operating system
+based on CPU and chipset identifications.
+
+The TSC in such a case may be corrected by catching it up to a known external
+clocksource.
+
+3.5) TSC frequency change / P-states
+
+To make things slightly more interesting, some CPUs may change frequency. They
+may or may not run the TSC at the same rate, and because the frequency change
+may be staggered or slewed, at some points in time, the TSC rate may not be
+known other than falling within a range of values. In this case, the TSC will
+not be a stable time source, and must be calibrated against a known, stable,
+external clock to be a usable source of time.
+
+Whether the TSC runs at a constant rate or scales with the P-state is model
+dependent and must be determined by inspecting CPUID, chipset or vendor
+specific MSR fields.
+
+In addition, some vendors have known bugs where the P-state is actually
+compensated for properly during normal operation, but when the processor is
+inactive, the P-state may be raised temporarily to service cache misses from
+other processors. In such cases, the TSC on halted CPUs could advance faster
+than that of non-halted processors. AMD Turion processors are known to have
+this problem.
+
+3.6) TSC and STPCLK / T-states
+
+External signals given to the processor may also have the effect of stopping
+the TSC. This is typically done for thermal emergency power control to prevent
+an overheating condition, and typically, there is no way to detect that this
+condition has happened.
+
+3.7) TSC virtualization - VMX
+
+VMX provides conditional trapping of RDTSC, RDMSR, WRMSR and RDTSCP
+instructions, which is enough for full virtualization of TSC in any manner. In
+addition, VMX allows passing through the host TSC plus an additional TSC_OFFSET
+field specified in the VMCS. Special instructions must be used to read and
+write the VMCS field.
+
+3.8) TSC virtualization - SVM
+
+SVM provides conditional trapping of RDTSC, RDMSR, WRMSR and RDTSCP
+instructions, which is enough for full virtualization of TSC in any manner. In
+addition, SVM allows passing through the host TSC plus an additional offset
+field specified in the SVM control block.
+
+3.9) TSC feature bits in Linux
+
+In summary, there is no way to guarantee the TSC remains in perfect
+synchronization unless it is explicitly guaranteed by the architecture. Even
+if so, the TSCs in multi-sockets or NUMA systems may still run independently
+despite being locally consistent.
+
+The following feature bits are used by Linux to signal various TSC attributes,
+but they can only be taken to be meaningful for UP or single node systems.
+
+X86_FEATURE_TSC : The TSC is available in hardware
+X86_FEATURE_RDTSCP : The RDTSCP instruction is available
+X86_FEATURE_CONSTANT_TSC : The TSC rate is unchanged with P-states
+X86_FEATURE_NONSTOP_TSC : The TSC does not stop in C-states
+X86_FEATURE_TSC_RELIABLE : TSC sync checks are skipped (VMware)
+
+4) Virtualization Problems
+
+Timekeeping is especially problematic for virtualization because a number of
+challenges arise. The most obvious problem is that time is now shared between
+the host and, potentially, a number of virtual machines. Thus the virtual
+operating system does not run with 100% usage of the CPU, despite the fact that
+it may very well make that assumption. It may expect it to remain true to very
+exacting bounds when interrupt sources are disabled, but in reality only its
+virtual interrupt sources are disabled, and the machine may still be preempted
+at any time. This causes problems as the passage of real time, the injection
+of machine interrupts and the associated clock sources are no longer completely
+synchronized with real time.
+
+This same problem can occur on native hardware to a degree, as SMM mode may
+steal cycles from the naturally on X86 systems when SMM mode is used by the
+BIOS, but not in such an extreme fashion. However, the fact that SMM mode may
+cause similar problems to virtualization makes it a good justification for
+solving many of these problems on bare metal.
+
+4.1) Interrupt clocking
+
+One of the most immediate problems that occurs with legacy operating systems
+is that the system timekeeping routines are often designed to keep track of
+time by counting periodic interrupts. These interrupts may come from the PIT
+or the RTC, but the problem is the same: the host virtualization engine may not
+be able to deliver the proper number of interrupts per second, and so guest
+time may fall behind. This is especially problematic if a high interrupt rate
+is selected, such as 1000 HZ, which is unfortunately the default for many Linux
+guests.
+
+There are three approaches to solving this problem; first, it may be possible
+to simply ignore it. Guests which have a separate time source for tracking
+'wall clock' or 'real time' may not need any adjustment of their interrupts to
+maintain proper time. If this is not sufficient, it may be necessary to inject
+additional interrupts into the guest in order to increase the effective
+interrupt rate. This approach leads to complications in extreme conditions,
+where host load or guest lag is too much to compensate for, and thus another
+solution to the problem has risen: the guest may need to become aware of lost
+ticks and compensate for them internally. Although promising in theory, the
+implementation of this policy in Linux has been extremely error prone, and a
+number of buggy variants of lost tick compensation are distributed across
+commonly used Linux systems.
+
+Windows uses periodic RTC clocking as a means of keeping time internally, and
+thus requires interrupt slewing to keep proper time. It does use a low enough
+rate (ed: is it 18.2 Hz?) however that it has not yet been a problem in
+practice.
+
+4.2) TSC sampling and serialization
+
+As the highest precision time source available, the cycle counter of the CPU
+has aroused much interest from developers. As explained above, this timer has
+many problems unique to its nature as a local, potentially unstable and
+potentially unsynchronized source. One issue which is not unique to the TSC,
+but is highlighted because of its very precise nature is sampling delay. By
+definition, the counter, once read is already old. However, it is also
+possible for the counter to be read ahead of the actual use of the result.
+This is a consequence of the superscalar execution of the instruction stream,
+which may execute instructions out of order. Such execution is called
+non-serialized. Forcing serialized execution is necessary for precise
+measurement with the TSC, and requires a serializing instruction, such as CPUID
+or an MSR read.
+
+Since CPUID may actually be virtualized by a trap and emulate mechanism, this
+serialization can pose a performance issue for hardware virtualization. An
+accurate time stamp counter reading may therefore not always be available, and
+it may be necessary for an implementation to guard against "backwards" reads of
+the TSC as seen from other CPUs, even in an otherwise perfectly synchronized
+system.
+
+4.3) Timespec aliasing
+
+Additionally, this lack of serialization from the TSC poses another challenge
+when using results of the TSC when measured against another time source. As
+the TSC is much higher precision, many possible values of the TSC may be read
+while another clock is still expressing the same value.
+
+That is, you may read (T,T+10) while external clock C maintains the same value.
+Due to non-serialized reads, you may actually end up with a range which
+fluctuates - from (T-1.. T+10). Thus, any time calculated from a TSC, but
+calibrated against an external value may have a range of valid values.
+Re-calibrating this computation may actually cause time, as computed after the
+calibration, to go backwards, compared with time computed before the
+calibration.
+
+This problem is particularly pronounced with an internal time source in Linux,
+the kernel time, which is expressed in the theoretically high resolution
+timespec - but which advances in much larger granularity intervals, sometimes
+at the rate of jiffies, and possibly in catchup modes, at a much larger step.
+
+This aliasing requires care in the computation and recalibration of kvmclock
+and any other values derived from TSC computation (such as TSC virtualization
+itself).
+
+4.4) Migration
+
+Migration of a virtual machine raises problems for timekeeping in two ways.
+First, the migration itself may take time, during which interrupts cannot be
+delivered, and after which, the guest time may need to be caught up. NTP may
+be able to help to some degree here, as the clock correction required is
+typically small enough to fall in the NTP-correctable window.
+
+An additional concern is that timers based off the TSC (or HPET, if the raw bus
+clock is exposed) may now be running at different rates, requiring compensation
+in some way in the hypervisor by virtualizing these timers. In addition,
+migrating to a faster machine may preclude the use of a passthrough TSC, as a
+faster clock cannot be made visible to a guest without the potential of time
+advancing faster than usual. A slower clock is less of a problem, as it can
+always be caught up to the original rate. KVM clock avoids these problems by
+simply storing multipliers and offsets against the TSC for the guest to convert
+back into nanosecond resolution values.
+
+4.5) Scheduling
+
+Since scheduling may be based on precise timing and firing of interrupts, the
+scheduling algorithms of an operating system may be adversely affected by
+virtualization. In theory, the effect is random and should be universally
+distributed, but in contrived as well as real scenarios (guest device access,
+causes of virtualization exits, possible context switch), this may not always
+be the case. The effect of this has not been well studied.
+
+In an attempt to work around this, several implementations have provided a
+paravirtualized scheduler clock, which reveals the true amount of CPU time for
+which a virtual machine has been running.
+
+4.6) Watchdogs
+
+Watchdog timers, such as the lock detector in Linux may fire accidentally when
+running under hardware virtualization due to timer interrupts being delayed or
+misinterpretation of the passage of real time. Usually, these warnings are
+spurious and can be ignored, but in some circumstances it may be necessary to
+disable such detection.
+
+4.7) Delays and precision timing
+
+Precise timing and delays may not be possible in a virtualized system. This
+can happen if the system is controlling physical hardware, or issues delays to
+compensate for slower I/O to and from devices. The first issue is not solvable
+in general for a virtualized system; hardware control software can't be
+adequately virtualized without a full real-time operating system, which would
+require an RT aware virtualization platform.
+
+The second issue may cause performance problems, but this is unlikely to be a
+significant issue. In many cases these delays may be eliminated through
+configuration or paravirtualization.
+
+4.8) Covert channels and leaks
+
+In addition to the above problems, time information will inevitably leak to the
+guest about the host in anything but a perfect implementation of virtualized
+time. This may allow the guest to infer the presence of a hypervisor (as in a
+red-pill type detection), and it may allow information to leak between guests
+by using CPU utilization itself as a signalling channel. Preventing such
+problems would require completely isolated virtual time which may not track
+real time any longer. This may be useful in certain security or QA contexts,
+but in general isn't recommended for real-world deployment scenarios.
--- /dev/null
+=================
+KVM VCPU Requests
+=================
+
+Overview
+========
+
+KVM supports an internal API enabling threads to request a VCPU thread to
+perform some activity. For example, a thread may request a VCPU to flush
+its TLB with a VCPU request. The API consists of the following functions::
+
+ /* Check if any requests are pending for VCPU @vcpu. */
+ bool kvm_request_pending(struct kvm_vcpu *vcpu);
+
+ /* Check if VCPU @vcpu has request @req pending. */
+ bool kvm_test_request(int req, struct kvm_vcpu *vcpu);
+
+ /* Clear request @req for VCPU @vcpu. */
+ void kvm_clear_request(int req, struct kvm_vcpu *vcpu);
+
+ /*
+ * Check if VCPU @vcpu has request @req pending. When the request is
+ * pending it will be cleared and a memory barrier, which pairs with
+ * another in kvm_make_request(), will be issued.
+ */
+ bool kvm_check_request(int req, struct kvm_vcpu *vcpu);
+
+ /*
+ * Make request @req of VCPU @vcpu. Issues a memory barrier, which pairs
+ * with another in kvm_check_request(), prior to setting the request.
+ */
+ void kvm_make_request(int req, struct kvm_vcpu *vcpu);
+
+ /* Make request @req of all VCPUs of the VM with struct kvm @kvm. */
+ bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req);
+
+Typically a requester wants the VCPU to perform the activity as soon
+as possible after making the request. This means most requests
+(kvm_make_request() calls) are followed by a call to kvm_vcpu_kick(),
+and kvm_make_all_cpus_request() has the kicking of all VCPUs built
+into it.
+
+VCPU Kicks
+----------
+
+The goal of a VCPU kick is to bring a VCPU thread out of guest mode in
+order to perform some KVM maintenance. To do so, an IPI is sent, forcing
+a guest mode exit. However, a VCPU thread may not be in guest mode at the
+time of the kick. Therefore, depending on the mode and state of the VCPU
+thread, there are two other actions a kick may take. All three actions
+are listed below:
+
+1) Send an IPI. This forces a guest mode exit.
+2) Waking a sleeping VCPU. Sleeping VCPUs are VCPU threads outside guest
+ mode that wait on waitqueues. Waking them removes the threads from
+ the waitqueues, allowing the threads to run again. This behavior
+ may be suppressed, see KVM_REQUEST_NO_WAKEUP below.
+3) Nothing. When the VCPU is not in guest mode and the VCPU thread is not
+ sleeping, then there is nothing to do.
+
+VCPU Mode
+---------
+
+VCPUs have a mode state, ``vcpu->mode``, that is used to track whether the
+guest is running in guest mode or not, as well as some specific
+outside guest mode states. The architecture may use ``vcpu->mode`` to
+ensure VCPU requests are seen by VCPUs (see "Ensuring Requests Are Seen"),
+as well as to avoid sending unnecessary IPIs (see "IPI Reduction"), and
+even to ensure IPI acknowledgements are waited upon (see "Waiting for
+Acknowledgements"). The following modes are defined:
+
+OUTSIDE_GUEST_MODE
+
+ The VCPU thread is outside guest mode.
+
+IN_GUEST_MODE
+
+ The VCPU thread is in guest mode.
+
+EXITING_GUEST_MODE
+
+ The VCPU thread is transitioning from IN_GUEST_MODE to
+ OUTSIDE_GUEST_MODE.
+
+READING_SHADOW_PAGE_TABLES
+
+ The VCPU thread is outside guest mode, but it wants the sender of
+ certain VCPU requests, namely KVM_REQ_TLB_FLUSH, to wait until the VCPU
+ thread is done reading the page tables.
+
+VCPU Request Internals
+======================
+
+VCPU requests are simply bit indices of the ``vcpu->requests`` bitmap.
+This means general bitops, like those documented in [atomic-ops]_ could
+also be used, e.g. ::
+
+ clear_bit(KVM_REQ_UNHALT & KVM_REQUEST_MASK, &vcpu->requests);
+
+However, VCPU request users should refrain from doing so, as it would
+break the abstraction. The first 8 bits are reserved for architecture
+independent requests, all additional bits are available for architecture
+dependent requests.
+
+Architecture Independent Requests
+---------------------------------
+
+KVM_REQ_TLB_FLUSH
+
+ KVM's common MMU notifier may need to flush all of a guest's TLB
+ entries, calling kvm_flush_remote_tlbs() to do so. Architectures that
+ choose to use the common kvm_flush_remote_tlbs() implementation will
+ need to handle this VCPU request.
+
+KVM_REQ_MMU_RELOAD
+
+ When shadow page tables are used and memory slots are removed it's
+ necessary to inform each VCPU to completely refresh the tables. This
+ request is used for that.
+
+KVM_REQ_PENDING_TIMER
+
+ This request may be made from a timer handler run on the host on behalf
+ of a VCPU. It informs the VCPU thread to inject a timer interrupt.
+
+KVM_REQ_UNHALT
+
+ This request may be made from the KVM common function kvm_vcpu_block(),
+ which is used to emulate an instruction that causes a CPU to halt until
+ one of an architectural specific set of events and/or interrupts is
+ received (determined by checking kvm_arch_vcpu_runnable()). When that
+ event or interrupt arrives kvm_vcpu_block() makes the request. This is
+ in contrast to when kvm_vcpu_block() returns due to any other reason,
+ such as a pending signal, which does not indicate the VCPU's halt
+ emulation should stop, and therefore does not make the request.
+
+KVM_REQUEST_MASK
+----------------
+
+VCPU requests should be masked by KVM_REQUEST_MASK before using them with
+bitops. This is because only the lower 8 bits are used to represent the
+request's number. The upper bits are used as flags. Currently only two
+flags are defined.
+
+VCPU Request Flags
+------------------
+
+KVM_REQUEST_NO_WAKEUP
+
+ This flag is applied to requests that only need immediate attention
+ from VCPUs running in guest mode. That is, sleeping VCPUs do not need
+ to be awaken for these requests. Sleeping VCPUs will handle the
+ requests when they are awaken later for some other reason.
+
+KVM_REQUEST_WAIT
+
+ When requests with this flag are made with kvm_make_all_cpus_request(),
+ then the caller will wait for each VCPU to acknowledge its IPI before
+ proceeding. This flag only applies to VCPUs that would receive IPIs.
+ If, for example, the VCPU is sleeping, so no IPI is necessary, then
+ the requesting thread does not wait. This means that this flag may be
+ safely combined with KVM_REQUEST_NO_WAKEUP. See "Waiting for
+ Acknowledgements" for more information about requests with
+ KVM_REQUEST_WAIT.
+
+VCPU Requests with Associated State
+===================================
+
+Requesters that want the receiving VCPU to handle new state need to ensure
+the newly written state is observable to the receiving VCPU thread's CPU
+by the time it observes the request. This means a write memory barrier
+must be inserted after writing the new state and before setting the VCPU
+request bit. Additionally, on the receiving VCPU thread's side, a
+corresponding read barrier must be inserted after reading the request bit
+and before proceeding to read the new state associated with it. See
+scenario 3, Message and Flag, of [lwn-mb]_ and the kernel documentation
+[memory-barriers]_.
+
+The pair of functions, kvm_check_request() and kvm_make_request(), provide
+the memory barriers, allowing this requirement to be handled internally by
+the API.
+
+Ensuring Requests Are Seen
+==========================
+
+When making requests to VCPUs, we want to avoid the receiving VCPU
+executing in guest mode for an arbitrary long time without handling the
+request. We can be sure this won't happen as long as we ensure the VCPU
+thread checks kvm_request_pending() before entering guest mode and that a
+kick will send an IPI to force an exit from guest mode when necessary.
+Extra care must be taken to cover the period after the VCPU thread's last
+kvm_request_pending() check and before it has entered guest mode, as kick
+IPIs will only trigger guest mode exits for VCPU threads that are in guest
+mode or at least have already disabled interrupts in order to prepare to
+enter guest mode. This means that an optimized implementation (see "IPI
+Reduction") must be certain when it's safe to not send the IPI. One
+solution, which all architectures except s390 apply, is to:
+
+- set ``vcpu->mode`` to IN_GUEST_MODE between disabling the interrupts and
+ the last kvm_request_pending() check;
+- enable interrupts atomically when entering the guest.
+
+This solution also requires memory barriers to be placed carefully in both
+the requesting thread and the receiving VCPU. With the memory barriers we
+can exclude the possibility of a VCPU thread observing
+!kvm_request_pending() on its last check and then not receiving an IPI for
+the next request made of it, even if the request is made immediately after
+the check. This is done by way of the Dekker memory barrier pattern
+(scenario 10 of [lwn-mb]_). As the Dekker pattern requires two variables,
+this solution pairs ``vcpu->mode`` with ``vcpu->requests``. Substituting
+them into the pattern gives::
+
+ CPU1 CPU2
+ ================= =================
+ local_irq_disable();
+ WRITE_ONCE(vcpu->mode, IN_GUEST_MODE); kvm_make_request(REQ, vcpu);
+ smp_mb(); smp_mb();
+ if (kvm_request_pending(vcpu)) { if (READ_ONCE(vcpu->mode) ==
+ IN_GUEST_MODE) {
+ ...abort guest entry... ...send IPI...
+ } }
+
+As stated above, the IPI is only useful for VCPU threads in guest mode or
+that have already disabled interrupts. This is why this specific case of
+the Dekker pattern has been extended to disable interrupts before setting
+``vcpu->mode`` to IN_GUEST_MODE. WRITE_ONCE() and READ_ONCE() are used to
+pedantically implement the memory barrier pattern, guaranteeing the
+compiler doesn't interfere with ``vcpu->mode``'s carefully planned
+accesses.
+
+IPI Reduction
+-------------
+
+As only one IPI is needed to get a VCPU to check for any/all requests,
+then they may be coalesced. This is easily done by having the first IPI
+sending kick also change the VCPU mode to something !IN_GUEST_MODE. The
+transitional state, EXITING_GUEST_MODE, is used for this purpose.
+
+Waiting for Acknowledgements
+----------------------------
+
+Some requests, those with the KVM_REQUEST_WAIT flag set, require IPIs to
+be sent, and the acknowledgements to be waited upon, even when the target
+VCPU threads are in modes other than IN_GUEST_MODE. For example, one case
+is when a target VCPU thread is in READING_SHADOW_PAGE_TABLES mode, which
+is set after disabling interrupts. To support these cases, the
+KVM_REQUEST_WAIT flag changes the condition for sending an IPI from
+checking that the VCPU is IN_GUEST_MODE to checking that it is not
+OUTSIDE_GUEST_MODE.
+
+Request-less VCPU Kicks
+-----------------------
+
+As the determination of whether or not to send an IPI depends on the
+two-variable Dekker memory barrier pattern, then it's clear that
+request-less VCPU kicks are almost never correct. Without the assurance
+that a non-IPI generating kick will still result in an action by the
+receiving VCPU, as the final kvm_request_pending() check does for
+request-accompanying kicks, then the kick may not do anything useful at
+all. If, for instance, a request-less kick was made to a VCPU that was
+just about to set its mode to IN_GUEST_MODE, meaning no IPI is sent, then
+the VCPU thread may continue its entry without actually having done
+whatever it was the kick was meant to initiate.
+
+One exception is x86's posted interrupt mechanism. In this case, however,
+even the request-less VCPU kick is coupled with the same
+local_irq_disable() + smp_mb() pattern described above; the ON bit
+(Outstanding Notification) in the posted interrupt descriptor takes the
+role of ``vcpu->requests``. When sending a posted interrupt, PIR.ON is
+set before reading ``vcpu->mode``; dually, in the VCPU thread,
+vmx_sync_pir_to_irr() reads PIR after setting ``vcpu->mode`` to
+IN_GUEST_MODE.
+
+Additional Considerations
+=========================
+
+Sleeping VCPUs
+--------------
+
+VCPU threads may need to consider requests before and/or after calling
+functions that may put them to sleep, e.g. kvm_vcpu_block(). Whether they
+do or not, and, if they do, which requests need consideration, is
+architecture dependent. kvm_vcpu_block() calls kvm_arch_vcpu_runnable()
+to check if it should awaken. One reason to do so is to provide
+architectures a function where requests may be checked if necessary.
+
+Clearing Requests
+-----------------
+
+Generally it only makes sense for the receiving VCPU thread to clear a
+request. However, in some circumstances, such as when the requesting
+thread and the receiving VCPU thread are executed serially, such as when
+they are the same thread, or when they are using some form of concurrency
+control to temporarily execute synchronously, then it's possible to know
+that the request may be cleared immediately, rather than waiting for the
+receiving VCPU thread to handle the request in VCPU RUN. The only current
+examples of this are kvm_vcpu_block() calls made by VCPUs to block
+themselves. A possible side-effect of that call is to make the
+KVM_REQ_UNHALT request, which may then be cleared immediately when the
+VCPU returns from the call.
+
+References
+==========
+
+.. [atomic-ops] Documentation/core-api/atomic_ops.rst
+.. [memory-barriers] Documentation/memory-barriers.txt
+.. [lwn-mb] https://lwn.net/Articles/573436/
--- /dev/null
+.. SPDX-License-Identifier: GPL-2.0
+
+============
+Paravirt_ops
+============
+
+Linux provides support for different hypervisor virtualization technologies.
+Historically different binary kernels would be required in order to support
+different hypervisors, this restriction was removed with pv_ops.
+Linux pv_ops is a virtualization API which enables support for different
+hypervisors. It allows each hypervisor to override critical operations and
+allows a single kernel binary to run on all supported execution environments
+including native machine -- without any hypervisors.
+
+pv_ops provides a set of function pointers which represent operations
+corresponding to low level critical instructions and high level
+functionalities in various areas. pv-ops allows for optimizations at run
+time by enabling binary patching of the low-ops critical operations
+at boot time.
+
+pv_ops operations are classified into three categories:
+
+- simple indirect call
+ These operations correspond to high level functionality where it is
+ known that the overhead of indirect call isn't very important.
+
+- indirect call which allows optimization with binary patch
+ Usually these operations correspond to low level critical instructions. They
+ are called frequently and are performance critical. The overhead is
+ very important.
+
+- a set of macros for hand written assembly code
+ Hand written assembly codes (.S files) also need paravirtualization
+ because they include sensitive instructions or some of code paths in
+ them are very performance critical.
--- /dev/null
+ User Mode Linux HOWTO
+ User Mode Linux Core Team
+ Mon Nov 18 14:16:16 EST 2002
+
+ This document describes the use and abuse of Jeff Dike's User Mode
+ Linux: a port of the Linux kernel as a normal Intel Linux process.
+ ______________________________________________________________________
+
+ Table of Contents
+
+ 1. Introduction
+
+ 1.1 How is User Mode Linux Different?
+ 1.2 Why Would I Want User Mode Linux?
+
+ 2. Compiling the kernel and modules
+
+ 2.1 Compiling the kernel
+ 2.2 Compiling and installing kernel modules
+ 2.3 Compiling and installing uml_utilities
+
+ 3. Running UML and logging in
+
+ 3.1 Running UML
+ 3.2 Logging in
+ 3.3 Examples
+
+ 4. UML on 2G/2G hosts
+
+ 4.1 Introduction
+ 4.2 The problem
+ 4.3 The solution
+
+ 5. Setting up serial lines and consoles
+
+ 5.1 Specifying the device
+ 5.2 Specifying the channel
+ 5.3 Examples
+
+ 6. Setting up the network
+
+ 6.1 General setup
+ 6.2 Userspace daemons
+ 6.3 Specifying ethernet addresses
+ 6.4 UML interface setup
+ 6.5 Multicast
+ 6.6 TUN/TAP with the uml_net helper
+ 6.7 TUN/TAP with a preconfigured tap device
+ 6.8 Ethertap
+ 6.9 The switch daemon
+ 6.10 Slip
+ 6.11 Slirp
+ 6.12 pcap
+ 6.13 Setting up the host yourself
+
+ 7. Sharing Filesystems between Virtual Machines
+
+ 7.1 A warning
+ 7.2 Using layered block devices
+ 7.3 Note!
+ 7.4 Another warning
+ 7.5 uml_moo : Merging a COW file with its backing file
+
+ 8. Creating filesystems
+
+ 8.1 Create the filesystem file
+ 8.2 Assign the file to a UML device
+ 8.3 Creating and mounting the filesystem
+
+ 9. Host file access
+
+ 9.1 Using hostfs
+ 9.2 hostfs as the root filesystem
+ 9.3 Building hostfs
+
+ 10. The Management Console
+ 10.1 version
+ 10.2 halt and reboot
+ 10.3 config
+ 10.4 remove
+ 10.5 sysrq
+ 10.6 help
+ 10.7 cad
+ 10.8 stop
+ 10.9 go
+
+ 11. Kernel debugging
+
+ 11.1 Starting the kernel under gdb
+ 11.2 Examining sleeping processes
+ 11.3 Running ddd on UML
+ 11.4 Debugging modules
+ 11.5 Attaching gdb to the kernel
+ 11.6 Using alternate debuggers
+
+ 12. Kernel debugging examples
+
+ 12.1 The case of the hung fsck
+ 12.2 Episode 2: The case of the hung fsck
+
+ 13. What to do when UML doesn't work
+
+ 13.1 Strange compilation errors when you build from source
+ 13.2 (obsolete)
+ 13.3 A variety of panics and hangs with /tmp on a reiserfs filesystem
+ 13.4 The compile fails with errors about conflicting types for 'open', 'dup', and 'waitpid'
+ 13.5 UML doesn't work when /tmp is an NFS filesystem
+ 13.6 UML hangs on boot when compiled with gprof support
+ 13.7 syslogd dies with a SIGTERM on startup
+ 13.8 TUN/TAP networking doesn't work on a 2.4 host
+ 13.9 You can network to the host but not to other machines on the net
+ 13.10 I have no root and I want to scream
+ 13.11 UML build conflict between ptrace.h and ucontext.h
+ 13.12 The UML BogoMips is exactly half the host's BogoMips
+ 13.13 When you run UML, it immediately segfaults
+ 13.14 xterms appear, then immediately disappear
+ 13.15 Any other panic, hang, or strange behavior
+
+ 14. Diagnosing Problems
+
+ 14.1 Case 1 : Normal kernel panics
+ 14.2 Case 2 : Tracing thread panics
+ 14.3 Case 3 : Tracing thread panics caused by other threads
+ 14.4 Case 4 : Hangs
+
+ 15. Thanks
+
+ 15.1 Code and Documentation
+ 15.2 Flushing out bugs
+ 15.3 Buglets and clean-ups
+ 15.4 Case Studies
+ 15.5 Other contributions
+
+
+ ______________________________________________________________________
+
+ 1. Introduction
+
+ Welcome to User Mode Linux. It's going to be fun.
+
+
+
+ 1.1. How is User Mode Linux Different?
+
+ Normally, the Linux Kernel talks straight to your hardware (video
+ card, keyboard, hard drives, etc), and any programs which run ask the
+ kernel to operate the hardware, like so:
+
+
+
+ +-----------+-----------+----+
+ | Process 1 | Process 2 | ...|
+ +-----------+-----------+----+
+ | Linux Kernel |
+ +----------------------------+
+ | Hardware |
+ +----------------------------+
+
+
+
+
+ The User Mode Linux Kernel is different; instead of talking to the
+ hardware, it talks to a `real' Linux kernel (called the `host kernel'
+ from now on), like any other program. Programs can then run inside
+ User-Mode Linux as if they were running under a normal kernel, like
+ so:
+
+
+
+ +----------------+
+ | Process 2 | ...|
+ +-----------+----------------+
+ | Process 1 | User-Mode Linux|
+ +----------------------------+
+ | Linux Kernel |
+ +----------------------------+
+ | Hardware |
+ +----------------------------+
+
+
+
+
+
+ 1.2. Why Would I Want User Mode Linux?
+
+
+ 1. If User Mode Linux crashes, your host kernel is still fine.
+
+ 2. You can run a usermode kernel as a non-root user.
+
+ 3. You can debug the User Mode Linux like any normal process.
+
+ 4. You can run gprof (profiling) and gcov (coverage testing).
+
+ 5. You can play with your kernel without breaking things.
+
+ 6. You can use it as a sandbox for testing new apps.
+
+ 7. You can try new development kernels safely.
+
+ 8. You can run different distributions simultaneously.
+
+ 9. It's extremely fun.
+
+
+
+
+
+ 2. Compiling the kernel and modules
+
+
+
+
+ 2.1. Compiling the kernel
+
+
+ Compiling the user mode kernel is just like compiling any other
+ kernel. Let's go through the steps, using 2.4.0-prerelease (current
+ as of this writing) as an example:
+
+
+ 1. Download the latest UML patch from
+
+ the download page <http://user-mode-linux.sourceforge.net/
+
+ In this example, the file is uml-patch-2.4.0-prerelease.bz2.
+
+
+ 2. Download the matching kernel from your favourite kernel mirror,
+ such as:
+
+ ftp://ftp.ca.kernel.org/pub/kernel/v2.4/linux-2.4.0-prerelease.tar.bz2
+ <ftp://ftp.ca.kernel.org/pub/kernel/v2.4/linux-2.4.0-prerelease.tar.bz2>
+ .
+
+
+ 3. Make a directory and unpack the kernel into it.
+
+
+
+ host%
+ mkdir ~/uml
+
+
+
+
+
+
+ host%
+ cd ~/uml
+
+
+
+
+
+
+ host%
+ tar -xzvf linux-2.4.0-prerelease.tar.bz2
+
+
+
+
+
+
+ 4. Apply the patch using
+
+
+
+ host%
+ cd ~/uml/linux
+
+
+
+ host%
+ bzcat uml-patch-2.4.0-prerelease.bz2 | patch -p1
+
+
+
+
+
+
+ 5. Run your favorite config; `make xconfig ARCH=um' is the most
+ convenient. `make config ARCH=um' and 'make menuconfig ARCH=um'
+ will work as well. The defaults will give you a useful kernel. If
+ you want to change something, go ahead, it probably won't hurt
+ anything.
+
+
+ Note: If the host is configured with a 2G/2G address space split
+ rather than the usual 3G/1G split, then the packaged UML binaries
+ will not run. They will immediately segfault. See ``UML on 2G/2G
+ hosts'' for the scoop on running UML on your system.
+
+
+
+ 6. Finish with `make linux ARCH=um': the result is a file called
+ `linux' in the top directory of your source tree.
+
+ Make sure that you don't build this kernel in /usr/src/linux. On some
+ distributions, /usr/include/asm is a link into this pool. The user-
+ mode build changes the other end of that link, and things that include
+ <asm/anything.h> stop compiling.
+
+ The sources are also available from cvs at the project's cvs page,
+ which has directions on getting the sources. You can also browse the
+ CVS pool from there.
+
+ If you get the CVS sources, you will have to check them out into an
+ empty directory. You will then have to copy each file into the
+ corresponding directory in the appropriate kernel pool.
+
+ If you don't have the latest kernel pool, you can get the
+ corresponding user-mode sources with
+
+
+ host% cvs co -r v_2_3_x linux
+
+
+
+
+ where 'x' is the version in your pool. Note that you will not get the
+ bug fixes and enhancements that have gone into subsequent releases.
+
+
+ 2.2. Compiling and installing kernel modules
+
+ UML modules are built in the same way as the native kernel (with the
+ exception of the 'ARCH=um' that you always need for UML):
+
+
+ host% make modules ARCH=um
+
+
+
+
+ Any modules that you want to load into this kernel need to be built in
+ the user-mode pool. Modules from the native kernel won't work.
+
+ You can install them by using ftp or something to copy them into the
+ virtual machine and dropping them into /lib/modules/`uname -r`.
+
+ You can also get the kernel build process to install them as follows:
+
+ 1. with the kernel not booted, mount the root filesystem in the top
+ level of the kernel pool:
+
+
+ host% mount root_fs mnt -o loop
+
+
+
+
+
+
+ 2. run
+
+
+ host%
+ make modules_install INSTALL_MOD_PATH=`pwd`/mnt ARCH=um
+
+
+
+
+
+
+ 3. unmount the filesystem
+
+
+ host% umount mnt
+
+
+
+
+
+
+ 4. boot the kernel on it
+
+
+ When the system is booted, you can use insmod as usual to get the
+ modules into the kernel. A number of things have been loaded into UML
+ as modules, especially filesystems and network protocols and filters,
+ so most symbols which need to be exported probably already are.
+ However, if you do find symbols that need exporting, let us
+ <http://user-mode-linux.sourceforge.net/> know, and
+ they'll be "taken care of".
+
+
+
+ 2.3. Compiling and installing uml_utilities
+
+ Many features of the UML kernel require a user-space helper program,
+ so a uml_utilities package is distributed separately from the kernel
+ patch which provides these helpers. Included within this is:
+
+ o port-helper - Used by consoles which connect to xterms or ports
+
+ o tunctl - Configuration tool to create and delete tap devices
+
+ o uml_net - Setuid binary for automatic tap device configuration
+
+ o uml_switch - User-space virtual switch required for daemon
+ transport
+
+ The uml_utilities tree is compiled with:
+
+
+ host#
+ make && make install
+
+
+
+
+ Note that UML kernel patches may require a specific version of the
+ uml_utilities distribution. If you don't keep up with the mailing
+ lists, ensure that you have the latest release of uml_utilities if you
+ are experiencing problems with your UML kernel, particularly when
+ dealing with consoles or command-line switches to the helper programs
+
+
+
+
+
+
+
+
+ 3. Running UML and logging in
+
+
+
+ 3.1. Running UML
+
+ It runs on 2.2.15 or later, and all 2.4 kernels.
+
+
+ Booting UML is straightforward. Simply run 'linux': it will try to
+ mount the file `root_fs' in the current directory. You do not need to
+ run it as root. If your root filesystem is not named `root_fs', then
+ you need to put a `ubd0=root_fs_whatever' switch on the linux command
+ line.
+
+
+ You will need a filesystem to boot UML from. There are a number
+ available for download from here <http://user-mode-
+ linux.sourceforge.net/> . There are also several tools
+ <http://user-mode-linux.sourceforge.net/> which can be
+ used to generate UML-compatible filesystem images from media.
+ The kernel will boot up and present you with a login prompt.
+
+
+ Note: If the host is configured with a 2G/2G address space split
+ rather than the usual 3G/1G split, then the packaged UML binaries will
+ not run. They will immediately segfault. See ``UML on 2G/2G hosts''
+ for the scoop on running UML on your system.
+
+
+
+ 3.2. Logging in
+
+
+
+ The prepackaged filesystems have a root account with password 'root'
+ and a user account with password 'user'. The login banner will
+ generally tell you how to log in. So, you log in and you will find
+ yourself inside a little virtual machine. Our filesystems have a
+ variety of commands and utilities installed (and it is fairly easy to
+ add more), so you will have a lot of tools with which to poke around
+ the system.
+
+ There are a couple of other ways to log in:
+
+ o On a virtual console
+
+
+
+ Each virtual console that is configured (i.e. the device exists in
+ /dev and /etc/inittab runs a getty on it) will come up in its own
+ xterm. If you get tired of the xterms, read ``Setting up serial
+ lines and consoles'' to see how to attach the consoles to
+ something else, like host ptys.
+
+
+
+ o Over the serial line
+
+
+ In the boot output, find a line that looks like:
+
+
+
+ serial line 0 assigned pty /dev/ptyp1
+
+
+
+
+ Attach your favorite terminal program to the corresponding tty. I.e.
+ for minicom, the command would be
+
+
+ host% minicom -o -p /dev/ttyp1
+
+
+
+
+
+
+ o Over the net
+
+
+ If the network is running, then you can telnet to the virtual
+ machine and log in to it. See ``Setting up the network'' to learn
+ about setting up a virtual network.
+
+ When you're done using it, run halt, and the kernel will bring itself
+ down and the process will exit.
+
+
+ 3.3. Examples
+
+ Here are some examples of UML in action:
+
+ o A login session <http://user-mode-linux.sourceforge.net/login.html>
+
+ o A virtual network <http://user-mode-linux.sourceforge.net/net.html>
+
+
+
+
+
+
+
+ 4. UML on 2G/2G hosts
+
+
+
+
+ 4.1. Introduction
+
+
+ Most Linux machines are configured so that the kernel occupies the
+ upper 1G (0xc0000000 - 0xffffffff) of the 4G address space and
+ processes use the lower 3G (0x00000000 - 0xbfffffff). However, some
+ machine are configured with a 2G/2G split, with the kernel occupying
+ the upper 2G (0x80000000 - 0xffffffff) and processes using the lower
+ 2G (0x00000000 - 0x7fffffff).
+
+
+
+
+ 4.2. The problem
+
+
+ The prebuilt UML binaries on this site will not run on 2G/2G hosts
+ because UML occupies the upper .5G of the 3G process address space
+ (0xa0000000 - 0xbfffffff). Obviously, on 2G/2G hosts, this is right
+ in the middle of the kernel address space, so UML won't even load - it
+ will immediately segfault.
+
+
+
+
+ 4.3. The solution
+
+
+ The fix for this is to rebuild UML from source after enabling
+ CONFIG_HOST_2G_2G (under 'General Setup'). This will cause UML to
+ load itself in the top .5G of that smaller process address space,
+ where it will run fine. See ``Compiling the kernel and modules'' if
+ you need help building UML from source.
+
+
+
+
+
+
+
+
+
+
+ 5. Setting up serial lines and consoles
+
+
+ It is possible to attach UML serial lines and consoles to many types
+ of host I/O channels by specifying them on the command line.
+
+
+ You can attach them to host ptys, ttys, file descriptors, and ports.
+ This allows you to do things like
+
+ o have a UML console appear on an unused host console,
+
+ o hook two virtual machines together by having one attach to a pty
+ and having the other attach to the corresponding tty
+
+ o make a virtual machine accessible from the net by attaching a
+ console to a port on the host.
+
+
+ The general format of the command line option is device=channel.
+
+
+
+ 5.1. Specifying the device
+
+ Devices are specified with "con" or "ssl" (console or serial line,
+ respectively), optionally with a device number if you are talking
+ about a specific device.
+
+
+ Using just "con" or "ssl" describes all of the consoles or serial
+ lines. If you want to talk about console #3 or serial line #10, they
+ would be "con3" and "ssl10", respectively.
+
+
+ A specific device name will override a less general "con=" or "ssl=".
+ So, for example, you can assign a pty to each of the serial lines
+ except for the first two like this:
+
+
+ ssl=pty ssl0=tty:/dev/tty0 ssl1=tty:/dev/tty1
+
+
+
+
+ The specificity of the device name is all that matters; order on the
+ command line is irrelevant.
+
+
+
+ 5.2. Specifying the channel
+
+ There are a number of different types of channels to attach a UML
+ device to, each with a different way of specifying exactly what to
+ attach to.
+
+ o pseudo-terminals - device=pty pts terminals - device=pts
+
+
+ This will cause UML to allocate a free host pseudo-terminal for the
+ device. The terminal that it got will be announced in the boot
+ log. You access it by attaching a terminal program to the
+ corresponding tty:
+
+ o screen /dev/pts/n
+
+ o screen /dev/ttyxx
+
+ o minicom -o -p /dev/ttyxx - minicom seems not able to handle pts
+ devices
+
+ o kermit - start it up, 'open' the device, then 'connect'
+
+
+
+
+
+ o terminals - device=tty:tty device file
+
+
+ This will make UML attach the device to the specified tty (i.e
+
+
+ con1=tty:/dev/tty3
+
+
+
+
+ will attach UML's console 1 to the host's /dev/tty3). If the tty that
+ you specify is the slave end of a tty/pty pair, something else must
+ have already opened the corresponding pty in order for this to work.
+
+
+
+
+
+ o xterms - device=xterm
+
+
+ UML will run an xterm and the device will be attached to it.
+
+
+
+
+
+ o Port - device=port:port number
+
+
+ This will attach the UML devices to the specified host port.
+ Attaching console 1 to the host's port 9000 would be done like
+ this:
+
+
+ con1=port:9000
+
+
+
+
+ Attaching all the serial lines to that port would be done similarly:
+
+
+ ssl=port:9000
+
+
+
+
+ You access these devices by telnetting to that port. Each active tel-
+ net session gets a different device. If there are more telnets to a
+ port than UML devices attached to it, then the extra telnet sessions
+ will block until an existing telnet detaches, or until another device
+ becomes active (i.e. by being activated in /etc/inittab).
+
+ This channel has the advantage that you can both attach multiple UML
+ devices to it and know how to access them without reading the UML boot
+ log. It is also unique in allowing access to a UML from remote
+ machines without requiring that the UML be networked. This could be
+ useful in allowing public access to UMLs because they would be
+ accessible from the net, but wouldn't need any kind of network
+ filtering or access control because they would have no network access.
+
+
+ If you attach the main console to a portal, then the UML boot will
+ appear to hang. In reality, it's waiting for a telnet to connect, at
+ which point the boot will proceed.
+
+
+
+
+
+ o already-existing file descriptors - device=file descriptor
+
+
+ If you set up a file descriptor on the UML command line, you can
+ attach a UML device to it. This is most commonly used to put the
+ main console back on stdin and stdout after assigning all the other
+ consoles to something else:
+
+
+ con0=fd:0,fd:1 con=pts
+
+
+
+
+
+
+
+
+ o Nothing - device=null
+
+
+ This allows the device to be opened, in contrast to 'none', but
+ reads will block, and writes will succeed and the data will be
+ thrown out.
+
+
+
+
+
+ o None - device=none
+
+
+ This causes the device to disappear.
+
+
+
+ You can also specify different input and output channels for a device
+ by putting a comma between them:
+
+
+ ssl3=tty:/dev/tty2,xterm
+
+
+
+
+ will cause serial line 3 to accept input on the host's /dev/tty2 and
+ display output on an xterm. That's a silly example - the most common
+ use of this syntax is to reattach the main console to stdin and stdout
+ as shown above.
+
+
+ If you decide to move the main console away from stdin/stdout, the
+ initial boot output will appear in the terminal that you're running
+ UML in. However, once the console driver has been officially
+ initialized, then the boot output will start appearing wherever you
+ specified that console 0 should be. That device will receive all
+ subsequent output.
+
+
+
+ 5.3. Examples
+
+ There are a number of interesting things you can do with this
+ capability.
+
+
+ First, this is how you get rid of those bleeding console xterms by
+ attaching them to host ptys:
+
+
+ con=pty con0=fd:0,fd:1
+
+
+
+
+ This will make a UML console take over an unused host virtual console,
+ so that when you switch to it, you will see the UML login prompt
+ rather than the host login prompt:
+
+
+ con1=tty:/dev/tty6
+
+
+
+
+ You can attach two virtual machines together with what amounts to a
+ serial line as follows:
+
+ Run one UML with a serial line attached to a pty -
+
+
+ ssl1=pty
+
+
+
+
+ Look at the boot log to see what pty it got (this example will assume
+ that it got /dev/ptyp1).
+
+ Boot the other UML with a serial line attached to the corresponding
+ tty -
+
+
+ ssl1=tty:/dev/ttyp1
+
+
+
+
+ Log in, make sure that it has no getty on that serial line, attach a
+ terminal program like minicom to it, and you should see the login
+ prompt of the other virtual machine.
+
+
+ 6. Setting up the network
+
+
+
+ This page describes how to set up the various transports and to
+ provide a UML instance with network access to the host, other machines
+ on the local net, and the rest of the net.
+
+
+ As of 2.4.5, UML networking has been completely redone to make it much
+ easier to set up, fix bugs, and add new features.
+
+
+ There is a new helper, uml_net, which does the host setup that
+ requires root privileges.
+
+
+ There are currently five transport types available for a UML virtual
+ machine to exchange packets with other hosts:
+
+ o ethertap
+
+ o TUN/TAP
+
+ o Multicast
+
+ o a switch daemon
+
+ o slip
+
+ o slirp
+
+ o pcap
+
+ The TUN/TAP, ethertap, slip, and slirp transports allow a UML
+ instance to exchange packets with the host. They may be directed
+ to the host or the host may just act as a router to provide access
+ to other physical or virtual machines.
+
+
+ The pcap transport is a synthetic read-only interface, using the
+ libpcap binary to collect packets from interfaces on the host and
+ filter them. This is useful for building preconfigured traffic
+ monitors or sniffers.
+
+
+ The daemon and multicast transports provide a completely virtual
+ network to other virtual machines. This network is completely
+ disconnected from the physical network unless one of the virtual
+ machines on it is acting as a gateway.
+
+
+ With so many host transports, which one should you use? Here's when
+ you should use each one:
+
+ o ethertap - if you want access to the host networking and it is
+ running 2.2
+
+ o TUN/TAP - if you want access to the host networking and it is
+ running 2.4. Also, the TUN/TAP transport is able to use a
+ preconfigured device, allowing it to avoid using the setuid uml_net
+ helper, which is a security advantage.
+
+ o Multicast - if you want a purely virtual network and you don't want
+ to set up anything but the UML
+
+ o a switch daemon - if you want a purely virtual network and you
+ don't mind running the daemon in order to get somewhat better
+ performance
+
+ o slip - there is no particular reason to run the slip backend unless
+ ethertap and TUN/TAP are just not available for some reason
+
+ o slirp - if you don't have root access on the host to setup
+ networking, or if you don't want to allocate an IP to your UML
+
+ o pcap - not much use for actual network connectivity, but great for
+ monitoring traffic on the host
+
+ Ethertap is available on 2.4 and works fine. TUN/TAP is preferred
+ to it because it has better performance and ethertap is officially
+ considered obsolete in 2.4. Also, the root helper only needs to
+ run occasionally for TUN/TAP, rather than handling every packet, as
+ it does with ethertap. This is a slight security advantage since
+ it provides fewer opportunities for a nasty UML user to somehow
+ exploit the helper's root privileges.
+
+
+ 6.1. General setup
+
+ First, you must have the virtual network enabled in your UML. If are
+ running a prebuilt kernel from this site, everything is already
+ enabled. If you build the kernel yourself, under the "Network device
+ support" menu, enable "Network device support", and then the three
+ transports.
+
+
+ The next step is to provide a network device to the virtual machine.
+ This is done by describing it on the kernel command line.
+
+ The general format is
+
+
+ eth <n> = <transport> , <transport args>
+
+
+
+
+ For example, a virtual ethernet device may be attached to a host
+ ethertap device as follows:
+
+
+ eth0=ethertap,tap0,fe:fd:0:0:0:1,192.168.0.254
+
+
+
+
+ This sets up eth0 inside the virtual machine to attach itself to the
+ host /dev/tap0, assigns it an ethernet address, and assigns the host
+ tap0 interface an IP address.
+
+
+
+ Note that the IP address you assign to the host end of the tap device
+ must be different than the IP you assign to the eth device inside UML.
+ If you are short on IPs and don't want to consume two per UML, then
+ you can reuse the host's eth IP address for the host ends of the tap
+ devices. Internally, the UMLs must still get unique IPs for their eth
+ devices. You can also give the UMLs non-routable IPs (192.168.x.x or
+ 10.x.x.x) and have the host masquerade them. This will let outgoing
+ connections work, but incoming connections won't without more work,
+ such as port forwarding from the host.
+ Also note that when you configure the host side of an interface, it is
+ only acting as a gateway. It will respond to pings sent to it
+ locally, but is not useful to do that since it's a host interface.
+ You are not talking to the UML when you ping that interface and get a
+ response.
+
+
+ You can also add devices to a UML and remove them at runtime. See the
+ ``The Management Console'' page for details.
+
+
+ The sections below describe this in more detail.
+
+
+ Once you've decided how you're going to set up the devices, you boot
+ UML, log in, configure the UML side of the devices, and set up routes
+ to the outside world. At that point, you will be able to talk to any
+ other machines, physical or virtual, on the net.
+
+
+ If ifconfig inside UML fails and the network refuses to come up, run
+ tell you what went wrong.
+
+
+
+ 6.2. Userspace daemons
+
+ You will likely need the setuid helper, or the switch daemon, or both.
+ They are both installed with the RPM and deb, so if you've installed
+ either, you can skip the rest of this section.
+
+
+ If not, then you need to check them out of CVS, build them, and
+ install them. The helper is uml_net, in CVS /tools/uml_net, and the
+ daemon is uml_switch, in CVS /tools/uml_router. They are both built
+ with a plain 'make'. Both need to be installed in a directory that's
+ in your path - /usr/bin is recommend. On top of that, uml_net needs
+ to be setuid root.
+
+
+
+ 6.3. Specifying ethernet addresses
+
+ Below, you will see that the TUN/TAP, ethertap, and daemon interfaces
+ allow you to specify hardware addresses for the virtual ethernet
+ devices. This is generally not necessary. If you don't have a
+ specific reason to do it, you probably shouldn't. If one is not
+ specified on the command line, the driver will assign one based on the
+ device IP address. It will provide the address fe:fd:nn:nn:nn:nn
+ where nn.nn.nn.nn is the device IP address. This is nearly always
+ sufficient to guarantee a unique hardware address for the device. A
+ couple of exceptions are:
+
+ o Another set of virtual ethernet devices are on the same network and
+ they are assigned hardware addresses using a different scheme which
+ may conflict with the UML IP address-based scheme
+
+ o You aren't going to use the device for IP networking, so you don't
+ assign the device an IP address
+
+ If you let the driver provide the hardware address, you should make
+ sure that the device IP address is known before the interface is
+ brought up. So, inside UML, this will guarantee that:
+
+
+
+ UML#
+ ifconfig eth0 192.168.0.250 up
+
+
+
+
+ If you decide to assign the hardware address yourself, make sure that
+ the first byte of the address is even. Addresses with an odd first
+ byte are broadcast addresses, which you don't want assigned to a
+ device.
+
+
+
+ 6.4. UML interface setup
+
+ Once the network devices have been described on the command line, you
+ should boot UML and log in.
+
+
+ The first thing to do is bring the interface up:
+
+
+ UML# ifconfig ethn ip-address up
+
+
+
+
+ You should be able to ping the host at this point.
+
+
+ To reach the rest of the world, you should set a default route to the
+ host:
+
+
+ UML# route add default gw host ip
+
+
+
+
+ Again, with host ip of 192.168.0.4:
+
+
+ UML# route add default gw 192.168.0.4
+
+
+
+
+ This page used to recommend setting a network route to your local net.
+ This is wrong, because it will cause UML to try to figure out hardware
+ addresses of the local machines by arping on the interface to the
+ host. Since that interface is basically a single strand of ethernet
+ with two nodes on it (UML and the host) and arp requests don't cross
+ networks, they will fail to elicit any responses. So, what you want
+ is for UML to just blindly throw all packets at the host and let it
+ figure out what to do with them, which is what leaving out the network
+ route and adding the default route does.
+
+
+ Note: If you can't communicate with other hosts on your physical
+ ethernet, it's probably because of a network route that's
+ automatically set up. If you run 'route -n' and see a route that
+ looks like this:
+
+
+
+
+ Destination Gateway Genmask Flags Metric Ref Use Iface
+ 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
+
+
+
+
+ with a mask that's not 255.255.255.255, then replace it with a route
+ to your host:
+
+
+ UML#
+ route del -net 192.168.0.0 dev eth0 netmask 255.255.255.0
+
+
+
+
+
+
+ UML#
+ route add -host 192.168.0.4 dev eth0
+
+
+
+
+ This, plus the default route to the host, will allow UML to exchange
+ packets with any machine on your ethernet.
+
+
+
+ 6.5. Multicast
+
+ The simplest way to set up a virtual network between multiple UMLs is
+ to use the mcast transport. This was written by Harald Welte and is
+ present in UML version 2.4.5-5um and later. Your system must have
+ multicast enabled in the kernel and there must be a multicast-capable
+ network device on the host. Normally, this is eth0, but if there is
+ no ethernet card on the host, then you will likely get strange error
+ messages when you bring the device up inside UML.
+
+
+ To use it, run two UMLs with
+
+
+ eth0=mcast
+
+
+
+
+ on their command lines. Log in, configure the ethernet device in each
+ machine with different IP addresses:
+
+
+ UML1# ifconfig eth0 192.168.0.254
+
+
+
+
+
+
+ UML2# ifconfig eth0 192.168.0.253
+
+
+
+
+ and they should be able to talk to each other.
+
+ The full set of command line options for this transport are
+
+
+
+ ethn=mcast,ethernet address,multicast
+ address,multicast port,ttl
+
+
+
+
+ Harald's original README is here <http://user-mode-linux.source-
+ forge.net/> and explains these in detail, as well as
+ some other issues.
+
+ There is also a related point-to-point only "ucast" transport.
+ This is useful when your network does not support multicast, and
+ all network connections are simple point to point links.
+
+ The full set of command line options for this transport are
+
+
+ ethn=ucast,ethernet address,remote address,listen port,remote port
+
+
+
+
+ 6.6. TUN/TAP with the uml_net helper
+
+ TUN/TAP is the preferred mechanism on 2.4 to exchange packets with the
+ host. The TUN/TAP backend has been in UML since 2.4.9-3um.
+
+
+ The easiest way to get up and running is to let the setuid uml_net
+ helper do the host setup for you. This involves insmod-ing the tun.o
+ module if necessary, configuring the device, and setting up IP
+ forwarding, routing, and proxy arp. If you are new to UML networking,
+ do this first. If you're concerned about the security implications of
+ the setuid helper, use it to get up and running, then read the next
+ section to see how to have UML use a preconfigured tap device, which
+ avoids the use of uml_net.
+
+
+ If you specify an IP address for the host side of the device, the
+ uml_net helper will do all necessary setup on the host - the only
+ requirement is that TUN/TAP be available, either built in to the host
+ kernel or as the tun.o module.
+
+ The format of the command line switch to attach a device to a TUN/TAP
+ device is
+
+
+ eth <n> =tuntap,,, <IP address>
+
+
+
+
+ For example, this argument will attach the UML's eth0 to the next
+ available tap device and assign an ethernet address to it based on its
+ IP address
+
+
+ eth0=tuntap,,,192.168.0.254
+
+
+
+
+
+
+ Note that the IP address that must be used for the eth device inside
+ UML is fixed by the routing and proxy arp that is set up on the
+ TUN/TAP device on the host. You can use a different one, but it won't
+ work because reply packets won't reach the UML. This is a feature.
+ It prevents a nasty UML user from doing things like setting the UML IP
+ to the same as the network's nameserver or mail server.
+
+
+ There are a couple potential problems with running the TUN/TAP
+ transport on a 2.4 host kernel
+
+ o TUN/TAP seems not to work on 2.4.3 and earlier. Upgrade the host
+ kernel or use the ethertap transport.
+
+ o With an upgraded kernel, TUN/TAP may fail with
+
+
+ File descriptor in bad state
+
+
+
+
+ This is due to a header mismatch between the upgraded kernel and the
+ kernel that was originally installed on the machine. The fix is to
+ make sure that /usr/src/linux points to the headers for the running
+ kernel.
+
+ These were pointed out by Tim Robinson <timro at trkr dot net> in
+ <http://www.geocrawler.com/> name="this uml-
+ user post"> .
+
+
+
+ 6.7. TUN/TAP with a preconfigured tap device
+
+ If you prefer not to have UML use uml_net (which is somewhat
+ insecure), with UML 2.4.17-11, you can set up a TUN/TAP device
+ beforehand. The setup needs to be done as root, but once that's done,
+ there is no need for root assistance. Setting up the device is done
+ as follows:
+
+ o Create the device with tunctl (available from the UML utilities
+ tarball)
+
+
+
+
+ host# tunctl -u uid
+
+
+
+
+ where uid is the user id or username that UML will be run as. This
+ will tell you what device was created.
+
+ o Configure the device IP (change IP addresses and device name to
+ suit)
+
+
+
+
+ host# ifconfig tap0 192.168.0.254 up
+
+
+
+
+
+ o Set up routing and arping if desired - this is my recipe, there are
+ other ways of doing the same thing
+
+
+ host#
+ bash -c 'echo 1 > /proc/sys/net/ipv4/ip_forward'
+
+ host#
+ route add -host 192.168.0.253 dev tap0
+
+
+
+
+
+
+ host#
+ bash -c 'echo 1 > /proc/sys/net/ipv4/conf/tap0/proxy_arp'
+
+
+
+
+
+
+ host#
+ arp -Ds 192.168.0.253 eth0 pub
+
+
+
+
+ Note that this must be done every time the host boots - this configu-
+ ration is not stored across host reboots. So, it's probably a good
+ idea to stick it in an rc file. An even better idea would be a little
+ utility which reads the information from a config file and sets up
+ devices at boot time.
+
+ o Rather than using up two IPs and ARPing for one of them, you can
+ also provide direct access to your LAN by the UML by using a
+ bridge.
+
+
+ host#
+ brctl addbr br0
+
+
+
+
+
+
+ host#
+ ifconfig eth0 0.0.0.0 promisc up
+
+
+
+
+
+
+ host#
+ ifconfig tap0 0.0.0.0 promisc up
+
+
+
+
+
+
+ host#
+ ifconfig br0 192.168.0.1 netmask 255.255.255.0 up
+
+
+
+
+
+
+
+ host#
+ brctl stp br0 off
+
+
+
+
+
+
+ host#
+ brctl setfd br0 1
+
+
+
+
+
+
+ host#
+ brctl sethello br0 1
+
+
+
+
+
+
+ host#
+ brctl addif br0 eth0
+
+
+
+
+
+
+ host#
+ brctl addif br0 tap0
+
+
+
+
+ Note that 'br0' should be setup using ifconfig with the existing IP
+ address of eth0, as eth0 no longer has its own IP.
+
+ o
+
+
+ Also, the /dev/net/tun device must be writable by the user running
+ UML in order for the UML to use the device that's been configured
+ for it. The simplest thing to do is
+
+
+ host# chmod 666 /dev/net/tun
+
+
+
+
+ Making it world-writable looks bad, but it seems not to be
+ exploitable as a security hole. However, it does allow anyone to cre-
+ ate useless tap devices (useless because they can't configure them),
+ which is a DOS attack. A somewhat more secure alternative would to be
+ to create a group containing all the users who have preconfigured tap
+ devices and chgrp /dev/net/tun to that group with mode 664 or 660.
+
+
+ o Once the device is set up, run UML with 'eth0=tuntap,device name'
+ (i.e. 'eth0=tuntap,tap0') on the command line (or do it with the
+ mconsole config command).
+
+ o Bring the eth device up in UML and you're in business.
+
+ If you don't want that tap device any more, you can make it non-
+ persistent with
+
+
+ host# tunctl -d tap device
+
+
+
+
+ Finally, tunctl has a -b (for brief mode) switch which causes it to
+ output only the name of the tap device it created. This makes it
+ suitable for capture by a script:
+
+
+ host# TAP=`tunctl -u 1000 -b`
+
+
+
+
+
+
+ 6.8. Ethertap
+
+ Ethertap is the general mechanism on 2.2 for userspace processes to
+ exchange packets with the kernel.
+
+
+
+ To use this transport, you need to describe the virtual network device
+ on the UML command line. The general format for this is
+
+
+ eth <n> =ethertap, <device> , <ethernet address> , <tap IP address>
+
+
+
+
+ So, the previous example
+
+
+ eth0=ethertap,tap0,fe:fd:0:0:0:1,192.168.0.254
+
+
+
+
+ attaches the UML eth0 device to the host /dev/tap0, assigns it the
+ ethernet address fe:fd:0:0:0:1, and assigns the IP address
+ 192.168.0.254 to the tap device.
+
+
+
+ The tap device is mandatory, but the others are optional. If the
+ ethernet address is omitted, one will be assigned to it.
+
+
+ The presence of the tap IP address will cause the helper to run and do
+ whatever host setup is needed to allow the virtual machine to
+ communicate with the outside world. If you're not sure you know what
+ you're doing, this is the way to go.
+
+
+ If it is absent, then you must configure the tap device and whatever
+ arping and routing you will need on the host. However, even in this
+ case, the uml_net helper still needs to be in your path and it must be
+ setuid root if you're not running UML as root. This is because the
+ tap device doesn't support SIGIO, which UML needs in order to use
+ something as a source of input. So, the helper is used as a
+ convenient asynchronous IO thread.
+
+ If you're using the uml_net helper, you can ignore the following host
+ setup - uml_net will do it for you. You just need to make sure you
+ have ethertap available, either built in to the host kernel or
+ available as a module.
+
+
+ If you want to set things up yourself, you need to make sure that the
+ appropriate /dev entry exists. If it doesn't, become root and create
+ it as follows:
+
+
+ mknod /dev/tap <minor> c 36 <minor> + 16
+
+
+
+
+ For example, this is how to create /dev/tap0:
+
+
+ mknod /dev/tap0 c 36 0 + 16
+
+
+
+
+ You also need to make sure that the host kernel has ethertap support.
+ If ethertap is enabled as a module, you apparently need to insmod
+ ethertap once for each ethertap device you want to enable. So,
+
+
+ host#
+ insmod ethertap
+
+
+
+
+ will give you the tap0 interface. To get the tap1 interface, you need
+ to run
+
+
+ host#
+ insmod ethertap unit=1 -o ethertap1
+
+
+
+
+
+
+
+ 6.9. The switch daemon
+
+ Note: This is the daemon formerly known as uml_router, but which was
+ renamed so the network weenies of the world would stop growling at me.
+
+
+ The switch daemon, uml_switch, provides a mechanism for creating a
+ totally virtual network. By default, it provides no connection to the
+ host network (but see -tap, below).
+
+
+ The first thing you need to do is run the daemon. Running it with no
+ arguments will make it listen on a default pair of unix domain
+ sockets.
+
+
+ If you want it to listen on a different pair of sockets, use
+
+
+ -unix control socket data socket
+
+
+
+
+
+ If you want it to act as a hub rather than a switch, use
+
+
+ -hub
+
+
+
+
+
+ If you want the switch to be connected to host networking (allowing
+ the umls to get access to the outside world through the host), use
+
+
+ -tap tap0
+
+
+
+
+
+ Note that the tap device must be preconfigured (see "TUN/TAP with a
+ preconfigured tap device", above). If you're using a different tap
+ device than tap0, specify that instead of tap0.
+
+
+ uml_switch can be backgrounded as follows
+
+
+ host%
+ uml_switch [ options ] < /dev/null > /dev/null
+
+
+
+
+ The reason it doesn't background by default is that it listens to
+ stdin for EOF. When it sees that, it exits.
+
+
+ The general format of the kernel command line switch is
+
+
+
+ ethn=daemon,ethernet address,socket
+ type,control socket,data socket
+
+
+
+
+ You can leave off everything except the 'daemon'. You only need to
+ specify the ethernet address if the one that will be assigned to it
+ isn't acceptable for some reason. The rest of the arguments describe
+ how to communicate with the daemon. You should only specify them if
+ you told the daemon to use different sockets than the default. So, if
+ you ran the daemon with no arguments, running the UML on the same
+ machine with
+ eth0=daemon
+
+
+
+
+ will cause the eth0 driver to attach itself to the daemon correctly.
+
+
+
+ 6.10. Slip
+
+ Slip is another, less general, mechanism for a process to communicate
+ with the host networking. In contrast to the ethertap interface,
+ which exchanges ethernet frames with the host and can be used to
+ transport any higher-level protocol, it can only be used to transport
+ IP.
+
+
+ The general format of the command line switch is
+
+
+
+ ethn=slip,slip IP
+
+
+
+
+ The slip IP argument is the IP address that will be assigned to the
+ host end of the slip device. If it is specified, the helper will run
+ and will set up the host so that the virtual machine can reach it and
+ the rest of the network.
+
+
+ There are some oddities with this interface that you should be aware
+ of. You should only specify one slip device on a given virtual
+ machine, and its name inside UML will be 'umn', not 'eth0' or whatever
+ you specified on the command line. These problems will be fixed at
+ some point.
+
+
+
+ 6.11. Slirp
+
+ slirp uses an external program, usually /usr/bin/slirp, to provide IP
+ only networking connectivity through the host. This is similar to IP
+ masquerading with a firewall, although the translation is performed in
+ user-space, rather than by the kernel. As slirp does not set up any
+ interfaces on the host, or changes routing, slirp does not require
+ root access or setuid binaries on the host.
+
+
+ The general format of the command line switch for slirp is:
+
+
+
+ ethn=slirp,ethernet address,slirp path
+
+
+
+
+ The ethernet address is optional, as UML will set up the interface
+ with an ethernet address based upon the initial IP address of the
+ interface. The slirp path is generally /usr/bin/slirp, although it
+ will depend on distribution.
+
+
+ The slirp program can have a number of options passed to the command
+ line and we can't add them to the UML command line, as they will be
+ parsed incorrectly. Instead, a wrapper shell script can be written or
+ the options inserted into the /.slirprc file. More information on
+ all of the slirp options can be found in its man pages.
+
+
+ The eth0 interface on UML should be set up with the IP 10.2.0.15,
+ although you can use anything as long as it is not used by a network
+ you will be connecting to. The default route on UML should be set to
+ use
+
+
+ UML#
+ route add default dev eth0
+
+
+
+
+ slirp provides a number of useful IP addresses which can be used by
+ UML, such as 10.0.2.3 which is an alias for the DNS server specified
+ in /etc/resolv.conf on the host or the IP given in the 'dns' option
+ for slirp.
+
+
+ Even with a baudrate setting higher than 115200, the slirp connection
+ is limited to 115200. If you need it to go faster, the slirp binary
+ needs to be compiled with FULL_BOLT defined in config.h.
+
+
+
+ 6.12. pcap
+
+ The pcap transport is attached to a UML ethernet device on the command
+ line or with uml_mconsole with the following syntax:
+
+
+
+ ethn=pcap,host interface,filter
+ expression,option1,option2
+
+
+
+
+ The expression and options are optional.
+
+
+ The interface is whatever network device on the host you want to
+ sniff. The expression is a pcap filter expression, which is also what
+ tcpdump uses, so if you know how to specify tcpdump filters, you will
+ use the same expressions here. The options are up to two of
+ 'promisc', control whether pcap puts the host interface into
+ promiscuous mode. 'optimize' and 'nooptimize' control whether the pcap
+ expression optimizer is used.
+
+
+ Example:
+
+
+
+ eth0=pcap,eth0,tcp
+
+ eth1=pcap,eth0,!tcp
+
+
+
+ will cause the UML eth0 to emit all tcp packets on the host eth0 and
+ the UML eth1 to emit all non-tcp packets on the host eth0.
+
+
+
+ 6.13. Setting up the host yourself
+
+ If you don't specify an address for the host side of the ethertap or
+ slip device, UML won't do any setup on the host. So this is what is
+ needed to get things working (the examples use a host-side IP of
+ 192.168.0.251 and a UML-side IP of 192.168.0.250 - adjust to suit your
+ own network):
+
+ o The device needs to be configured with its IP address. Tap devices
+ are also configured with an mtu of 1484. Slip devices are
+ configured with a point-to-point address pointing at the UML ip
+ address.
+
+
+ host# ifconfig tap0 arp mtu 1484 192.168.0.251 up
+
+
+
+
+
+
+ host#
+ ifconfig sl0 192.168.0.251 pointopoint 192.168.0.250 up
+
+
+
+
+
+ o If a tap device is being set up, a route is set to the UML IP.
+
+
+ UML# route add -host 192.168.0.250 gw 192.168.0.251
+
+
+
+
+
+ o To allow other hosts on your network to see the virtual machine,
+ proxy arp is set up for it.
+
+
+ host# arp -Ds 192.168.0.250 eth0 pub
+
+
+
+
+
+ o Finally, the host is set up to route packets.
+
+
+ host# echo 1 > /proc/sys/net/ipv4/ip_forward
+
+
+
+
+
+
+
+
+
+
+ 7. Sharing Filesystems between Virtual Machines
+
+
+
+
+ 7.1. A warning
+
+ Don't attempt to share filesystems simply by booting two UMLs from the
+ same file. That's the same thing as booting two physical machines
+ from a shared disk. It will result in filesystem corruption.
+
+
+
+ 7.2. Using layered block devices
+
+ The way to share a filesystem between two virtual machines is to use
+ the copy-on-write (COW) layering capability of the ubd block driver.
+ As of 2.4.6-2um, the driver supports layering a read-write private
+ device over a read-only shared device. A machine's writes are stored
+ in the private device, while reads come from either device - the
+ private one if the requested block is valid in it, the shared one if
+ not. Using this scheme, the majority of data which is unchanged is
+ shared between an arbitrary number of virtual machines, each of which
+ has a much smaller file containing the changes that it has made. With
+ a large number of UMLs booting from a large root filesystem, this
+ leads to a huge disk space saving. It will also help performance,
+ since the host will be able to cache the shared data using a much
+ smaller amount of memory, so UML disk requests will be served from the
+ host's memory rather than its disks.
+
+
+
+
+ To add a copy-on-write layer to an existing block device file, simply
+ add the name of the COW file to the appropriate ubd switch:
+
+
+ ubd0=root_fs_cow,root_fs_debian_22
+
+
+
+
+ where 'root_fs_cow' is the private COW file and 'root_fs_debian_22' is
+ the existing shared filesystem. The COW file need not exist. If it
+ doesn't, the driver will create and initialize it. Once the COW file
+ has been initialized, it can be used on its own on the command line:
+
+
+ ubd0=root_fs_cow
+
+
+
+
+ The name of the backing file is stored in the COW file header, so it
+ would be redundant to continue specifying it on the command line.
+
+
+
+ 7.3. Note!
+
+ When checking the size of the COW file in order to see the gobs of
+ space that you're saving, make sure you use 'ls -ls' to see the actual
+ disk consumption rather than the length of the file. The COW file is
+ sparse, so the length will be very different from the disk usage.
+ Here is a 'ls -l' of a COW file and backing file from one boot and
+ shutdown:
+ host% ls -l cow.debian debian2.2
+ -rw-r--r-- 1 jdike jdike 492504064 Aug 6 21:16 cow.debian
+ -rwxrw-rw- 1 jdike jdike 537919488 Aug 6 20:42 debian2.2
+
+
+
+
+ Doesn't look like much saved space, does it? Well, here's 'ls -ls':
+
+
+ host% ls -ls cow.debian debian2.2
+ 880 -rw-r--r-- 1 jdike jdike 492504064 Aug 6 21:16 cow.debian
+ 525832 -rwxrw-rw- 1 jdike jdike 537919488 Aug 6 20:42 debian2.2
+
+
+
+
+ Now, you can see that the COW file has less than a meg of disk, rather
+ than 492 meg.
+
+
+
+ 7.4. Another warning
+
+ Once a filesystem is being used as a readonly backing file for a COW
+ file, do not boot directly from it or modify it in any way. Doing so
+ will invalidate any COW files that are using it. The mtime and size
+ of the backing file are stored in the COW file header at its creation,
+ and they must continue to match. If they don't, the driver will
+ refuse to use the COW file.
+
+
+
+
+ If you attempt to evade this restriction by changing either the
+ backing file or the COW header by hand, you will get a corrupted
+ filesystem.
+
+
+
+
+ Among other things, this means that upgrading the distribution in a
+ backing file and expecting that all of the COW files using it will see
+ the upgrade will not work.
+
+
+
+
+ 7.5. uml_moo : Merging a COW file with its backing file
+
+ Depending on how you use UML and COW devices, it may be advisable to
+ merge the changes in the COW file into the backing file every once in
+ a while.
+
+
+
+
+ The utility that does this is uml_moo. Its usage is
+
+
+ host% uml_moo COW file new backing file
+
+
+
+
+ There's no need to specify the backing file since that information is
+ already in the COW file header. If you're paranoid, boot the new
+ merged file, and if you're happy with it, move it over the old backing
+ file.
+
+
+
+
+ uml_moo creates a new backing file by default as a safety measure. It
+ also has a destructive merge option which will merge the COW file
+ directly into its current backing file. This is really only usable
+ when the backing file only has one COW file associated with it. If
+ there are multiple COWs associated with a backing file, a -d merge of
+ one of them will invalidate all of the others. However, it is
+ convenient if you're short of disk space, and it should also be
+ noticeably faster than a non-destructive merge.
+
+
+
+
+ uml_moo is installed with the UML deb and RPM. If you didn't install
+ UML from one of those packages, you can also get it from the UML
+ utilities <http://user-mode-linux.sourceforge.net/
+ utilities> tar file in tools/moo.
+
+
+
+
+
+
+
+
+ 8. Creating filesystems
+
+
+ You may want to create and mount new UML filesystems, either because
+ your root filesystem isn't large enough or because you want to use a
+ filesystem other than ext2.
+
+
+ This was written on the occasion of reiserfs being included in the
+ 2.4.1 kernel pool, and therefore the 2.4.1 UML, so the examples will
+ talk about reiserfs. This information is generic, and the examples
+ should be easy to translate to the filesystem of your choice.
+
+
+ 8.1. Create the filesystem file
+
+ dd is your friend. All you need to do is tell dd to create an empty
+ file of the appropriate size. I usually make it sparse to save time
+ and to avoid allocating disk space until it's actually used. For
+ example, the following command will create a sparse 100 meg file full
+ of zeroes.
+
+
+ host%
+ dd if=/dev/zero of=new_filesystem seek=100 count=1 bs=1M
+
+
+
+
+
+
+ 8.2. Assign the file to a UML device
+
+ Add an argument like the following to the UML command line:
+
+ ubd4=new_filesystem
+
+
+
+
+ making sure that you use an unassigned ubd device number.
+
+
+
+ 8.3. Creating and mounting the filesystem
+
+ Make sure that the filesystem is available, either by being built into
+ the kernel, or available as a module, then boot up UML and log in. If
+ the root filesystem doesn't have the filesystem utilities (mkfs, fsck,
+ etc), then get them into UML by way of the net or hostfs.
+
+
+ Make the new filesystem on the device assigned to the new file:
+
+
+ host# mkreiserfs /dev/ubd/4
+
+
+ <----------- MKREISERFSv2 ----------->
+
+ ReiserFS version 3.6.25
+ Block size 4096 bytes
+ Block count 25856
+ Used blocks 8212
+ Journal - 8192 blocks (18-8209), journal header is in block 8210
+ Bitmaps: 17
+ Root block 8211
+ Hash function "r5"
+ ATTENTION: ALL DATA WILL BE LOST ON '/dev/ubd/4'! (y/n)y
+ journal size 8192 (from 18)
+ Initializing journal - 0%....20%....40%....60%....80%....100%
+ Syncing..done.
+
+
+
+
+ Now, mount it:
+
+
+ UML#
+ mount /dev/ubd/4 /mnt
+
+
+
+
+ and you're in business.
+
+
+
+
+
+
+
+
+
+ 9. Host file access
+
+
+ If you want to access files on the host machine from inside UML, you
+ can treat it as a separate machine and either nfs mount directories
+ from the host or copy files into the virtual machine with scp or rcp.
+ However, since UML is running on the host, it can access those
+ files just like any other process and make them available inside the
+ virtual machine without needing to use the network.
+
+
+ This is now possible with the hostfs virtual filesystem. With it, you
+ can mount a host directory into the UML filesystem and access the
+ files contained in it just as you would on the host.
+
+
+ 9.1. Using hostfs
+
+ To begin with, make sure that hostfs is available inside the virtual
+ machine with
+
+
+ UML# cat /proc/filesystems
+
+
+
+ . hostfs should be listed. If it's not, either rebuild the kernel
+ with hostfs configured into it or make sure that hostfs is built as a
+ module and available inside the virtual machine, and insmod it.
+
+
+ Now all you need to do is run mount:
+
+
+ UML# mount none /mnt/host -t hostfs
+
+
+
+
+ will mount the host's / on the virtual machine's /mnt/host.
+
+
+ If you don't want to mount the host root directory, then you can
+ specify a subdirectory to mount with the -o switch to mount:
+
+
+ UML# mount none /mnt/home -t hostfs -o /home
+
+
+
+
+ will mount the hosts's /home on the virtual machine's /mnt/home.
+
+
+
+ 9.2. hostfs as the root filesystem
+
+ It's possible to boot from a directory hierarchy on the host using
+ hostfs rather than using the standard filesystem in a file.
+
+ To start, you need that hierarchy. The easiest way is to loop mount
+ an existing root_fs file:
+
+
+ host# mount root_fs uml_root_dir -o loop
+
+
+
+
+ You need to change the filesystem type of / in etc/fstab to be
+ 'hostfs', so that line looks like this:
+
+ /dev/ubd/0 / hostfs defaults 1 1
+
+
+
+
+ Then you need to chown to yourself all the files in that directory
+ that are owned by root. This worked for me:
+
+
+ host# find . -uid 0 -exec chown jdike {} \;
+
+
+
+
+ Next, make sure that your UML kernel has hostfs compiled in, not as a
+ module. Then run UML with the boot device pointing at that directory:
+
+
+ ubd0=/path/to/uml/root/directory
+
+
+
+
+ UML should then boot as it does normally.
+
+
+ 9.3. Building hostfs
+
+ If you need to build hostfs because it's not in your kernel, you have
+ two choices:
+
+
+
+ o Compiling hostfs into the kernel:
+
+
+ Reconfigure the kernel and set the 'Host filesystem' option under
+
+
+ o Compiling hostfs as a module:
+
+
+ Reconfigure the kernel and set the 'Host filesystem' option under
+ be in arch/um/fs/hostfs/hostfs.o. Install that in
+ /lib/modules/`uname -r`/fs in the virtual machine, boot it up, and
+
+
+ UML# insmod hostfs
+
+
+
+
+
+
+
+
+
+
+
+
+ 10. The Management Console
+
+
+
+ The UML management console is a low-level interface to the kernel,
+ somewhat like the i386 SysRq interface. Since there is a full-blown
+ operating system under UML, there is much greater flexibility possible
+ than with the SysRq mechanism.
+
+
+ There are a number of things you can do with the mconsole interface:
+
+ o get the kernel version
+
+ o add and remove devices
+
+ o halt or reboot the machine
+
+ o Send SysRq commands
+
+ o Pause and resume the UML
+
+
+ You need the mconsole client (uml_mconsole) which is present in CVS
+ (/tools/mconsole) in 2.4.5-9um and later, and will be in the RPM in
+ 2.4.6.
+
+
+ You also need CONFIG_MCONSOLE (under 'General Setup') enabled in UML.
+ When you boot UML, you'll see a line like:
+
+
+ mconsole initialized on /home/jdike/.uml/umlNJ32yL/mconsole
+
+
+
+
+ If you specify a unique machine id one the UML command line, i.e.
+
+
+ umid=debian
+
+
+
+
+ you'll see this
+
+
+ mconsole initialized on /home/jdike/.uml/debian/mconsole
+
+
+
+
+ That file is the socket that uml_mconsole will use to communicate with
+ UML. Run it with either the umid or the full path as its argument:
+
+
+ host% uml_mconsole debian
+
+
+
+
+ or
+
+
+ host% uml_mconsole /home/jdike/.uml/debian/mconsole
+
+
+
+
+ You'll get a prompt, at which you can run one of these commands:
+
+ o version
+
+ o halt
+
+ o reboot
+
+ o config
+
+ o remove
+
+ o sysrq
+
+ o help
+
+ o cad
+
+ o stop
+
+ o go
+
+
+ 10.1. version
+
+ This takes no arguments. It prints the UML version.
+
+
+ (mconsole) version
+ OK Linux usermode 2.4.5-9um #1 Wed Jun 20 22:47:08 EDT 2001 i686
+
+
+
+
+ There are a couple actual uses for this. It's a simple no-op which
+ can be used to check that a UML is running. It's also a way of
+ sending an interrupt to the UML. This is sometimes useful on SMP
+ hosts, where there's a bug which causes signals to UML to be lost,
+ often causing it to appear to hang. Sending such a UML the mconsole
+ version command is a good way to 'wake it up' before networking has
+ been enabled, as it does not do anything to the function of the UML.
+
+
+
+ 10.2. halt and reboot
+
+ These take no arguments. They shut the machine down immediately, with
+ no syncing of disks and no clean shutdown of userspace. So, they are
+ pretty close to crashing the machine.
+
+
+ (mconsole) halt
+ OK
+
+
+
+
+
+
+ 10.3. config
+
+ "config" adds a new device to the virtual machine. Currently the ubd
+ and network drivers support this. It takes one argument, which is the
+ device to add, with the same syntax as the kernel command line.
+
+
+
+
+ (mconsole)
+ config ubd3=/home/jdike/incoming/roots/root_fs_debian22
+
+ OK
+ (mconsole) config eth1=mcast
+ OK
+
+
+
+
+
+
+ 10.4. remove
+
+ "remove" deletes a device from the system. Its argument is just the
+ name of the device to be removed. The device must be idle in whatever
+ sense the driver considers necessary. In the case of the ubd driver,
+ the removed block device must not be mounted, swapped on, or otherwise
+ open, and in the case of the network driver, the device must be down.
+
+
+ (mconsole) remove ubd3
+ OK
+ (mconsole) remove eth1
+ OK
+
+
+
+
+
+
+ 10.5. sysrq
+
+ This takes one argument, which is a single letter. It calls the
+ generic kernel's SysRq driver, which does whatever is called for by
+ that argument. See the SysRq documentation in
+ Documentation/admin-guide/sysrq.rst in your favorite kernel tree to
+ see what letters are valid and what they do.
+
+
+
+ 10.6. help
+
+ "help" returns a string listing the valid commands and what each one
+ does.
+
+
+
+ 10.7. cad
+
+ This invokes the Ctl-Alt-Del action on init. What exactly this ends
+ up doing is up to /etc/inittab. Normally, it reboots the machine.
+ With UML, this is usually not desired, so if a halt would be better,
+ then find the section of inittab that looks like this
+
+
+ # What to do when CTRL-ALT-DEL is pressed.
+ ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now
+
+
+
+
+ and change the command to halt.
+
+
+
+ 10.8. stop
+
+ This puts the UML in a loop reading mconsole requests until a 'go'
+ mconsole command is received. This is very useful for making backups
+ of UML filesystems, as the UML can be stopped, then synced via 'sysrq
+ s', so that everything is written to the filesystem. You can then copy
+ the filesystem and then send the UML 'go' via mconsole.
+
+
+ Note that a UML running with more than one CPU will have problems
+ after you send the 'stop' command, as only one CPU will be held in a
+ mconsole loop and all others will continue as normal. This is a bug,
+ and will be fixed.
+
+
+
+ 10.9. go
+
+ This resumes a UML after being paused by a 'stop' command. Note that
+ when the UML has resumed, TCP connections may have timed out and if
+ the UML is paused for a long period of time, crond might go a little
+ crazy, running all the jobs it didn't do earlier.
+
+
+
+
+
+
+
+
+ 11. Kernel debugging
+
+
+ Note: The interface that makes debugging, as described here, possible
+ is present in 2.4.0-test6 kernels and later.
+
+
+ Since the user-mode kernel runs as a normal Linux process, it is
+ possible to debug it with gdb almost like any other process. It is
+ slightly different because the kernel's threads are already being
+ ptraced for system call interception, so gdb can't ptrace them.
+ However, a mechanism has been added to work around that problem.
+
+
+ In order to debug the kernel, you need build it from source. See
+ ``Compiling the kernel and modules'' for information on doing that.
+ Make sure that you enable CONFIG_DEBUGSYM and CONFIG_PT_PROXY during
+ the config. These will compile the kernel with -g, and enable the
+ ptrace proxy so that gdb works with UML, respectively.
+
+
+
+
+ 11.1. Starting the kernel under gdb
+
+ You can have the kernel running under the control of gdb from the
+ beginning by putting 'debug' on the command line. You will get an
+ xterm with gdb running inside it. The kernel will send some commands
+ to gdb which will leave it stopped at the beginning of start_kernel.
+ At this point, you can get things going with 'next', 'step', or
+ 'cont'.
+
+
+ There is a transcript of a debugging session here <debug-
+ session.html> , with breakpoints being set in the scheduler and in an
+ interrupt handler.
+ 11.2. Examining sleeping processes
+
+ Not every bug is evident in the currently running process. Sometimes,
+ processes hang in the kernel when they shouldn't because they've
+ deadlocked on a semaphore or something similar. In this case, when
+ you ^C gdb and get a backtrace, you will see the idle thread, which
+ isn't very relevant.
+
+
+ What you want is the stack of whatever process is sleeping when it
+ shouldn't be. You need to figure out which process that is, which is
+ generally fairly easy. Then you need to get its host process id,
+ which you can do either by looking at ps on the host or at
+ task.thread.extern_pid in gdb.
+
+
+ Now what you do is this:
+
+ o detach from the current thread
+
+
+ (UML gdb) det
+
+
+
+
+
+ o attach to the thread you are interested in
+
+
+ (UML gdb) att <host pid>
+
+
+
+
+
+ o look at its stack and anything else of interest
+
+
+ (UML gdb) bt
+
+
+
+
+ Note that you can't do anything at this point that requires that a
+ process execute, e.g. calling a function
+
+ o when you're done looking at that process, reattach to the current
+ thread and continue it
+
+
+ (UML gdb)
+ att 1
+
+
+
+
+
+
+ (UML gdb)
+ c
+
+
+
+
+ Here, specifying any pid which is not the process id of a UML thread
+ will cause gdb to reattach to the current thread. I commonly use 1,
+ but any other invalid pid would work.
+
+
+
+ 11.3. Running ddd on UML
+
+ ddd works on UML, but requires a special kludge. The process goes
+ like this:
+
+ o Start ddd
+
+
+ host% ddd linux
+
+
+
+
+
+ o With ps, get the pid of the gdb that ddd started. You can ask the
+ gdb to tell you, but for some reason that confuses things and
+ causes a hang.
+
+ o run UML with 'debug=parent gdb-pid=<pid>' added to the command line
+ - it will just sit there after you hit return
+
+ o type 'att 1' to the ddd gdb and you will see something like
+
+
+ 0xa013dc51 in __kill ()
+
+
+ (gdb)
+
+
+
+
+
+ o At this point, type 'c', UML will boot up, and you can use ddd just
+ as you do on any other process.
+
+
+
+ 11.4. Debugging modules
+
+ gdb has support for debugging code which is dynamically loaded into
+ the process. This support is what is needed to debug kernel modules
+ under UML.
+
+
+ Using that support is somewhat complicated. You have to tell gdb what
+ object file you just loaded into UML and where in memory it is. Then,
+ it can read the symbol table, and figure out where all the symbols are
+ from the load address that you provided. It gets more interesting
+ when you load the module again (i.e. after an rmmod). You have to
+ tell gdb to forget about all its symbols, including the main UML ones
+ for some reason, then load then all back in again.
+
+
+ There's an easy way and a hard way to do this. The easy way is to use
+ the umlgdb expect script written by Chandan Kudige. It basically
+ automates the process for you.
+
+
+ First, you must tell it where your modules are. There is a list in
+ the script that looks like this:
+ set MODULE_PATHS {
+ "fat" "/usr/src/uml/linux-2.4.18/fs/fat/fat.o"
+ "isofs" "/usr/src/uml/linux-2.4.18/fs/isofs/isofs.o"
+ "minix" "/usr/src/uml/linux-2.4.18/fs/minix/minix.o"
+ }
+
+
+
+
+ You change that to list the names and paths of the modules that you
+ are going to debug. Then you run it from the toplevel directory of
+ your UML pool and it basically tells you what to do:
+
+
+
+
+ ******** GDB pid is 21903 ********
+ Start UML as: ./linux <kernel switches> debug gdb-pid=21903
+
+
+
+ GNU gdb 5.0rh-5 Red Hat Linux 7.1
+ Copyright 2001 Free Software Foundation, Inc.
+ GDB is free software, covered by the GNU General Public License, and you are
+ welcome to change it and/or distribute copies of it under certain conditions.
+ Type "show copying" to see the conditions.
+ There is absolutely no warranty for GDB. Type "show warranty" for details.
+ This GDB was configured as "i386-redhat-linux"...
+ (gdb) b sys_init_module
+ Breakpoint 1 at 0xa0011923: file module.c, line 349.
+ (gdb) att 1
+
+
+
+
+ After you run UML and it sits there doing nothing, you hit return at
+ the 'att 1' and continue it:
+
+
+ Attaching to program: /home/jdike/linux/2.4/um/./linux, process 1
+ 0xa00f4221 in __kill ()
+ (UML gdb) c
+ Continuing.
+
+
+
+
+ At this point, you debug normally. When you insmod something, the
+ expect magic will kick in and you'll see something like:
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ *** Module hostfs loaded ***
+ Breakpoint 1, sys_init_module (name_user=0x805abb0 "hostfs",
+ mod_user=0x8070e00) at module.c:349
+ 349 char *name, *n_name, *name_tmp = NULL;
+ (UML gdb) finish
+ Run till exit from #0 sys_init_module (name_user=0x805abb0 "hostfs",
+ mod_user=0x8070e00) at module.c:349
+ 0xa00e2e23 in execute_syscall (r=0xa8140284) at syscall_kern.c:411
+ 411 else res = EXECUTE_SYSCALL(syscall, regs);
+ Value returned is $1 = 0
+ (UML gdb)
+ p/x (int)module_list + module_list->size_of_struct
+
+ $2 = 0xa9021054
+ (UML gdb) symbol-file ./linux
+ Load new symbol table from "./linux"? (y or n) y
+ Reading symbols from ./linux...
+ done.
+ (UML gdb)
+ add-symbol-file /home/jdike/linux/2.4/um/arch/um/fs/hostfs/hostfs.o 0xa9021054
+
+ add symbol table from file "/home/jdike/linux/2.4/um/arch/um/fs/hostfs/hostfs.o" at
+ .text_addr = 0xa9021054
+ (y or n) y
+
+ Reading symbols from /home/jdike/linux/2.4/um/arch/um/fs/hostfs/hostfs.o...
+ done.
+ (UML gdb) p *module_list
+ $1 = {size_of_struct = 84, next = 0xa0178720, name = 0xa9022de0 "hostfs",
+ size = 9016, uc = {usecount = {counter = 0}, pad = 0}, flags = 1,
+ nsyms = 57, ndeps = 0, syms = 0xa9023170, deps = 0x0, refs = 0x0,
+ init = 0xa90221f0 <init_hostfs>, cleanup = 0xa902222c <exit_hostfs>,
+ ex_table_start = 0x0, ex_table_end = 0x0, persist_start = 0x0,
+ persist_end = 0x0, can_unload = 0, runsize = 0, kallsyms_start = 0x0,
+ kallsyms_end = 0x0,
+ archdata_start = 0x1b855 <Address 0x1b855 out of bounds>,
+ archdata_end = 0xe5890000 <Address 0xe5890000 out of bounds>,
+ kernel_data = 0xf689c35d <Address 0xf689c35d out of bounds>}
+ >> Finished loading symbols for hostfs ...
+
+
+
+
+ That's the easy way. It's highly recommended. The hard way is
+ described below in case you're interested in what's going on.
+
+
+ Boot the kernel under the debugger and load the module with insmod or
+ modprobe. With gdb, do:
+
+
+ (UML gdb) p module_list
+
+
+
+
+ This is a list of modules that have been loaded into the kernel, with
+ the most recently loaded module first. Normally, the module you want
+ is at module_list. If it's not, walk down the next links, looking at
+ the name fields until find the module you want to debug. Take the
+ address of that structure, and add module.size_of_struct (which in
+ 2.4.10 kernels is 96 (0x60)) to it. Gdb can make this hard addition
+ for you :-):
+
+
+
+ (UML gdb)
+ printf "%#x\n", (int)module_list module_list->size_of_struct
+
+
+
+
+ The offset from the module start occasionally changes (before 2.4.0,
+ it was module.size_of_struct + 4), so it's a good idea to check the
+ init and cleanup addresses once in a while, as describe below. Now
+ do:
+
+
+ (UML gdb)
+ add-symbol-file /path/to/module/on/host that_address
+
+
+
+
+ Tell gdb you really want to do it, and you're in business.
+
+
+ If there's any doubt that you got the offset right, like breakpoints
+ appear not to work, or they're appearing in the wrong place, you can
+ check it by looking at the module structure. The init and cleanup
+ fields should look like:
+
+
+ init = 0x588066b0 <init_hostfs>, cleanup = 0x588066c0 <exit_hostfs>
+
+
+
+
+ with no offsets on the symbol names. If the names are right, but they
+ are offset, then the offset tells you how much you need to add to the
+ address you gave to add-symbol-file.
+
+
+ When you want to load in a new version of the module, you need to get
+ gdb to forget about the old one. The only way I've found to do that
+ is to tell gdb to forget about all symbols that it knows about:
+
+
+ (UML gdb) symbol-file
+
+
+
+
+ Then reload the symbols from the kernel binary:
+
+
+ (UML gdb) symbol-file /path/to/kernel
+
+
+
+
+ and repeat the process above. You'll also need to re-enable break-
+ points. They were disabled when you dumped all the symbols because
+ gdb couldn't figure out where they should go.
+
+
+
+ 11.5. Attaching gdb to the kernel
+
+ If you don't have the kernel running under gdb, you can attach gdb to
+ it later by sending the tracing thread a SIGUSR1. The first line of
+ the console output identifies its pid:
+ tracing thread pid = 20093
+
+
+
+
+ When you send it the signal:
+
+
+ host% kill -USR1 20093
+
+
+
+
+ you will get an xterm with gdb running in it.
+
+
+ If you have the mconsole compiled into UML, then the mconsole client
+ can be used to start gdb:
+
+
+ (mconsole) (mconsole) config gdb=xterm
+
+
+
+
+ will fire up an xterm with gdb running in it.
+
+
+
+ 11.6. Using alternate debuggers
+
+ UML has support for attaching to an already running debugger rather
+ than starting gdb itself. This is present in CVS as of 17 Apr 2001.
+ I sent it to Alan for inclusion in the ac tree, and it will be in my
+ 2.4.4 release.
+
+
+ This is useful when gdb is a subprocess of some UI, such as emacs or
+ ddd. It can also be used to run debuggers other than gdb on UML.
+ Below is an example of using strace as an alternate debugger.
+
+
+ To do this, you need to get the pid of the debugger and pass it in
+ with the
+
+
+ If you are using gdb under some UI, then tell it to 'att 1', and
+ you'll find yourself attached to UML.
+
+
+ If you are using something other than gdb as your debugger, then
+ you'll need to get it to do the equivalent of 'att 1' if it doesn't do
+ it automatically.
+
+
+ An example of an alternate debugger is strace. You can strace the
+ actual kernel as follows:
+
+ o Run the following in a shell
+
+
+ host%
+ sh -c 'echo pid=$$; echo -n hit return; read x; exec strace -p 1 -o strace.out'
+
+
+
+ o Run UML with 'debug' and 'gdb-pid=<pid>' with the pid printed out
+ by the previous command
+
+ o Hit return in the shell, and UML will start running, and strace
+ output will start accumulating in the output file.
+
+ Note that this is different from running
+
+
+ host% strace ./linux
+
+
+
+
+ That will strace only the main UML thread, the tracing thread, which
+ doesn't do any of the actual kernel work. It just oversees the vir-
+ tual machine. In contrast, using strace as described above will show
+ you the low-level activity of the virtual machine.
+
+
+
+
+
+ 12. Kernel debugging examples
+
+ 12.1. The case of the hung fsck
+
+ When booting up the kernel, fsck failed, and dropped me into a shell
+ to fix things up. I ran fsck -y, which hung:
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Setting hostname uml [ OK ]
+ Checking root filesystem
+ /dev/fhd0 was not cleanly unmounted, check forced.
+ Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780.
+
+ /dev/fhd0: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.
+ (i.e., without -a or -p options)
+ [ FAILED ]
+
+ *** An error occurred during the file system check.
+ *** Dropping you to a shell; the system will reboot
+ *** when you leave the shell.
+ Give root password for maintenance
+ (or type Control-D for normal startup):
+
+ [root@uml /root]# fsck -y /dev/fhd0
+ fsck -y /dev/fhd0
+ Parallelizing fsck version 1.14 (9-Jan-1999)
+ e2fsck 1.14, 9-Jan-1999 for EXT2 FS 0.5b, 95/08/09
+ /dev/fhd0 contains a file system with errors, check forced.
+ Pass 1: Checking inodes, blocks, and sizes
+ Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780. Ignore error? yes
+
+ Inode 19780, i_blocks is 1548, should be 540. Fix? yes
+
+ Pass 2: Checking directory structure
+ Error reading block 49405 (Attempt to read block from filesystem resulted in short read). Ignore error? yes
+
+ Directory inode 11858, block 0, offset 0: directory corrupted
+ Salvage? yes
+
+ Missing '.' in directory inode 11858.
+ Fix? yes
+
+ Missing '..' in directory inode 11858.
+ Fix? yes
+
+
+
+
+
+ The standard drill in this sort of situation is to fire up gdb on the
+ signal thread, which, in this case, was pid 1935. In another window,
+ I run gdb and attach pid 1935.
+
+
+
+
+ ~/linux/2.3.26/um 1016: gdb linux
+ GNU gdb 4.17.0.11 with Linux support
+ Copyright 1998 Free Software Foundation, Inc.
+ GDB is free software, covered by the GNU General Public License, and you are
+ welcome to change it and/or distribute copies of it under certain conditions.
+ Type "show copying" to see the conditions.
+ There is absolutely no warranty for GDB. Type "show warranty" for details.
+ This GDB was configured as "i386-redhat-linux"...
+
+ (gdb) att 1935
+ Attaching to program `/home/dike/linux/2.3.26/um/linux', Pid 1935
+ 0x100756d9 in __wait4 ()
+
+
+
+
+
+
+ Let's see what's currently running:
+
+
+
+ (gdb) p current_task.pid
+ $1 = 0
+
+
+
+
+
+ It's the idle thread, which means that fsck went to sleep for some
+ reason and never woke up.
+
+
+ Let's guess that the last process in the process list is fsck:
+
+
+
+ (gdb) p current_task.prev_task.comm
+ $13 = "fsck.ext2\000\000\000\000\000\000"
+
+
+
+
+
+ It is, so let's see what it thinks it's up to:
+
+
+
+ (gdb) p current_task.prev_task.thread
+ $14 = {extern_pid = 1980, tracing = 0, want_tracing = 0, forking = 0,
+ kernel_stack_page = 0, signal_stack = 1342627840, syscall = {id = 4, args = {
+ 3, 134973440, 1024, 0, 1024}, have_result = 0, result = 50590720},
+ request = {op = 2, u = {exec = {ip = 1350467584, sp = 2952789424}, fork = {
+ regs = {1350467584, 2952789424, 0 <repeats 15 times>}, sigstack = 0,
+ pid = 0}, switch_to = 0x507e8000, thread = {proc = 0x507e8000,
+ arg = 0xaffffdb0, flags = 0, new_pid = 0}, input_request = {
+ op = 1350467584, fd = -1342177872, proc = 0, pid = 0}}}}
+
+
+
+
+
+ The interesting things here are the fact that its .thread.syscall.id
+ is __NR_write (see the big switch in arch/um/kernel/syscall_kern.c or
+ the defines in include/asm-um/arch/unistd.h), and that it never
+ returned. Also, its .request.op is OP_SWITCH (see
+ arch/um/include/user_util.h). These mean that it went into a write,
+ and, for some reason, called schedule().
+
+
+ The fact that it never returned from write means that its stack should
+ be fairly interesting. Its pid is 1980 (.thread.extern_pid). That
+ process is being ptraced by the signal thread, so it must be detached
+ before gdb can attach it:
+
+
+
+
+
+
+
+
+
+
+ (gdb) call detach(1980)
+
+ Program received signal SIGSEGV, Segmentation fault.
+ <function called from gdb>
+ The program being debugged stopped while in a function called from GDB.
+ When the function (detach) is done executing, GDB will silently
+ stop (instead of continuing to evaluate the expression containing
+ the function call).
+ (gdb) call detach(1980)
+ $15 = 0
+
+
+
+
+
+ The first detach segfaults for some reason, and the second one
+ succeeds.
+
+
+ Now I detach from the signal thread, attach to the fsck thread, and
+ look at its stack:
+
+
+ (gdb) det
+ Detaching from program: /home/dike/linux/2.3.26/um/linux Pid 1935
+ (gdb) att 1980
+ Attaching to program `/home/dike/linux/2.3.26/um/linux', Pid 1980
+ 0x10070451 in __kill ()
+ (gdb) bt
+ #0 0x10070451 in __kill ()
+ #1 0x10068ccd in usr1_pid (pid=1980) at process.c:30
+ #2 0x1006a03f in _switch_to (prev=0x50072000, next=0x507e8000)
+ at process_kern.c:156
+ #3 0x1006a052 in switch_to (prev=0x50072000, next=0x507e8000, last=0x50072000)
+ at process_kern.c:161
+ #4 0x10001d12 in schedule () at core.c:777
+ #5 0x1006a744 in __down (sem=0x507d241c) at semaphore.c:71
+ #6 0x1006aa10 in __down_failed () at semaphore.c:157
+ #7 0x1006c5d8 in segv_handler (sc=0x5006e940) at trap_user.c:174
+ #8 0x1006c5ec in kern_segv_handler (sig=11) at trap_user.c:182
+ #9 <signal handler called>
+ #10 0x10155404 in errno ()
+ #11 0x1006c0aa in segv (address=1342179328, is_write=2) at trap_kern.c:50
+ #12 0x1006c5d8 in segv_handler (sc=0x5006eaf8) at trap_user.c:174
+ #13 0x1006c5ec in kern_segv_handler (sig=11) at trap_user.c:182
+ #14 <signal handler called>
+ #15 0xc0fd in ?? ()
+ #16 0x10016647 in sys_write (fd=3,
+ buf=0x80b8800 <Address 0x80b8800 out of bounds>, count=1024)
+ at read_write.c:159
+ #17 0x1006d5b3 in execute_syscall (syscall=4, args=0x5006ef08)
+ at syscall_kern.c:254
+ #18 0x1006af87 in really_do_syscall (sig=12) at syscall_user.c:35
+ #19 <signal handler called>
+ #20 0x400dc8b0 in ?? ()
+
+
+
+
+
+ The interesting things here are :
+
+ o There are two segfaults on this stack (frames 9 and 14)
+
+ o The first faulting address (frame 11) is 0x50000800
+
+ (gdb) p (void *)1342179328
+ $16 = (void *) 0x50000800
+
+
+
+
+
+ The initial faulting address is interesting because it is on the idle
+ thread's stack. I had been seeing the idle thread segfault for no
+ apparent reason, and the cause looked like stack corruption. In hopes
+ of catching the culprit in the act, I had turned off all protections
+ to that stack while the idle thread wasn't running. This apparently
+ tripped that trap.
+
+
+ However, the more immediate problem is that second segfault and I'm
+ going to concentrate on that. First, I want to see where the fault
+ happened, so I have to go look at the sigcontent struct in frame 8:
+
+
+
+ (gdb) up
+ #1 0x10068ccd in usr1_pid (pid=1980) at process.c:30
+ 30 kill(pid, SIGUSR1);
+ (gdb)
+ #2 0x1006a03f in _switch_to (prev=0x50072000, next=0x507e8000)
+ at process_kern.c:156
+ 156 usr1_pid(getpid());
+ (gdb)
+ #3 0x1006a052 in switch_to (prev=0x50072000, next=0x507e8000, last=0x50072000)
+ at process_kern.c:161
+ 161 _switch_to(prev, next);
+ (gdb)
+ #4 0x10001d12 in schedule () at core.c:777
+ 777 switch_to(prev, next, prev);
+ (gdb)
+ #5 0x1006a744 in __down (sem=0x507d241c) at semaphore.c:71
+ 71 schedule();
+ (gdb)
+ #6 0x1006aa10 in __down_failed () at semaphore.c:157
+ 157 }
+ (gdb)
+ #7 0x1006c5d8 in segv_handler (sc=0x5006e940) at trap_user.c:174
+ 174 segv(sc->cr2, sc->err & 2);
+ (gdb)
+ #8 0x1006c5ec in kern_segv_handler (sig=11) at trap_user.c:182
+ 182 segv_handler(sc);
+ (gdb) p *sc
+ Cannot access memory at address 0x0.
+
+
+
+
+ That's not very useful, so I'll try a more manual method:
+
+
+ (gdb) p *((struct sigcontext *) (&sig + 1))
+ $19 = {gs = 0, __gsh = 0, fs = 0, __fsh = 0, es = 43, __esh = 0, ds = 43,
+ __dsh = 0, edi = 1342179328, esi = 1350378548, ebp = 1342630440,
+ esp = 1342630420, ebx = 1348150624, edx = 1280, ecx = 0, eax = 0,
+ trapno = 14, err = 4, eip = 268480945, cs = 35, __csh = 0, eflags = 66118,
+ esp_at_signal = 1342630420, ss = 43, __ssh = 0, fpstate = 0x0, oldmask = 0,
+ cr2 = 1280}
+
+
+
+ The ip is in handle_mm_fault:
+
+
+ (gdb) p (void *)268480945
+ $20 = (void *) 0x1000b1b1
+ (gdb) i sym $20
+ handle_mm_fault + 57 in section .text
+
+
+
+
+
+ Specifically, it's in pte_alloc:
+
+
+ (gdb) i line *$20
+ Line 124 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
+ starts at address 0x1000b1b1 <handle_mm_fault+57>
+ and ends at 0x1000b1b7 <handle_mm_fault+63>.
+
+
+
+
+
+ To find where in handle_mm_fault this is, I'll jump forward in the
+ code until I see an address in that procedure:
+
+
+
+ (gdb) i line *0x1000b1c0
+ Line 126 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
+ starts at address 0x1000b1b7 <handle_mm_fault+63>
+ and ends at 0x1000b1c3 <handle_mm_fault+75>.
+ (gdb) i line *0x1000b1d0
+ Line 131 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
+ starts at address 0x1000b1d0 <handle_mm_fault+88>
+ and ends at 0x1000b1da <handle_mm_fault+98>.
+ (gdb) i line *0x1000b1e0
+ Line 61 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
+ starts at address 0x1000b1da <handle_mm_fault+98>
+ and ends at 0x1000b1e1 <handle_mm_fault+105>.
+ (gdb) i line *0x1000b1f0
+ Line 134 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
+ starts at address 0x1000b1f0 <handle_mm_fault+120>
+ and ends at 0x1000b200 <handle_mm_fault+136>.
+ (gdb) i line *0x1000b200
+ Line 135 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
+ starts at address 0x1000b200 <handle_mm_fault+136>
+ and ends at 0x1000b208 <handle_mm_fault+144>.
+ (gdb) i line *0x1000b210
+ Line 139 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
+ starts at address 0x1000b210 <handle_mm_fault+152>
+ and ends at 0x1000b219 <handle_mm_fault+161>.
+ (gdb) i line *0x1000b220
+ Line 1168 of "memory.c" starts at address 0x1000b21e <handle_mm_fault+166>
+ and ends at 0x1000b222 <handle_mm_fault+170>.
+
+
+
+
+
+ Something is apparently wrong with the page tables or vma_structs, so
+ lets go back to frame 11 and have a look at them:
+
+
+
+ #11 0x1006c0aa in segv (address=1342179328, is_write=2) at trap_kern.c:50
+ 50 handle_mm_fault(current, vma, address, is_write);
+ (gdb) call pgd_offset_proc(vma->vm_mm, address)
+ $22 = (pgd_t *) 0x80a548c
+
+
+
+
+
+ That's pretty bogus. Page tables aren't supposed to be in process
+ text or data areas. Let's see what's in the vma:
+
+
+ (gdb) p *vma
+ $23 = {vm_mm = 0x507d2434, vm_start = 0, vm_end = 134512640,
+ vm_next = 0x80a4f8c, vm_page_prot = {pgprot = 0}, vm_flags = 31200,
+ vm_avl_height = 2058, vm_avl_left = 0x80a8c94, vm_avl_right = 0x80d1000,
+ vm_next_share = 0xaffffdb0, vm_pprev_share = 0xaffffe63,
+ vm_ops = 0xaffffe7a, vm_pgoff = 2952789626, vm_file = 0xafffffec,
+ vm_private_data = 0x62}
+ (gdb) p *vma.vm_mm
+ $24 = {mmap = 0x507d2434, mmap_avl = 0x0, mmap_cache = 0x8048000,
+ pgd = 0x80a4f8c, mm_users = {counter = 0}, mm_count = {counter = 134904288},
+ map_count = 134909076, mmap_sem = {count = {counter = 135073792},
+ sleepers = -1342177872, wait = {lock = <optimized out or zero length>,
+ task_list = {next = 0xaffffe63, prev = 0xaffffe7a},
+ __magic = -1342177670, __creator = -1342177300}, __magic = 98},
+ page_table_lock = {}, context = 138, start_code = 0, end_code = 0,
+ start_data = 0, end_data = 0, start_brk = 0, brk = 0, start_stack = 0,
+ arg_start = 0, arg_end = 0, env_start = 0, env_end = 0, rss = 1350381536,
+ total_vm = 0, locked_vm = 0, def_flags = 0, cpu_vm_mask = 0, swap_cnt = 0,
+ swap_address = 0, segments = 0x0}
+
+
+
+
+
+ This also pretty bogus. With all of the 0x80xxxxx and 0xaffffxxx
+ addresses, this is looking like a stack was plonked down on top of
+ these structures. Maybe it's a stack overflow from the next page:
+
+
+
+ (gdb) p vma
+ $25 = (struct vm_area_struct *) 0x507d2434
+
+
+
+
+
+ That's towards the lower quarter of the page, so that would have to
+ have been pretty heavy stack overflow:
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ (gdb) x/100x $25
+ 0x507d2434: 0x507d2434 0x00000000 0x08048000 0x080a4f8c
+ 0x507d2444: 0x00000000 0x080a79e0 0x080a8c94 0x080d1000
+ 0x507d2454: 0xaffffdb0 0xaffffe63 0xaffffe7a 0xaffffe7a
+ 0x507d2464: 0xafffffec 0x00000062 0x0000008a 0x00000000
+ 0x507d2474: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2484: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2494: 0x00000000 0x00000000 0x507d2fe0 0x00000000
+ 0x507d24a4: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d24b4: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d24c4: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d24d4: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d24e4: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d24f4: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2504: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2514: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2524: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2534: 0x00000000 0x00000000 0x507d25dc 0x00000000
+ 0x507d2544: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2554: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2564: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2574: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2584: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d2594: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d25a4: 0x00000000 0x00000000 0x00000000 0x00000000
+ 0x507d25b4: 0x00000000 0x00000000 0x00000000 0x00000000
+
+
+
+
+
+ It's not stack overflow. The only "stack-like" piece of this data is
+ the vma_struct itself.
+
+
+ At this point, I don't see any avenues to pursue, so I just have to
+ admit that I have no idea what's going on. What I will do, though, is
+ stick a trap on the segfault handler which will stop if it sees any
+ writes to the idle thread's stack. That was the thing that happened
+ first, and it may be that if I can catch it immediately, what's going
+ on will be somewhat clearer.
+
+
+ 12.2. Episode 2: The case of the hung fsck
+
+ After setting a trap in the SEGV handler for accesses to the signal
+ thread's stack, I reran the kernel.
+
+
+ fsck hung again, this time by hitting the trap:
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ Setting hostname uml [ OK ]
+ Checking root filesystem
+ /dev/fhd0 contains a file system with errors, check forced.
+ Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780.
+
+ /dev/fhd0: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.
+ (i.e., without -a or -p options)
+ [ FAILED ]
+
+ *** An error occurred during the file system check.
+ *** Dropping you to a shell; the system will reboot
+ *** when you leave the shell.
+ Give root password for maintenance
+ (or type Control-D for normal startup):
+
+ [root@uml /root]# fsck -y /dev/fhd0
+ fsck -y /dev/fhd0
+ Parallelizing fsck version 1.14 (9-Jan-1999)
+ e2fsck 1.14, 9-Jan-1999 for EXT2 FS 0.5b, 95/08/09
+ /dev/fhd0 contains a file system with errors, check forced.
+ Pass 1: Checking inodes, blocks, and sizes
+ Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780. Ignore error? yes
+
+ Pass 2: Checking directory structure
+ Error reading block 49405 (Attempt to read block from filesystem resulted in short read). Ignore error? yes
+
+ Directory inode 11858, block 0, offset 0: directory corrupted
+ Salvage? yes
+
+ Missing '.' in directory inode 11858.
+ Fix? yes
+
+ Missing '..' in directory inode 11858.
+ Fix? yes
+
+ Untested (4127) [100fe44c]: trap_kern.c line 31
+
+
+
+
+
+ I need to get the signal thread to detach from pid 4127 so that I can
+ attach to it with gdb. This is done by sending it a SIGUSR1, which is
+ caught by the signal thread, which detaches the process:
+
+
+ kill -USR1 4127
+
+
+
+
+
+ Now I can run gdb on it:
+
+
+
+
+
+
+
+
+
+
+
+
+
+ ~/linux/2.3.26/um 1034: gdb linux
+ GNU gdb 4.17.0.11 with Linux support
+ Copyright 1998 Free Software Foundation, Inc.
+ GDB is free software, covered by the GNU General Public License, and you are
+ welcome to change it and/or distribute copies of it under certain conditions.
+ Type "show copying" to see the conditions.
+ There is absolutely no warranty for GDB. Type "show warranty" for details.
+ This GDB was configured as "i386-redhat-linux"...
+ (gdb) att 4127
+ Attaching to program `/home/dike/linux/2.3.26/um/linux', Pid 4127
+ 0x10075891 in __libc_nanosleep ()
+
+
+
+
+
+ The backtrace shows that it was in a write and that the fault address
+ (address in frame 3) is 0x50000800, which is right in the middle of
+ the signal thread's stack page:
+
+
+ (gdb) bt
+ #0 0x10075891 in __libc_nanosleep ()
+ #1 0x1007584d in __sleep (seconds=1000000)
+ at ../sysdeps/unix/sysv/linux/sleep.c:78
+ #2 0x1006ce9a in stop () at user_util.c:191
+ #3 0x1006bf88 in segv (address=1342179328, is_write=2) at trap_kern.c:31
+ #4 0x1006c628 in segv_handler (sc=0x5006eaf8) at trap_user.c:174
+ #5 0x1006c63c in kern_segv_handler (sig=11) at trap_user.c:182
+ #6 <signal handler called>
+ #7 0xc0fd in ?? ()
+ #8 0x10016647 in sys_write (fd=3, buf=0x80b8800 "R.", count=1024)
+ at read_write.c:159
+ #9 0x1006d603 in execute_syscall (syscall=4, args=0x5006ef08)
+ at syscall_kern.c:254
+ #10 0x1006af87 in really_do_syscall (sig=12) at syscall_user.c:35
+ #11 <signal handler called>
+ #12 0x400dc8b0 in ?? ()
+ #13 <signal handler called>
+ #14 0x400dc8b0 in ?? ()
+ #15 0x80545fd in ?? ()
+ #16 0x804daae in ?? ()
+ #17 0x8054334 in ?? ()
+ #18 0x804d23e in ?? ()
+ #19 0x8049632 in ?? ()
+ #20 0x80491d2 in ?? ()
+ #21 0x80596b5 in ?? ()
+ (gdb) p (void *)1342179328
+ $3 = (void *) 0x50000800
+
+
+
+
+
+ Going up the stack to the segv_handler frame and looking at where in
+ the code the access happened shows that it happened near line 110 of
+ block_dev.c:
+
+
+
+
+
+
+
+
+
+ (gdb) up
+ #1 0x1007584d in __sleep (seconds=1000000)
+ at ../sysdeps/unix/sysv/linux/sleep.c:78
+ ../sysdeps/unix/sysv/linux/sleep.c:78: No such file or directory.
+ (gdb)
+ #2 0x1006ce9a in stop () at user_util.c:191
+ 191 while(1) sleep(1000000);
+ (gdb)
+ #3 0x1006bf88 in segv (address=1342179328, is_write=2) at trap_kern.c:31
+ 31 KERN_UNTESTED();
+ (gdb)
+ #4 0x1006c628 in segv_handler (sc=0x5006eaf8) at trap_user.c:174
+ 174 segv(sc->cr2, sc->err & 2);
+ (gdb) p *sc
+ $1 = {gs = 0, __gsh = 0, fs = 0, __fsh = 0, es = 43, __esh = 0, ds = 43,
+ __dsh = 0, edi = 1342179328, esi = 134973440, ebp = 1342631484,
+ esp = 1342630864, ebx = 256, edx = 0, ecx = 256, eax = 1024, trapno = 14,
+ err = 6, eip = 268550834, cs = 35, __csh = 0, eflags = 66070,
+ esp_at_signal = 1342630864, ss = 43, __ssh = 0, fpstate = 0x0, oldmask = 0,
+ cr2 = 1342179328}
+ (gdb) p (void *)268550834
+ $2 = (void *) 0x1001c2b2
+ (gdb) i sym $2
+ block_write + 1090 in section .text
+ (gdb) i line *$2
+ Line 209 of "/home/dike/linux/2.3.26/um/include/asm/arch/string.h"
+ starts at address 0x1001c2a1 <block_write+1073>
+ and ends at 0x1001c2bf <block_write+1103>.
+ (gdb) i line *0x1001c2c0
+ Line 110 of "block_dev.c" starts at address 0x1001c2bf <block_write+1103>
+ and ends at 0x1001c2e3 <block_write+1139>.
+
+
+
+
+
+ Looking at the source shows that the fault happened during a call to
+ copy_from_user to copy the data into the kernel:
+
+
+ 107 count -= chars;
+ 108 copy_from_user(p,buf,chars);
+ 109 p += chars;
+ 110 buf += chars;
+
+
+
+
+
+ p is the pointer which must contain 0x50000800, since buf contains
+ 0x80b8800 (frame 8 above). It is defined as:
+
+
+ p = offset + bh->b_data;
+
+
+
+
+
+ I need to figure out what bh is, and it just so happens that bh is
+ passed as an argument to mark_buffer_uptodate and mark_buffer_dirty a
+ few lines later, so I do a little disassembly:
+
+
+
+
+ (gdb) disas 0x1001c2bf 0x1001c2e0
+ Dump of assembler code from 0x1001c2bf to 0x1001c2d0:
+ 0x1001c2bf <block_write+1103>: addl %eax,0xc(%ebp)
+ 0x1001c2c2 <block_write+1106>: movl 0xfffffdd4(%ebp),%edx
+ 0x1001c2c8 <block_write+1112>: btsl $0x0,0x18(%edx)
+ 0x1001c2cd <block_write+1117>: btsl $0x1,0x18(%edx)
+ 0x1001c2d2 <block_write+1122>: sbbl %ecx,%ecx
+ 0x1001c2d4 <block_write+1124>: testl %ecx,%ecx
+ 0x1001c2d6 <block_write+1126>: jne 0x1001c2e3 <block_write+1139>
+ 0x1001c2d8 <block_write+1128>: pushl $0x0
+ 0x1001c2da <block_write+1130>: pushl %edx
+ 0x1001c2db <block_write+1131>: call 0x1001819c <__mark_buffer_dirty>
+ End of assembler dump.
+
+
+
+
+
+ At that point, bh is in %edx (address 0x1001c2da), which is calculated
+ at 0x1001c2c2 as %ebp + 0xfffffdd4, so I figure exactly what that is,
+ taking %ebp from the sigcontext_struct above:
+
+
+ (gdb) p (void *)1342631484
+ $5 = (void *) 0x5006ee3c
+ (gdb) p 0x5006ee3c+0xfffffdd4
+ $6 = 1342630928
+ (gdb) p (void *)$6
+ $7 = (void *) 0x5006ec10
+ (gdb) p *((void **)$7)
+ $8 = (void *) 0x50100200
+
+
+
+
+
+ Now, I look at the structure to see what's in it, and particularly,
+ what its b_data field contains:
+
+
+ (gdb) p *((struct buffer_head *)0x50100200)
+ $13 = {b_next = 0x50289380, b_blocknr = 49405, b_size = 1024, b_list = 0,
+ b_dev = 15872, b_count = {counter = 1}, b_rdev = 15872, b_state = 24,
+ b_flushtime = 0, b_next_free = 0x501001a0, b_prev_free = 0x50100260,
+ b_this_page = 0x501001a0, b_reqnext = 0x0, b_pprev = 0x507fcf58,
+ b_data = 0x50000800 "", b_page = 0x50004000,
+ b_end_io = 0x10017f60 <end_buffer_io_sync>, b_dev_id = 0x0,
+ b_rsector = 98810, b_wait = {lock = <optimized out or zero length>,
+ task_list = {next = 0x50100248, prev = 0x50100248}, __magic = 1343226448,
+ __creator = 0}, b_kiobuf = 0x0}
+
+
+
+
+
+ The b_data field is indeed 0x50000800, so the question becomes how
+ that happened. The rest of the structure looks fine, so this probably
+ is not a case of data corruption. It happened on purpose somehow.
+
+
+ The b_page field is a pointer to the page_struct representing the
+ 0x50000000 page. Looking at it shows the kernel's idea of the state
+ of that page:
+
+
+
+ (gdb) p *$13.b_page
+ $17 = {list = {next = 0x50004a5c, prev = 0x100c5174}, mapping = 0x0,
+ index = 0, next_hash = 0x0, count = {counter = 1}, flags = 132, lru = {
+ next = 0x50008460, prev = 0x50019350}, wait = {
+ lock = <optimized out or zero length>, task_list = {next = 0x50004024,
+ prev = 0x50004024}, __magic = 1342193708, __creator = 0},
+ pprev_hash = 0x0, buffers = 0x501002c0, virtual = 1342177280,
+ zone = 0x100c5160}
+
+
+
+
+
+ Some sanity-checking: the virtual field shows the "virtual" address of
+ this page, which in this kernel is the same as its "physical" address,
+ and the page_struct itself should be mem_map[0], since it represents
+ the first page of memory:
+
+
+
+ (gdb) p (void *)1342177280
+ $18 = (void *) 0x50000000
+ (gdb) p mem_map
+ $19 = (mem_map_t *) 0x50004000
+
+
+
+
+
+ These check out fine.
+
+
+ Now to check out the page_struct itself. In particular, the flags
+ field shows whether the page is considered free or not:
+
+
+ (gdb) p (void *)132
+ $21 = (void *) 0x84
+
+
+
+
+
+ The "reserved" bit is the high bit, which is definitely not set, so
+ the kernel considers the signal stack page to be free and available to
+ be used.
+
+
+ At this point, I jump to conclusions and start looking at my early
+ boot code, because that's where that page is supposed to be reserved.
+
+
+ In my setup_arch procedure, I have the following code which looks just
+ fine:
+
+
+
+ bootmap_size = init_bootmem(start_pfn, end_pfn - start_pfn);
+ free_bootmem(__pa(low_physmem) + bootmap_size, high_physmem - low_physmem);
+
+
+
+
+
+ Two stack pages have already been allocated, and low_physmem points to
+ the third page, which is the beginning of free memory.
+ The init_bootmem call declares the entire memory to the boot memory
+ manager, which marks it all reserved. The free_bootmem call frees up
+ all of it, except for the first two pages. This looks correct to me.
+
+
+ So, I decide to see init_bootmem run and make sure that it is marking
+ those first two pages as reserved. I never get that far.
+
+
+ Stepping into init_bootmem, and looking at bootmem_map before looking
+ at what it contains shows the following:
+
+
+
+ (gdb) p bootmem_map
+ $3 = (void *) 0x50000000
+
+
+
+
+
+ Aha! The light dawns. That first page is doing double duty as a
+ stack and as the boot memory map. The last thing that the boot memory
+ manager does is to free the pages used by its memory map, so this page
+ is getting freed even its marked as reserved.
+
+
+ The fix was to initialize the boot memory manager before allocating
+ those two stack pages, and then allocate them through the boot memory
+ manager. After doing this, and fixing a couple of subsequent buglets,
+ the stack corruption problem disappeared.
+
+
+
+
+
+ 13. What to do when UML doesn't work
+
+
+
+
+ 13.1. Strange compilation errors when you build from source
+
+ As of test11, it is necessary to have "ARCH=um" in the environment or
+ on the make command line for all steps in building UML, including
+ clean, distclean, or mrproper, config, menuconfig, or xconfig, dep,
+ and linux. If you forget for any of them, the i386 build seems to
+ contaminate the UML build. If this happens, start from scratch with
+
+
+ host%
+ make mrproper ARCH=um
+
+
+
+
+ and repeat the build process with ARCH=um on all the steps.
+
+
+ See ``Compiling the kernel and modules'' for more details.
+
+
+ Another cause of strange compilation errors is building UML in
+ /usr/src/linux. If you do this, the first thing you need to do is
+ clean up the mess you made. The /usr/src/linux/asm link will now
+ point to /usr/src/linux/asm-um. Make it point back to
+ /usr/src/linux/asm-i386. Then, move your UML pool someplace else and
+ build it there. Also see below, where a more specific set of symptoms
+ is described.
+
+
+
+ 13.3. A variety of panics and hangs with /tmp on a reiserfs filesys-
+ tem
+
+ I saw this on reiserfs 3.5.21 and it seems to be fixed in 3.5.27.
+ Panics preceded by
+
+
+ Detaching pid nnnn
+
+
+
+ are diagnostic of this problem. This is a reiserfs bug which causes a
+ thread to occasionally read stale data from a mmapped page shared with
+ another thread. The fix is to upgrade the filesystem or to have /tmp
+ be an ext2 filesystem.
+
+
+
+ 13.4. The compile fails with errors about conflicting types for
+ 'open', 'dup', and 'waitpid'
+
+ This happens when you build in /usr/src/linux. The UML build makes
+ the include/asm link point to include/asm-um. /usr/include/asm points
+ to /usr/src/linux/include/asm, so when that link gets moved, files
+ which need to include the asm-i386 versions of headers get the
+ incompatible asm-um versions. The fix is to move the include/asm link
+ back to include/asm-i386 and to do UML builds someplace else.
+
+
+
+ 13.5. UML doesn't work when /tmp is an NFS filesystem
+
+ This seems to be a similar situation with the ReiserFS problem above.
+ Some versions of NFS seems not to handle mmap correctly, which UML
+ depends on. The workaround is have /tmp be a non-NFS directory.
+
+
+ 13.6. UML hangs on boot when compiled with gprof support
+
+ If you build UML with gprof support and, early in the boot, it does
+ this
+
+
+ kernel BUG at page_alloc.c:100!
+
+
+
+
+ you have a buggy gcc. You can work around the problem by removing
+ UM_FASTCALL from CFLAGS in arch/um/Makefile-i386. This will open up
+ another bug, but that one is fairly hard to reproduce.
+
+
+
+ 13.7. syslogd dies with a SIGTERM on startup
+
+ The exact boot error depends on the distribution that you're booting,
+ but Debian produces this:
+
+
+ /etc/rc2.d/S10sysklogd: line 49: 93 Terminated
+ start-stop-daemon --start --quiet --exec /sbin/syslogd -- $SYSLOGD
+
+
+
+
+ This is a syslogd bug. There's a race between a parent process
+ installing a signal handler and its child sending the signal. See
+ this uml-devel post <http://www.geocrawler.com/lists/3/Source-
+ Forge/709/0/6612801> for the details.
+
+
+
+ 13.8. TUN/TAP networking doesn't work on a 2.4 host
+
+ There are a couple of problems which were
+ <http://www.geocrawler.com/lists/3/SourceForge/597/0/> name="pointed
+ out"> by Tim Robinson <timro at trkr dot net>
+
+ o It doesn't work on hosts running 2.4.7 (or thereabouts) or earlier.
+ The fix is to upgrade to something more recent and then read the
+ next item.
+
+ o If you see
+
+
+ File descriptor in bad state
+
+
+
+ when you bring up the device inside UML, you have a header mismatch
+ between the original kernel and the upgraded one. Make /usr/src/linux
+ point at the new headers. This will only be a problem if you build
+ uml_net yourself.
+
+
+
+ 13.9. You can network to the host but not to other machines on the
+ net
+
+ If you can connect to the host, and the host can connect to UML, but
+ you cannot connect to any other machines, then you may need to enable
+ IP Masquerading on the host. Usually this is only experienced when
+ using private IP addresses (192.168.x.x or 10.x.x.x) for host/UML
+ networking, rather than the public address space that your host is
+ connected to. UML does not enable IP Masquerading, so you will need
+ to create a static rule to enable it:
+
+
+ host%
+ iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
+
+
+
+
+ Replace eth0 with the interface that you use to talk to the rest of
+ the world.
+
+
+ Documentation on IP Masquerading, and SNAT, can be found at
+ www.netfilter.org <http://www.netfilter.org> .
+
+
+ If you can reach the local net, but not the outside Internet, then
+ that is usually a routing problem. The UML needs a default route:
+
+
+ UML#
+ route add default gw gateway IP
+
+
+
+
+ The gateway IP can be any machine on the local net that knows how to
+ reach the outside world. Usually, this is the host or the local net-
+ work's gateway.
+
+
+ Occasionally, we hear from someone who can reach some machines, but
+ not others on the same net, or who can reach some ports on other
+ machines, but not others. These are usually caused by strange
+ firewalling somewhere between the UML and the other box. You track
+ this down by running tcpdump on every interface the packets travel
+ over and see where they disappear. When you find a machine that takes
+ the packets in, but does not send them onward, that's the culprit.
+
+
+
+ 13.10. I have no root and I want to scream
+
+ Thanks to Birgit Wahlich for telling me about this strange one. It
+ turns out that there's a limit of six environment variables on the
+ kernel command line. When that limit is reached or exceeded, argument
+ processing stops, which means that the 'root=' argument that UML
+ usually adds is not seen. So, the filesystem has no idea what the
+ root device is, so it panics.
+
+
+ The fix is to put less stuff on the command line. Glomming all your
+ setup variables into one is probably the best way to go.
+
+
+
+ 13.11. UML build conflict between ptrace.h and ucontext.h
+
+ On some older systems, /usr/include/asm/ptrace.h and
+ /usr/include/sys/ucontext.h define the same names. So, when they're
+ included together, the defines from one completely mess up the parsing
+ of the other, producing errors like:
+ /usr/include/sys/ucontext.h:47: parse error before
+ `10'
+
+
+
+
+ plus a pile of warnings.
+
+
+ This is a libc botch, which has since been fixed, and I don't see any
+ way around it besides upgrading.
+
+
+
+ 13.12. The UML BogoMips is exactly half the host's BogoMips
+
+ On i386 kernels, there are two ways of running the loop that is used
+ to calculate the BogoMips rating, using the TSC if it's there or using
+ a one-instruction loop. The TSC produces twice the BogoMips as the
+ loop. UML uses the loop, since it has nothing resembling a TSC, and
+ will get almost exactly the same BogoMips as a host using the loop.
+ However, on a host with a TSC, its BogoMips will be double the loop
+ BogoMips, and therefore double the UML BogoMips.
+
+
+
+ 13.13. When you run UML, it immediately segfaults
+
+ If the host is configured with the 2G/2G address space split, that's
+ why. See ``UML on 2G/2G hosts'' for the details on getting UML to
+ run on your host.
+
+
+
+ 13.14. xterms appear, then immediately disappear
+
+ If you're running an up to date kernel with an old release of
+ uml_utilities, the port-helper program will not work properly, so
+ xterms will exit straight after they appear. The solution is to
+ upgrade to the latest release of uml_utilities. Usually this problem
+ occurs when you have installed a packaged release of UML then compiled
+ your own development kernel without upgrading the uml_utilities from
+ the source distribution.
+
+
+
+ 13.15. Any other panic, hang, or strange behavior
+
+ If you're seeing truly strange behavior, such as hangs or panics that
+ happen in random places, or you try running the debugger to see what's
+ happening and it acts strangely, then it could be a problem in the
+ host kernel. If you're not running a stock Linus or -ac kernel, then
+ try that. An early version of the preemption patch and a 2.4.10 SuSE
+ kernel have caused very strange problems in UML.
+
+
+ Otherwise, let me know about it. Send a message to one of the UML
+ mailing lists - either the developer list - user-mode-linux-devel at
+ lists dot sourceforge dot net (subscription info) or the user list -
+ user-mode-linux-user at lists dot sourceforge do net (subscription
+ info), whichever you prefer. Don't assume that everyone knows about
+ it and that a fix is imminent.
+
+
+ If you want to be super-helpful, read ``Diagnosing Problems'' and
+ follow the instructions contained therein.
+ 14. Diagnosing Problems
+
+
+ If you get UML to crash, hang, or otherwise misbehave, you should
+ report this on one of the project mailing lists, either the developer
+ list - user-mode-linux-devel at lists dot sourceforge dot net
+ (subscription info) or the user list - user-mode-linux-user at lists
+ dot sourceforge dot net (subscription info). When you do, it is
+ likely that I will want more information. So, it would be helpful to
+ read the stuff below, do whatever is applicable in your case, and
+ report the results to the list.
+
+
+ For any diagnosis, you're going to need to build a debugging kernel.
+ The binaries from this site aren't debuggable. If you haven't done
+ this before, read about ``Compiling the kernel and modules'' and
+ ``Kernel debugging'' UML first.
+
+
+ 14.1. Case 1 : Normal kernel panics
+
+ The most common case is for a normal thread to panic. To debug this,
+ you will need to run it under the debugger (add 'debug' to the command
+ line). An xterm will start up with gdb running inside it. Continue
+ it when it stops in start_kernel and make it crash. Now ^C gdb and
+
+
+ If the panic was a "Kernel mode fault", then there will be a segv
+ frame on the stack and I'm going to want some more information. The
+ stack might look something like this:
+
+
+ (UML gdb) backtrace
+ #0 0x1009bf76 in __sigprocmask (how=1, set=0x5f347940, oset=0x0)
+ at ../sysdeps/unix/sysv/linux/sigprocmask.c:49
+ #1 0x10091411 in change_sig (signal=10, on=1) at process.c:218
+ #2 0x10094785 in timer_handler (sig=26) at time_kern.c:32
+ #3 0x1009bf38 in __restore ()
+ at ../sysdeps/unix/sysv/linux/i386/sigaction.c:125
+ #4 0x1009534c in segv (address=8, ip=268849158, is_write=2, is_user=0)
+ at trap_kern.c:66
+ #5 0x10095c04 in segv_handler (sig=11) at trap_user.c:285
+ #6 0x1009bf38 in __restore ()
+
+
+
+
+ I'm going to want to see the symbol and line information for the value
+ of ip in the segv frame. In this case, you would do the following:
+
+
+ (UML gdb) i sym 268849158
+
+
+
+
+ and
+
+
+ (UML gdb) i line *268849158
+
+
+
+
+ The reason for this is the __restore frame right above the segv_han-
+ dler frame is hiding the frame that actually segfaulted. So, I have
+ to get that information from the faulting ip.
+
+
+ 14.2. Case 2 : Tracing thread panics
+
+ The less common and more painful case is when the tracing thread
+ panics. In this case, the kernel debugger will be useless because it
+ needs a healthy tracing thread in order to work. The first thing to
+ do is get a backtrace from the tracing thread. This is done by
+ figuring out what its pid is, firing up gdb, and attaching it to that
+ pid. You can figure out the tracing thread pid by looking at the
+ first line of the console output, which will look like this:
+
+
+ tracing thread pid = 15851
+
+
+
+
+ or by running ps on the host and finding the line that looks like
+ this:
+
+
+ jdike 15851 4.5 0.4 132568 1104 pts/0 S 21:34 0:05 ./linux [(tracing thread)]
+
+
+
+
+ If the panic was 'segfault in signals', then follow the instructions
+ above for collecting information about the location of the seg fault.
+
+
+ If the tracing thread flaked out all by itself, then send that
+ backtrace in and wait for our crack debugging team to fix the problem.
+
+
+ 14.3. Case 3 : Tracing thread panics caused by other threads
+
+ However, there are cases where the misbehavior of another thread
+ caused the problem. The most common panic of this type is:
+
+
+ wait_for_stop failed to wait for <pid> to stop with <signal number>
+
+
+
+
+ In this case, you'll need to get a backtrace from the process men-
+ tioned in the panic, which is complicated by the fact that the kernel
+ debugger is defunct and without some fancy footwork, another gdb can't
+ attach to it. So, this is how the fancy footwork goes:
+
+ In a shell:
+
+
+ host% kill -STOP pid
+
+
+
+
+ Run gdb on the tracing thread as described in case 2 and do:
+
+
+ (host gdb) call detach(pid)
+
+
+ If you get a segfault, do it again. It always works the second time.
+
+ Detach from the tracing thread and attach to that other thread:
+
+
+ (host gdb) detach
+
+
+
+
+
+
+ (host gdb) attach pid
+
+
+
+
+ If gdb hangs when attaching to that process, go back to a shell and
+ do:
+
+
+ host%
+ kill -CONT pid
+
+
+
+
+ And then get the backtrace:
+
+
+ (host gdb) backtrace
+
+
+
+
+
+ 14.4. Case 4 : Hangs
+
+ Hangs seem to be fairly rare, but they sometimes happen. When a hang
+ happens, we need a backtrace from the offending process. Run the
+ kernel debugger as described in case 1 and get a backtrace. If the
+ current process is not the idle thread, then send in the backtrace.
+ You can tell that it's the idle thread if the stack looks like this:
+
+
+ #0 0x100b1401 in __libc_nanosleep ()
+ #1 0x100a2885 in idle_sleep (secs=10) at time.c:122
+ #2 0x100a546f in do_idle () at process_kern.c:445
+ #3 0x100a5508 in cpu_idle () at process_kern.c:471
+ #4 0x100ec18f in start_kernel () at init/main.c:592
+ #5 0x100a3e10 in start_kernel_proc (unused=0x0) at um_arch.c:71
+ #6 0x100a383f in signal_tramp (arg=0x100a3dd8) at trap_user.c:50
+
+
+
+
+ If this is the case, then some other process is at fault, and went to
+ sleep when it shouldn't have. Run ps on the host and figure out which
+ process should not have gone to sleep and stayed asleep. Then attach
+ to it with gdb and get a backtrace as described in case 3.
+
+
+
+
+
+
+ 15. Thanks
+
+
+ A number of people have helped this project in various ways, and this
+ page gives recognition where recognition is due.
+
+
+ If you're listed here and you would prefer a real link on your name,
+ or no link at all, instead of the despammed email address pseudo-link,
+ let me know.
+
+
+ If you're not listed here and you think maybe you should be, please
+ let me know that as well. I try to get everyone, but sometimes my
+ bookkeeping lapses and I forget about contributions.
+
+
+ 15.1. Code and Documentation
+
+ Rusty Russell <rusty at linuxcare.com.au> -
+
+ o wrote the HOWTO <http://user-mode-
+ linux.sourceforge.net/UserModeLinux-HOWTO.html>
+
+ o prodded me into making this project official and putting it on
+ SourceForge
+
+ o came up with the way cool UML logo <http://user-mode-
+ linux.sourceforge.net/uml-small.png>
+
+ o redid the config process
+
+
+ Peter Moulder <reiter at netspace.net.au> - Fixed my config and build
+ processes, and added some useful code to the block driver
+
+
+ Bill Stearns <wstearns at pobox.com> -
+
+ o HOWTO updates
+
+ o lots of bug reports
+
+ o lots of testing
+
+ o dedicated a box (uml.ists.dartmouth.edu) to support UML development
+
+ o wrote the mkrootfs script, which allows bootable filesystems of
+ RPM-based distributions to be cranked out
+
+ o cranked out a large number of filesystems with said script
+
+
+ Jim Leu <jleu at mindspring.com> - Wrote the virtual ethernet driver
+ and associated usermode tools
+
+ Lars Brinkhoff <http://lars.nocrew.org/> - Contributed the ptrace
+ proxy from his own project <http://a386.nocrew.org/> to allow easier
+ kernel debugging
+
+
+ Andrea Arcangeli <andrea at suse.de> - Redid some of the early boot
+ code so that it would work on machines with Large File Support
+
+
+ Chris Emerson <http://www.chiark.greenend.org.uk/~cemerson/> - Did
+ the first UML port to Linux/ppc
+
+
+ Harald Welte <laforge at gnumonks.org> - Wrote the multicast
+ transport for the network driver
+
+
+ Jorgen Cederlof - Added special file support to hostfs
+
+
+ Greg Lonnon <glonnon at ridgerun dot com> - Changed the ubd driver
+ to allow it to layer a COW file on a shared read-only filesystem and
+ wrote the iomem emulation support
+
+
+ Henrik Nordstrom <http://hem.passagen.se/hno/> - Provided a variety
+ of patches, fixes, and clues
+
+
+ Lennert Buytenhek - Contributed various patches, a rewrite of the
+ network driver, the first implementation of the mconsole driver, and
+ did the bulk of the work needed to get SMP working again.
+
+
+ Yon Uriarte - Fixed the TUN/TAP network backend while I slept.
+
+
+ Adam Heath - Made a bunch of nice cleanups to the initialization code,
+ plus various other small patches.
+
+
+ Matt Zimmerman - Matt volunteered to be the UML Debian maintainer and
+ is doing a real nice job of it. He also noticed and fixed a number of
+ actually and potentially exploitable security holes in uml_net. Plus
+ the occasional patch. I like patches.
+
+
+ James McMechan - James seems to have taken over maintenance of the ubd
+ driver and is doing a nice job of it.
+
+
+ Chandan Kudige - wrote the umlgdb script which automates the reloading
+ of module symbols.
+
+
+ Steve Schmidtke - wrote the UML slirp transport and hostaudio drivers,
+ enabling UML processes to access audio devices on the host. He also
+ submitted patches for the slip transport and lots of other things.
+
+
+ David Coulson <http://davidcoulson.net> -
+
+ o Set up the usermodelinux.org <http://usermodelinux.org> site,
+ which is a great way of keeping the UML user community on top of
+ UML goings-on.
+
+ o Site documentation and updates
+
+ o Nifty little UML management daemon UMLd
+ <http://uml.openconsultancy.com/umld/>
+
+ o Lots of testing and bug reports
+
+
+
+
+ 15.2. Flushing out bugs
+
+
+
+ o Yuri Pudgorodsky
+
+ o Gerald Britton
+
+ o Ian Wehrman
+
+ o Gord Lamb
+
+ o Eugene Koontz
+
+ o John H. Hartman
+
+ o Anders Karlsson
+
+ o Daniel Phillips
+
+ o John Fremlin
+
+ o Rainer Burgstaller
+
+ o James Stevenson
+
+ o Matt Clay
+
+ o Cliff Jefferies
+
+ o Geoff Hoff
+
+ o Lennert Buytenhek
+
+ o Al Viro
+
+ o Frank Klingenhoefer
+
+ o Livio Baldini Soares
+
+ o Jon Burgess
+
+ o Petru Paler
+
+ o Paul
+
+ o Chris Reahard
+
+ o Sverker Nilsson
+
+ o Gong Su
+
+ o johan verrept
+
+ o Bjorn Eriksson
+
+ o Lorenzo Allegrucci
+
+ o Muli Ben-Yehuda
+
+ o David Mansfield
+
+ o Howard Goff
+
+ o Mike Anderson
+
+ o John Byrne
+
+ o Sapan J. Batia
+
+ o Iris Huang
+
+ o Jan Hudec
+
+ o Voluspa
+
+
+
+
+ 15.3. Buglets and clean-ups
+
+
+
+ o Dave Zarzycki
+
+ o Adam Lazur
+
+ o Boria Feigin
+
+ o Brian J. Murrell
+
+ o JS
+
+ o Roman Zippel
+
+ o Wil Cooley
+
+ o Ayelet Shemesh
+
+ o Will Dyson
+
+ o Sverker Nilsson
+
+ o dvorak
+
+ o v.naga srinivas
+
+ o Shlomi Fish
+
+ o Roger Binns
+
+ o johan verrept
+
+ o MrChuoi
+
+ o Peter Cleve
+
+ o Vincent Guffens
+
+ o Nathan Scott
+
+ o Patrick Caulfield
+
+ o jbearce
+
+ o Catalin Marinas
+
+ o Shane Spencer
+
+ o Zou Min
+
+
+ o Ryan Boder
+
+ o Lorenzo Colitti
+
+ o Gwendal Grignou
+
+ o Andre' Breiler
+
+ o Tsutomu Yasuda
+
+
+
+ 15.4. Case Studies
+
+
+ o Jon Wright
+
+ o William McEwan
+
+ o Michael Richardson
+
+
+
+ 15.5. Other contributions
+
+
+ Bill Carr <Bill.Carr at compaq.com> made the Red Hat mkrootfs script
+ work with RH 6.2.
+
+ Michael Jennings <mikejen at hevanet.com> sent in some material which
+ is now gracing the top of the index page <http://user-mode-
+ linux.sourceforge.net/> of this site.
+
+ SGI <http://www.sgi.com> (and more specifically Ralf Baechle <ralf at
+ uni-koblenz.de> ) gave me an account on oss.sgi.com
+ <http://www.oss.sgi.com> . The bandwidth there made it possible to
+ produce most of the filesystems available on the project download
+ page.
+
+ Laurent Bonnaud <Laurent.Bonnaud at inpg.fr> took the old grotty
+ Debian filesystem that I've been distributing and updated it to 2.2.
+ It is now available by itself here.
+
+ Rik van Riel gave me some ftp space on ftp.nl.linux.org so I can make
+ releases even when Sourceforge is broken.
+
+ Rodrigo de Castro looked at my broken pte code and told me what was
+ wrong with it, letting me fix a long-standing (several weeks) and
+ serious set of bugs.
+
+ Chris Reahard built a specialized root filesystem for running a DNS
+ server jailed inside UML. It's available from the download
+ <http://user-mode-linux.sourceforge.net/dl-sf.html> page in the Jail
+ Filesystems section.
+
+
+
+
+
+
+
+
+
+
+
+
+++ /dev/null
-.. SPDX-License-Identifier: GPL-2.0
-
-============================
-Linux Virtualization Support
-============================
-
-.. toctree::
- :maxdepth: 2
-
- kvm/index
- paravirt_ops
-
-.. only:: html and subproject
-
- Indices
- =======
-
- * :ref:`genindex`
+++ /dev/null
-======================================
-Secure Encrypted Virtualization (SEV)
-======================================
-
-Overview
-========
-
-Secure Encrypted Virtualization (SEV) is a feature found on AMD processors.
-
-SEV is an extension to the AMD-V architecture which supports running
-virtual machines (VMs) under the control of a hypervisor. When enabled,
-the memory contents of a VM will be transparently encrypted with a key
-unique to that VM.
-
-The hypervisor can determine the SEV support through the CPUID
-instruction. The CPUID function 0x8000001f reports information related
-to SEV::
-
- 0x8000001f[eax]:
- Bit[1] indicates support for SEV
- ...
- [ecx]:
- Bits[31:0] Number of encrypted guests supported simultaneously
-
-If support for SEV is present, MSR 0xc001_0010 (MSR_K8_SYSCFG) and MSR 0xc001_0015
-(MSR_K7_HWCR) can be used to determine if it can be enabled::
-
- 0xc001_0010:
- Bit[23] 1 = memory encryption can be enabled
- 0 = memory encryption can not be enabled
-
- 0xc001_0015:
- Bit[0] 1 = memory encryption can be enabled
- 0 = memory encryption can not be enabled
-
-When SEV support is available, it can be enabled in a specific VM by
-setting the SEV bit before executing VMRUN.::
-
- VMCB[0x90]:
- Bit[1] 1 = SEV is enabled
- 0 = SEV is disabled
-
-SEV hardware uses ASIDs to associate a memory encryption key with a VM.
-Hence, the ASID for the SEV-enabled guests must be from 1 to a maximum value
-defined in the CPUID 0x8000001f[ecx] field.
-
-SEV Key Management
-==================
-
-The SEV guest key management is handled by a separate processor called the AMD
-Secure Processor (AMD-SP). Firmware running inside the AMD-SP provides a secure
-key management interface to perform common hypervisor activities such as
-encrypting bootstrap code, snapshot, migrating and debugging the guest. For more
-information, see the SEV Key Management spec [api-spec]_
-
-KVM implements the following commands to support common lifecycle events of SEV
-guests, such as launching, running, snapshotting, migrating and decommissioning.
-
-1. KVM_SEV_INIT
----------------
-
-The KVM_SEV_INIT command is used by the hypervisor to initialize the SEV platform
-context. In a typical workflow, this command should be the first command issued.
-
-Returns: 0 on success, -negative on error
-
-2. KVM_SEV_LAUNCH_START
------------------------
-
-The KVM_SEV_LAUNCH_START command is used for creating the memory encryption
-context. To create the encryption context, user must provide a guest policy,
-the owner's public Diffie-Hellman (PDH) key and session information.
-
-Parameters: struct kvm_sev_launch_start (in/out)
-
-Returns: 0 on success, -negative on error
-
-::
-
- struct kvm_sev_launch_start {
- __u32 handle; /* if zero then firmware creates a new handle */
- __u32 policy; /* guest's policy */
-
- __u64 dh_uaddr; /* userspace address pointing to the guest owner's PDH key */
- __u32 dh_len;
-
- __u64 session_addr; /* userspace address which points to the guest session information */
- __u32 session_len;
- };
-
-On success, the 'handle' field contains a new handle and on error, a negative value.
-
-For more details, see SEV spec Section 6.2.
-
-3. KVM_SEV_LAUNCH_UPDATE_DATA
------------------------------
-
-The KVM_SEV_LAUNCH_UPDATE_DATA is used for encrypting a memory region. It also
-calculates a measurement of the memory contents. The measurement is a signature
-of the memory contents that can be sent to the guest owner as an attestation
-that the memory was encrypted correctly by the firmware.
-
-Parameters (in): struct kvm_sev_launch_update_data
-
-Returns: 0 on success, -negative on error
-
-::
-
- struct kvm_sev_launch_update {
- __u64 uaddr; /* userspace address to be encrypted (must be 16-byte aligned) */
- __u32 len; /* length of the data to be encrypted (must be 16-byte aligned) */
- };
-
-For more details, see SEV spec Section 6.3.
-
-4. KVM_SEV_LAUNCH_MEASURE
--------------------------
-
-The KVM_SEV_LAUNCH_MEASURE command is used to retrieve the measurement of the
-data encrypted by the KVM_SEV_LAUNCH_UPDATE_DATA command. The guest owner may
-wait to provide the guest with confidential information until it can verify the
-measurement. Since the guest owner knows the initial contents of the guest at
-boot, the measurement can be verified by comparing it to what the guest owner
-expects.
-
-Parameters (in): struct kvm_sev_launch_measure
-
-Returns: 0 on success, -negative on error
-
-::
-
- struct kvm_sev_launch_measure {
- __u64 uaddr; /* where to copy the measurement */
- __u32 len; /* length of measurement blob */
- };
-
-For more details on the measurement verification flow, see SEV spec Section 6.4.
-
-5. KVM_SEV_LAUNCH_FINISH
-------------------------
-
-After completion of the launch flow, the KVM_SEV_LAUNCH_FINISH command can be
-issued to make the guest ready for the execution.
-
-Returns: 0 on success, -negative on error
-
-6. KVM_SEV_GUEST_STATUS
------------------------
-
-The KVM_SEV_GUEST_STATUS command is used to retrieve status information about a
-SEV-enabled guest.
-
-Parameters (out): struct kvm_sev_guest_status
-
-Returns: 0 on success, -negative on error
-
-::
-
- struct kvm_sev_guest_status {
- __u32 handle; /* guest handle */
- __u32 policy; /* guest policy */
- __u8 state; /* guest state (see enum below) */
- };
-
-SEV guest state:
-
-::
-
- enum {
- SEV_STATE_INVALID = 0;
- SEV_STATE_LAUNCHING, /* guest is currently being launched */
- SEV_STATE_SECRET, /* guest is being launched and ready to accept the ciphertext data */
- SEV_STATE_RUNNING, /* guest is fully launched and running */
- SEV_STATE_RECEIVING, /* guest is being migrated in from another SEV machine */
- SEV_STATE_SENDING /* guest is getting migrated out to another SEV machine */
- };
-
-7. KVM_SEV_DBG_DECRYPT
-----------------------
-
-The KVM_SEV_DEBUG_DECRYPT command can be used by the hypervisor to request the
-firmware to decrypt the data at the given memory region.
-
-Parameters (in): struct kvm_sev_dbg
-
-Returns: 0 on success, -negative on error
-
-::
-
- struct kvm_sev_dbg {
- __u64 src_uaddr; /* userspace address of data to decrypt */
- __u64 dst_uaddr; /* userspace address of destination */
- __u32 len; /* length of memory region to decrypt */
- };
-
-The command returns an error if the guest policy does not allow debugging.
-
-8. KVM_SEV_DBG_ENCRYPT
-----------------------
-
-The KVM_SEV_DEBUG_ENCRYPT command can be used by the hypervisor to request the
-firmware to encrypt the data at the given memory region.
-
-Parameters (in): struct kvm_sev_dbg
-
-Returns: 0 on success, -negative on error
-
-::
-
- struct kvm_sev_dbg {
- __u64 src_uaddr; /* userspace address of data to encrypt */
- __u64 dst_uaddr; /* userspace address of destination */
- __u32 len; /* length of memory region to encrypt */
- };
-
-The command returns an error if the guest policy does not allow debugging.
-
-9. KVM_SEV_LAUNCH_SECRET
-------------------------
-
-The KVM_SEV_LAUNCH_SECRET command can be used by the hypervisor to inject secret
-data after the measurement has been validated by the guest owner.
-
-Parameters (in): struct kvm_sev_launch_secret
-
-Returns: 0 on success, -negative on error
-
-::
-
- struct kvm_sev_launch_secret {
- __u64 hdr_uaddr; /* userspace address containing the packet header */
- __u32 hdr_len;
-
- __u64 guest_uaddr; /* the guest memory region where the secret should be injected */
- __u32 guest_len;
-
- __u64 trans_uaddr; /* the hypervisor memory region which contains the secret */
- __u32 trans_len;
- };
-
-References
-==========
-
-
-See [white-paper]_, [api-spec]_, [amd-apm]_ and [kvm-forum]_ for more info.
-
-.. [white-paper] http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2013/12/AMD_Memory_Encryption_Whitepaper_v7-Public.pdf
-.. [api-spec] http://support.amd.com/TechDocs/55766_SEV-KM_API_Specification.pdf
-.. [amd-apm] http://support.amd.com/TechDocs/24593.pdf (section 15.34)
-.. [kvm-forum] http://www.linux-kvm.org/images/7/74/02x08A-Thomas_Lendacky-AMDs_Virtualizatoin_Memory_Encryption_Technology.pdf
+++ /dev/null
-The Definitive KVM (Kernel-based Virtual Machine) API Documentation
-===================================================================
-
-1. General description
-----------------------
-
-The kvm API is a set of ioctls that are issued to control various aspects
-of a virtual machine. The ioctls belong to three classes:
-
- - System ioctls: These query and set global attributes which affect the
- whole kvm subsystem. In addition a system ioctl is used to create
- virtual machines.
-
- - VM ioctls: These query and set attributes that affect an entire virtual
- machine, for example memory layout. In addition a VM ioctl is used to
- create virtual cpus (vcpus) and devices.
-
- VM ioctls must be issued from the same process (address space) that was
- used to create the VM.
-
- - vcpu ioctls: These query and set attributes that control the operation
- of a single virtual cpu.
-
- vcpu ioctls should be issued from the same thread that was used to create
- the vcpu, except for asynchronous vcpu ioctl that are marked as such in
- the documentation. Otherwise, the first ioctl after switching threads
- could see a performance impact.
-
- - device ioctls: These query and set attributes that control the operation
- of a single device.
-
- device ioctls must be issued from the same process (address space) that
- was used to create the VM.
-
-2. File descriptors
--------------------
-
-The kvm API is centered around file descriptors. An initial
-open("/dev/kvm") obtains a handle to the kvm subsystem; this handle
-can be used to issue system ioctls. A KVM_CREATE_VM ioctl on this
-handle will create a VM file descriptor which can be used to issue VM
-ioctls. A KVM_CREATE_VCPU or KVM_CREATE_DEVICE ioctl on a VM fd will
-create a virtual cpu or device and return a file descriptor pointing to
-the new resource. Finally, ioctls on a vcpu or device fd can be used
-to control the vcpu or device. For vcpus, this includes the important
-task of actually running guest code.
-
-In general file descriptors can be migrated among processes by means
-of fork() and the SCM_RIGHTS facility of unix domain socket. These
-kinds of tricks are explicitly not supported by kvm. While they will
-not cause harm to the host, their actual behavior is not guaranteed by
-the API. See "General description" for details on the ioctl usage
-model that is supported by KVM.
-
-It is important to note that althought VM ioctls may only be issued from
-the process that created the VM, a VM's lifecycle is associated with its
-file descriptor, not its creator (process). In other words, the VM and
-its resources, *including the associated address space*, are not freed
-until the last reference to the VM's file descriptor has been released.
-For example, if fork() is issued after ioctl(KVM_CREATE_VM), the VM will
-not be freed until both the parent (original) process and its child have
-put their references to the VM's file descriptor.
-
-Because a VM's resources are not freed until the last reference to its
-file descriptor is released, creating additional references to a VM via
-via fork(), dup(), etc... without careful consideration is strongly
-discouraged and may have unwanted side effects, e.g. memory allocated
-by and on behalf of the VM's process may not be freed/unaccounted when
-the VM is shut down.
-
-
-3. Extensions
--------------
-
-As of Linux 2.6.22, the KVM ABI has been stabilized: no backward
-incompatible change are allowed. However, there is an extension
-facility that allows backward-compatible extensions to the API to be
-queried and used.
-
-The extension mechanism is not based on the Linux version number.
-Instead, kvm defines extension identifiers and a facility to query
-whether a particular extension identifier is available. If it is, a
-set of ioctls is available for application use.
-
-
-4. API description
-------------------
-
-This section describes ioctls that can be used to control kvm guests.
-For each ioctl, the following information is provided along with a
-description:
-
- Capability: which KVM extension provides this ioctl. Can be 'basic',
- which means that is will be provided by any kernel that supports
- API version 12 (see section 4.1), a KVM_CAP_xyz constant, which
- means availability needs to be checked with KVM_CHECK_EXTENSION
- (see section 4.4), or 'none' which means that while not all kernels
- support this ioctl, there's no capability bit to check its
- availability: for kernels that don't support the ioctl,
- the ioctl returns -ENOTTY.
-
- Architectures: which instruction set architectures provide this ioctl.
- x86 includes both i386 and x86_64.
-
- Type: system, vm, or vcpu.
-
- Parameters: what parameters are accepted by the ioctl.
-
- Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
- are not detailed, but errors with specific meanings are.
-
-
-4.1 KVM_GET_API_VERSION
-
-Capability: basic
-Architectures: all
-Type: system ioctl
-Parameters: none
-Returns: the constant KVM_API_VERSION (=12)
-
-This identifies the API version as the stable kvm API. It is not
-expected that this number will change. However, Linux 2.6.20 and
-2.6.21 report earlier versions; these are not documented and not
-supported. Applications should refuse to run if KVM_GET_API_VERSION
-returns a value other than 12. If this check passes, all ioctls
-described as 'basic' will be available.
-
-
-4.2 KVM_CREATE_VM
-
-Capability: basic
-Architectures: all
-Type: system ioctl
-Parameters: machine type identifier (KVM_VM_*)
-Returns: a VM fd that can be used to control the new virtual machine.
-
-The new VM has no virtual cpus and no memory.
-You probably want to use 0 as machine type.
-
-In order to create user controlled virtual machines on S390, check
-KVM_CAP_S390_UCONTROL and use the flag KVM_VM_S390_UCONTROL as
-privileged user (CAP_SYS_ADMIN).
-
-To use hardware assisted virtualization on MIPS (VZ ASE) rather than
-the default trap & emulate implementation (which changes the virtual
-memory layout to fit in user mode), check KVM_CAP_MIPS_VZ and use the
-flag KVM_VM_MIPS_VZ.
-
-
-On arm64, the physical address size for a VM (IPA Size limit) is limited
-to 40bits by default. The limit can be configured if the host supports the
-extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use
-KVM_VM_TYPE_ARM_IPA_SIZE(IPA_Bits) to set the size in the machine type
-identifier, where IPA_Bits is the maximum width of any physical
-address used by the VM. The IPA_Bits is encoded in bits[7-0] of the
-machine type identifier.
-
-e.g, to configure a guest to use 48bit physical address size :
-
- vm_fd = ioctl(dev_fd, KVM_CREATE_VM, KVM_VM_TYPE_ARM_IPA_SIZE(48));
-
-The requested size (IPA_Bits) must be :
- 0 - Implies default size, 40bits (for backward compatibility)
-
- or
-
- N - Implies N bits, where N is a positive integer such that,
- 32 <= N <= Host_IPA_Limit
-
-Host_IPA_Limit is the maximum possible value for IPA_Bits on the host and
-is dependent on the CPU capability and the kernel configuration. The limit can
-be retrieved using KVM_CAP_ARM_VM_IPA_SIZE of the KVM_CHECK_EXTENSION
-ioctl() at run-time.
-
-Please note that configuring the IPA size does not affect the capability
-exposed by the guest CPUs in ID_AA64MMFR0_EL1[PARange]. It only affects
-size of the address translated by the stage2 level (guest physical to
-host physical address translations).
-
-
-4.3 KVM_GET_MSR_INDEX_LIST, KVM_GET_MSR_FEATURE_INDEX_LIST
-
-Capability: basic, KVM_CAP_GET_MSR_FEATURES for KVM_GET_MSR_FEATURE_INDEX_LIST
-Architectures: x86
-Type: system ioctl
-Parameters: struct kvm_msr_list (in/out)
-Returns: 0 on success; -1 on error
-Errors:
- EFAULT: the msr index list cannot be read from or written to
- E2BIG: the msr index list is to be to fit in the array specified by
- the user.
-
-struct kvm_msr_list {
- __u32 nmsrs; /* number of msrs in entries */
- __u32 indices[0];
-};
-
-The user fills in the size of the indices array in nmsrs, and in return
-kvm adjusts nmsrs to reflect the actual number of msrs and fills in the
-indices array with their numbers.
-
-KVM_GET_MSR_INDEX_LIST returns the guest msrs that are supported. The list
-varies by kvm version and host processor, but does not change otherwise.
-
-Note: if kvm indicates supports MCE (KVM_CAP_MCE), then the MCE bank MSRs are
-not returned in the MSR list, as different vcpus can have a different number
-of banks, as set via the KVM_X86_SETUP_MCE ioctl.
-
-KVM_GET_MSR_FEATURE_INDEX_LIST returns the list of MSRs that can be passed
-to the KVM_GET_MSRS system ioctl. This lets userspace probe host capabilities
-and processor features that are exposed via MSRs (e.g., VMX capabilities).
-This list also varies by kvm version and host processor, but does not change
-otherwise.
-
-
-4.4 KVM_CHECK_EXTENSION
-
-Capability: basic, KVM_CAP_CHECK_EXTENSION_VM for vm ioctl
-Architectures: all
-Type: system ioctl, vm ioctl
-Parameters: extension identifier (KVM_CAP_*)
-Returns: 0 if unsupported; 1 (or some other positive integer) if supported
-
-The API allows the application to query about extensions to the core
-kvm API. Userspace passes an extension identifier (an integer) and
-receives an integer that describes the extension availability.
-Generally 0 means no and 1 means yes, but some extensions may report
-additional information in the integer return value.
-
-Based on their initialization different VMs may have different capabilities.
-It is thus encouraged to use the vm ioctl to query for capabilities (available
-with KVM_CAP_CHECK_EXTENSION_VM on the vm fd)
-
-4.5 KVM_GET_VCPU_MMAP_SIZE
-
-Capability: basic
-Architectures: all
-Type: system ioctl
-Parameters: none
-Returns: size of vcpu mmap area, in bytes
-
-The KVM_RUN ioctl (cf.) communicates with userspace via a shared
-memory region. This ioctl returns the size of that region. See the
-KVM_RUN documentation for details.
-
-
-4.6 KVM_SET_MEMORY_REGION
-
-Capability: basic
-Architectures: all
-Type: vm ioctl
-Parameters: struct kvm_memory_region (in)
-Returns: 0 on success, -1 on error
-
-This ioctl is obsolete and has been removed.
-
-
-4.7 KVM_CREATE_VCPU
-
-Capability: basic
-Architectures: all
-Type: vm ioctl
-Parameters: vcpu id (apic id on x86)
-Returns: vcpu fd on success, -1 on error
-
-This API adds a vcpu to a virtual machine. No more than max_vcpus may be added.
-The vcpu id is an integer in the range [0, max_vcpu_id).
-
-The recommended max_vcpus value can be retrieved using the KVM_CAP_NR_VCPUS of
-the KVM_CHECK_EXTENSION ioctl() at run-time.
-The maximum possible value for max_vcpus can be retrieved using the
-KVM_CAP_MAX_VCPUS of the KVM_CHECK_EXTENSION ioctl() at run-time.
-
-If the KVM_CAP_NR_VCPUS does not exist, you should assume that max_vcpus is 4
-cpus max.
-If the KVM_CAP_MAX_VCPUS does not exist, you should assume that max_vcpus is
-same as the value returned from KVM_CAP_NR_VCPUS.
-
-The maximum possible value for max_vcpu_id can be retrieved using the
-KVM_CAP_MAX_VCPU_ID of the KVM_CHECK_EXTENSION ioctl() at run-time.
-
-If the KVM_CAP_MAX_VCPU_ID does not exist, you should assume that max_vcpu_id
-is the same as the value returned from KVM_CAP_MAX_VCPUS.
-
-On powerpc using book3s_hv mode, the vcpus are mapped onto virtual
-threads in one or more virtual CPU cores. (This is because the
-hardware requires all the hardware threads in a CPU core to be in the
-same partition.) The KVM_CAP_PPC_SMT capability indicates the number
-of vcpus per virtual core (vcore). The vcore id is obtained by
-dividing the vcpu id by the number of vcpus per vcore. The vcpus in a
-given vcore will always be in the same physical core as each other
-(though that might be a different physical core from time to time).
-Userspace can control the threading (SMT) mode of the guest by its
-allocation of vcpu ids. For example, if userspace wants
-single-threaded guest vcpus, it should make all vcpu ids be a multiple
-of the number of vcpus per vcore.
-
-For virtual cpus that have been created with S390 user controlled virtual
-machines, the resulting vcpu fd can be memory mapped at page offset
-KVM_S390_SIE_PAGE_OFFSET in order to obtain a memory map of the virtual
-cpu's hardware control block.
-
-
-4.8 KVM_GET_DIRTY_LOG (vm ioctl)
-
-Capability: basic
-Architectures: all
-Type: vm ioctl
-Parameters: struct kvm_dirty_log (in/out)
-Returns: 0 on success, -1 on error
-
-/* for KVM_GET_DIRTY_LOG */
-struct kvm_dirty_log {
- __u32 slot;
- __u32 padding;
- union {
- void __user *dirty_bitmap; /* one bit per page */
- __u64 padding;
- };
-};
-
-Given a memory slot, return a bitmap containing any pages dirtied
-since the last call to this ioctl. Bit 0 is the first page in the
-memory slot. Ensure the entire structure is cleared to avoid padding
-issues.
-
-If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 specifies
-the address space for which you want to return the dirty bitmap.
-They must be less than the value that KVM_CHECK_EXTENSION returns for
-the KVM_CAP_MULTI_ADDRESS_SPACE capability.
-
-The bits in the dirty bitmap are cleared before the ioctl returns, unless
-KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is enabled. For more information,
-see the description of the capability.
-
-4.9 KVM_SET_MEMORY_ALIAS
-
-Capability: basic
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_memory_alias (in)
-Returns: 0 (success), -1 (error)
-
-This ioctl is obsolete and has been removed.
-
-
-4.10 KVM_RUN
-
-Capability: basic
-Architectures: all
-Type: vcpu ioctl
-Parameters: none
-Returns: 0 on success, -1 on error
-Errors:
- EINTR: an unmasked signal is pending
-
-This ioctl is used to run a guest virtual cpu. While there are no
-explicit parameters, there is an implicit parameter block that can be
-obtained by mmap()ing the vcpu fd at offset 0, with the size given by
-KVM_GET_VCPU_MMAP_SIZE. The parameter block is formatted as a 'struct
-kvm_run' (see below).
-
-
-4.11 KVM_GET_REGS
-
-Capability: basic
-Architectures: all except ARM, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_regs (out)
-Returns: 0 on success, -1 on error
-
-Reads the general purpose registers from the vcpu.
-
-/* x86 */
-struct kvm_regs {
- /* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
- __u64 rax, rbx, rcx, rdx;
- __u64 rsi, rdi, rsp, rbp;
- __u64 r8, r9, r10, r11;
- __u64 r12, r13, r14, r15;
- __u64 rip, rflags;
-};
-
-/* mips */
-struct kvm_regs {
- /* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
- __u64 gpr[32];
- __u64 hi;
- __u64 lo;
- __u64 pc;
-};
-
-
-4.12 KVM_SET_REGS
-
-Capability: basic
-Architectures: all except ARM, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_regs (in)
-Returns: 0 on success, -1 on error
-
-Writes the general purpose registers into the vcpu.
-
-See KVM_GET_REGS for the data structure.
-
-
-4.13 KVM_GET_SREGS
-
-Capability: basic
-Architectures: x86, ppc
-Type: vcpu ioctl
-Parameters: struct kvm_sregs (out)
-Returns: 0 on success, -1 on error
-
-Reads special registers from the vcpu.
-
-/* x86 */
-struct kvm_sregs {
- struct kvm_segment cs, ds, es, fs, gs, ss;
- struct kvm_segment tr, ldt;
- struct kvm_dtable gdt, idt;
- __u64 cr0, cr2, cr3, cr4, cr8;
- __u64 efer;
- __u64 apic_base;
- __u64 interrupt_bitmap[(KVM_NR_INTERRUPTS + 63) / 64];
-};
-
-/* ppc -- see arch/powerpc/include/uapi/asm/kvm.h */
-
-interrupt_bitmap is a bitmap of pending external interrupts. At most
-one bit may be set. This interrupt has been acknowledged by the APIC
-but not yet injected into the cpu core.
-
-
-4.14 KVM_SET_SREGS
-
-Capability: basic
-Architectures: x86, ppc
-Type: vcpu ioctl
-Parameters: struct kvm_sregs (in)
-Returns: 0 on success, -1 on error
-
-Writes special registers into the vcpu. See KVM_GET_SREGS for the
-data structures.
-
-
-4.15 KVM_TRANSLATE
-
-Capability: basic
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_translation (in/out)
-Returns: 0 on success, -1 on error
-
-Translates a virtual address according to the vcpu's current address
-translation mode.
-
-struct kvm_translation {
- /* in */
- __u64 linear_address;
-
- /* out */
- __u64 physical_address;
- __u8 valid;
- __u8 writeable;
- __u8 usermode;
- __u8 pad[5];
-};
-
-
-4.16 KVM_INTERRUPT
-
-Capability: basic
-Architectures: x86, ppc, mips
-Type: vcpu ioctl
-Parameters: struct kvm_interrupt (in)
-Returns: 0 on success, negative on failure.
-
-Queues a hardware interrupt vector to be injected.
-
-/* for KVM_INTERRUPT */
-struct kvm_interrupt {
- /* in */
- __u32 irq;
-};
-
-X86:
-
-Returns: 0 on success,
- -EEXIST if an interrupt is already enqueued
- -EINVAL the the irq number is invalid
- -ENXIO if the PIC is in the kernel
- -EFAULT if the pointer is invalid
-
-Note 'irq' is an interrupt vector, not an interrupt pin or line. This
-ioctl is useful if the in-kernel PIC is not used.
-
-PPC:
-
-Queues an external interrupt to be injected. This ioctl is overleaded
-with 3 different irq values:
-
-a) KVM_INTERRUPT_SET
-
- This injects an edge type external interrupt into the guest once it's ready
- to receive interrupts. When injected, the interrupt is done.
-
-b) KVM_INTERRUPT_UNSET
-
- This unsets any pending interrupt.
-
- Only available with KVM_CAP_PPC_UNSET_IRQ.
-
-c) KVM_INTERRUPT_SET_LEVEL
-
- This injects a level type external interrupt into the guest context. The
- interrupt stays pending until a specific ioctl with KVM_INTERRUPT_UNSET
- is triggered.
-
- Only available with KVM_CAP_PPC_IRQ_LEVEL.
-
-Note that any value for 'irq' other than the ones stated above is invalid
-and incurs unexpected behavior.
-
-This is an asynchronous vcpu ioctl and can be invoked from any thread.
-
-MIPS:
-
-Queues an external interrupt to be injected into the virtual CPU. A negative
-interrupt number dequeues the interrupt.
-
-This is an asynchronous vcpu ioctl and can be invoked from any thread.
-
-
-4.17 KVM_DEBUG_GUEST
-
-Capability: basic
-Architectures: none
-Type: vcpu ioctl
-Parameters: none)
-Returns: -1 on error
-
-Support for this has been removed. Use KVM_SET_GUEST_DEBUG instead.
-
-
-4.18 KVM_GET_MSRS
-
-Capability: basic (vcpu), KVM_CAP_GET_MSR_FEATURES (system)
-Architectures: x86
-Type: system ioctl, vcpu ioctl
-Parameters: struct kvm_msrs (in/out)
-Returns: number of msrs successfully returned;
- -1 on error
-
-When used as a system ioctl:
-Reads the values of MSR-based features that are available for the VM. This
-is similar to KVM_GET_SUPPORTED_CPUID, but it returns MSR indices and values.
-The list of msr-based features can be obtained using KVM_GET_MSR_FEATURE_INDEX_LIST
-in a system ioctl.
-
-When used as a vcpu ioctl:
-Reads model-specific registers from the vcpu. Supported msr indices can
-be obtained using KVM_GET_MSR_INDEX_LIST in a system ioctl.
-
-struct kvm_msrs {
- __u32 nmsrs; /* number of msrs in entries */
- __u32 pad;
-
- struct kvm_msr_entry entries[0];
-};
-
-struct kvm_msr_entry {
- __u32 index;
- __u32 reserved;
- __u64 data;
-};
-
-Application code should set the 'nmsrs' member (which indicates the
-size of the entries array) and the 'index' member of each array entry.
-kvm will fill in the 'data' member.
-
-
-4.19 KVM_SET_MSRS
-
-Capability: basic
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_msrs (in)
-Returns: 0 on success, -1 on error
-
-Writes model-specific registers to the vcpu. See KVM_GET_MSRS for the
-data structures.
-
-Application code should set the 'nmsrs' member (which indicates the
-size of the entries array), and the 'index' and 'data' members of each
-array entry.
-
-
-4.20 KVM_SET_CPUID
-
-Capability: basic
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_cpuid (in)
-Returns: 0 on success, -1 on error
-
-Defines the vcpu responses to the cpuid instruction. Applications
-should use the KVM_SET_CPUID2 ioctl if available.
-
-
-struct kvm_cpuid_entry {
- __u32 function;
- __u32 eax;
- __u32 ebx;
- __u32 ecx;
- __u32 edx;
- __u32 padding;
-};
-
-/* for KVM_SET_CPUID */
-struct kvm_cpuid {
- __u32 nent;
- __u32 padding;
- struct kvm_cpuid_entry entries[0];
-};
-
-
-4.21 KVM_SET_SIGNAL_MASK
-
-Capability: basic
-Architectures: all
-Type: vcpu ioctl
-Parameters: struct kvm_signal_mask (in)
-Returns: 0 on success, -1 on error
-
-Defines which signals are blocked during execution of KVM_RUN. This
-signal mask temporarily overrides the threads signal mask. Any
-unblocked signal received (except SIGKILL and SIGSTOP, which retain
-their traditional behaviour) will cause KVM_RUN to return with -EINTR.
-
-Note the signal will only be delivered if not blocked by the original
-signal mask.
-
-/* for KVM_SET_SIGNAL_MASK */
-struct kvm_signal_mask {
- __u32 len;
- __u8 sigset[0];
-};
-
-
-4.22 KVM_GET_FPU
-
-Capability: basic
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_fpu (out)
-Returns: 0 on success, -1 on error
-
-Reads the floating point state from the vcpu.
-
-/* for KVM_GET_FPU and KVM_SET_FPU */
-struct kvm_fpu {
- __u8 fpr[8][16];
- __u16 fcw;
- __u16 fsw;
- __u8 ftwx; /* in fxsave format */
- __u8 pad1;
- __u16 last_opcode;
- __u64 last_ip;
- __u64 last_dp;
- __u8 xmm[16][16];
- __u32 mxcsr;
- __u32 pad2;
-};
-
-
-4.23 KVM_SET_FPU
-
-Capability: basic
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_fpu (in)
-Returns: 0 on success, -1 on error
-
-Writes the floating point state to the vcpu.
-
-/* for KVM_GET_FPU and KVM_SET_FPU */
-struct kvm_fpu {
- __u8 fpr[8][16];
- __u16 fcw;
- __u16 fsw;
- __u8 ftwx; /* in fxsave format */
- __u8 pad1;
- __u16 last_opcode;
- __u64 last_ip;
- __u64 last_dp;
- __u8 xmm[16][16];
- __u32 mxcsr;
- __u32 pad2;
-};
-
-
-4.24 KVM_CREATE_IRQCHIP
-
-Capability: KVM_CAP_IRQCHIP, KVM_CAP_S390_IRQCHIP (s390)
-Architectures: x86, ARM, arm64, s390
-Type: vm ioctl
-Parameters: none
-Returns: 0 on success, -1 on error
-
-Creates an interrupt controller model in the kernel.
-On x86, creates a virtual ioapic, a virtual PIC (two PICs, nested), and sets up
-future vcpus to have a local APIC. IRQ routing for GSIs 0-15 is set to both
-PIC and IOAPIC; GSI 16-23 only go to the IOAPIC.
-On ARM/arm64, a GICv2 is created. Any other GIC versions require the usage of
-KVM_CREATE_DEVICE, which also supports creating a GICv2. Using
-KVM_CREATE_DEVICE is preferred over KVM_CREATE_IRQCHIP for GICv2.
-On s390, a dummy irq routing table is created.
-
-Note that on s390 the KVM_CAP_S390_IRQCHIP vm capability needs to be enabled
-before KVM_CREATE_IRQCHIP can be used.
-
-
-4.25 KVM_IRQ_LINE
-
-Capability: KVM_CAP_IRQCHIP
-Architectures: x86, arm, arm64
-Type: vm ioctl
-Parameters: struct kvm_irq_level
-Returns: 0 on success, -1 on error
-
-Sets the level of a GSI input to the interrupt controller model in the kernel.
-On some architectures it is required that an interrupt controller model has
-been previously created with KVM_CREATE_IRQCHIP. Note that edge-triggered
-interrupts require the level to be set to 1 and then back to 0.
-
-On real hardware, interrupt pins can be active-low or active-high. This
-does not matter for the level field of struct kvm_irq_level: 1 always
-means active (asserted), 0 means inactive (deasserted).
-
-x86 allows the operating system to program the interrupt polarity
-(active-low/active-high) for level-triggered interrupts, and KVM used
-to consider the polarity. However, due to bitrot in the handling of
-active-low interrupts, the above convention is now valid on x86 too.
-This is signaled by KVM_CAP_X86_IOAPIC_POLARITY_IGNORED. Userspace
-should not present interrupts to the guest as active-low unless this
-capability is present (or unless it is not using the in-kernel irqchip,
-of course).
-
-
-ARM/arm64 can signal an interrupt either at the CPU level, or at the
-in-kernel irqchip (GIC), and for in-kernel irqchip can tell the GIC to
-use PPIs designated for specific cpus. The irq field is interpreted
-like this:
-
- bits: | 31 ... 24 | 23 ... 16 | 15 ... 0 |
- field: | irq_type | vcpu_index | irq_id |
-
-The irq_type field has the following values:
-- irq_type[0]: out-of-kernel GIC: irq_id 0 is IRQ, irq_id 1 is FIQ
-- irq_type[1]: in-kernel GIC: SPI, irq_id between 32 and 1019 (incl.)
- (the vcpu_index field is ignored)
-- irq_type[2]: in-kernel GIC: PPI, irq_id between 16 and 31 (incl.)
-
-(The irq_id field thus corresponds nicely to the IRQ ID in the ARM GIC specs)
-
-In both cases, level is used to assert/deassert the line.
-
-struct kvm_irq_level {
- union {
- __u32 irq; /* GSI */
- __s32 status; /* not used for KVM_IRQ_LEVEL */
- };
- __u32 level; /* 0 or 1 */
-};
-
-
-4.26 KVM_GET_IRQCHIP
-
-Capability: KVM_CAP_IRQCHIP
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_irqchip (in/out)
-Returns: 0 on success, -1 on error
-
-Reads the state of a kernel interrupt controller created with
-KVM_CREATE_IRQCHIP into a buffer provided by the caller.
-
-struct kvm_irqchip {
- __u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */
- __u32 pad;
- union {
- char dummy[512]; /* reserving space */
- struct kvm_pic_state pic;
- struct kvm_ioapic_state ioapic;
- } chip;
-};
-
-
-4.27 KVM_SET_IRQCHIP
-
-Capability: KVM_CAP_IRQCHIP
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_irqchip (in)
-Returns: 0 on success, -1 on error
-
-Sets the state of a kernel interrupt controller created with
-KVM_CREATE_IRQCHIP from a buffer provided by the caller.
-
-struct kvm_irqchip {
- __u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */
- __u32 pad;
- union {
- char dummy[512]; /* reserving space */
- struct kvm_pic_state pic;
- struct kvm_ioapic_state ioapic;
- } chip;
-};
-
-
-4.28 KVM_XEN_HVM_CONFIG
-
-Capability: KVM_CAP_XEN_HVM
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_xen_hvm_config (in)
-Returns: 0 on success, -1 on error
-
-Sets the MSR that the Xen HVM guest uses to initialize its hypercall
-page, and provides the starting address and size of the hypercall
-blobs in userspace. When the guest writes the MSR, kvm copies one
-page of a blob (32- or 64-bit, depending on the vcpu mode) to guest
-memory.
-
-struct kvm_xen_hvm_config {
- __u32 flags;
- __u32 msr;
- __u64 blob_addr_32;
- __u64 blob_addr_64;
- __u8 blob_size_32;
- __u8 blob_size_64;
- __u8 pad2[30];
-};
-
-
-4.29 KVM_GET_CLOCK
-
-Capability: KVM_CAP_ADJUST_CLOCK
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_clock_data (out)
-Returns: 0 on success, -1 on error
-
-Gets the current timestamp of kvmclock as seen by the current guest. In
-conjunction with KVM_SET_CLOCK, it is used to ensure monotonicity on scenarios
-such as migration.
-
-When KVM_CAP_ADJUST_CLOCK is passed to KVM_CHECK_EXTENSION, it returns the
-set of bits that KVM can return in struct kvm_clock_data's flag member.
-
-The only flag defined now is KVM_CLOCK_TSC_STABLE. If set, the returned
-value is the exact kvmclock value seen by all VCPUs at the instant
-when KVM_GET_CLOCK was called. If clear, the returned value is simply
-CLOCK_MONOTONIC plus a constant offset; the offset can be modified
-with KVM_SET_CLOCK. KVM will try to make all VCPUs follow this clock,
-but the exact value read by each VCPU could differ, because the host
-TSC is not stable.
-
-struct kvm_clock_data {
- __u64 clock; /* kvmclock current value */
- __u32 flags;
- __u32 pad[9];
-};
-
-
-4.30 KVM_SET_CLOCK
-
-Capability: KVM_CAP_ADJUST_CLOCK
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_clock_data (in)
-Returns: 0 on success, -1 on error
-
-Sets the current timestamp of kvmclock to the value specified in its parameter.
-In conjunction with KVM_GET_CLOCK, it is used to ensure monotonicity on scenarios
-such as migration.
-
-struct kvm_clock_data {
- __u64 clock; /* kvmclock current value */
- __u32 flags;
- __u32 pad[9];
-};
-
-
-4.31 KVM_GET_VCPU_EVENTS
-
-Capability: KVM_CAP_VCPU_EVENTS
-Extended by: KVM_CAP_INTR_SHADOW
-Architectures: x86, arm, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_vcpu_event (out)
-Returns: 0 on success, -1 on error
-
-X86:
-
-Gets currently pending exceptions, interrupts, and NMIs as well as related
-states of the vcpu.
-
-struct kvm_vcpu_events {
- struct {
- __u8 injected;
- __u8 nr;
- __u8 has_error_code;
- __u8 pending;
- __u32 error_code;
- } exception;
- struct {
- __u8 injected;
- __u8 nr;
- __u8 soft;
- __u8 shadow;
- } interrupt;
- struct {
- __u8 injected;
- __u8 pending;
- __u8 masked;
- __u8 pad;
- } nmi;
- __u32 sipi_vector;
- __u32 flags;
- struct {
- __u8 smm;
- __u8 pending;
- __u8 smm_inside_nmi;
- __u8 latched_init;
- } smi;
- __u8 reserved[27];
- __u8 exception_has_payload;
- __u64 exception_payload;
-};
-
-The following bits are defined in the flags field:
-
-- KVM_VCPUEVENT_VALID_SHADOW may be set to signal that
- interrupt.shadow contains a valid state.
-
-- KVM_VCPUEVENT_VALID_SMM may be set to signal that smi contains a
- valid state.
-
-- KVM_VCPUEVENT_VALID_PAYLOAD may be set to signal that the
- exception_has_payload, exception_payload, and exception.pending
- fields contain a valid state. This bit will be set whenever
- KVM_CAP_EXCEPTION_PAYLOAD is enabled.
-
-ARM/ARM64:
-
-If the guest accesses a device that is being emulated by the host kernel in
-such a way that a real device would generate a physical SError, KVM may make
-a virtual SError pending for that VCPU. This system error interrupt remains
-pending until the guest takes the exception by unmasking PSTATE.A.
-
-Running the VCPU may cause it to take a pending SError, or make an access that
-causes an SError to become pending. The event's description is only valid while
-the VPCU is not running.
-
-This API provides a way to read and write the pending 'event' state that is not
-visible to the guest. To save, restore or migrate a VCPU the struct representing
-the state can be read then written using this GET/SET API, along with the other
-guest-visible registers. It is not possible to 'cancel' an SError that has been
-made pending.
-
-A device being emulated in user-space may also wish to generate an SError. To do
-this the events structure can be populated by user-space. The current state
-should be read first, to ensure no existing SError is pending. If an existing
-SError is pending, the architecture's 'Multiple SError interrupts' rules should
-be followed. (2.5.3 of DDI0587.a "ARM Reliability, Availability, and
-Serviceability (RAS) Specification").
-
-SError exceptions always have an ESR value. Some CPUs have the ability to
-specify what the virtual SError's ESR value should be. These systems will
-advertise KVM_CAP_ARM_INJECT_SERROR_ESR. In this case exception.has_esr will
-always have a non-zero value when read, and the agent making an SError pending
-should specify the ISS field in the lower 24 bits of exception.serror_esr. If
-the system supports KVM_CAP_ARM_INJECT_SERROR_ESR, but user-space sets the events
-with exception.has_esr as zero, KVM will choose an ESR.
-
-Specifying exception.has_esr on a system that does not support it will return
--EINVAL. Setting anything other than the lower 24bits of exception.serror_esr
-will return -EINVAL.
-
-struct kvm_vcpu_events {
- struct {
- __u8 serror_pending;
- __u8 serror_has_esr;
- /* Align it to 8 bytes */
- __u8 pad[6];
- __u64 serror_esr;
- } exception;
- __u32 reserved[12];
-};
-
-4.32 KVM_SET_VCPU_EVENTS
-
-Capability: KVM_CAP_VCPU_EVENTS
-Extended by: KVM_CAP_INTR_SHADOW
-Architectures: x86, arm, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_vcpu_event (in)
-Returns: 0 on success, -1 on error
-
-X86:
-
-Set pending exceptions, interrupts, and NMIs as well as related states of the
-vcpu.
-
-See KVM_GET_VCPU_EVENTS for the data structure.
-
-Fields that may be modified asynchronously by running VCPUs can be excluded
-from the update. These fields are nmi.pending, sipi_vector, smi.smm,
-smi.pending. Keep the corresponding bits in the flags field cleared to
-suppress overwriting the current in-kernel state. The bits are:
-
-KVM_VCPUEVENT_VALID_NMI_PENDING - transfer nmi.pending to the kernel
-KVM_VCPUEVENT_VALID_SIPI_VECTOR - transfer sipi_vector
-KVM_VCPUEVENT_VALID_SMM - transfer the smi sub-struct.
-
-If KVM_CAP_INTR_SHADOW is available, KVM_VCPUEVENT_VALID_SHADOW can be set in
-the flags field to signal that interrupt.shadow contains a valid state and
-shall be written into the VCPU.
-
-KVM_VCPUEVENT_VALID_SMM can only be set if KVM_CAP_X86_SMM is available.
-
-If KVM_CAP_EXCEPTION_PAYLOAD is enabled, KVM_VCPUEVENT_VALID_PAYLOAD
-can be set in the flags field to signal that the
-exception_has_payload, exception_payload, and exception.pending fields
-contain a valid state and shall be written into the VCPU.
-
-ARM/ARM64:
-
-Set the pending SError exception state for this VCPU. It is not possible to
-'cancel' an Serror that has been made pending.
-
-See KVM_GET_VCPU_EVENTS for the data structure.
-
-
-4.33 KVM_GET_DEBUGREGS
-
-Capability: KVM_CAP_DEBUGREGS
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_debugregs (out)
-Returns: 0 on success, -1 on error
-
-Reads debug registers from the vcpu.
-
-struct kvm_debugregs {
- __u64 db[4];
- __u64 dr6;
- __u64 dr7;
- __u64 flags;
- __u64 reserved[9];
-};
-
-
-4.34 KVM_SET_DEBUGREGS
-
-Capability: KVM_CAP_DEBUGREGS
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_debugregs (in)
-Returns: 0 on success, -1 on error
-
-Writes debug registers into the vcpu.
-
-See KVM_GET_DEBUGREGS for the data structure. The flags field is unused
-yet and must be cleared on entry.
-
-
-4.35 KVM_SET_USER_MEMORY_REGION
-
-Capability: KVM_CAP_USER_MEMORY
-Architectures: all
-Type: vm ioctl
-Parameters: struct kvm_userspace_memory_region (in)
-Returns: 0 on success, -1 on error
-
-struct kvm_userspace_memory_region {
- __u32 slot;
- __u32 flags;
- __u64 guest_phys_addr;
- __u64 memory_size; /* bytes */
- __u64 userspace_addr; /* start of the userspace allocated memory */
-};
-
-/* for kvm_memory_region::flags */
-#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
-#define KVM_MEM_READONLY (1UL << 1)
-
-This ioctl allows the user to create, modify or delete a guest physical
-memory slot. Bits 0-15 of "slot" specify the slot id and this value
-should be less than the maximum number of user memory slots supported per
-VM. The maximum allowed slots can be queried using KVM_CAP_NR_MEMSLOTS.
-Slots may not overlap in guest physical address space.
-
-If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 of "slot"
-specifies the address space which is being modified. They must be
-less than the value that KVM_CHECK_EXTENSION returns for the
-KVM_CAP_MULTI_ADDRESS_SPACE capability. Slots in separate address spaces
-are unrelated; the restriction on overlapping slots only applies within
-each address space.
-
-Deleting a slot is done by passing zero for memory_size. When changing
-an existing slot, it may be moved in the guest physical memory space,
-or its flags may be modified, but it may not be resized.
-
-Memory for the region is taken starting at the address denoted by the
-field userspace_addr, which must point at user addressable memory for
-the entire memory slot size. Any object may back this memory, including
-anonymous memory, ordinary files, and hugetlbfs.
-
-It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr
-be identical. This allows large pages in the guest to be backed by large
-pages in the host.
-
-The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and
-KVM_MEM_READONLY. The former can be set to instruct KVM to keep track of
-writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to
-use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it,
-to make a new slot read-only. In this case, writes to this memory will be
-posted to userspace as KVM_EXIT_MMIO exits.
-
-When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of
-the memory region are automatically reflected into the guest. For example, an
-mmap() that affects the region will be made visible immediately. Another
-example is madvise(MADV_DROP).
-
-It is recommended to use this API instead of the KVM_SET_MEMORY_REGION ioctl.
-The KVM_SET_MEMORY_REGION does not allow fine grained control over memory
-allocation and is deprecated.
-
-
-4.36 KVM_SET_TSS_ADDR
-
-Capability: KVM_CAP_SET_TSS_ADDR
-Architectures: x86
-Type: vm ioctl
-Parameters: unsigned long tss_address (in)
-Returns: 0 on success, -1 on error
-
-This ioctl defines the physical address of a three-page region in the guest
-physical address space. The region must be within the first 4GB of the
-guest physical address space and must not conflict with any memory slot
-or any mmio address. The guest may malfunction if it accesses this memory
-region.
-
-This ioctl is required on Intel-based hosts. This is needed on Intel hardware
-because of a quirk in the virtualization implementation (see the internals
-documentation when it pops into existence).
-
-
-4.37 KVM_ENABLE_CAP
-
-Capability: KVM_CAP_ENABLE_CAP
-Architectures: mips, ppc, s390
-Type: vcpu ioctl
-Parameters: struct kvm_enable_cap (in)
-Returns: 0 on success; -1 on error
-
-Capability: KVM_CAP_ENABLE_CAP_VM
-Architectures: all
-Type: vcpu ioctl
-Parameters: struct kvm_enable_cap (in)
-Returns: 0 on success; -1 on error
-
-+Not all extensions are enabled by default. Using this ioctl the application
-can enable an extension, making it available to the guest.
-
-On systems that do not support this ioctl, it always fails. On systems that
-do support it, it only works for extensions that are supported for enablement.
-
-To check if a capability can be enabled, the KVM_CHECK_EXTENSION ioctl should
-be used.
-
-struct kvm_enable_cap {
- /* in */
- __u32 cap;
-
-The capability that is supposed to get enabled.
-
- __u32 flags;
-
-A bitfield indicating future enhancements. Has to be 0 for now.
-
- __u64 args[4];
-
-Arguments for enabling a feature. If a feature needs initial values to
-function properly, this is the place to put them.
-
- __u8 pad[64];
-};
-
-The vcpu ioctl should be used for vcpu-specific capabilities, the vm ioctl
-for vm-wide capabilities.
-
-4.38 KVM_GET_MP_STATE
-
-Capability: KVM_CAP_MP_STATE
-Architectures: x86, s390, arm, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_mp_state (out)
-Returns: 0 on success; -1 on error
-
-struct kvm_mp_state {
- __u32 mp_state;
-};
-
-Returns the vcpu's current "multiprocessing state" (though also valid on
-uniprocessor guests).
-
-Possible values are:
-
- - KVM_MP_STATE_RUNNABLE: the vcpu is currently running [x86,arm/arm64]
- - KVM_MP_STATE_UNINITIALIZED: the vcpu is an application processor (AP)
- which has not yet received an INIT signal [x86]
- - KVM_MP_STATE_INIT_RECEIVED: the vcpu has received an INIT signal, and is
- now ready for a SIPI [x86]
- - KVM_MP_STATE_HALTED: the vcpu has executed a HLT instruction and
- is waiting for an interrupt [x86]
- - KVM_MP_STATE_SIPI_RECEIVED: the vcpu has just received a SIPI (vector
- accessible via KVM_GET_VCPU_EVENTS) [x86]
- - KVM_MP_STATE_STOPPED: the vcpu is stopped [s390,arm/arm64]
- - KVM_MP_STATE_CHECK_STOP: the vcpu is in a special error state [s390]
- - KVM_MP_STATE_OPERATING: the vcpu is operating (running or halted)
- [s390]
- - KVM_MP_STATE_LOAD: the vcpu is in a special load/startup state
- [s390]
-
-On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an
-in-kernel irqchip, the multiprocessing state must be maintained by userspace on
-these architectures.
-
-For arm/arm64:
-
-The only states that are valid are KVM_MP_STATE_STOPPED and
-KVM_MP_STATE_RUNNABLE which reflect if the vcpu is paused or not.
-
-4.39 KVM_SET_MP_STATE
-
-Capability: KVM_CAP_MP_STATE
-Architectures: x86, s390, arm, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_mp_state (in)
-Returns: 0 on success; -1 on error
-
-Sets the vcpu's current "multiprocessing state"; see KVM_GET_MP_STATE for
-arguments.
-
-On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an
-in-kernel irqchip, the multiprocessing state must be maintained by userspace on
-these architectures.
-
-For arm/arm64:
-
-The only states that are valid are KVM_MP_STATE_STOPPED and
-KVM_MP_STATE_RUNNABLE which reflect if the vcpu should be paused or not.
-
-4.40 KVM_SET_IDENTITY_MAP_ADDR
-
-Capability: KVM_CAP_SET_IDENTITY_MAP_ADDR
-Architectures: x86
-Type: vm ioctl
-Parameters: unsigned long identity (in)
-Returns: 0 on success, -1 on error
-
-This ioctl defines the physical address of a one-page region in the guest
-physical address space. The region must be within the first 4GB of the
-guest physical address space and must not conflict with any memory slot
-or any mmio address. The guest may malfunction if it accesses this memory
-region.
-
-Setting the address to 0 will result in resetting the address to its default
-(0xfffbc000).
-
-This ioctl is required on Intel-based hosts. This is needed on Intel hardware
-because of a quirk in the virtualization implementation (see the internals
-documentation when it pops into existence).
-
-Fails if any VCPU has already been created.
-
-4.41 KVM_SET_BOOT_CPU_ID
-
-Capability: KVM_CAP_SET_BOOT_CPU_ID
-Architectures: x86
-Type: vm ioctl
-Parameters: unsigned long vcpu_id
-Returns: 0 on success, -1 on error
-
-Define which vcpu is the Bootstrap Processor (BSP). Values are the same
-as the vcpu id in KVM_CREATE_VCPU. If this ioctl is not called, the default
-is vcpu 0.
-
-
-4.42 KVM_GET_XSAVE
-
-Capability: KVM_CAP_XSAVE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_xsave (out)
-Returns: 0 on success, -1 on error
-
-struct kvm_xsave {
- __u32 region[1024];
-};
-
-This ioctl would copy current vcpu's xsave struct to the userspace.
-
-
-4.43 KVM_SET_XSAVE
-
-Capability: KVM_CAP_XSAVE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_xsave (in)
-Returns: 0 on success, -1 on error
-
-struct kvm_xsave {
- __u32 region[1024];
-};
-
-This ioctl would copy userspace's xsave struct to the kernel.
-
-
-4.44 KVM_GET_XCRS
-
-Capability: KVM_CAP_XCRS
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_xcrs (out)
-Returns: 0 on success, -1 on error
-
-struct kvm_xcr {
- __u32 xcr;
- __u32 reserved;
- __u64 value;
-};
-
-struct kvm_xcrs {
- __u32 nr_xcrs;
- __u32 flags;
- struct kvm_xcr xcrs[KVM_MAX_XCRS];
- __u64 padding[16];
-};
-
-This ioctl would copy current vcpu's xcrs to the userspace.
-
-
-4.45 KVM_SET_XCRS
-
-Capability: KVM_CAP_XCRS
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_xcrs (in)
-Returns: 0 on success, -1 on error
-
-struct kvm_xcr {
- __u32 xcr;
- __u32 reserved;
- __u64 value;
-};
-
-struct kvm_xcrs {
- __u32 nr_xcrs;
- __u32 flags;
- struct kvm_xcr xcrs[KVM_MAX_XCRS];
- __u64 padding[16];
-};
-
-This ioctl would set vcpu's xcr to the value userspace specified.
-
-
-4.46 KVM_GET_SUPPORTED_CPUID
-
-Capability: KVM_CAP_EXT_CPUID
-Architectures: x86
-Type: system ioctl
-Parameters: struct kvm_cpuid2 (in/out)
-Returns: 0 on success, -1 on error
-
-struct kvm_cpuid2 {
- __u32 nent;
- __u32 padding;
- struct kvm_cpuid_entry2 entries[0];
-};
-
-#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0)
-#define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1)
-#define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2)
-
-struct kvm_cpuid_entry2 {
- __u32 function;
- __u32 index;
- __u32 flags;
- __u32 eax;
- __u32 ebx;
- __u32 ecx;
- __u32 edx;
- __u32 padding[3];
-};
-
-This ioctl returns x86 cpuid features which are supported by both the
-hardware and kvm in its default configuration. Userspace can use the
-information returned by this ioctl to construct cpuid information (for
-KVM_SET_CPUID2) that is consistent with hardware, kernel, and
-userspace capabilities, and with user requirements (for example, the
-user may wish to constrain cpuid to emulate older hardware, or for
-feature consistency across a cluster).
-
-Note that certain capabilities, such as KVM_CAP_X86_DISABLE_EXITS, may
-expose cpuid features (e.g. MONITOR) which are not supported by kvm in
-its default configuration. If userspace enables such capabilities, it
-is responsible for modifying the results of this ioctl appropriately.
-
-Userspace invokes KVM_GET_SUPPORTED_CPUID by passing a kvm_cpuid2 structure
-with the 'nent' field indicating the number of entries in the variable-size
-array 'entries'. If the number of entries is too low to describe the cpu
-capabilities, an error (E2BIG) is returned. If the number is too high,
-the 'nent' field is adjusted and an error (ENOMEM) is returned. If the
-number is just right, the 'nent' field is adjusted to the number of valid
-entries in the 'entries' array, which is then filled.
-
-The entries returned are the host cpuid as returned by the cpuid instruction,
-with unknown or unsupported features masked out. Some features (for example,
-x2apic), may not be present in the host cpu, but are exposed by kvm if it can
-emulate them efficiently. The fields in each entry are defined as follows:
-
- function: the eax value used to obtain the entry
- index: the ecx value used to obtain the entry (for entries that are
- affected by ecx)
- flags: an OR of zero or more of the following:
- KVM_CPUID_FLAG_SIGNIFCANT_INDEX:
- if the index field is valid
- KVM_CPUID_FLAG_STATEFUL_FUNC:
- if cpuid for this function returns different values for successive
- invocations; there will be several entries with the same function,
- all with this flag set
- KVM_CPUID_FLAG_STATE_READ_NEXT:
- for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is
- the first entry to be read by a cpu
- eax, ebx, ecx, edx: the values returned by the cpuid instruction for
- this function/index combination
-
-The TSC deadline timer feature (CPUID leaf 1, ecx[24]) is always returned
-as false, since the feature depends on KVM_CREATE_IRQCHIP for local APIC
-support. Instead it is reported via
-
- ioctl(KVM_CHECK_EXTENSION, KVM_CAP_TSC_DEADLINE_TIMER)
-
-if that returns true and you use KVM_CREATE_IRQCHIP, or if you emulate the
-feature in userspace, then you can enable the feature for KVM_SET_CPUID2.
-
-
-4.47 KVM_PPC_GET_PVINFO
-
-Capability: KVM_CAP_PPC_GET_PVINFO
-Architectures: ppc
-Type: vm ioctl
-Parameters: struct kvm_ppc_pvinfo (out)
-Returns: 0 on success, !0 on error
-
-struct kvm_ppc_pvinfo {
- __u32 flags;
- __u32 hcall[4];
- __u8 pad[108];
-};
-
-This ioctl fetches PV specific information that need to be passed to the guest
-using the device tree or other means from vm context.
-
-The hcall array defines 4 instructions that make up a hypercall.
-
-If any additional field gets added to this structure later on, a bit for that
-additional piece of information will be set in the flags bitmap.
-
-The flags bitmap is defined as:
-
- /* the host supports the ePAPR idle hcall
- #define KVM_PPC_PVINFO_FLAGS_EV_IDLE (1<<0)
-
-4.52 KVM_SET_GSI_ROUTING
-
-Capability: KVM_CAP_IRQ_ROUTING
-Architectures: x86 s390 arm arm64
-Type: vm ioctl
-Parameters: struct kvm_irq_routing (in)
-Returns: 0 on success, -1 on error
-
-Sets the GSI routing table entries, overwriting any previously set entries.
-
-On arm/arm64, GSI routing has the following limitation:
-- GSI routing does not apply to KVM_IRQ_LINE but only to KVM_IRQFD.
-
-struct kvm_irq_routing {
- __u32 nr;
- __u32 flags;
- struct kvm_irq_routing_entry entries[0];
-};
-
-No flags are specified so far, the corresponding field must be set to zero.
-
-struct kvm_irq_routing_entry {
- __u32 gsi;
- __u32 type;
- __u32 flags;
- __u32 pad;
- union {
- struct kvm_irq_routing_irqchip irqchip;
- struct kvm_irq_routing_msi msi;
- struct kvm_irq_routing_s390_adapter adapter;
- struct kvm_irq_routing_hv_sint hv_sint;
- __u32 pad[8];
- } u;
-};
-
-/* gsi routing entry types */
-#define KVM_IRQ_ROUTING_IRQCHIP 1
-#define KVM_IRQ_ROUTING_MSI 2
-#define KVM_IRQ_ROUTING_S390_ADAPTER 3
-#define KVM_IRQ_ROUTING_HV_SINT 4
-
-flags:
-- KVM_MSI_VALID_DEVID: used along with KVM_IRQ_ROUTING_MSI routing entry
- type, specifies that the devid field contains a valid value. The per-VM
- KVM_CAP_MSI_DEVID capability advertises the requirement to provide
- the device ID. If this capability is not available, userspace should
- never set the KVM_MSI_VALID_DEVID flag as the ioctl might fail.
-- zero otherwise
-
-struct kvm_irq_routing_irqchip {
- __u32 irqchip;
- __u32 pin;
-};
-
-struct kvm_irq_routing_msi {
- __u32 address_lo;
- __u32 address_hi;
- __u32 data;
- union {
- __u32 pad;
- __u32 devid;
- };
-};
-
-If KVM_MSI_VALID_DEVID is set, devid contains a unique device identifier
-for the device that wrote the MSI message. For PCI, this is usually a
-BFD identifier in the lower 16 bits.
-
-On x86, address_hi is ignored unless the KVM_X2APIC_API_USE_32BIT_IDS
-feature of KVM_CAP_X2APIC_API capability is enabled. If it is enabled,
-address_hi bits 31-8 provide bits 31-8 of the destination id. Bits 7-0 of
-address_hi must be zero.
-
-struct kvm_irq_routing_s390_adapter {
- __u64 ind_addr;
- __u64 summary_addr;
- __u64 ind_offset;
- __u32 summary_offset;
- __u32 adapter_id;
-};
-
-struct kvm_irq_routing_hv_sint {
- __u32 vcpu;
- __u32 sint;
-};
-
-
-4.55 KVM_SET_TSC_KHZ
-
-Capability: KVM_CAP_TSC_CONTROL
-Architectures: x86
-Type: vcpu ioctl
-Parameters: virtual tsc_khz
-Returns: 0 on success, -1 on error
-
-Specifies the tsc frequency for the virtual machine. The unit of the
-frequency is KHz.
-
-
-4.56 KVM_GET_TSC_KHZ
-
-Capability: KVM_CAP_GET_TSC_KHZ
-Architectures: x86
-Type: vcpu ioctl
-Parameters: none
-Returns: virtual tsc-khz on success, negative value on error
-
-Returns the tsc frequency of the guest. The unit of the return value is
-KHz. If the host has unstable tsc this ioctl returns -EIO instead as an
-error.
-
-
-4.57 KVM_GET_LAPIC
-
-Capability: KVM_CAP_IRQCHIP
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_lapic_state (out)
-Returns: 0 on success, -1 on error
-
-#define KVM_APIC_REG_SIZE 0x400
-struct kvm_lapic_state {
- char regs[KVM_APIC_REG_SIZE];
-};
-
-Reads the Local APIC registers and copies them into the input argument. The
-data format and layout are the same as documented in the architecture manual.
-
-If KVM_X2APIC_API_USE_32BIT_IDS feature of KVM_CAP_X2APIC_API is
-enabled, then the format of APIC_ID register depends on the APIC mode
-(reported by MSR_IA32_APICBASE) of its VCPU. x2APIC stores APIC ID in
-the APIC_ID register (bytes 32-35). xAPIC only allows an 8-bit APIC ID
-which is stored in bits 31-24 of the APIC register, or equivalently in
-byte 35 of struct kvm_lapic_state's regs field. KVM_GET_LAPIC must then
-be called after MSR_IA32_APICBASE has been set with KVM_SET_MSR.
-
-If KVM_X2APIC_API_USE_32BIT_IDS feature is disabled, struct kvm_lapic_state
-always uses xAPIC format.
-
-
-4.58 KVM_SET_LAPIC
-
-Capability: KVM_CAP_IRQCHIP
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_lapic_state (in)
-Returns: 0 on success, -1 on error
-
-#define KVM_APIC_REG_SIZE 0x400
-struct kvm_lapic_state {
- char regs[KVM_APIC_REG_SIZE];
-};
-
-Copies the input argument into the Local APIC registers. The data format
-and layout are the same as documented in the architecture manual.
-
-The format of the APIC ID register (bytes 32-35 of struct kvm_lapic_state's
-regs field) depends on the state of the KVM_CAP_X2APIC_API capability.
-See the note in KVM_GET_LAPIC.
-
-
-4.59 KVM_IOEVENTFD
-
-Capability: KVM_CAP_IOEVENTFD
-Architectures: all
-Type: vm ioctl
-Parameters: struct kvm_ioeventfd (in)
-Returns: 0 on success, !0 on error
-
-This ioctl attaches or detaches an ioeventfd to a legal pio/mmio address
-within the guest. A guest write in the registered address will signal the
-provided event instead of triggering an exit.
-
-struct kvm_ioeventfd {
- __u64 datamatch;
- __u64 addr; /* legal pio/mmio address */
- __u32 len; /* 0, 1, 2, 4, or 8 bytes */
- __s32 fd;
- __u32 flags;
- __u8 pad[36];
-};
-
-For the special case of virtio-ccw devices on s390, the ioevent is matched
-to a subchannel/virtqueue tuple instead.
-
-The following flags are defined:
-
-#define KVM_IOEVENTFD_FLAG_DATAMATCH (1 << kvm_ioeventfd_flag_nr_datamatch)
-#define KVM_IOEVENTFD_FLAG_PIO (1 << kvm_ioeventfd_flag_nr_pio)
-#define KVM_IOEVENTFD_FLAG_DEASSIGN (1 << kvm_ioeventfd_flag_nr_deassign)
-#define KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY \
- (1 << kvm_ioeventfd_flag_nr_virtio_ccw_notify)
-
-If datamatch flag is set, the event will be signaled only if the written value
-to the registered address is equal to datamatch in struct kvm_ioeventfd.
-
-For virtio-ccw devices, addr contains the subchannel id and datamatch the
-virtqueue index.
-
-With KVM_CAP_IOEVENTFD_ANY_LENGTH, a zero length ioeventfd is allowed, and
-the kernel will ignore the length of guest write and may get a faster vmexit.
-The speedup may only apply to specific architectures, but the ioeventfd will
-work anyway.
-
-4.60 KVM_DIRTY_TLB
-
-Capability: KVM_CAP_SW_TLB
-Architectures: ppc
-Type: vcpu ioctl
-Parameters: struct kvm_dirty_tlb (in)
-Returns: 0 on success, -1 on error
-
-struct kvm_dirty_tlb {
- __u64 bitmap;
- __u32 num_dirty;
-};
-
-This must be called whenever userspace has changed an entry in the shared
-TLB, prior to calling KVM_RUN on the associated vcpu.
-
-The "bitmap" field is the userspace address of an array. This array
-consists of a number of bits, equal to the total number of TLB entries as
-determined by the last successful call to KVM_CONFIG_TLB, rounded up to the
-nearest multiple of 64.
-
-Each bit corresponds to one TLB entry, ordered the same as in the shared TLB
-array.
-
-The array is little-endian: the bit 0 is the least significant bit of the
-first byte, bit 8 is the least significant bit of the second byte, etc.
-This avoids any complications with differing word sizes.
-
-The "num_dirty" field is a performance hint for KVM to determine whether it
-should skip processing the bitmap and just invalidate everything. It must
-be set to the number of set bits in the bitmap.
-
-
-4.62 KVM_CREATE_SPAPR_TCE
-
-Capability: KVM_CAP_SPAPR_TCE
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_create_spapr_tce (in)
-Returns: file descriptor for manipulating the created TCE table
-
-This creates a virtual TCE (translation control entry) table, which
-is an IOMMU for PAPR-style virtual I/O. It is used to translate
-logical addresses used in virtual I/O into guest physical addresses,
-and provides a scatter/gather capability for PAPR virtual I/O.
-
-/* for KVM_CAP_SPAPR_TCE */
-struct kvm_create_spapr_tce {
- __u64 liobn;
- __u32 window_size;
-};
-
-The liobn field gives the logical IO bus number for which to create a
-TCE table. The window_size field specifies the size of the DMA window
-which this TCE table will translate - the table will contain one 64
-bit TCE entry for every 4kiB of the DMA window.
-
-When the guest issues an H_PUT_TCE hcall on a liobn for which a TCE
-table has been created using this ioctl(), the kernel will handle it
-in real mode, updating the TCE table. H_PUT_TCE calls for other
-liobns will cause a vm exit and must be handled by userspace.
-
-The return value is a file descriptor which can be passed to mmap(2)
-to map the created TCE table into userspace. This lets userspace read
-the entries written by kernel-handled H_PUT_TCE calls, and also lets
-userspace update the TCE table directly which is useful in some
-circumstances.
-
-
-4.63 KVM_ALLOCATE_RMA
-
-Capability: KVM_CAP_PPC_RMA
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_allocate_rma (out)
-Returns: file descriptor for mapping the allocated RMA
-
-This allocates a Real Mode Area (RMA) from the pool allocated at boot
-time by the kernel. An RMA is a physically-contiguous, aligned region
-of memory used on older POWER processors to provide the memory which
-will be accessed by real-mode (MMU off) accesses in a KVM guest.
-POWER processors support a set of sizes for the RMA that usually
-includes 64MB, 128MB, 256MB and some larger powers of two.
-
-/* for KVM_ALLOCATE_RMA */
-struct kvm_allocate_rma {
- __u64 rma_size;
-};
-
-The return value is a file descriptor which can be passed to mmap(2)
-to map the allocated RMA into userspace. The mapped area can then be
-passed to the KVM_SET_USER_MEMORY_REGION ioctl to establish it as the
-RMA for a virtual machine. The size of the RMA in bytes (which is
-fixed at host kernel boot time) is returned in the rma_size field of
-the argument structure.
-
-The KVM_CAP_PPC_RMA capability is 1 or 2 if the KVM_ALLOCATE_RMA ioctl
-is supported; 2 if the processor requires all virtual machines to have
-an RMA, or 1 if the processor can use an RMA but doesn't require it,
-because it supports the Virtual RMA (VRMA) facility.
-
-
-4.64 KVM_NMI
-
-Capability: KVM_CAP_USER_NMI
-Architectures: x86
-Type: vcpu ioctl
-Parameters: none
-Returns: 0 on success, -1 on error
-
-Queues an NMI on the thread's vcpu. Note this is well defined only
-when KVM_CREATE_IRQCHIP has not been called, since this is an interface
-between the virtual cpu core and virtual local APIC. After KVM_CREATE_IRQCHIP
-has been called, this interface is completely emulated within the kernel.
-
-To use this to emulate the LINT1 input with KVM_CREATE_IRQCHIP, use the
-following algorithm:
-
- - pause the vcpu
- - read the local APIC's state (KVM_GET_LAPIC)
- - check whether changing LINT1 will queue an NMI (see the LVT entry for LINT1)
- - if so, issue KVM_NMI
- - resume the vcpu
-
-Some guests configure the LINT1 NMI input to cause a panic, aiding in
-debugging.
-
-
-4.65 KVM_S390_UCAS_MAP
-
-Capability: KVM_CAP_S390_UCONTROL
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_ucas_mapping (in)
-Returns: 0 in case of success
-
-The parameter is defined like this:
- struct kvm_s390_ucas_mapping {
- __u64 user_addr;
- __u64 vcpu_addr;
- __u64 length;
- };
-
-This ioctl maps the memory at "user_addr" with the length "length" to
-the vcpu's address space starting at "vcpu_addr". All parameters need to
-be aligned by 1 megabyte.
-
-
-4.66 KVM_S390_UCAS_UNMAP
-
-Capability: KVM_CAP_S390_UCONTROL
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_ucas_mapping (in)
-Returns: 0 in case of success
-
-The parameter is defined like this:
- struct kvm_s390_ucas_mapping {
- __u64 user_addr;
- __u64 vcpu_addr;
- __u64 length;
- };
-
-This ioctl unmaps the memory in the vcpu's address space starting at
-"vcpu_addr" with the length "length". The field "user_addr" is ignored.
-All parameters need to be aligned by 1 megabyte.
-
-
-4.67 KVM_S390_VCPU_FAULT
-
-Capability: KVM_CAP_S390_UCONTROL
-Architectures: s390
-Type: vcpu ioctl
-Parameters: vcpu absolute address (in)
-Returns: 0 in case of success
-
-This call creates a page table entry on the virtual cpu's address space
-(for user controlled virtual machines) or the virtual machine's address
-space (for regular virtual machines). This only works for minor faults,
-thus it's recommended to access subject memory page via the user page
-table upfront. This is useful to handle validity intercepts for user
-controlled virtual machines to fault in the virtual cpu's lowcore pages
-prior to calling the KVM_RUN ioctl.
-
-
-4.68 KVM_SET_ONE_REG
-
-Capability: KVM_CAP_ONE_REG
-Architectures: all
-Type: vcpu ioctl
-Parameters: struct kvm_one_reg (in)
-Returns: 0 on success, negative value on failure
-Errors:
- ENOENT: no such register
- EINVAL: invalid register ID, or no such register
- EPERM: (arm64) register access not allowed before vcpu finalization
-(These error codes are indicative only: do not rely on a specific error
-code being returned in a specific situation.)
-
-struct kvm_one_reg {
- __u64 id;
- __u64 addr;
-};
-
-Using this ioctl, a single vcpu register can be set to a specific value
-defined by user space with the passed in struct kvm_one_reg, where id
-refers to the register identifier as described below and addr is a pointer
-to a variable with the respective size. There can be architecture agnostic
-and architecture specific registers. Each have their own range of operation
-and their own constants and width. To keep track of the implemented
-registers, find a list below:
-
- Arch | Register | Width (bits)
- | |
- PPC | KVM_REG_PPC_HIOR | 64
- PPC | KVM_REG_PPC_IAC1 | 64
- PPC | KVM_REG_PPC_IAC2 | 64
- PPC | KVM_REG_PPC_IAC3 | 64
- PPC | KVM_REG_PPC_IAC4 | 64
- PPC | KVM_REG_PPC_DAC1 | 64
- PPC | KVM_REG_PPC_DAC2 | 64
- PPC | KVM_REG_PPC_DABR | 64
- PPC | KVM_REG_PPC_DSCR | 64
- PPC | KVM_REG_PPC_PURR | 64
- PPC | KVM_REG_PPC_SPURR | 64
- PPC | KVM_REG_PPC_DAR | 64
- PPC | KVM_REG_PPC_DSISR | 32
- PPC | KVM_REG_PPC_AMR | 64
- PPC | KVM_REG_PPC_UAMOR | 64
- PPC | KVM_REG_PPC_MMCR0 | 64
- PPC | KVM_REG_PPC_MMCR1 | 64
- PPC | KVM_REG_PPC_MMCRA | 64
- PPC | KVM_REG_PPC_MMCR2 | 64
- PPC | KVM_REG_PPC_MMCRS | 64
- PPC | KVM_REG_PPC_SIAR | 64
- PPC | KVM_REG_PPC_SDAR | 64
- PPC | KVM_REG_PPC_SIER | 64
- PPC | KVM_REG_PPC_PMC1 | 32
- PPC | KVM_REG_PPC_PMC2 | 32
- PPC | KVM_REG_PPC_PMC3 | 32
- PPC | KVM_REG_PPC_PMC4 | 32
- PPC | KVM_REG_PPC_PMC5 | 32
- PPC | KVM_REG_PPC_PMC6 | 32
- PPC | KVM_REG_PPC_PMC7 | 32
- PPC | KVM_REG_PPC_PMC8 | 32
- PPC | KVM_REG_PPC_FPR0 | 64
- ...
- PPC | KVM_REG_PPC_FPR31 | 64
- PPC | KVM_REG_PPC_VR0 | 128
- ...
- PPC | KVM_REG_PPC_VR31 | 128
- PPC | KVM_REG_PPC_VSR0 | 128
- ...
- PPC | KVM_REG_PPC_VSR31 | 128
- PPC | KVM_REG_PPC_FPSCR | 64
- PPC | KVM_REG_PPC_VSCR | 32
- PPC | KVM_REG_PPC_VPA_ADDR | 64
- PPC | KVM_REG_PPC_VPA_SLB | 128
- PPC | KVM_REG_PPC_VPA_DTL | 128
- PPC | KVM_REG_PPC_EPCR | 32
- PPC | KVM_REG_PPC_EPR | 32
- PPC | KVM_REG_PPC_TCR | 32
- PPC | KVM_REG_PPC_TSR | 32
- PPC | KVM_REG_PPC_OR_TSR | 32
- PPC | KVM_REG_PPC_CLEAR_TSR | 32
- PPC | KVM_REG_PPC_MAS0 | 32
- PPC | KVM_REG_PPC_MAS1 | 32
- PPC | KVM_REG_PPC_MAS2 | 64
- PPC | KVM_REG_PPC_MAS7_3 | 64
- PPC | KVM_REG_PPC_MAS4 | 32
- PPC | KVM_REG_PPC_MAS6 | 32
- PPC | KVM_REG_PPC_MMUCFG | 32
- PPC | KVM_REG_PPC_TLB0CFG | 32
- PPC | KVM_REG_PPC_TLB1CFG | 32
- PPC | KVM_REG_PPC_TLB2CFG | 32
- PPC | KVM_REG_PPC_TLB3CFG | 32
- PPC | KVM_REG_PPC_TLB0PS | 32
- PPC | KVM_REG_PPC_TLB1PS | 32
- PPC | KVM_REG_PPC_TLB2PS | 32
- PPC | KVM_REG_PPC_TLB3PS | 32
- PPC | KVM_REG_PPC_EPTCFG | 32
- PPC | KVM_REG_PPC_ICP_STATE | 64
- PPC | KVM_REG_PPC_VP_STATE | 128
- PPC | KVM_REG_PPC_TB_OFFSET | 64
- PPC | KVM_REG_PPC_SPMC1 | 32
- PPC | KVM_REG_PPC_SPMC2 | 32
- PPC | KVM_REG_PPC_IAMR | 64
- PPC | KVM_REG_PPC_TFHAR | 64
- PPC | KVM_REG_PPC_TFIAR | 64
- PPC | KVM_REG_PPC_TEXASR | 64
- PPC | KVM_REG_PPC_FSCR | 64
- PPC | KVM_REG_PPC_PSPB | 32
- PPC | KVM_REG_PPC_EBBHR | 64
- PPC | KVM_REG_PPC_EBBRR | 64
- PPC | KVM_REG_PPC_BESCR | 64
- PPC | KVM_REG_PPC_TAR | 64
- PPC | KVM_REG_PPC_DPDES | 64
- PPC | KVM_REG_PPC_DAWR | 64
- PPC | KVM_REG_PPC_DAWRX | 64
- PPC | KVM_REG_PPC_CIABR | 64
- PPC | KVM_REG_PPC_IC | 64
- PPC | KVM_REG_PPC_VTB | 64
- PPC | KVM_REG_PPC_CSIGR | 64
- PPC | KVM_REG_PPC_TACR | 64
- PPC | KVM_REG_PPC_TCSCR | 64
- PPC | KVM_REG_PPC_PID | 64
- PPC | KVM_REG_PPC_ACOP | 64
- PPC | KVM_REG_PPC_VRSAVE | 32
- PPC | KVM_REG_PPC_LPCR | 32
- PPC | KVM_REG_PPC_LPCR_64 | 64
- PPC | KVM_REG_PPC_PPR | 64
- PPC | KVM_REG_PPC_ARCH_COMPAT | 32
- PPC | KVM_REG_PPC_DABRX | 32
- PPC | KVM_REG_PPC_WORT | 64
- PPC | KVM_REG_PPC_SPRG9 | 64
- PPC | KVM_REG_PPC_DBSR | 32
- PPC | KVM_REG_PPC_TIDR | 64
- PPC | KVM_REG_PPC_PSSCR | 64
- PPC | KVM_REG_PPC_DEC_EXPIRY | 64
- PPC | KVM_REG_PPC_PTCR | 64
- PPC | KVM_REG_PPC_TM_GPR0 | 64
- ...
- PPC | KVM_REG_PPC_TM_GPR31 | 64
- PPC | KVM_REG_PPC_TM_VSR0 | 128
- ...
- PPC | KVM_REG_PPC_TM_VSR63 | 128
- PPC | KVM_REG_PPC_TM_CR | 64
- PPC | KVM_REG_PPC_TM_LR | 64
- PPC | KVM_REG_PPC_TM_CTR | 64
- PPC | KVM_REG_PPC_TM_FPSCR | 64
- PPC | KVM_REG_PPC_TM_AMR | 64
- PPC | KVM_REG_PPC_TM_PPR | 64
- PPC | KVM_REG_PPC_TM_VRSAVE | 64
- PPC | KVM_REG_PPC_TM_VSCR | 32
- PPC | KVM_REG_PPC_TM_DSCR | 64
- PPC | KVM_REG_PPC_TM_TAR | 64
- PPC | KVM_REG_PPC_TM_XER | 64
- | |
- MIPS | KVM_REG_MIPS_R0 | 64
- ...
- MIPS | KVM_REG_MIPS_R31 | 64
- MIPS | KVM_REG_MIPS_HI | 64
- MIPS | KVM_REG_MIPS_LO | 64
- MIPS | KVM_REG_MIPS_PC | 64
- MIPS | KVM_REG_MIPS_CP0_INDEX | 32
- MIPS | KVM_REG_MIPS_CP0_ENTRYLO0 | 64
- MIPS | KVM_REG_MIPS_CP0_ENTRYLO1 | 64
- MIPS | KVM_REG_MIPS_CP0_CONTEXT | 64
- MIPS | KVM_REG_MIPS_CP0_CONTEXTCONFIG| 32
- MIPS | KVM_REG_MIPS_CP0_USERLOCAL | 64
- MIPS | KVM_REG_MIPS_CP0_XCONTEXTCONFIG| 64
- MIPS | KVM_REG_MIPS_CP0_PAGEMASK | 32
- MIPS | KVM_REG_MIPS_CP0_PAGEGRAIN | 32
- MIPS | KVM_REG_MIPS_CP0_SEGCTL0 | 64
- MIPS | KVM_REG_MIPS_CP0_SEGCTL1 | 64
- MIPS | KVM_REG_MIPS_CP0_SEGCTL2 | 64
- MIPS | KVM_REG_MIPS_CP0_PWBASE | 64
- MIPS | KVM_REG_MIPS_CP0_PWFIELD | 64
- MIPS | KVM_REG_MIPS_CP0_PWSIZE | 64
- MIPS | KVM_REG_MIPS_CP0_WIRED | 32
- MIPS | KVM_REG_MIPS_CP0_PWCTL | 32
- MIPS | KVM_REG_MIPS_CP0_HWRENA | 32
- MIPS | KVM_REG_MIPS_CP0_BADVADDR | 64
- MIPS | KVM_REG_MIPS_CP0_BADINSTR | 32
- MIPS | KVM_REG_MIPS_CP0_BADINSTRP | 32
- MIPS | KVM_REG_MIPS_CP0_COUNT | 32
- MIPS | KVM_REG_MIPS_CP0_ENTRYHI | 64
- MIPS | KVM_REG_MIPS_CP0_COMPARE | 32
- MIPS | KVM_REG_MIPS_CP0_STATUS | 32
- MIPS | KVM_REG_MIPS_CP0_INTCTL | 32
- MIPS | KVM_REG_MIPS_CP0_CAUSE | 32
- MIPS | KVM_REG_MIPS_CP0_EPC | 64
- MIPS | KVM_REG_MIPS_CP0_PRID | 32
- MIPS | KVM_REG_MIPS_CP0_EBASE | 64
- MIPS | KVM_REG_MIPS_CP0_CONFIG | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG1 | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG2 | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG3 | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG4 | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG5 | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG7 | 32
- MIPS | KVM_REG_MIPS_CP0_XCONTEXT | 64
- MIPS | KVM_REG_MIPS_CP0_ERROREPC | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH1 | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH2 | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH3 | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH4 | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH5 | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH6 | 64
- MIPS | KVM_REG_MIPS_CP0_MAAR(0..63) | 64
- MIPS | KVM_REG_MIPS_COUNT_CTL | 64
- MIPS | KVM_REG_MIPS_COUNT_RESUME | 64
- MIPS | KVM_REG_MIPS_COUNT_HZ | 64
- MIPS | KVM_REG_MIPS_FPR_32(0..31) | 32
- MIPS | KVM_REG_MIPS_FPR_64(0..31) | 64
- MIPS | KVM_REG_MIPS_VEC_128(0..31) | 128
- MIPS | KVM_REG_MIPS_FCR_IR | 32
- MIPS | KVM_REG_MIPS_FCR_CSR | 32
- MIPS | KVM_REG_MIPS_MSA_IR | 32
- MIPS | KVM_REG_MIPS_MSA_CSR | 32
-
-ARM registers are mapped using the lower 32 bits. The upper 16 of that
-is the register group type, or coprocessor number:
-
-ARM core registers have the following id bit patterns:
- 0x4020 0000 0010 <index into the kvm_regs struct:16>
-
-ARM 32-bit CP15 registers have the following id bit patterns:
- 0x4020 0000 000F <zero:1> <crn:4> <crm:4> <opc1:4> <opc2:3>
-
-ARM 64-bit CP15 registers have the following id bit patterns:
- 0x4030 0000 000F <zero:1> <zero:4> <crm:4> <opc1:4> <zero:3>
-
-ARM CCSIDR registers are demultiplexed by CSSELR value:
- 0x4020 0000 0011 00 <csselr:8>
-
-ARM 32-bit VFP control registers have the following id bit patterns:
- 0x4020 0000 0012 1 <regno:12>
-
-ARM 64-bit FP registers have the following id bit patterns:
- 0x4030 0000 0012 0 <regno:12>
-
-ARM firmware pseudo-registers have the following bit pattern:
- 0x4030 0000 0014 <regno:16>
-
-
-arm64 registers are mapped using the lower 32 bits. The upper 16 of
-that is the register group type, or coprocessor number:
-
-arm64 core/FP-SIMD registers have the following id bit patterns. Note
-that the size of the access is variable, as the kvm_regs structure
-contains elements ranging from 32 to 128 bits. The index is a 32bit
-value in the kvm_regs structure seen as a 32bit array.
- 0x60x0 0000 0010 <index into the kvm_regs struct:16>
-
-Specifically:
- Encoding Register Bits kvm_regs member
-----------------------------------------------------------------
- 0x6030 0000 0010 0000 X0 64 regs.regs[0]
- 0x6030 0000 0010 0002 X1 64 regs.regs[1]
- ...
- 0x6030 0000 0010 003c X30 64 regs.regs[30]
- 0x6030 0000 0010 003e SP 64 regs.sp
- 0x6030 0000 0010 0040 PC 64 regs.pc
- 0x6030 0000 0010 0042 PSTATE 64 regs.pstate
- 0x6030 0000 0010 0044 SP_EL1 64 sp_el1
- 0x6030 0000 0010 0046 ELR_EL1 64 elr_el1
- 0x6030 0000 0010 0048 SPSR_EL1 64 spsr[KVM_SPSR_EL1] (alias SPSR_SVC)
- 0x6030 0000 0010 004a SPSR_ABT 64 spsr[KVM_SPSR_ABT]
- 0x6030 0000 0010 004c SPSR_UND 64 spsr[KVM_SPSR_UND]
- 0x6030 0000 0010 004e SPSR_IRQ 64 spsr[KVM_SPSR_IRQ]
- 0x6060 0000 0010 0050 SPSR_FIQ 64 spsr[KVM_SPSR_FIQ]
- 0x6040 0000 0010 0054 V0 128 fp_regs.vregs[0] (*)
- 0x6040 0000 0010 0058 V1 128 fp_regs.vregs[1] (*)
- ...
- 0x6040 0000 0010 00d0 V31 128 fp_regs.vregs[31] (*)
- 0x6020 0000 0010 00d4 FPSR 32 fp_regs.fpsr
- 0x6020 0000 0010 00d5 FPCR 32 fp_regs.fpcr
-
-(*) These encodings are not accepted for SVE-enabled vcpus. See
- KVM_ARM_VCPU_INIT.
-
- The equivalent register content can be accessed via bits [127:0] of
- the corresponding SVE Zn registers instead for vcpus that have SVE
- enabled (see below).
-
-arm64 CCSIDR registers are demultiplexed by CSSELR value:
- 0x6020 0000 0011 00 <csselr:8>
-
-arm64 system registers have the following id bit patterns:
- 0x6030 0000 0013 <op0:2> <op1:3> <crn:4> <crm:4> <op2:3>
-
-arm64 firmware pseudo-registers have the following bit pattern:
- 0x6030 0000 0014 <regno:16>
-
-arm64 SVE registers have the following bit patterns:
- 0x6080 0000 0015 00 <n:5> <slice:5> Zn bits[2048*slice + 2047 : 2048*slice]
- 0x6050 0000 0015 04 <n:4> <slice:5> Pn bits[256*slice + 255 : 256*slice]
- 0x6050 0000 0015 060 <slice:5> FFR bits[256*slice + 255 : 256*slice]
- 0x6060 0000 0015 ffff KVM_REG_ARM64_SVE_VLS pseudo-register
-
-Access to register IDs where 2048 * slice >= 128 * max_vq will fail with
-ENOENT. max_vq is the vcpu's maximum supported vector length in 128-bit
-quadwords: see (**) below.
-
-These registers are only accessible on vcpus for which SVE is enabled.
-See KVM_ARM_VCPU_INIT for details.
-
-In addition, except for KVM_REG_ARM64_SVE_VLS, these registers are not
-accessible until the vcpu's SVE configuration has been finalized
-using KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE). See KVM_ARM_VCPU_INIT
-and KVM_ARM_VCPU_FINALIZE for more information about this procedure.
-
-KVM_REG_ARM64_SVE_VLS is a pseudo-register that allows the set of vector
-lengths supported by the vcpu to be discovered and configured by
-userspace. When transferred to or from user memory via KVM_GET_ONE_REG
-or KVM_SET_ONE_REG, the value of this register is of type
-__u64[KVM_ARM64_SVE_VLS_WORDS], and encodes the set of vector lengths as
-follows:
-
-__u64 vector_lengths[KVM_ARM64_SVE_VLS_WORDS];
-
-if (vq >= SVE_VQ_MIN && vq <= SVE_VQ_MAX &&
- ((vector_lengths[(vq - KVM_ARM64_SVE_VQ_MIN) / 64] >>
- ((vq - KVM_ARM64_SVE_VQ_MIN) % 64)) & 1))
- /* Vector length vq * 16 bytes supported */
-else
- /* Vector length vq * 16 bytes not supported */
-
-(**) The maximum value vq for which the above condition is true is
-max_vq. This is the maximum vector length available to the guest on
-this vcpu, and determines which register slices are visible through
-this ioctl interface.
-
-(See Documentation/arm64/sve.rst for an explanation of the "vq"
-nomenclature.)
-
-KVM_REG_ARM64_SVE_VLS is only accessible after KVM_ARM_VCPU_INIT.
-KVM_ARM_VCPU_INIT initialises it to the best set of vector lengths that
-the host supports.
-
-Userspace may subsequently modify it if desired until the vcpu's SVE
-configuration is finalized using KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE).
-
-Apart from simply removing all vector lengths from the host set that
-exceed some value, support for arbitrarily chosen sets of vector lengths
-is hardware-dependent and may not be available. Attempting to configure
-an invalid set of vector lengths via KVM_SET_ONE_REG will fail with
-EINVAL.
-
-After the vcpu's SVE configuration is finalized, further attempts to
-write this register will fail with EPERM.
-
-
-MIPS registers are mapped using the lower 32 bits. The upper 16 of that is
-the register group type:
-
-MIPS core registers (see above) have the following id bit patterns:
- 0x7030 0000 0000 <reg:16>
-
-MIPS CP0 registers (see KVM_REG_MIPS_CP0_* above) have the following id bit
-patterns depending on whether they're 32-bit or 64-bit registers:
- 0x7020 0000 0001 00 <reg:5> <sel:3> (32-bit)
- 0x7030 0000 0001 00 <reg:5> <sel:3> (64-bit)
-
-Note: KVM_REG_MIPS_CP0_ENTRYLO0 and KVM_REG_MIPS_CP0_ENTRYLO1 are the MIPS64
-versions of the EntryLo registers regardless of the word size of the host
-hardware, host kernel, guest, and whether XPA is present in the guest, i.e.
-with the RI and XI bits (if they exist) in bits 63 and 62 respectively, and
-the PFNX field starting at bit 30.
-
-MIPS MAARs (see KVM_REG_MIPS_CP0_MAAR(*) above) have the following id bit
-patterns:
- 0x7030 0000 0001 01 <reg:8>
-
-MIPS KVM control registers (see above) have the following id bit patterns:
- 0x7030 0000 0002 <reg:16>
-
-MIPS FPU registers (see KVM_REG_MIPS_FPR_{32,64}() above) have the following
-id bit patterns depending on the size of the register being accessed. They are
-always accessed according to the current guest FPU mode (Status.FR and
-Config5.FRE), i.e. as the guest would see them, and they become unpredictable
-if the guest FPU mode is changed. MIPS SIMD Architecture (MSA) vector
-registers (see KVM_REG_MIPS_VEC_128() above) have similar patterns as they
-overlap the FPU registers:
- 0x7020 0000 0003 00 <0:3> <reg:5> (32-bit FPU registers)
- 0x7030 0000 0003 00 <0:3> <reg:5> (64-bit FPU registers)
- 0x7040 0000 0003 00 <0:3> <reg:5> (128-bit MSA vector registers)
-
-MIPS FPU control registers (see KVM_REG_MIPS_FCR_{IR,CSR} above) have the
-following id bit patterns:
- 0x7020 0000 0003 01 <0:3> <reg:5>
-
-MIPS MSA control registers (see KVM_REG_MIPS_MSA_{IR,CSR} above) have the
-following id bit patterns:
- 0x7020 0000 0003 02 <0:3> <reg:5>
-
-
-4.69 KVM_GET_ONE_REG
-
-Capability: KVM_CAP_ONE_REG
-Architectures: all
-Type: vcpu ioctl
-Parameters: struct kvm_one_reg (in and out)
-Returns: 0 on success, negative value on failure
-Errors include:
- ENOENT: no such register
- EINVAL: invalid register ID, or no such register
- EPERM: (arm64) register access not allowed before vcpu finalization
-(These error codes are indicative only: do not rely on a specific error
-code being returned in a specific situation.)
-
-This ioctl allows to receive the value of a single register implemented
-in a vcpu. The register to read is indicated by the "id" field of the
-kvm_one_reg struct passed in. On success, the register value can be found
-at the memory location pointed to by "addr".
-
-The list of registers accessible using this interface is identical to the
-list in 4.68.
-
-
-4.70 KVM_KVMCLOCK_CTRL
-
-Capability: KVM_CAP_KVMCLOCK_CTRL
-Architectures: Any that implement pvclocks (currently x86 only)
-Type: vcpu ioctl
-Parameters: None
-Returns: 0 on success, -1 on error
-
-This signals to the host kernel that the specified guest is being paused by
-userspace. The host will set a flag in the pvclock structure that is checked
-from the soft lockup watchdog. The flag is part of the pvclock structure that
-is shared between guest and host, specifically the second bit of the flags
-field of the pvclock_vcpu_time_info structure. It will be set exclusively by
-the host and read/cleared exclusively by the guest. The guest operation of
-checking and clearing the flag must an atomic operation so
-load-link/store-conditional, or equivalent must be used. There are two cases
-where the guest will clear the flag: when the soft lockup watchdog timer resets
-itself or when a soft lockup is detected. This ioctl can be called any time
-after pausing the vcpu, but before it is resumed.
-
-
-4.71 KVM_SIGNAL_MSI
-
-Capability: KVM_CAP_SIGNAL_MSI
-Architectures: x86 arm arm64
-Type: vm ioctl
-Parameters: struct kvm_msi (in)
-Returns: >0 on delivery, 0 if guest blocked the MSI, and -1 on error
-
-Directly inject a MSI message. Only valid with in-kernel irqchip that handles
-MSI messages.
-
-struct kvm_msi {
- __u32 address_lo;
- __u32 address_hi;
- __u32 data;
- __u32 flags;
- __u32 devid;
- __u8 pad[12];
-};
-
-flags: KVM_MSI_VALID_DEVID: devid contains a valid value. The per-VM
- KVM_CAP_MSI_DEVID capability advertises the requirement to provide
- the device ID. If this capability is not available, userspace
- should never set the KVM_MSI_VALID_DEVID flag as the ioctl might fail.
-
-If KVM_MSI_VALID_DEVID is set, devid contains a unique device identifier
-for the device that wrote the MSI message. For PCI, this is usually a
-BFD identifier in the lower 16 bits.
-
-On x86, address_hi is ignored unless the KVM_X2APIC_API_USE_32BIT_IDS
-feature of KVM_CAP_X2APIC_API capability is enabled. If it is enabled,
-address_hi bits 31-8 provide bits 31-8 of the destination id. Bits 7-0 of
-address_hi must be zero.
-
-
-4.71 KVM_CREATE_PIT2
-
-Capability: KVM_CAP_PIT2
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_pit_config (in)
-Returns: 0 on success, -1 on error
-
-Creates an in-kernel device model for the i8254 PIT. This call is only valid
-after enabling in-kernel irqchip support via KVM_CREATE_IRQCHIP. The following
-parameters have to be passed:
-
-struct kvm_pit_config {
- __u32 flags;
- __u32 pad[15];
-};
-
-Valid flags are:
-
-#define KVM_PIT_SPEAKER_DUMMY 1 /* emulate speaker port stub */
-
-PIT timer interrupts may use a per-VM kernel thread for injection. If it
-exists, this thread will have a name of the following pattern:
-
-kvm-pit/<owner-process-pid>
-
-When running a guest with elevated priorities, the scheduling parameters of
-this thread may have to be adjusted accordingly.
-
-This IOCTL replaces the obsolete KVM_CREATE_PIT.
-
-
-4.72 KVM_GET_PIT2
-
-Capability: KVM_CAP_PIT_STATE2
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_pit_state2 (out)
-Returns: 0 on success, -1 on error
-
-Retrieves the state of the in-kernel PIT model. Only valid after
-KVM_CREATE_PIT2. The state is returned in the following structure:
-
-struct kvm_pit_state2 {
- struct kvm_pit_channel_state channels[3];
- __u32 flags;
- __u32 reserved[9];
-};
-
-Valid flags are:
-
-/* disable PIT in HPET legacy mode */
-#define KVM_PIT_FLAGS_HPET_LEGACY 0x00000001
-
-This IOCTL replaces the obsolete KVM_GET_PIT.
-
-
-4.73 KVM_SET_PIT2
-
-Capability: KVM_CAP_PIT_STATE2
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_pit_state2 (in)
-Returns: 0 on success, -1 on error
-
-Sets the state of the in-kernel PIT model. Only valid after KVM_CREATE_PIT2.
-See KVM_GET_PIT2 for details on struct kvm_pit_state2.
-
-This IOCTL replaces the obsolete KVM_SET_PIT.
-
-
-4.74 KVM_PPC_GET_SMMU_INFO
-
-Capability: KVM_CAP_PPC_GET_SMMU_INFO
-Architectures: powerpc
-Type: vm ioctl
-Parameters: None
-Returns: 0 on success, -1 on error
-
-This populates and returns a structure describing the features of
-the "Server" class MMU emulation supported by KVM.
-This can in turn be used by userspace to generate the appropriate
-device-tree properties for the guest operating system.
-
-The structure contains some global information, followed by an
-array of supported segment page sizes:
-
- struct kvm_ppc_smmu_info {
- __u64 flags;
- __u32 slb_size;
- __u32 pad;
- struct kvm_ppc_one_seg_page_size sps[KVM_PPC_PAGE_SIZES_MAX_SZ];
- };
-
-The supported flags are:
-
- - KVM_PPC_PAGE_SIZES_REAL:
- When that flag is set, guest page sizes must "fit" the backing
- store page sizes. When not set, any page size in the list can
- be used regardless of how they are backed by userspace.
-
- - KVM_PPC_1T_SEGMENTS
- The emulated MMU supports 1T segments in addition to the
- standard 256M ones.
-
- - KVM_PPC_NO_HASH
- This flag indicates that HPT guests are not supported by KVM,
- thus all guests must use radix MMU mode.
-
-The "slb_size" field indicates how many SLB entries are supported
-
-The "sps" array contains 8 entries indicating the supported base
-page sizes for a segment in increasing order. Each entry is defined
-as follow:
-
- struct kvm_ppc_one_seg_page_size {
- __u32 page_shift; /* Base page shift of segment (or 0) */
- __u32 slb_enc; /* SLB encoding for BookS */
- struct kvm_ppc_one_page_size enc[KVM_PPC_PAGE_SIZES_MAX_SZ];
- };
-
-An entry with a "page_shift" of 0 is unused. Because the array is
-organized in increasing order, a lookup can stop when encoutering
-such an entry.
-
-The "slb_enc" field provides the encoding to use in the SLB for the
-page size. The bits are in positions such as the value can directly
-be OR'ed into the "vsid" argument of the slbmte instruction.
-
-The "enc" array is a list which for each of those segment base page
-size provides the list of supported actual page sizes (which can be
-only larger or equal to the base page size), along with the
-corresponding encoding in the hash PTE. Similarly, the array is
-8 entries sorted by increasing sizes and an entry with a "0" shift
-is an empty entry and a terminator:
-
- struct kvm_ppc_one_page_size {
- __u32 page_shift; /* Page shift (or 0) */
- __u32 pte_enc; /* Encoding in the HPTE (>>12) */
- };
-
-The "pte_enc" field provides a value that can OR'ed into the hash
-PTE's RPN field (ie, it needs to be shifted left by 12 to OR it
-into the hash PTE second double word).
-
-4.75 KVM_IRQFD
-
-Capability: KVM_CAP_IRQFD
-Architectures: x86 s390 arm arm64
-Type: vm ioctl
-Parameters: struct kvm_irqfd (in)
-Returns: 0 on success, -1 on error
-
-Allows setting an eventfd to directly trigger a guest interrupt.
-kvm_irqfd.fd specifies the file descriptor to use as the eventfd and
-kvm_irqfd.gsi specifies the irqchip pin toggled by this event. When
-an event is triggered on the eventfd, an interrupt is injected into
-the guest using the specified gsi pin. The irqfd is removed using
-the KVM_IRQFD_FLAG_DEASSIGN flag, specifying both kvm_irqfd.fd
-and kvm_irqfd.gsi.
-
-With KVM_CAP_IRQFD_RESAMPLE, KVM_IRQFD supports a de-assert and notify
-mechanism allowing emulation of level-triggered, irqfd-based
-interrupts. When KVM_IRQFD_FLAG_RESAMPLE is set the user must pass an
-additional eventfd in the kvm_irqfd.resamplefd field. When operating
-in resample mode, posting of an interrupt through kvm_irq.fd asserts
-the specified gsi in the irqchip. When the irqchip is resampled, such
-as from an EOI, the gsi is de-asserted and the user is notified via
-kvm_irqfd.resamplefd. It is the user's responsibility to re-queue
-the interrupt if the device making use of it still requires service.
-Note that closing the resamplefd is not sufficient to disable the
-irqfd. The KVM_IRQFD_FLAG_RESAMPLE is only necessary on assignment
-and need not be specified with KVM_IRQFD_FLAG_DEASSIGN.
-
-On arm/arm64, gsi routing being supported, the following can happen:
-- in case no routing entry is associated to this gsi, injection fails
-- in case the gsi is associated to an irqchip routing entry,
- irqchip.pin + 32 corresponds to the injected SPI ID.
-- in case the gsi is associated to an MSI routing entry, the MSI
- message and device ID are translated into an LPI (support restricted
- to GICv3 ITS in-kernel emulation).
-
-4.76 KVM_PPC_ALLOCATE_HTAB
-
-Capability: KVM_CAP_PPC_ALLOC_HTAB
-Architectures: powerpc
-Type: vm ioctl
-Parameters: Pointer to u32 containing hash table order (in/out)
-Returns: 0 on success, -1 on error
-
-This requests the host kernel to allocate an MMU hash table for a
-guest using the PAPR paravirtualization interface. This only does
-anything if the kernel is configured to use the Book 3S HV style of
-virtualization. Otherwise the capability doesn't exist and the ioctl
-returns an ENOTTY error. The rest of this description assumes Book 3S
-HV.
-
-There must be no vcpus running when this ioctl is called; if there
-are, it will do nothing and return an EBUSY error.
-
-The parameter is a pointer to a 32-bit unsigned integer variable
-containing the order (log base 2) of the desired size of the hash
-table, which must be between 18 and 46. On successful return from the
-ioctl, the value will not be changed by the kernel.
-
-If no hash table has been allocated when any vcpu is asked to run
-(with the KVM_RUN ioctl), the host kernel will allocate a
-default-sized hash table (16 MB).
-
-If this ioctl is called when a hash table has already been allocated,
-with a different order from the existing hash table, the existing hash
-table will be freed and a new one allocated. If this is ioctl is
-called when a hash table has already been allocated of the same order
-as specified, the kernel will clear out the existing hash table (zero
-all HPTEs). In either case, if the guest is using the virtualized
-real-mode area (VRMA) facility, the kernel will re-create the VMRA
-HPTEs on the next KVM_RUN of any vcpu.
-
-4.77 KVM_S390_INTERRUPT
-
-Capability: basic
-Architectures: s390
-Type: vm ioctl, vcpu ioctl
-Parameters: struct kvm_s390_interrupt (in)
-Returns: 0 on success, -1 on error
-
-Allows to inject an interrupt to the guest. Interrupts can be floating
-(vm ioctl) or per cpu (vcpu ioctl), depending on the interrupt type.
-
-Interrupt parameters are passed via kvm_s390_interrupt:
-
-struct kvm_s390_interrupt {
- __u32 type;
- __u32 parm;
- __u64 parm64;
-};
-
-type can be one of the following:
-
-KVM_S390_SIGP_STOP (vcpu) - sigp stop; optional flags in parm
-KVM_S390_PROGRAM_INT (vcpu) - program check; code in parm
-KVM_S390_SIGP_SET_PREFIX (vcpu) - sigp set prefix; prefix address in parm
-KVM_S390_RESTART (vcpu) - restart
-KVM_S390_INT_CLOCK_COMP (vcpu) - clock comparator interrupt
-KVM_S390_INT_CPU_TIMER (vcpu) - CPU timer interrupt
-KVM_S390_INT_VIRTIO (vm) - virtio external interrupt; external interrupt
- parameters in parm and parm64
-KVM_S390_INT_SERVICE (vm) - sclp external interrupt; sclp parameter in parm
-KVM_S390_INT_EMERGENCY (vcpu) - sigp emergency; source cpu in parm
-KVM_S390_INT_EXTERNAL_CALL (vcpu) - sigp external call; source cpu in parm
-KVM_S390_INT_IO(ai,cssid,ssid,schid) (vm) - compound value to indicate an
- I/O interrupt (ai - adapter interrupt; cssid,ssid,schid - subchannel);
- I/O interruption parameters in parm (subchannel) and parm64 (intparm,
- interruption subclass)
-KVM_S390_MCHK (vm, vcpu) - machine check interrupt; cr 14 bits in parm,
- machine check interrupt code in parm64 (note that
- machine checks needing further payload are not
- supported by this ioctl)
-
-This is an asynchronous vcpu ioctl and can be invoked from any thread.
-
-4.78 KVM_PPC_GET_HTAB_FD
-
-Capability: KVM_CAP_PPC_HTAB_FD
-Architectures: powerpc
-Type: vm ioctl
-Parameters: Pointer to struct kvm_get_htab_fd (in)
-Returns: file descriptor number (>= 0) on success, -1 on error
-
-This returns a file descriptor that can be used either to read out the
-entries in the guest's hashed page table (HPT), or to write entries to
-initialize the HPT. The returned fd can only be written to if the
-KVM_GET_HTAB_WRITE bit is set in the flags field of the argument, and
-can only be read if that bit is clear. The argument struct looks like
-this:
-
-/* For KVM_PPC_GET_HTAB_FD */
-struct kvm_get_htab_fd {
- __u64 flags;
- __u64 start_index;
- __u64 reserved[2];
-};
-
-/* Values for kvm_get_htab_fd.flags */
-#define KVM_GET_HTAB_BOLTED_ONLY ((__u64)0x1)
-#define KVM_GET_HTAB_WRITE ((__u64)0x2)
-
-The `start_index' field gives the index in the HPT of the entry at
-which to start reading. It is ignored when writing.
-
-Reads on the fd will initially supply information about all
-"interesting" HPT entries. Interesting entries are those with the
-bolted bit set, if the KVM_GET_HTAB_BOLTED_ONLY bit is set, otherwise
-all entries. When the end of the HPT is reached, the read() will
-return. If read() is called again on the fd, it will start again from
-the beginning of the HPT, but will only return HPT entries that have
-changed since they were last read.
-
-Data read or written is structured as a header (8 bytes) followed by a
-series of valid HPT entries (16 bytes) each. The header indicates how
-many valid HPT entries there are and how many invalid entries follow
-the valid entries. The invalid entries are not represented explicitly
-in the stream. The header format is:
-
-struct kvm_get_htab_header {
- __u32 index;
- __u16 n_valid;
- __u16 n_invalid;
-};
-
-Writes to the fd create HPT entries starting at the index given in the
-header; first `n_valid' valid entries with contents from the data
-written, then `n_invalid' invalid entries, invalidating any previously
-valid entries found.
-
-4.79 KVM_CREATE_DEVICE
-
-Capability: KVM_CAP_DEVICE_CTRL
-Type: vm ioctl
-Parameters: struct kvm_create_device (in/out)
-Returns: 0 on success, -1 on error
-Errors:
- ENODEV: The device type is unknown or unsupported
- EEXIST: Device already created, and this type of device may not
- be instantiated multiple times
-
- Other error conditions may be defined by individual device types or
- have their standard meanings.
-
-Creates an emulated device in the kernel. The file descriptor returned
-in fd can be used with KVM_SET/GET/HAS_DEVICE_ATTR.
-
-If the KVM_CREATE_DEVICE_TEST flag is set, only test whether the
-device type is supported (not necessarily whether it can be created
-in the current vm).
-
-Individual devices should not define flags. Attributes should be used
-for specifying any behavior that is not implied by the device type
-number.
-
-struct kvm_create_device {
- __u32 type; /* in: KVM_DEV_TYPE_xxx */
- __u32 fd; /* out: device handle */
- __u32 flags; /* in: KVM_CREATE_DEVICE_xxx */
-};
-
-4.80 KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR
-
-Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device,
- KVM_CAP_VCPU_ATTRIBUTES for vcpu device
-Type: device ioctl, vm ioctl, vcpu ioctl
-Parameters: struct kvm_device_attr
-Returns: 0 on success, -1 on error
-Errors:
- ENXIO: The group or attribute is unknown/unsupported for this device
- or hardware support is missing.
- EPERM: The attribute cannot (currently) be accessed this way
- (e.g. read-only attribute, or attribute that only makes
- sense when the device is in a different state)
-
- Other error conditions may be defined by individual device types.
-
-Gets/sets a specified piece of device configuration and/or state. The
-semantics are device-specific. See individual device documentation in
-the "devices" directory. As with ONE_REG, the size of the data
-transferred is defined by the particular attribute.
-
-struct kvm_device_attr {
- __u32 flags; /* no flags currently defined */
- __u32 group; /* device-defined */
- __u64 attr; /* group-defined */
- __u64 addr; /* userspace address of attr data */
-};
-
-4.81 KVM_HAS_DEVICE_ATTR
-
-Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device,
- KVM_CAP_VCPU_ATTRIBUTES for vcpu device
-Type: device ioctl, vm ioctl, vcpu ioctl
-Parameters: struct kvm_device_attr
-Returns: 0 on success, -1 on error
-Errors:
- ENXIO: The group or attribute is unknown/unsupported for this device
- or hardware support is missing.
-
-Tests whether a device supports a particular attribute. A successful
-return indicates the attribute is implemented. It does not necessarily
-indicate that the attribute can be read or written in the device's
-current state. "addr" is ignored.
-
-4.82 KVM_ARM_VCPU_INIT
-
-Capability: basic
-Architectures: arm, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_vcpu_init (in)
-Returns: 0 on success; -1 on error
-Errors:
- EINVAL: the target is unknown, or the combination of features is invalid.
- ENOENT: a features bit specified is unknown.
-
-This tells KVM what type of CPU to present to the guest, and what
-optional features it should have. This will cause a reset of the cpu
-registers to their initial values. If this is not called, KVM_RUN will
-return ENOEXEC for that vcpu.
-
-Note that because some registers reflect machine topology, all vcpus
-should be created before this ioctl is invoked.
-
-Userspace can call this function multiple times for a given vcpu, including
-after the vcpu has been run. This will reset the vcpu to its initial
-state. All calls to this function after the initial call must use the same
-target and same set of feature flags, otherwise EINVAL will be returned.
-
-Possible features:
- - KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state.
- Depends on KVM_CAP_ARM_PSCI. If not set, the CPU will be powered on
- and execute guest code when KVM_RUN is called.
- - KVM_ARM_VCPU_EL1_32BIT: Starts the CPU in a 32bit mode.
- Depends on KVM_CAP_ARM_EL1_32BIT (arm64 only).
- - KVM_ARM_VCPU_PSCI_0_2: Emulate PSCI v0.2 (or a future revision
- backward compatible with v0.2) for the CPU.
- Depends on KVM_CAP_ARM_PSCI_0_2.
- - KVM_ARM_VCPU_PMU_V3: Emulate PMUv3 for the CPU.
- Depends on KVM_CAP_ARM_PMU_V3.
-
- - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication
- for arm64 only.
- Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS.
- If KVM_CAP_ARM_PTRAUTH_ADDRESS and KVM_CAP_ARM_PTRAUTH_GENERIC are
- both present, then both KVM_ARM_VCPU_PTRAUTH_ADDRESS and
- KVM_ARM_VCPU_PTRAUTH_GENERIC must be requested or neither must be
- requested.
-
- - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication
- for arm64 only.
- Depends on KVM_CAP_ARM_PTRAUTH_GENERIC.
- If KVM_CAP_ARM_PTRAUTH_ADDRESS and KVM_CAP_ARM_PTRAUTH_GENERIC are
- both present, then both KVM_ARM_VCPU_PTRAUTH_ADDRESS and
- KVM_ARM_VCPU_PTRAUTH_GENERIC must be requested or neither must be
- requested.
-
- - KVM_ARM_VCPU_SVE: Enables SVE for the CPU (arm64 only).
- Depends on KVM_CAP_ARM_SVE.
- Requires KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE):
-
- * After KVM_ARM_VCPU_INIT:
-
- - KVM_REG_ARM64_SVE_VLS may be read using KVM_GET_ONE_REG: the
- initial value of this pseudo-register indicates the best set of
- vector lengths possible for a vcpu on this host.
-
- * Before KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE):
-
- - KVM_RUN and KVM_GET_REG_LIST are not available;
-
- - KVM_GET_ONE_REG and KVM_SET_ONE_REG cannot be used to access
- the scalable archietctural SVE registers
- KVM_REG_ARM64_SVE_ZREG(), KVM_REG_ARM64_SVE_PREG() or
- KVM_REG_ARM64_SVE_FFR;
-
- - KVM_REG_ARM64_SVE_VLS may optionally be written using
- KVM_SET_ONE_REG, to modify the set of vector lengths available
- for the vcpu.
-
- * After KVM_ARM_VCPU_FINALIZE(KVM_ARM_VCPU_SVE):
-
- - the KVM_REG_ARM64_SVE_VLS pseudo-register is immutable, and can
- no longer be written using KVM_SET_ONE_REG.
-
-4.83 KVM_ARM_PREFERRED_TARGET
-
-Capability: basic
-Architectures: arm, arm64
-Type: vm ioctl
-Parameters: struct struct kvm_vcpu_init (out)
-Returns: 0 on success; -1 on error
-Errors:
- ENODEV: no preferred target available for the host
-
-This queries KVM for preferred CPU target type which can be emulated
-by KVM on underlying host.
-
-The ioctl returns struct kvm_vcpu_init instance containing information
-about preferred CPU target type and recommended features for it. The
-kvm_vcpu_init->features bitmap returned will have feature bits set if
-the preferred target recommends setting these features, but this is
-not mandatory.
-
-The information returned by this ioctl can be used to prepare an instance
-of struct kvm_vcpu_init for KVM_ARM_VCPU_INIT ioctl which will result in
-in VCPU matching underlying host.
-
-
-4.84 KVM_GET_REG_LIST
-
-Capability: basic
-Architectures: arm, arm64, mips
-Type: vcpu ioctl
-Parameters: struct kvm_reg_list (in/out)
-Returns: 0 on success; -1 on error
-Errors:
- E2BIG: the reg index list is too big to fit in the array specified by
- the user (the number required will be written into n).
-
-struct kvm_reg_list {
- __u64 n; /* number of registers in reg[] */
- __u64 reg[0];
-};
-
-This ioctl returns the guest registers that are supported for the
-KVM_GET_ONE_REG/KVM_SET_ONE_REG calls.
-
-
-4.85 KVM_ARM_SET_DEVICE_ADDR (deprecated)
-
-Capability: KVM_CAP_ARM_SET_DEVICE_ADDR
-Architectures: arm, arm64
-Type: vm ioctl
-Parameters: struct kvm_arm_device_address (in)
-Returns: 0 on success, -1 on error
-Errors:
- ENODEV: The device id is unknown
- ENXIO: Device not supported on current system
- EEXIST: Address already set
- E2BIG: Address outside guest physical address space
- EBUSY: Address overlaps with other device range
-
-struct kvm_arm_device_addr {
- __u64 id;
- __u64 addr;
-};
-
-Specify a device address in the guest's physical address space where guests
-can access emulated or directly exposed devices, which the host kernel needs
-to know about. The id field is an architecture specific identifier for a
-specific device.
-
-ARM/arm64 divides the id field into two parts, a device id and an
-address type id specific to the individual device.
-
- bits: | 63 ... 32 | 31 ... 16 | 15 ... 0 |
- field: | 0x00000000 | device id | addr type id |
-
-ARM/arm64 currently only require this when using the in-kernel GIC
-support for the hardware VGIC features, using KVM_ARM_DEVICE_VGIC_V2
-as the device id. When setting the base address for the guest's
-mapping of the VGIC virtual CPU and distributor interface, the ioctl
-must be called after calling KVM_CREATE_IRQCHIP, but before calling
-KVM_RUN on any of the VCPUs. Calling this ioctl twice for any of the
-base addresses will return -EEXIST.
-
-Note, this IOCTL is deprecated and the more flexible SET/GET_DEVICE_ATTR API
-should be used instead.
-
-
-4.86 KVM_PPC_RTAS_DEFINE_TOKEN
-
-Capability: KVM_CAP_PPC_RTAS
-Architectures: ppc
-Type: vm ioctl
-Parameters: struct kvm_rtas_token_args
-Returns: 0 on success, -1 on error
-
-Defines a token value for a RTAS (Run Time Abstraction Services)
-service in order to allow it to be handled in the kernel. The
-argument struct gives the name of the service, which must be the name
-of a service that has a kernel-side implementation. If the token
-value is non-zero, it will be associated with that service, and
-subsequent RTAS calls by the guest specifying that token will be
-handled by the kernel. If the token value is 0, then any token
-associated with the service will be forgotten, and subsequent RTAS
-calls by the guest for that service will be passed to userspace to be
-handled.
-
-4.87 KVM_SET_GUEST_DEBUG
-
-Capability: KVM_CAP_SET_GUEST_DEBUG
-Architectures: x86, s390, ppc, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_guest_debug (in)
-Returns: 0 on success; -1 on error
-
-struct kvm_guest_debug {
- __u32 control;
- __u32 pad;
- struct kvm_guest_debug_arch arch;
-};
-
-Set up the processor specific debug registers and configure vcpu for
-handling guest debug events. There are two parts to the structure, the
-first a control bitfield indicates the type of debug events to handle
-when running. Common control bits are:
-
- - KVM_GUESTDBG_ENABLE: guest debugging is enabled
- - KVM_GUESTDBG_SINGLESTEP: the next run should single-step
-
-The top 16 bits of the control field are architecture specific control
-flags which can include the following:
-
- - KVM_GUESTDBG_USE_SW_BP: using software breakpoints [x86, arm64]
- - KVM_GUESTDBG_USE_HW_BP: using hardware breakpoints [x86, s390, arm64]
- - KVM_GUESTDBG_INJECT_DB: inject DB type exception [x86]
- - KVM_GUESTDBG_INJECT_BP: inject BP type exception [x86]
- - KVM_GUESTDBG_EXIT_PENDING: trigger an immediate guest exit [s390]
-
-For example KVM_GUESTDBG_USE_SW_BP indicates that software breakpoints
-are enabled in memory so we need to ensure breakpoint exceptions are
-correctly trapped and the KVM run loop exits at the breakpoint and not
-running off into the normal guest vector. For KVM_GUESTDBG_USE_HW_BP
-we need to ensure the guest vCPUs architecture specific registers are
-updated to the correct (supplied) values.
-
-The second part of the structure is architecture specific and
-typically contains a set of debug registers.
-
-For arm64 the number of debug registers is implementation defined and
-can be determined by querying the KVM_CAP_GUEST_DEBUG_HW_BPS and
-KVM_CAP_GUEST_DEBUG_HW_WPS capabilities which return a positive number
-indicating the number of supported registers.
-
-When debug events exit the main run loop with the reason
-KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run
-structure containing architecture specific debug information.
-
-4.88 KVM_GET_EMULATED_CPUID
-
-Capability: KVM_CAP_EXT_EMUL_CPUID
-Architectures: x86
-Type: system ioctl
-Parameters: struct kvm_cpuid2 (in/out)
-Returns: 0 on success, -1 on error
-
-struct kvm_cpuid2 {
- __u32 nent;
- __u32 flags;
- struct kvm_cpuid_entry2 entries[0];
-};
-
-The member 'flags' is used for passing flags from userspace.
-
-#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0)
-#define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1)
-#define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2)
-
-struct kvm_cpuid_entry2 {
- __u32 function;
- __u32 index;
- __u32 flags;
- __u32 eax;
- __u32 ebx;
- __u32 ecx;
- __u32 edx;
- __u32 padding[3];
-};
-
-This ioctl returns x86 cpuid features which are emulated by
-kvm.Userspace can use the information returned by this ioctl to query
-which features are emulated by kvm instead of being present natively.
-
-Userspace invokes KVM_GET_EMULATED_CPUID by passing a kvm_cpuid2
-structure with the 'nent' field indicating the number of entries in
-the variable-size array 'entries'. If the number of entries is too low
-to describe the cpu capabilities, an error (E2BIG) is returned. If the
-number is too high, the 'nent' field is adjusted and an error (ENOMEM)
-is returned. If the number is just right, the 'nent' field is adjusted
-to the number of valid entries in the 'entries' array, which is then
-filled.
-
-The entries returned are the set CPUID bits of the respective features
-which kvm emulates, as returned by the CPUID instruction, with unknown
-or unsupported feature bits cleared.
-
-Features like x2apic, for example, may not be present in the host cpu
-but are exposed by kvm in KVM_GET_SUPPORTED_CPUID because they can be
-emulated efficiently and thus not included here.
-
-The fields in each entry are defined as follows:
-
- function: the eax value used to obtain the entry
- index: the ecx value used to obtain the entry (for entries that are
- affected by ecx)
- flags: an OR of zero or more of the following:
- KVM_CPUID_FLAG_SIGNIFCANT_INDEX:
- if the index field is valid
- KVM_CPUID_FLAG_STATEFUL_FUNC:
- if cpuid for this function returns different values for successive
- invocations; there will be several entries with the same function,
- all with this flag set
- KVM_CPUID_FLAG_STATE_READ_NEXT:
- for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is
- the first entry to be read by a cpu
- eax, ebx, ecx, edx: the values returned by the cpuid instruction for
- this function/index combination
-
-4.89 KVM_S390_MEM_OP
-
-Capability: KVM_CAP_S390_MEM_OP
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_mem_op (in)
-Returns: = 0 on success,
- < 0 on generic error (e.g. -EFAULT or -ENOMEM),
- > 0 if an exception occurred while walking the page tables
-
-Read or write data from/to the logical (virtual) memory of a VCPU.
-
-Parameters are specified via the following structure:
-
-struct kvm_s390_mem_op {
- __u64 gaddr; /* the guest address */
- __u64 flags; /* flags */
- __u32 size; /* amount of bytes */
- __u32 op; /* type of operation */
- __u64 buf; /* buffer in userspace */
- __u8 ar; /* the access register number */
- __u8 reserved[31]; /* should be set to 0 */
-};
-
-The type of operation is specified in the "op" field. It is either
-KVM_S390_MEMOP_LOGICAL_READ for reading from logical memory space or
-KVM_S390_MEMOP_LOGICAL_WRITE for writing to logical memory space. The
-KVM_S390_MEMOP_F_CHECK_ONLY flag can be set in the "flags" field to check
-whether the corresponding memory access would create an access exception
-(without touching the data in the memory at the destination). In case an
-access exception occurred while walking the MMU tables of the guest, the
-ioctl returns a positive error number to indicate the type of exception.
-This exception is also raised directly at the corresponding VCPU if the
-flag KVM_S390_MEMOP_F_INJECT_EXCEPTION is set in the "flags" field.
-
-The start address of the memory region has to be specified in the "gaddr"
-field, and the length of the region in the "size" field. "buf" is the buffer
-supplied by the userspace application where the read data should be written
-to for KVM_S390_MEMOP_LOGICAL_READ, or where the data that should be written
-is stored for a KVM_S390_MEMOP_LOGICAL_WRITE. "buf" is unused and can be NULL
-when KVM_S390_MEMOP_F_CHECK_ONLY is specified. "ar" designates the access
-register number to be used.
-
-The "reserved" field is meant for future extensions. It is not used by
-KVM with the currently defined set of flags.
-
-4.90 KVM_S390_GET_SKEYS
-
-Capability: KVM_CAP_S390_SKEYS
-Architectures: s390
-Type: vm ioctl
-Parameters: struct kvm_s390_skeys
-Returns: 0 on success, KVM_S390_GET_KEYS_NONE if guest is not using storage
- keys, negative value on error
-
-This ioctl is used to get guest storage key values on the s390
-architecture. The ioctl takes parameters via the kvm_s390_skeys struct.
-
-struct kvm_s390_skeys {
- __u64 start_gfn;
- __u64 count;
- __u64 skeydata_addr;
- __u32 flags;
- __u32 reserved[9];
-};
-
-The start_gfn field is the number of the first guest frame whose storage keys
-you want to get.
-
-The count field is the number of consecutive frames (starting from start_gfn)
-whose storage keys to get. The count field must be at least 1 and the maximum
-allowed value is defined as KVM_S390_SKEYS_ALLOC_MAX. Values outside this range
-will cause the ioctl to return -EINVAL.
-
-The skeydata_addr field is the address to a buffer large enough to hold count
-bytes. This buffer will be filled with storage key data by the ioctl.
-
-4.91 KVM_S390_SET_SKEYS
-
-Capability: KVM_CAP_S390_SKEYS
-Architectures: s390
-Type: vm ioctl
-Parameters: struct kvm_s390_skeys
-Returns: 0 on success, negative value on error
-
-This ioctl is used to set guest storage key values on the s390
-architecture. The ioctl takes parameters via the kvm_s390_skeys struct.
-See section on KVM_S390_GET_SKEYS for struct definition.
-
-The start_gfn field is the number of the first guest frame whose storage keys
-you want to set.
-
-The count field is the number of consecutive frames (starting from start_gfn)
-whose storage keys to get. The count field must be at least 1 and the maximum
-allowed value is defined as KVM_S390_SKEYS_ALLOC_MAX. Values outside this range
-will cause the ioctl to return -EINVAL.
-
-The skeydata_addr field is the address to a buffer containing count bytes of
-storage keys. Each byte in the buffer will be set as the storage key for a
-single frame starting at start_gfn for count frames.
-
-Note: If any architecturally invalid key value is found in the given data then
-the ioctl will return -EINVAL.
-
-4.92 KVM_S390_IRQ
-
-Capability: KVM_CAP_S390_INJECT_IRQ
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_irq (in)
-Returns: 0 on success, -1 on error
-Errors:
- EINVAL: interrupt type is invalid
- type is KVM_S390_SIGP_STOP and flag parameter is invalid value
- type is KVM_S390_INT_EXTERNAL_CALL and code is bigger
- than the maximum of VCPUs
- EBUSY: type is KVM_S390_SIGP_SET_PREFIX and vcpu is not stopped
- type is KVM_S390_SIGP_STOP and a stop irq is already pending
- type is KVM_S390_INT_EXTERNAL_CALL and an external call interrupt
- is already pending
-
-Allows to inject an interrupt to the guest.
-
-Using struct kvm_s390_irq as a parameter allows
-to inject additional payload which is not
-possible via KVM_S390_INTERRUPT.
-
-Interrupt parameters are passed via kvm_s390_irq:
-
-struct kvm_s390_irq {
- __u64 type;
- union {
- struct kvm_s390_io_info io;
- struct kvm_s390_ext_info ext;
- struct kvm_s390_pgm_info pgm;
- struct kvm_s390_emerg_info emerg;
- struct kvm_s390_extcall_info extcall;
- struct kvm_s390_prefix_info prefix;
- struct kvm_s390_stop_info stop;
- struct kvm_s390_mchk_info mchk;
- char reserved[64];
- } u;
-};
-
-type can be one of the following:
-
-KVM_S390_SIGP_STOP - sigp stop; parameter in .stop
-KVM_S390_PROGRAM_INT - program check; parameters in .pgm
-KVM_S390_SIGP_SET_PREFIX - sigp set prefix; parameters in .prefix
-KVM_S390_RESTART - restart; no parameters
-KVM_S390_INT_CLOCK_COMP - clock comparator interrupt; no parameters
-KVM_S390_INT_CPU_TIMER - CPU timer interrupt; no parameters
-KVM_S390_INT_EMERGENCY - sigp emergency; parameters in .emerg
-KVM_S390_INT_EXTERNAL_CALL - sigp external call; parameters in .extcall
-KVM_S390_MCHK - machine check interrupt; parameters in .mchk
-
-This is an asynchronous vcpu ioctl and can be invoked from any thread.
-
-4.94 KVM_S390_GET_IRQ_STATE
-
-Capability: KVM_CAP_S390_IRQ_STATE
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_irq_state (out)
-Returns: >= number of bytes copied into buffer,
- -EINVAL if buffer size is 0,
- -ENOBUFS if buffer size is too small to fit all pending interrupts,
- -EFAULT if the buffer address was invalid
-
-This ioctl allows userspace to retrieve the complete state of all currently
-pending interrupts in a single buffer. Use cases include migration
-and introspection. The parameter structure contains the address of a
-userspace buffer and its length:
-
-struct kvm_s390_irq_state {
- __u64 buf;
- __u32 flags; /* will stay unused for compatibility reasons */
- __u32 len;
- __u32 reserved[4]; /* will stay unused for compatibility reasons */
-};
-
-Userspace passes in the above struct and for each pending interrupt a
-struct kvm_s390_irq is copied to the provided buffer.
-
-The structure contains a flags and a reserved field for future extensions. As
-the kernel never checked for flags == 0 and QEMU never pre-zeroed flags and
-reserved, these fields can not be used in the future without breaking
-compatibility.
-
-If -ENOBUFS is returned the buffer provided was too small and userspace
-may retry with a bigger buffer.
-
-4.95 KVM_S390_SET_IRQ_STATE
-
-Capability: KVM_CAP_S390_IRQ_STATE
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_irq_state (in)
-Returns: 0 on success,
- -EFAULT if the buffer address was invalid,
- -EINVAL for an invalid buffer length (see below),
- -EBUSY if there were already interrupts pending,
- errors occurring when actually injecting the
- interrupt. See KVM_S390_IRQ.
-
-This ioctl allows userspace to set the complete state of all cpu-local
-interrupts currently pending for the vcpu. It is intended for restoring
-interrupt state after a migration. The input parameter is a userspace buffer
-containing a struct kvm_s390_irq_state:
-
-struct kvm_s390_irq_state {
- __u64 buf;
- __u32 flags; /* will stay unused for compatibility reasons */
- __u32 len;
- __u32 reserved[4]; /* will stay unused for compatibility reasons */
-};
-
-The restrictions for flags and reserved apply as well.
-(see KVM_S390_GET_IRQ_STATE)
-
-The userspace memory referenced by buf contains a struct kvm_s390_irq
-for each interrupt to be injected into the guest.
-If one of the interrupts could not be injected for some reason the
-ioctl aborts.
-
-len must be a multiple of sizeof(struct kvm_s390_irq). It must be > 0
-and it must not exceed (max_vcpus + 32) * sizeof(struct kvm_s390_irq),
-which is the maximum number of possibly pending cpu-local interrupts.
-
-4.96 KVM_SMI
-
-Capability: KVM_CAP_X86_SMM
-Architectures: x86
-Type: vcpu ioctl
-Parameters: none
-Returns: 0 on success, -1 on error
-
-Queues an SMI on the thread's vcpu.
-
-4.97 KVM_CAP_PPC_MULTITCE
-
-Capability: KVM_CAP_PPC_MULTITCE
-Architectures: ppc
-Type: vm
-
-This capability means the kernel is capable of handling hypercalls
-H_PUT_TCE_INDIRECT and H_STUFF_TCE without passing those into the user
-space. This significantly accelerates DMA operations for PPC KVM guests.
-User space should expect that its handlers for these hypercalls
-are not going to be called if user space previously registered LIOBN
-in KVM (via KVM_CREATE_SPAPR_TCE or similar calls).
-
-In order to enable H_PUT_TCE_INDIRECT and H_STUFF_TCE use in the guest,
-user space might have to advertise it for the guest. For example,
-IBM pSeries (sPAPR) guest starts using them if "hcall-multi-tce" is
-present in the "ibm,hypertas-functions" device-tree property.
-
-The hypercalls mentioned above may or may not be processed successfully
-in the kernel based fast path. If they can not be handled by the kernel,
-they will get passed on to user space. So user space still has to have
-an implementation for these despite the in kernel acceleration.
-
-This capability is always enabled.
-
-4.98 KVM_CREATE_SPAPR_TCE_64
-
-Capability: KVM_CAP_SPAPR_TCE_64
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_create_spapr_tce_64 (in)
-Returns: file descriptor for manipulating the created TCE table
-
-This is an extension for KVM_CAP_SPAPR_TCE which only supports 32bit
-windows, described in 4.62 KVM_CREATE_SPAPR_TCE
-
-This capability uses extended struct in ioctl interface:
-
-/* for KVM_CAP_SPAPR_TCE_64 */
-struct kvm_create_spapr_tce_64 {
- __u64 liobn;
- __u32 page_shift;
- __u32 flags;
- __u64 offset; /* in pages */
- __u64 size; /* in pages */
-};
-
-The aim of extension is to support an additional bigger DMA window with
-a variable page size.
-KVM_CREATE_SPAPR_TCE_64 receives a 64bit window size, an IOMMU page shift and
-a bus offset of the corresponding DMA window, @size and @offset are numbers
-of IOMMU pages.
-
-@flags are not used at the moment.
-
-The rest of functionality is identical to KVM_CREATE_SPAPR_TCE.
-
-4.99 KVM_REINJECT_CONTROL
-
-Capability: KVM_CAP_REINJECT_CONTROL
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_reinject_control (in)
-Returns: 0 on success,
- -EFAULT if struct kvm_reinject_control cannot be read,
- -ENXIO if KVM_CREATE_PIT or KVM_CREATE_PIT2 didn't succeed earlier.
-
-i8254 (PIT) has two modes, reinject and !reinject. The default is reinject,
-where KVM queues elapsed i8254 ticks and monitors completion of interrupt from
-vector(s) that i8254 injects. Reinject mode dequeues a tick and injects its
-interrupt whenever there isn't a pending interrupt from i8254.
-!reinject mode injects an interrupt as soon as a tick arrives.
-
-struct kvm_reinject_control {
- __u8 pit_reinject;
- __u8 reserved[31];
-};
-
-pit_reinject = 0 (!reinject mode) is recommended, unless running an old
-operating system that uses the PIT for timing (e.g. Linux 2.4.x).
-
-4.100 KVM_PPC_CONFIGURE_V3_MMU
-
-Capability: KVM_CAP_PPC_RADIX_MMU or KVM_CAP_PPC_HASH_MMU_V3
-Architectures: ppc
-Type: vm ioctl
-Parameters: struct kvm_ppc_mmuv3_cfg (in)
-Returns: 0 on success,
- -EFAULT if struct kvm_ppc_mmuv3_cfg cannot be read,
- -EINVAL if the configuration is invalid
-
-This ioctl controls whether the guest will use radix or HPT (hashed
-page table) translation, and sets the pointer to the process table for
-the guest.
-
-struct kvm_ppc_mmuv3_cfg {
- __u64 flags;
- __u64 process_table;
-};
-
-There are two bits that can be set in flags; KVM_PPC_MMUV3_RADIX and
-KVM_PPC_MMUV3_GTSE. KVM_PPC_MMUV3_RADIX, if set, configures the guest
-to use radix tree translation, and if clear, to use HPT translation.
-KVM_PPC_MMUV3_GTSE, if set and if KVM permits it, configures the guest
-to be able to use the global TLB and SLB invalidation instructions;
-if clear, the guest may not use these instructions.
-
-The process_table field specifies the address and size of the guest
-process table, which is in the guest's space. This field is formatted
-as the second doubleword of the partition table entry, as defined in
-the Power ISA V3.00, Book III section 5.7.6.1.
-
-4.101 KVM_PPC_GET_RMMU_INFO
-
-Capability: KVM_CAP_PPC_RADIX_MMU
-Architectures: ppc
-Type: vm ioctl
-Parameters: struct kvm_ppc_rmmu_info (out)
-Returns: 0 on success,
- -EFAULT if struct kvm_ppc_rmmu_info cannot be written,
- -EINVAL if no useful information can be returned
-
-This ioctl returns a structure containing two things: (a) a list
-containing supported radix tree geometries, and (b) a list that maps
-page sizes to put in the "AP" (actual page size) field for the tlbie
-(TLB invalidate entry) instruction.
-
-struct kvm_ppc_rmmu_info {
- struct kvm_ppc_radix_geom {
- __u8 page_shift;
- __u8 level_bits[4];
- __u8 pad[3];
- } geometries[8];
- __u32 ap_encodings[8];
-};
-
-The geometries[] field gives up to 8 supported geometries for the
-radix page table, in terms of the log base 2 of the smallest page
-size, and the number of bits indexed at each level of the tree, from
-the PTE level up to the PGD level in that order. Any unused entries
-will have 0 in the page_shift field.
-
-The ap_encodings gives the supported page sizes and their AP field
-encodings, encoded with the AP value in the top 3 bits and the log
-base 2 of the page size in the bottom 6 bits.
-
-4.102 KVM_PPC_RESIZE_HPT_PREPARE
-
-Capability: KVM_CAP_SPAPR_RESIZE_HPT
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_ppc_resize_hpt (in)
-Returns: 0 on successful completion,
- >0 if a new HPT is being prepared, the value is an estimated
- number of milliseconds until preparation is complete
- -EFAULT if struct kvm_reinject_control cannot be read,
- -EINVAL if the supplied shift or flags are invalid
- -ENOMEM if unable to allocate the new HPT
- -ENOSPC if there was a hash collision when moving existing
- HPT entries to the new HPT
- -EIO on other error conditions
-
-Used to implement the PAPR extension for runtime resizing of a guest's
-Hashed Page Table (HPT). Specifically this starts, stops or monitors
-the preparation of a new potential HPT for the guest, essentially
-implementing the H_RESIZE_HPT_PREPARE hypercall.
-
-If called with shift > 0 when there is no pending HPT for the guest,
-this begins preparation of a new pending HPT of size 2^(shift) bytes.
-It then returns a positive integer with the estimated number of
-milliseconds until preparation is complete.
-
-If called when there is a pending HPT whose size does not match that
-requested in the parameters, discards the existing pending HPT and
-creates a new one as above.
-
-If called when there is a pending HPT of the size requested, will:
- * If preparation of the pending HPT is already complete, return 0
- * If preparation of the pending HPT has failed, return an error
- code, then discard the pending HPT.
- * If preparation of the pending HPT is still in progress, return an
- estimated number of milliseconds until preparation is complete.
-
-If called with shift == 0, discards any currently pending HPT and
-returns 0 (i.e. cancels any in-progress preparation).
-
-flags is reserved for future expansion, currently setting any bits in
-flags will result in an -EINVAL.
-
-Normally this will be called repeatedly with the same parameters until
-it returns <= 0. The first call will initiate preparation, subsequent
-ones will monitor preparation until it completes or fails.
-
-struct kvm_ppc_resize_hpt {
- __u64 flags;
- __u32 shift;
- __u32 pad;
-};
-
-4.103 KVM_PPC_RESIZE_HPT_COMMIT
-
-Capability: KVM_CAP_SPAPR_RESIZE_HPT
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_ppc_resize_hpt (in)
-Returns: 0 on successful completion,
- -EFAULT if struct kvm_reinject_control cannot be read,
- -EINVAL if the supplied shift or flags are invalid
- -ENXIO is there is no pending HPT, or the pending HPT doesn't
- have the requested size
- -EBUSY if the pending HPT is not fully prepared
- -ENOSPC if there was a hash collision when moving existing
- HPT entries to the new HPT
- -EIO on other error conditions
-
-Used to implement the PAPR extension for runtime resizing of a guest's
-Hashed Page Table (HPT). Specifically this requests that the guest be
-transferred to working with the new HPT, essentially implementing the
-H_RESIZE_HPT_COMMIT hypercall.
-
-This should only be called after KVM_PPC_RESIZE_HPT_PREPARE has
-returned 0 with the same parameters. In other cases
-KVM_PPC_RESIZE_HPT_COMMIT will return an error (usually -ENXIO or
--EBUSY, though others may be possible if the preparation was started,
-but failed).
-
-This will have undefined effects on the guest if it has not already
-placed itself in a quiescent state where no vcpu will make MMU enabled
-memory accesses.
-
-On succsful completion, the pending HPT will become the guest's active
-HPT and the previous HPT will be discarded.
-
-On failure, the guest will still be operating on its previous HPT.
-
-struct kvm_ppc_resize_hpt {
- __u64 flags;
- __u32 shift;
- __u32 pad;
-};
-
-4.104 KVM_X86_GET_MCE_CAP_SUPPORTED
-
-Capability: KVM_CAP_MCE
-Architectures: x86
-Type: system ioctl
-Parameters: u64 mce_cap (out)
-Returns: 0 on success, -1 on error
-
-Returns supported MCE capabilities. The u64 mce_cap parameter
-has the same format as the MSR_IA32_MCG_CAP register. Supported
-capabilities will have the corresponding bits set.
-
-4.105 KVM_X86_SETUP_MCE
-
-Capability: KVM_CAP_MCE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: u64 mcg_cap (in)
-Returns: 0 on success,
- -EFAULT if u64 mcg_cap cannot be read,
- -EINVAL if the requested number of banks is invalid,
- -EINVAL if requested MCE capability is not supported.
-
-Initializes MCE support for use. The u64 mcg_cap parameter
-has the same format as the MSR_IA32_MCG_CAP register and
-specifies which capabilities should be enabled. The maximum
-supported number of error-reporting banks can be retrieved when
-checking for KVM_CAP_MCE. The supported capabilities can be
-retrieved with KVM_X86_GET_MCE_CAP_SUPPORTED.
-
-4.106 KVM_X86_SET_MCE
-
-Capability: KVM_CAP_MCE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_x86_mce (in)
-Returns: 0 on success,
- -EFAULT if struct kvm_x86_mce cannot be read,
- -EINVAL if the bank number is invalid,
- -EINVAL if VAL bit is not set in status field.
-
-Inject a machine check error (MCE) into the guest. The input
-parameter is:
-
-struct kvm_x86_mce {
- __u64 status;
- __u64 addr;
- __u64 misc;
- __u64 mcg_status;
- __u8 bank;
- __u8 pad1[7];
- __u64 pad2[3];
-};
-
-If the MCE being reported is an uncorrected error, KVM will
-inject it as an MCE exception into the guest. If the guest
-MCG_STATUS register reports that an MCE is in progress, KVM
-causes an KVM_EXIT_SHUTDOWN vmexit.
-
-Otherwise, if the MCE is a corrected error, KVM will just
-store it in the corresponding bank (provided this bank is
-not holding a previously reported uncorrected error).
-
-4.107 KVM_S390_GET_CMMA_BITS
-
-Capability: KVM_CAP_S390_CMMA_MIGRATION
-Architectures: s390
-Type: vm ioctl
-Parameters: struct kvm_s390_cmma_log (in, out)
-Returns: 0 on success, a negative value on error
-
-This ioctl is used to get the values of the CMMA bits on the s390
-architecture. It is meant to be used in two scenarios:
-- During live migration to save the CMMA values. Live migration needs
- to be enabled via the KVM_REQ_START_MIGRATION VM property.
-- To non-destructively peek at the CMMA values, with the flag
- KVM_S390_CMMA_PEEK set.
-
-The ioctl takes parameters via the kvm_s390_cmma_log struct. The desired
-values are written to a buffer whose location is indicated via the "values"
-member in the kvm_s390_cmma_log struct. The values in the input struct are
-also updated as needed.
-Each CMMA value takes up one byte.
-
-struct kvm_s390_cmma_log {
- __u64 start_gfn;
- __u32 count;
- __u32 flags;
- union {
- __u64 remaining;
- __u64 mask;
- };
- __u64 values;
-};
-
-start_gfn is the number of the first guest frame whose CMMA values are
-to be retrieved,
-
-count is the length of the buffer in bytes,
-
-values points to the buffer where the result will be written to.
-
-If count is greater than KVM_S390_SKEYS_MAX, then it is considered to be
-KVM_S390_SKEYS_MAX. KVM_S390_SKEYS_MAX is re-used for consistency with
-other ioctls.
-
-The result is written in the buffer pointed to by the field values, and
-the values of the input parameter are updated as follows.
-
-Depending on the flags, different actions are performed. The only
-supported flag so far is KVM_S390_CMMA_PEEK.
-
-The default behaviour if KVM_S390_CMMA_PEEK is not set is:
-start_gfn will indicate the first page frame whose CMMA bits were dirty.
-It is not necessarily the same as the one passed as input, as clean pages
-are skipped.
-
-count will indicate the number of bytes actually written in the buffer.
-It can (and very often will) be smaller than the input value, since the
-buffer is only filled until 16 bytes of clean values are found (which
-are then not copied in the buffer). Since a CMMA migration block needs
-the base address and the length, for a total of 16 bytes, we will send
-back some clean data if there is some dirty data afterwards, as long as
-the size of the clean data does not exceed the size of the header. This
-allows to minimize the amount of data to be saved or transferred over
-the network at the expense of more roundtrips to userspace. The next
-invocation of the ioctl will skip over all the clean values, saving
-potentially more than just the 16 bytes we found.
-
-If KVM_S390_CMMA_PEEK is set:
-the existing storage attributes are read even when not in migration
-mode, and no other action is performed;
-
-the output start_gfn will be equal to the input start_gfn,
-
-the output count will be equal to the input count, except if the end of
-memory has been reached.
-
-In both cases:
-the field "remaining" will indicate the total number of dirty CMMA values
-still remaining, or 0 if KVM_S390_CMMA_PEEK is set and migration mode is
-not enabled.
-
-mask is unused.
-
-values points to the userspace buffer where the result will be stored.
-
-This ioctl can fail with -ENOMEM if not enough memory can be allocated to
-complete the task, with -ENXIO if CMMA is not enabled, with -EINVAL if
-KVM_S390_CMMA_PEEK is not set but migration mode was not enabled, with
--EFAULT if the userspace address is invalid or if no page table is
-present for the addresses (e.g. when using hugepages).
-
-4.108 KVM_S390_SET_CMMA_BITS
-
-Capability: KVM_CAP_S390_CMMA_MIGRATION
-Architectures: s390
-Type: vm ioctl
-Parameters: struct kvm_s390_cmma_log (in)
-Returns: 0 on success, a negative value on error
-
-This ioctl is used to set the values of the CMMA bits on the s390
-architecture. It is meant to be used during live migration to restore
-the CMMA values, but there are no restrictions on its use.
-The ioctl takes parameters via the kvm_s390_cmma_values struct.
-Each CMMA value takes up one byte.
-
-struct kvm_s390_cmma_log {
- __u64 start_gfn;
- __u32 count;
- __u32 flags;
- union {
- __u64 remaining;
- __u64 mask;
- };
- __u64 values;
-};
-
-start_gfn indicates the starting guest frame number,
-
-count indicates how many values are to be considered in the buffer,
-
-flags is not used and must be 0.
-
-mask indicates which PGSTE bits are to be considered.
-
-remaining is not used.
-
-values points to the buffer in userspace where to store the values.
-
-This ioctl can fail with -ENOMEM if not enough memory can be allocated to
-complete the task, with -ENXIO if CMMA is not enabled, with -EINVAL if
-the count field is too large (e.g. more than KVM_S390_CMMA_SIZE_MAX) or
-if the flags field was not 0, with -EFAULT if the userspace address is
-invalid, if invalid pages are written to (e.g. after the end of memory)
-or if no page table is present for the addresses (e.g. when using
-hugepages).
-
-4.109 KVM_PPC_GET_CPU_CHAR
-
-Capability: KVM_CAP_PPC_GET_CPU_CHAR
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_ppc_cpu_char (out)
-Returns: 0 on successful completion
- -EFAULT if struct kvm_ppc_cpu_char cannot be written
-
-This ioctl gives userspace information about certain characteristics
-of the CPU relating to speculative execution of instructions and
-possible information leakage resulting from speculative execution (see
-CVE-2017-5715, CVE-2017-5753 and CVE-2017-5754). The information is
-returned in struct kvm_ppc_cpu_char, which looks like this:
-
-struct kvm_ppc_cpu_char {
- __u64 character; /* characteristics of the CPU */
- __u64 behaviour; /* recommended software behaviour */
- __u64 character_mask; /* valid bits in character */
- __u64 behaviour_mask; /* valid bits in behaviour */
-};
-
-For extensibility, the character_mask and behaviour_mask fields
-indicate which bits of character and behaviour have been filled in by
-the kernel. If the set of defined bits is extended in future then
-userspace will be able to tell whether it is running on a kernel that
-knows about the new bits.
-
-The character field describes attributes of the CPU which can help
-with preventing inadvertent information disclosure - specifically,
-whether there is an instruction to flash-invalidate the L1 data cache
-(ori 30,30,0 or mtspr SPRN_TRIG2,rN), whether the L1 data cache is set
-to a mode where entries can only be used by the thread that created
-them, whether the bcctr[l] instruction prevents speculation, and
-whether a speculation barrier instruction (ori 31,31,0) is provided.
-
-The behaviour field describes actions that software should take to
-prevent inadvertent information disclosure, and thus describes which
-vulnerabilities the hardware is subject to; specifically whether the
-L1 data cache should be flushed when returning to user mode from the
-kernel, and whether a speculation barrier should be placed between an
-array bounds check and the array access.
-
-These fields use the same bit definitions as the new
-H_GET_CPU_CHARACTERISTICS hypercall.
-
-4.110 KVM_MEMORY_ENCRYPT_OP
-
-Capability: basic
-Architectures: x86
-Type: system
-Parameters: an opaque platform specific structure (in/out)
-Returns: 0 on success; -1 on error
-
-If the platform supports creating encrypted VMs then this ioctl can be used
-for issuing platform-specific memory encryption commands to manage those
-encrypted VMs.
-
-Currently, this ioctl is used for issuing Secure Encrypted Virtualization
-(SEV) commands on AMD Processors. The SEV commands are defined in
-Documentation/virtual/kvm/amd-memory-encryption.rst.
-
-4.111 KVM_MEMORY_ENCRYPT_REG_REGION
-
-Capability: basic
-Architectures: x86
-Type: system
-Parameters: struct kvm_enc_region (in)
-Returns: 0 on success; -1 on error
-
-This ioctl can be used to register a guest memory region which may
-contain encrypted data (e.g. guest RAM, SMRAM etc).
-
-It is used in the SEV-enabled guest. When encryption is enabled, a guest
-memory region may contain encrypted data. The SEV memory encryption
-engine uses a tweak such that two identical plaintext pages, each at
-different locations will have differing ciphertexts. So swapping or
-moving ciphertext of those pages will not result in plaintext being
-swapped. So relocating (or migrating) physical backing pages for the SEV
-guest will require some additional steps.
-
-Note: The current SEV key management spec does not provide commands to
-swap or migrate (move) ciphertext pages. Hence, for now we pin the guest
-memory region registered with the ioctl.
-
-4.112 KVM_MEMORY_ENCRYPT_UNREG_REGION
-
-Capability: basic
-Architectures: x86
-Type: system
-Parameters: struct kvm_enc_region (in)
-Returns: 0 on success; -1 on error
-
-This ioctl can be used to unregister the guest memory region registered
-with KVM_MEMORY_ENCRYPT_REG_REGION ioctl above.
-
-4.113 KVM_HYPERV_EVENTFD
-
-Capability: KVM_CAP_HYPERV_EVENTFD
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_hyperv_eventfd (in)
-
-This ioctl (un)registers an eventfd to receive notifications from the guest on
-the specified Hyper-V connection id through the SIGNAL_EVENT hypercall, without
-causing a user exit. SIGNAL_EVENT hypercall with non-zero event flag number
-(bits 24-31) still triggers a KVM_EXIT_HYPERV_HCALL user exit.
-
-struct kvm_hyperv_eventfd {
- __u32 conn_id;
- __s32 fd;
- __u32 flags;
- __u32 padding[3];
-};
-
-The conn_id field should fit within 24 bits:
-
-#define KVM_HYPERV_CONN_ID_MASK 0x00ffffff
-
-The acceptable values for the flags field are:
-
-#define KVM_HYPERV_EVENTFD_DEASSIGN (1 << 0)
-
-Returns: 0 on success,
- -EINVAL if conn_id or flags is outside the allowed range
- -ENOENT on deassign if the conn_id isn't registered
- -EEXIST on assign if the conn_id is already registered
-
-4.114 KVM_GET_NESTED_STATE
-
-Capability: KVM_CAP_NESTED_STATE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_nested_state (in/out)
-Returns: 0 on success, -1 on error
-Errors:
- E2BIG: the total state size exceeds the value of 'size' specified by
- the user; the size required will be written into size.
-
-struct kvm_nested_state {
- __u16 flags;
- __u16 format;
- __u32 size;
-
- union {
- struct kvm_vmx_nested_state_hdr vmx;
- struct kvm_svm_nested_state_hdr svm;
-
- /* Pad the header to 128 bytes. */
- __u8 pad[120];
- } hdr;
-
- union {
- struct kvm_vmx_nested_state_data vmx[0];
- struct kvm_svm_nested_state_data svm[0];
- } data;
-};
-
-#define KVM_STATE_NESTED_GUEST_MODE 0x00000001
-#define KVM_STATE_NESTED_RUN_PENDING 0x00000002
-#define KVM_STATE_NESTED_EVMCS 0x00000004
-
-#define KVM_STATE_NESTED_FORMAT_VMX 0
-#define KVM_STATE_NESTED_FORMAT_SVM 1
-
-#define KVM_STATE_NESTED_VMX_VMCS_SIZE 0x1000
-
-#define KVM_STATE_NESTED_VMX_SMM_GUEST_MODE 0x00000001
-#define KVM_STATE_NESTED_VMX_SMM_VMXON 0x00000002
-
-struct kvm_vmx_nested_state_hdr {
- __u64 vmxon_pa;
- __u64 vmcs12_pa;
-
- struct {
- __u16 flags;
- } smm;
-};
-
-struct kvm_vmx_nested_state_data {
- __u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
- __u8 shadow_vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
-};
-
-This ioctl copies the vcpu's nested virtualization state from the kernel to
-userspace.
-
-The maximum size of the state can be retrieved by passing KVM_CAP_NESTED_STATE
-to the KVM_CHECK_EXTENSION ioctl().
-
-4.115 KVM_SET_NESTED_STATE
-
-Capability: KVM_CAP_NESTED_STATE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_nested_state (in)
-Returns: 0 on success, -1 on error
-
-This copies the vcpu's kvm_nested_state struct from userspace to the kernel.
-For the definition of struct kvm_nested_state, see KVM_GET_NESTED_STATE.
-
-4.116 KVM_(UN)REGISTER_COALESCED_MMIO
-
-Capability: KVM_CAP_COALESCED_MMIO (for coalesced mmio)
- KVM_CAP_COALESCED_PIO (for coalesced pio)
-Architectures: all
-Type: vm ioctl
-Parameters: struct kvm_coalesced_mmio_zone
-Returns: 0 on success, < 0 on error
-
-Coalesced I/O is a performance optimization that defers hardware
-register write emulation so that userspace exits are avoided. It is
-typically used to reduce the overhead of emulating frequently accessed
-hardware registers.
-
-When a hardware register is configured for coalesced I/O, write accesses
-do not exit to userspace and their value is recorded in a ring buffer
-that is shared between kernel and userspace.
-
-Coalesced I/O is used if one or more write accesses to a hardware
-register can be deferred until a read or a write to another hardware
-register on the same device. This last access will cause a vmexit and
-userspace will process accesses from the ring buffer before emulating
-it. That will avoid exiting to userspace on repeated writes.
-
-Coalesced pio is based on coalesced mmio. There is little difference
-between coalesced mmio and pio except that coalesced pio records accesses
-to I/O ports.
-
-4.117 KVM_CLEAR_DIRTY_LOG (vm ioctl)
-
-Capability: KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
-Architectures: x86, arm, arm64, mips
-Type: vm ioctl
-Parameters: struct kvm_dirty_log (in)
-Returns: 0 on success, -1 on error
-
-/* for KVM_CLEAR_DIRTY_LOG */
-struct kvm_clear_dirty_log {
- __u32 slot;
- __u32 num_pages;
- __u64 first_page;
- union {
- void __user *dirty_bitmap; /* one bit per page */
- __u64 padding;
- };
-};
-
-The ioctl clears the dirty status of pages in a memory slot, according to
-the bitmap that is passed in struct kvm_clear_dirty_log's dirty_bitmap
-field. Bit 0 of the bitmap corresponds to page "first_page" in the
-memory slot, and num_pages is the size in bits of the input bitmap.
-first_page must be a multiple of 64; num_pages must also be a multiple of
-64 unless first_page + num_pages is the size of the memory slot. For each
-bit that is set in the input bitmap, the corresponding page is marked "clean"
-in KVM's dirty bitmap, and dirty tracking is re-enabled for that page
-(for example via write-protection, or by clearing the dirty bit in
-a page table entry).
-
-If KVM_CAP_MULTI_ADDRESS_SPACE is available, bits 16-31 specifies
-the address space for which you want to return the dirty bitmap.
-They must be less than the value that KVM_CHECK_EXTENSION returns for
-the KVM_CAP_MULTI_ADDRESS_SPACE capability.
-
-This ioctl is mostly useful when KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
-is enabled; for more information, see the description of the capability.
-However, it can always be used as long as KVM_CHECK_EXTENSION confirms
-that KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is present.
-
-4.118 KVM_GET_SUPPORTED_HV_CPUID
-
-Capability: KVM_CAP_HYPERV_CPUID
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_cpuid2 (in/out)
-Returns: 0 on success, -1 on error
-
-struct kvm_cpuid2 {
- __u32 nent;
- __u32 padding;
- struct kvm_cpuid_entry2 entries[0];
-};
-
-struct kvm_cpuid_entry2 {
- __u32 function;
- __u32 index;
- __u32 flags;
- __u32 eax;
- __u32 ebx;
- __u32 ecx;
- __u32 edx;
- __u32 padding[3];
-};
-
-This ioctl returns x86 cpuid features leaves related to Hyper-V emulation in
-KVM. Userspace can use the information returned by this ioctl to construct
-cpuid information presented to guests consuming Hyper-V enlightenments (e.g.
-Windows or Hyper-V guests).
-
-CPUID feature leaves returned by this ioctl are defined by Hyper-V Top Level
-Functional Specification (TLFS). These leaves can't be obtained with
-KVM_GET_SUPPORTED_CPUID ioctl because some of them intersect with KVM feature
-leaves (0x40000000, 0x40000001).
-
-Currently, the following list of CPUID leaves are returned:
- HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS
- HYPERV_CPUID_INTERFACE
- HYPERV_CPUID_VERSION
- HYPERV_CPUID_FEATURES
- HYPERV_CPUID_ENLIGHTMENT_INFO
- HYPERV_CPUID_IMPLEMENT_LIMITS
- HYPERV_CPUID_NESTED_FEATURES
-
-HYPERV_CPUID_NESTED_FEATURES leaf is only exposed when Enlightened VMCS was
-enabled on the corresponding vCPU (KVM_CAP_HYPERV_ENLIGHTENED_VMCS).
-
-Userspace invokes KVM_GET_SUPPORTED_CPUID by passing a kvm_cpuid2 structure
-with the 'nent' field indicating the number of entries in the variable-size
-array 'entries'. If the number of entries is too low to describe all Hyper-V
-feature leaves, an error (E2BIG) is returned. If the number is more or equal
-to the number of Hyper-V feature leaves, the 'nent' field is adjusted to the
-number of valid entries in the 'entries' array, which is then filled.
-
-'index' and 'flags' fields in 'struct kvm_cpuid_entry2' are currently reserved,
-userspace should not expect to get any particular value there.
-
-4.119 KVM_ARM_VCPU_FINALIZE
-
-Architectures: arm, arm64
-Type: vcpu ioctl
-Parameters: int feature (in)
-Returns: 0 on success, -1 on error
-Errors:
- EPERM: feature not enabled, needs configuration, or already finalized
- EINVAL: feature unknown or not present
-
-Recognised values for feature:
- arm64 KVM_ARM_VCPU_SVE (requires KVM_CAP_ARM_SVE)
-
-Finalizes the configuration of the specified vcpu feature.
-
-The vcpu must already have been initialised, enabling the affected feature, by
-means of a successful KVM_ARM_VCPU_INIT call with the appropriate flag set in
-features[].
-
-For affected vcpu features, this is a mandatory step that must be performed
-before the vcpu is fully usable.
-
-Between KVM_ARM_VCPU_INIT and KVM_ARM_VCPU_FINALIZE, the feature may be
-configured by use of ioctls such as KVM_SET_ONE_REG. The exact configuration
-that should be performaned and how to do it are feature-dependent.
-
-Other calls that depend on a particular feature being finalized, such as
-KVM_RUN, KVM_GET_REG_LIST, KVM_GET_ONE_REG and KVM_SET_ONE_REG, will fail with
--EPERM unless the feature has already been finalized by means of a
-KVM_ARM_VCPU_FINALIZE call.
-
-See KVM_ARM_VCPU_INIT for details of vcpu features that require finalization
-using this ioctl.
-
-4.120 KVM_SET_PMU_EVENT_FILTER
-
-Capability: KVM_CAP_PMU_EVENT_FILTER
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_pmu_event_filter (in)
-Returns: 0 on success, -1 on error
-
-struct kvm_pmu_event_filter {
- __u32 action;
- __u32 nevents;
- __u32 fixed_counter_bitmap;
- __u32 flags;
- __u32 pad[4];
- __u64 events[0];
-};
-
-This ioctl restricts the set of PMU events that the guest can program.
-The argument holds a list of events which will be allowed or denied.
-The eventsel+umask of each event the guest attempts to program is compared
-against the events field to determine whether the guest should have access.
-The events field only controls general purpose counters; fixed purpose
-counters are controlled by the fixed_counter_bitmap.
-
-No flags are defined yet, the field must be zero.
-
-Valid values for 'action':
-#define KVM_PMU_EVENT_ALLOW 0
-#define KVM_PMU_EVENT_DENY 1
-
-
-5. The kvm_run structure
-------------------------
-
-Application code obtains a pointer to the kvm_run structure by
-mmap()ing a vcpu fd. From that point, application code can control
-execution by changing fields in kvm_run prior to calling the KVM_RUN
-ioctl, and obtain information about the reason KVM_RUN returned by
-looking up structure members.
-
-struct kvm_run {
- /* in */
- __u8 request_interrupt_window;
-
-Request that KVM_RUN return when it becomes possible to inject external
-interrupts into the guest. Useful in conjunction with KVM_INTERRUPT.
-
- __u8 immediate_exit;
-
-This field is polled once when KVM_RUN starts; if non-zero, KVM_RUN
-exits immediately, returning -EINTR. In the common scenario where a
-signal is used to "kick" a VCPU out of KVM_RUN, this field can be used
-to avoid usage of KVM_SET_SIGNAL_MASK, which has worse scalability.
-Rather than blocking the signal outside KVM_RUN, userspace can set up
-a signal handler that sets run->immediate_exit to a non-zero value.
-
-This field is ignored if KVM_CAP_IMMEDIATE_EXIT is not available.
-
- __u8 padding1[6];
-
- /* out */
- __u32 exit_reason;
-
-When KVM_RUN has returned successfully (return value 0), this informs
-application code why KVM_RUN has returned. Allowable values for this
-field are detailed below.
-
- __u8 ready_for_interrupt_injection;
-
-If request_interrupt_window has been specified, this field indicates
-an interrupt can be injected now with KVM_INTERRUPT.
-
- __u8 if_flag;
-
-The value of the current interrupt flag. Only valid if in-kernel
-local APIC is not used.
-
- __u16 flags;
-
-More architecture-specific flags detailing state of the VCPU that may
-affect the device's behavior. The only currently defined flag is
-KVM_RUN_X86_SMM, which is valid on x86 machines and is set if the
-VCPU is in system management mode.
-
- /* in (pre_kvm_run), out (post_kvm_run) */
- __u64 cr8;
-
-The value of the cr8 register. Only valid if in-kernel local APIC is
-not used. Both input and output.
-
- __u64 apic_base;
-
-The value of the APIC BASE msr. Only valid if in-kernel local
-APIC is not used. Both input and output.
-
- union {
- /* KVM_EXIT_UNKNOWN */
- struct {
- __u64 hardware_exit_reason;
- } hw;
-
-If exit_reason is KVM_EXIT_UNKNOWN, the vcpu has exited due to unknown
-reasons. Further architecture-specific information is available in
-hardware_exit_reason.
-
- /* KVM_EXIT_FAIL_ENTRY */
- struct {
- __u64 hardware_entry_failure_reason;
- } fail_entry;
-
-If exit_reason is KVM_EXIT_FAIL_ENTRY, the vcpu could not be run due
-to unknown reasons. Further architecture-specific information is
-available in hardware_entry_failure_reason.
-
- /* KVM_EXIT_EXCEPTION */
- struct {
- __u32 exception;
- __u32 error_code;
- } ex;
-
-Unused.
-
- /* KVM_EXIT_IO */
- struct {
-#define KVM_EXIT_IO_IN 0
-#define KVM_EXIT_IO_OUT 1
- __u8 direction;
- __u8 size; /* bytes */
- __u16 port;
- __u32 count;
- __u64 data_offset; /* relative to kvm_run start */
- } io;
-
-If exit_reason is KVM_EXIT_IO, then the vcpu has
-executed a port I/O instruction which could not be satisfied by kvm.
-data_offset describes where the data is located (KVM_EXIT_IO_OUT) or
-where kvm expects application code to place the data for the next
-KVM_RUN invocation (KVM_EXIT_IO_IN). Data format is a packed array.
-
- /* KVM_EXIT_DEBUG */
- struct {
- struct kvm_debug_exit_arch arch;
- } debug;
-
-If the exit_reason is KVM_EXIT_DEBUG, then a vcpu is processing a debug event
-for which architecture specific information is returned.
-
- /* KVM_EXIT_MMIO */
- struct {
- __u64 phys_addr;
- __u8 data[8];
- __u32 len;
- __u8 is_write;
- } mmio;
-
-If exit_reason is KVM_EXIT_MMIO, then the vcpu has
-executed a memory-mapped I/O instruction which could not be satisfied
-by kvm. The 'data' member contains the written data if 'is_write' is
-true, and should be filled by application code otherwise.
-
-The 'data' member contains, in its first 'len' bytes, the value as it would
-appear if the VCPU performed a load or store of the appropriate width directly
-to the byte array.
-
-NOTE: For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR and
- KVM_EXIT_EPR the corresponding
-operations are complete (and guest state is consistent) only after userspace
-has re-entered the kernel with KVM_RUN. The kernel side will first finish
-incomplete operations and then check for pending signals. Userspace
-can re-enter the guest with an unmasked signal pending to complete
-pending operations.
-
- /* KVM_EXIT_HYPERCALL */
- struct {
- __u64 nr;
- __u64 args[6];
- __u64 ret;
- __u32 longmode;
- __u32 pad;
- } hypercall;
-
-Unused. This was once used for 'hypercall to userspace'. To implement
-such functionality, use KVM_EXIT_IO (x86) or KVM_EXIT_MMIO (all except s390).
-Note KVM_EXIT_IO is significantly faster than KVM_EXIT_MMIO.
-
- /* KVM_EXIT_TPR_ACCESS */
- struct {
- __u64 rip;
- __u32 is_write;
- __u32 pad;
- } tpr_access;
-
-To be documented (KVM_TPR_ACCESS_REPORTING).
-
- /* KVM_EXIT_S390_SIEIC */
- struct {
- __u8 icptcode;
- __u64 mask; /* psw upper half */
- __u64 addr; /* psw lower half */
- __u16 ipa;
- __u32 ipb;
- } s390_sieic;
-
-s390 specific.
-
- /* KVM_EXIT_S390_RESET */
-#define KVM_S390_RESET_POR 1
-#define KVM_S390_RESET_CLEAR 2
-#define KVM_S390_RESET_SUBSYSTEM 4
-#define KVM_S390_RESET_CPU_INIT 8
-#define KVM_S390_RESET_IPL 16
- __u64 s390_reset_flags;
-
-s390 specific.
-
- /* KVM_EXIT_S390_UCONTROL */
- struct {
- __u64 trans_exc_code;
- __u32 pgm_code;
- } s390_ucontrol;
-
-s390 specific. A page fault has occurred for a user controlled virtual
-machine (KVM_VM_S390_UNCONTROL) on it's host page table that cannot be
-resolved by the kernel.
-The program code and the translation exception code that were placed
-in the cpu's lowcore are presented here as defined by the z Architecture
-Principles of Operation Book in the Chapter for Dynamic Address Translation
-(DAT)
-
- /* KVM_EXIT_DCR */
- struct {
- __u32 dcrn;
- __u32 data;
- __u8 is_write;
- } dcr;
-
-Deprecated - was used for 440 KVM.
-
- /* KVM_EXIT_OSI */
- struct {
- __u64 gprs[32];
- } osi;
-
-MOL uses a special hypercall interface it calls 'OSI'. To enable it, we catch
-hypercalls and exit with this exit struct that contains all the guest gprs.
-
-If exit_reason is KVM_EXIT_OSI, then the vcpu has triggered such a hypercall.
-Userspace can now handle the hypercall and when it's done modify the gprs as
-necessary. Upon guest entry all guest GPRs will then be replaced by the values
-in this struct.
-
- /* KVM_EXIT_PAPR_HCALL */
- struct {
- __u64 nr;
- __u64 ret;
- __u64 args[9];
- } papr_hcall;
-
-This is used on 64-bit PowerPC when emulating a pSeries partition,
-e.g. with the 'pseries' machine type in qemu. It occurs when the
-guest does a hypercall using the 'sc 1' instruction. The 'nr' field
-contains the hypercall number (from the guest R3), and 'args' contains
-the arguments (from the guest R4 - R12). Userspace should put the
-return code in 'ret' and any extra returned values in args[].
-The possible hypercalls are defined in the Power Architecture Platform
-Requirements (PAPR) document available from www.power.org (free
-developer registration required to access it).
-
- /* KVM_EXIT_S390_TSCH */
- struct {
- __u16 subchannel_id;
- __u16 subchannel_nr;
- __u32 io_int_parm;
- __u32 io_int_word;
- __u32 ipb;
- __u8 dequeued;
- } s390_tsch;
-
-s390 specific. This exit occurs when KVM_CAP_S390_CSS_SUPPORT has been enabled
-and TEST SUBCHANNEL was intercepted. If dequeued is set, a pending I/O
-interrupt for the target subchannel has been dequeued and subchannel_id,
-subchannel_nr, io_int_parm and io_int_word contain the parameters for that
-interrupt. ipb is needed for instruction parameter decoding.
-
- /* KVM_EXIT_EPR */
- struct {
- __u32 epr;
- } epr;
-
-On FSL BookE PowerPC chips, the interrupt controller has a fast patch
-interrupt acknowledge path to the core. When the core successfully
-delivers an interrupt, it automatically populates the EPR register with
-the interrupt vector number and acknowledges the interrupt inside
-the interrupt controller.
-
-In case the interrupt controller lives in user space, we need to do
-the interrupt acknowledge cycle through it to fetch the next to be
-delivered interrupt vector using this exit.
-
-It gets triggered whenever both KVM_CAP_PPC_EPR are enabled and an
-external interrupt has just been delivered into the guest. User space
-should put the acknowledged interrupt vector into the 'epr' field.
-
- /* KVM_EXIT_SYSTEM_EVENT */
- struct {
-#define KVM_SYSTEM_EVENT_SHUTDOWN 1
-#define KVM_SYSTEM_EVENT_RESET 2
-#define KVM_SYSTEM_EVENT_CRASH 3
- __u32 type;
- __u64 flags;
- } system_event;
-
-If exit_reason is KVM_EXIT_SYSTEM_EVENT then the vcpu has triggered
-a system-level event using some architecture specific mechanism (hypercall
-or some special instruction). In case of ARM/ARM64, this is triggered using
-HVC instruction based PSCI call from the vcpu. The 'type' field describes
-the system-level event type. The 'flags' field describes architecture
-specific flags for the system-level event.
-
-Valid values for 'type' are:
- KVM_SYSTEM_EVENT_SHUTDOWN -- the guest has requested a shutdown of the
- VM. Userspace is not obliged to honour this, and if it does honour
- this does not need to destroy the VM synchronously (ie it may call
- KVM_RUN again before shutdown finally occurs).
- KVM_SYSTEM_EVENT_RESET -- the guest has requested a reset of the VM.
- As with SHUTDOWN, userspace can choose to ignore the request, or
- to schedule the reset to occur in the future and may call KVM_RUN again.
- KVM_SYSTEM_EVENT_CRASH -- the guest crash occurred and the guest
- has requested a crash condition maintenance. Userspace can choose
- to ignore the request, or to gather VM memory core dump and/or
- reset/shutdown of the VM.
-
- /* KVM_EXIT_IOAPIC_EOI */
- struct {
- __u8 vector;
- } eoi;
-
-Indicates that the VCPU's in-kernel local APIC received an EOI for a
-level-triggered IOAPIC interrupt. This exit only triggers when the
-IOAPIC is implemented in userspace (i.e. KVM_CAP_SPLIT_IRQCHIP is enabled);
-the userspace IOAPIC should process the EOI and retrigger the interrupt if
-it is still asserted. Vector is the LAPIC interrupt vector for which the
-EOI was received.
-
- struct kvm_hyperv_exit {
-#define KVM_EXIT_HYPERV_SYNIC 1
-#define KVM_EXIT_HYPERV_HCALL 2
- __u32 type;
- union {
- struct {
- __u32 msr;
- __u64 control;
- __u64 evt_page;
- __u64 msg_page;
- } synic;
- struct {
- __u64 input;
- __u64 result;
- __u64 params[2];
- } hcall;
- } u;
- };
- /* KVM_EXIT_HYPERV */
- struct kvm_hyperv_exit hyperv;
-Indicates that the VCPU exits into userspace to process some tasks
-related to Hyper-V emulation.
-Valid values for 'type' are:
- KVM_EXIT_HYPERV_SYNIC -- synchronously notify user-space about
-Hyper-V SynIC state change. Notification is used to remap SynIC
-event/message pages and to enable/disable SynIC messages/events processing
-in userspace.
-
- /* Fix the size of the union. */
- char padding[256];
- };
-
- /*
- * shared registers between kvm and userspace.
- * kvm_valid_regs specifies the register classes set by the host
- * kvm_dirty_regs specified the register classes dirtied by userspace
- * struct kvm_sync_regs is architecture specific, as well as the
- * bits for kvm_valid_regs and kvm_dirty_regs
- */
- __u64 kvm_valid_regs;
- __u64 kvm_dirty_regs;
- union {
- struct kvm_sync_regs regs;
- char padding[SYNC_REGS_SIZE_BYTES];
- } s;
-
-If KVM_CAP_SYNC_REGS is defined, these fields allow userspace to access
-certain guest registers without having to call SET/GET_*REGS. Thus we can
-avoid some system call overhead if userspace has to handle the exit.
-Userspace can query the validity of the structure by checking
-kvm_valid_regs for specific bits. These bits are architecture specific
-and usually define the validity of a groups of registers. (e.g. one bit
- for general purpose registers)
-
-Please note that the kernel is allowed to use the kvm_run structure as the
-primary storage for certain register types. Therefore, the kernel may use the
-values in kvm_run even if the corresponding bit in kvm_dirty_regs is not set.
-
-};
-
-
-
-6. Capabilities that can be enabled on vCPUs
---------------------------------------------
-
-There are certain capabilities that change the behavior of the virtual CPU or
-the virtual machine when enabled. To enable them, please see section 4.37.
-Below you can find a list of capabilities and what their effect on the vCPU or
-the virtual machine is when enabling them.
-
-The following information is provided along with the description:
-
- Architectures: which instruction set architectures provide this ioctl.
- x86 includes both i386 and x86_64.
-
- Target: whether this is a per-vcpu or per-vm capability.
-
- Parameters: what parameters are accepted by the capability.
-
- Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
- are not detailed, but errors with specific meanings are.
-
-
-6.1 KVM_CAP_PPC_OSI
-
-Architectures: ppc
-Target: vcpu
-Parameters: none
-Returns: 0 on success; -1 on error
-
-This capability enables interception of OSI hypercalls that otherwise would
-be treated as normal system calls to be injected into the guest. OSI hypercalls
-were invented by Mac-on-Linux to have a standardized communication mechanism
-between the guest and the host.
-
-When this capability is enabled, KVM_EXIT_OSI can occur.
-
-
-6.2 KVM_CAP_PPC_PAPR
-
-Architectures: ppc
-Target: vcpu
-Parameters: none
-Returns: 0 on success; -1 on error
-
-This capability enables interception of PAPR hypercalls. PAPR hypercalls are
-done using the hypercall instruction "sc 1".
-
-It also sets the guest privilege level to "supervisor" mode. Usually the guest
-runs in "hypervisor" privilege mode with a few missing features.
-
-In addition to the above, it changes the semantics of SDR1. In this mode, the
-HTAB address part of SDR1 contains an HVA instead of a GPA, as PAPR keeps the
-HTAB invisible to the guest.
-
-When this capability is enabled, KVM_EXIT_PAPR_HCALL can occur.
-
-
-6.3 KVM_CAP_SW_TLB
-
-Architectures: ppc
-Target: vcpu
-Parameters: args[0] is the address of a struct kvm_config_tlb
-Returns: 0 on success; -1 on error
-
-struct kvm_config_tlb {
- __u64 params;
- __u64 array;
- __u32 mmu_type;
- __u32 array_len;
-};
-
-Configures the virtual CPU's TLB array, establishing a shared memory area
-between userspace and KVM. The "params" and "array" fields are userspace
-addresses of mmu-type-specific data structures. The "array_len" field is an
-safety mechanism, and should be set to the size in bytes of the memory that
-userspace has reserved for the array. It must be at least the size dictated
-by "mmu_type" and "params".
-
-While KVM_RUN is active, the shared region is under control of KVM. Its
-contents are undefined, and any modification by userspace results in
-boundedly undefined behavior.
-
-On return from KVM_RUN, the shared region will reflect the current state of
-the guest's TLB. If userspace makes any changes, it must call KVM_DIRTY_TLB
-to tell KVM which entries have been changed, prior to calling KVM_RUN again
-on this vcpu.
-
-For mmu types KVM_MMU_FSL_BOOKE_NOHV and KVM_MMU_FSL_BOOKE_HV:
- - The "params" field is of type "struct kvm_book3e_206_tlb_params".
- - The "array" field points to an array of type "struct
- kvm_book3e_206_tlb_entry".
- - The array consists of all entries in the first TLB, followed by all
- entries in the second TLB.
- - Within a TLB, entries are ordered first by increasing set number. Within a
- set, entries are ordered by way (increasing ESEL).
- - The hash for determining set number in TLB0 is: (MAS2 >> 12) & (num_sets - 1)
- where "num_sets" is the tlb_sizes[] value divided by the tlb_ways[] value.
- - The tsize field of mas1 shall be set to 4K on TLB0, even though the
- hardware ignores this value for TLB0.
-
-6.4 KVM_CAP_S390_CSS_SUPPORT
-
-Architectures: s390
-Target: vcpu
-Parameters: none
-Returns: 0 on success; -1 on error
-
-This capability enables support for handling of channel I/O instructions.
-
-TEST PENDING INTERRUPTION and the interrupt portion of TEST SUBCHANNEL are
-handled in-kernel, while the other I/O instructions are passed to userspace.
-
-When this capability is enabled, KVM_EXIT_S390_TSCH will occur on TEST
-SUBCHANNEL intercepts.
-
-Note that even though this capability is enabled per-vcpu, the complete
-virtual machine is affected.
-
-6.5 KVM_CAP_PPC_EPR
-
-Architectures: ppc
-Target: vcpu
-Parameters: args[0] defines whether the proxy facility is active
-Returns: 0 on success; -1 on error
-
-This capability enables or disables the delivery of interrupts through the
-external proxy facility.
-
-When enabled (args[0] != 0), every time the guest gets an external interrupt
-delivered, it automatically exits into user space with a KVM_EXIT_EPR exit
-to receive the topmost interrupt vector.
-
-When disabled (args[0] == 0), behavior is as if this facility is unsupported.
-
-When this capability is enabled, KVM_EXIT_EPR can occur.
-
-6.6 KVM_CAP_IRQ_MPIC
-
-Architectures: ppc
-Parameters: args[0] is the MPIC device fd
- args[1] is the MPIC CPU number for this vcpu
-
-This capability connects the vcpu to an in-kernel MPIC device.
-
-6.7 KVM_CAP_IRQ_XICS
-
-Architectures: ppc
-Target: vcpu
-Parameters: args[0] is the XICS device fd
- args[1] is the XICS CPU number (server ID) for this vcpu
-
-This capability connects the vcpu to an in-kernel XICS device.
-
-6.8 KVM_CAP_S390_IRQCHIP
-
-Architectures: s390
-Target: vm
-Parameters: none
-
-This capability enables the in-kernel irqchip for s390. Please refer to
-"4.24 KVM_CREATE_IRQCHIP" for details.
-
-6.9 KVM_CAP_MIPS_FPU
-
-Architectures: mips
-Target: vcpu
-Parameters: args[0] is reserved for future use (should be 0).
-
-This capability allows the use of the host Floating Point Unit by the guest. It
-allows the Config1.FP bit to be set to enable the FPU in the guest. Once this is
-done the KVM_REG_MIPS_FPR_* and KVM_REG_MIPS_FCR_* registers can be accessed
-(depending on the current guest FPU register mode), and the Status.FR,
-Config5.FRE bits are accessible via the KVM API and also from the guest,
-depending on them being supported by the FPU.
-
-6.10 KVM_CAP_MIPS_MSA
-
-Architectures: mips
-Target: vcpu
-Parameters: args[0] is reserved for future use (should be 0).
-
-This capability allows the use of the MIPS SIMD Architecture (MSA) by the guest.
-It allows the Config3.MSAP bit to be set to enable the use of MSA by the guest.
-Once this is done the KVM_REG_MIPS_VEC_* and KVM_REG_MIPS_MSA_* registers can be
-accessed, and the Config5.MSAEn bit is accessible via the KVM API and also from
-the guest.
-
-6.74 KVM_CAP_SYNC_REGS
-Architectures: s390, x86
-Target: s390: always enabled, x86: vcpu
-Parameters: none
-Returns: x86: KVM_CHECK_EXTENSION returns a bit-array indicating which register
-sets are supported (bitfields defined in arch/x86/include/uapi/asm/kvm.h).
-
-As described above in the kvm_sync_regs struct info in section 5 (kvm_run):
-KVM_CAP_SYNC_REGS "allow[s] userspace to access certain guest registers
-without having to call SET/GET_*REGS". This reduces overhead by eliminating
-repeated ioctl calls for setting and/or getting register values. This is
-particularly important when userspace is making synchronous guest state
-modifications, e.g. when emulating and/or intercepting instructions in
-userspace.
-
-For s390 specifics, please refer to the source code.
-
-For x86:
-- the register sets to be copied out to kvm_run are selectable
- by userspace (rather that all sets being copied out for every exit).
-- vcpu_events are available in addition to regs and sregs.
-
-For x86, the 'kvm_valid_regs' field of struct kvm_run is overloaded to
-function as an input bit-array field set by userspace to indicate the
-specific register sets to be copied out on the next exit.
-
-To indicate when userspace has modified values that should be copied into
-the vCPU, the all architecture bitarray field, 'kvm_dirty_regs' must be set.
-This is done using the same bitflags as for the 'kvm_valid_regs' field.
-If the dirty bit is not set, then the register set values will not be copied
-into the vCPU even if they've been modified.
-
-Unused bitfields in the bitarrays must be set to zero.
-
-struct kvm_sync_regs {
- struct kvm_regs regs;
- struct kvm_sregs sregs;
- struct kvm_vcpu_events events;
-};
-
-6.75 KVM_CAP_PPC_IRQ_XIVE
-
-Architectures: ppc
-Target: vcpu
-Parameters: args[0] is the XIVE device fd
- args[1] is the XIVE CPU number (server ID) for this vcpu
-
-This capability connects the vcpu to an in-kernel XIVE device.
-
-7. Capabilities that can be enabled on VMs
-------------------------------------------
-
-There are certain capabilities that change the behavior of the virtual
-machine when enabled. To enable them, please see section 4.37. Below
-you can find a list of capabilities and what their effect on the VM
-is when enabling them.
-
-The following information is provided along with the description:
-
- Architectures: which instruction set architectures provide this ioctl.
- x86 includes both i386 and x86_64.
-
- Parameters: what parameters are accepted by the capability.
-
- Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
- are not detailed, but errors with specific meanings are.
-
-
-7.1 KVM_CAP_PPC_ENABLE_HCALL
-
-Architectures: ppc
-Parameters: args[0] is the sPAPR hcall number
- args[1] is 0 to disable, 1 to enable in-kernel handling
-
-This capability controls whether individual sPAPR hypercalls (hcalls)
-get handled by the kernel or not. Enabling or disabling in-kernel
-handling of an hcall is effective across the VM. On creation, an
-initial set of hcalls are enabled for in-kernel handling, which
-consists of those hcalls for which in-kernel handlers were implemented
-before this capability was implemented. If disabled, the kernel will
-not to attempt to handle the hcall, but will always exit to userspace
-to handle it. Note that it may not make sense to enable some and
-disable others of a group of related hcalls, but KVM does not prevent
-userspace from doing that.
-
-If the hcall number specified is not one that has an in-kernel
-implementation, the KVM_ENABLE_CAP ioctl will fail with an EINVAL
-error.
-
-7.2 KVM_CAP_S390_USER_SIGP
-
-Architectures: s390
-Parameters: none
-
-This capability controls which SIGP orders will be handled completely in user
-space. With this capability enabled, all fast orders will be handled completely
-in the kernel:
-- SENSE
-- SENSE RUNNING
-- EXTERNAL CALL
-- EMERGENCY SIGNAL
-- CONDITIONAL EMERGENCY SIGNAL
-
-All other orders will be handled completely in user space.
-
-Only privileged operation exceptions will be checked for in the kernel (or even
-in the hardware prior to interception). If this capability is not enabled, the
-old way of handling SIGP orders is used (partially in kernel and user space).
-
-7.3 KVM_CAP_S390_VECTOR_REGISTERS
-
-Architectures: s390
-Parameters: none
-Returns: 0 on success, negative value on error
-
-Allows use of the vector registers introduced with z13 processor, and
-provides for the synchronization between host and user space. Will
-return -EINVAL if the machine does not support vectors.
-
-7.4 KVM_CAP_S390_USER_STSI
-
-Architectures: s390
-Parameters: none
-
-This capability allows post-handlers for the STSI instruction. After
-initial handling in the kernel, KVM exits to user space with
-KVM_EXIT_S390_STSI to allow user space to insert further data.
-
-Before exiting to userspace, kvm handlers should fill in s390_stsi field of
-vcpu->run:
-struct {
- __u64 addr;
- __u8 ar;
- __u8 reserved;
- __u8 fc;
- __u8 sel1;
- __u16 sel2;
-} s390_stsi;
-
-@addr - guest address of STSI SYSIB
-@fc - function code
-@sel1 - selector 1
-@sel2 - selector 2
-@ar - access register number
-
-KVM handlers should exit to userspace with rc = -EREMOTE.
-
-7.5 KVM_CAP_SPLIT_IRQCHIP
-
-Architectures: x86
-Parameters: args[0] - number of routes reserved for userspace IOAPICs
-Returns: 0 on success, -1 on error
-
-Create a local apic for each processor in the kernel. This can be used
-instead of KVM_CREATE_IRQCHIP if the userspace VMM wishes to emulate the
-IOAPIC and PIC (and also the PIT, even though this has to be enabled
-separately).
-
-This capability also enables in kernel routing of interrupt requests;
-when KVM_CAP_SPLIT_IRQCHIP only routes of KVM_IRQ_ROUTING_MSI type are
-used in the IRQ routing table. The first args[0] MSI routes are reserved
-for the IOAPIC pins. Whenever the LAPIC receives an EOI for these routes,
-a KVM_EXIT_IOAPIC_EOI vmexit will be reported to userspace.
-
-Fails if VCPU has already been created, or if the irqchip is already in the
-kernel (i.e. KVM_CREATE_IRQCHIP has already been called).
-
-7.6 KVM_CAP_S390_RI
-
-Architectures: s390
-Parameters: none
-
-Allows use of runtime-instrumentation introduced with zEC12 processor.
-Will return -EINVAL if the machine does not support runtime-instrumentation.
-Will return -EBUSY if a VCPU has already been created.
-
-7.7 KVM_CAP_X2APIC_API
-
-Architectures: x86
-Parameters: args[0] - features that should be enabled
-Returns: 0 on success, -EINVAL when args[0] contains invalid features
-
-Valid feature flags in args[0] are
-
-#define KVM_X2APIC_API_USE_32BIT_IDS (1ULL << 0)
-#define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK (1ULL << 1)
-
-Enabling KVM_X2APIC_API_USE_32BIT_IDS changes the behavior of
-KVM_SET_GSI_ROUTING, KVM_SIGNAL_MSI, KVM_SET_LAPIC, and KVM_GET_LAPIC,
-allowing the use of 32-bit APIC IDs. See KVM_CAP_X2APIC_API in their
-respective sections.
-
-KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK must be enabled for x2APIC to work
-in logical mode or with more than 255 VCPUs. Otherwise, KVM treats 0xff
-as a broadcast even in x2APIC mode in order to support physical x2APIC
-without interrupt remapping. This is undesirable in logical mode,
-where 0xff represents CPUs 0-7 in cluster 0.
-
-7.8 KVM_CAP_S390_USER_INSTR0
-
-Architectures: s390
-Parameters: none
-
-With this capability enabled, all illegal instructions 0x0000 (2 bytes) will
-be intercepted and forwarded to user space. User space can use this
-mechanism e.g. to realize 2-byte software breakpoints. The kernel will
-not inject an operating exception for these instructions, user space has
-to take care of that.
-
-This capability can be enabled dynamically even if VCPUs were already
-created and are running.
-
-7.9 KVM_CAP_S390_GS
-
-Architectures: s390
-Parameters: none
-Returns: 0 on success; -EINVAL if the machine does not support
- guarded storage; -EBUSY if a VCPU has already been created.
-
-Allows use of guarded storage for the KVM guest.
-
-7.10 KVM_CAP_S390_AIS
-
-Architectures: s390
-Parameters: none
-
-Allow use of adapter-interruption suppression.
-Returns: 0 on success; -EBUSY if a VCPU has already been created.
-
-7.11 KVM_CAP_PPC_SMT
-
-Architectures: ppc
-Parameters: vsmt_mode, flags
-
-Enabling this capability on a VM provides userspace with a way to set
-the desired virtual SMT mode (i.e. the number of virtual CPUs per
-virtual core). The virtual SMT mode, vsmt_mode, must be a power of 2
-between 1 and 8. On POWER8, vsmt_mode must also be no greater than
-the number of threads per subcore for the host. Currently flags must
-be 0. A successful call to enable this capability will result in
-vsmt_mode being returned when the KVM_CAP_PPC_SMT capability is
-subsequently queried for the VM. This capability is only supported by
-HV KVM, and can only be set before any VCPUs have been created.
-The KVM_CAP_PPC_SMT_POSSIBLE capability indicates which virtual SMT
-modes are available.
-
-7.12 KVM_CAP_PPC_FWNMI
-
-Architectures: ppc
-Parameters: none
-
-With this capability a machine check exception in the guest address
-space will cause KVM to exit the guest with NMI exit reason. This
-enables QEMU to build error log and branch to guest kernel registered
-machine check handling routine. Without this capability KVM will
-branch to guests' 0x200 interrupt vector.
-
-7.13 KVM_CAP_X86_DISABLE_EXITS
-
-Architectures: x86
-Parameters: args[0] defines which exits are disabled
-Returns: 0 on success, -EINVAL when args[0] contains invalid exits
-
-Valid bits in args[0] are
-
-#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
-#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
-#define KVM_X86_DISABLE_EXITS_PAUSE (1 << 2)
-#define KVM_X86_DISABLE_EXITS_CSTATE (1 << 3)
-
-Enabling this capability on a VM provides userspace with a way to no
-longer intercept some instructions for improved latency in some
-workloads, and is suggested when vCPUs are associated to dedicated
-physical CPUs. More bits can be added in the future; userspace can
-just pass the KVM_CHECK_EXTENSION result to KVM_ENABLE_CAP to disable
-all such vmexits.
-
-Do not enable KVM_FEATURE_PV_UNHALT if you disable HLT exits.
-
-7.14 KVM_CAP_S390_HPAGE_1M
-
-Architectures: s390
-Parameters: none
-Returns: 0 on success, -EINVAL if hpage module parameter was not set
- or cmma is enabled, or the VM has the KVM_VM_S390_UCONTROL
- flag set
-
-With this capability the KVM support for memory backing with 1m pages
-through hugetlbfs can be enabled for a VM. After the capability is
-enabled, cmma can't be enabled anymore and pfmfi and the storage key
-interpretation are disabled. If cmma has already been enabled or the
-hpage module parameter is not set to 1, -EINVAL is returned.
-
-While it is generally possible to create a huge page backed VM without
-this capability, the VM will not be able to run.
-
-7.15 KVM_CAP_MSR_PLATFORM_INFO
-
-Architectures: x86
-Parameters: args[0] whether feature should be enabled or not
-
-With this capability, a guest may read the MSR_PLATFORM_INFO MSR. Otherwise,
-a #GP would be raised when the guest tries to access. Currently, this
-capability does not enable write permissions of this MSR for the guest.
-
-7.16 KVM_CAP_PPC_NESTED_HV
-
-Architectures: ppc
-Parameters: none
-Returns: 0 on success, -EINVAL when the implementation doesn't support
- nested-HV virtualization.
-
-HV-KVM on POWER9 and later systems allows for "nested-HV"
-virtualization, which provides a way for a guest VM to run guests that
-can run using the CPU's supervisor mode (privileged non-hypervisor
-state). Enabling this capability on a VM depends on the CPU having
-the necessary functionality and on the facility being enabled with a
-kvm-hv module parameter.
-
-7.17 KVM_CAP_EXCEPTION_PAYLOAD
-
-Architectures: x86
-Parameters: args[0] whether feature should be enabled or not
-
-With this capability enabled, CR2 will not be modified prior to the
-emulated VM-exit when L1 intercepts a #PF exception that occurs in
-L2. Similarly, for kvm-intel only, DR6 will not be modified prior to
-the emulated VM-exit when L1 intercepts a #DB exception that occurs in
-L2. As a result, when KVM_GET_VCPU_EVENTS reports a pending #PF (or
-#DB) exception for L2, exception.has_payload will be set and the
-faulting address (or the new DR6 bits*) will be reported in the
-exception_payload field. Similarly, when userspace injects a #PF (or
-#DB) into L2 using KVM_SET_VCPU_EVENTS, it is expected to set
-exception.has_payload and to put the faulting address (or the new DR6
-bits*) in the exception_payload field.
-
-This capability also enables exception.pending in struct
-kvm_vcpu_events, which allows userspace to distinguish between pending
-and injected exceptions.
-
-
-* For the new DR6 bits, note that bit 16 is set iff the #DB exception
- will clear DR6.RTM.
-
-7.18 KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
-
-Architectures: x86, arm, arm64, mips
-Parameters: args[0] whether feature should be enabled or not
-
-With this capability enabled, KVM_GET_DIRTY_LOG will not automatically
-clear and write-protect all pages that are returned as dirty.
-Rather, userspace will have to do this operation separately using
-KVM_CLEAR_DIRTY_LOG.
-
-At the cost of a slightly more complicated operation, this provides better
-scalability and responsiveness for two reasons. First,
-KVM_CLEAR_DIRTY_LOG ioctl can operate on a 64-page granularity rather
-than requiring to sync a full memslot; this ensures that KVM does not
-take spinlocks for an extended period of time. Second, in some cases a
-large amount of time can pass between a call to KVM_GET_DIRTY_LOG and
-userspace actually using the data in the page. Pages can be modified
-during this time, which is inefficint for both the guest and userspace:
-the guest will incur a higher penalty due to write protection faults,
-while userspace can see false reports of dirty pages. Manual reprotection
-helps reducing this time, improving guest performance and reducing the
-number of dirty log false positives.
-
-KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 was previously available under the name
-KVM_CAP_MANUAL_DIRTY_LOG_PROTECT, but the implementation had bugs that make
-it hard or impossible to use it correctly. The availability of
-KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 signals that those bugs are fixed.
-Userspace should not try to use KVM_CAP_MANUAL_DIRTY_LOG_PROTECT.
-
-8. Other capabilities.
-----------------------
-
-This section lists capabilities that give information about other
-features of the KVM implementation.
-
-8.1 KVM_CAP_PPC_HWRNG
-
-Architectures: ppc
-
-This capability, if KVM_CHECK_EXTENSION indicates that it is
-available, means that that the kernel has an implementation of the
-H_RANDOM hypercall backed by a hardware random-number generator.
-If present, the kernel H_RANDOM handler can be enabled for guest use
-with the KVM_CAP_PPC_ENABLE_HCALL capability.
-
-8.2 KVM_CAP_HYPERV_SYNIC
-
-Architectures: x86
-This capability, if KVM_CHECK_EXTENSION indicates that it is
-available, means that that the kernel has an implementation of the
-Hyper-V Synthetic interrupt controller(SynIC). Hyper-V SynIC is
-used to support Windows Hyper-V based guest paravirt drivers(VMBus).
-
-In order to use SynIC, it has to be activated by setting this
-capability via KVM_ENABLE_CAP ioctl on the vcpu fd. Note that this
-will disable the use of APIC hardware virtualization even if supported
-by the CPU, as it's incompatible with SynIC auto-EOI behavior.
-
-8.3 KVM_CAP_PPC_RADIX_MMU
-
-Architectures: ppc
-
-This capability, if KVM_CHECK_EXTENSION indicates that it is
-available, means that that the kernel can support guests using the
-radix MMU defined in Power ISA V3.00 (as implemented in the POWER9
-processor).
-
-8.4 KVM_CAP_PPC_HASH_MMU_V3
-
-Architectures: ppc
-
-This capability, if KVM_CHECK_EXTENSION indicates that it is
-available, means that that the kernel can support guests using the
-hashed page table MMU defined in Power ISA V3.00 (as implemented in
-the POWER9 processor), including in-memory segment tables.
-
-8.5 KVM_CAP_MIPS_VZ
-
-Architectures: mips
-
-This capability, if KVM_CHECK_EXTENSION on the main kvm handle indicates that
-it is available, means that full hardware assisted virtualization capabilities
-of the hardware are available for use through KVM. An appropriate
-KVM_VM_MIPS_* type must be passed to KVM_CREATE_VM to create a VM which
-utilises it.
-
-If KVM_CHECK_EXTENSION on a kvm VM handle indicates that this capability is
-available, it means that the VM is using full hardware assisted virtualization
-capabilities of the hardware. This is useful to check after creating a VM with
-KVM_VM_MIPS_DEFAULT.
-
-The value returned by KVM_CHECK_EXTENSION should be compared against known
-values (see below). All other values are reserved. This is to allow for the
-possibility of other hardware assisted virtualization implementations which
-may be incompatible with the MIPS VZ ASE.
-
- 0: The trap & emulate implementation is in use to run guest code in user
- mode. Guest virtual memory segments are rearranged to fit the guest in the
- user mode address space.
-
- 1: The MIPS VZ ASE is in use, providing full hardware assisted
- virtualization, including standard guest virtual memory segments.
-
-8.6 KVM_CAP_MIPS_TE
-
-Architectures: mips
-
-This capability, if KVM_CHECK_EXTENSION on the main kvm handle indicates that
-it is available, means that the trap & emulate implementation is available to
-run guest code in user mode, even if KVM_CAP_MIPS_VZ indicates that hardware
-assisted virtualisation is also available. KVM_VM_MIPS_TE (0) must be passed
-to KVM_CREATE_VM to create a VM which utilises it.
-
-If KVM_CHECK_EXTENSION on a kvm VM handle indicates that this capability is
-available, it means that the VM is using trap & emulate.
-
-8.7 KVM_CAP_MIPS_64BIT
-
-Architectures: mips
-
-This capability indicates the supported architecture type of the guest, i.e. the
-supported register and address width.
-
-The values returned when this capability is checked by KVM_CHECK_EXTENSION on a
-kvm VM handle correspond roughly to the CP0_Config.AT register field, and should
-be checked specifically against known values (see below). All other values are
-reserved.
-
- 0: MIPS32 or microMIPS32.
- Both registers and addresses are 32-bits wide.
- It will only be possible to run 32-bit guest code.
-
- 1: MIPS64 or microMIPS64 with access only to 32-bit compatibility segments.
- Registers are 64-bits wide, but addresses are 32-bits wide.
- 64-bit guest code may run but cannot access MIPS64 memory segments.
- It will also be possible to run 32-bit guest code.
-
- 2: MIPS64 or microMIPS64 with access to all address segments.
- Both registers and addresses are 64-bits wide.
- It will be possible to run 64-bit or 32-bit guest code.
-
-8.9 KVM_CAP_ARM_USER_IRQ
-
-Architectures: arm, arm64
-This capability, if KVM_CHECK_EXTENSION indicates that it is available, means
-that if userspace creates a VM without an in-kernel interrupt controller, it
-will be notified of changes to the output level of in-kernel emulated devices,
-which can generate virtual interrupts, presented to the VM.
-For such VMs, on every return to userspace, the kernel
-updates the vcpu's run->s.regs.device_irq_level field to represent the actual
-output level of the device.
-
-Whenever kvm detects a change in the device output level, kvm guarantees at
-least one return to userspace before running the VM. This exit could either
-be a KVM_EXIT_INTR or any other exit event, like KVM_EXIT_MMIO. This way,
-userspace can always sample the device output level and re-compute the state of
-the userspace interrupt controller. Userspace should always check the state
-of run->s.regs.device_irq_level on every kvm exit.
-The value in run->s.regs.device_irq_level can represent both level and edge
-triggered interrupt signals, depending on the device. Edge triggered interrupt
-signals will exit to userspace with the bit in run->s.regs.device_irq_level
-set exactly once per edge signal.
-
-The field run->s.regs.device_irq_level is available independent of
-run->kvm_valid_regs or run->kvm_dirty_regs bits.
-
-If KVM_CAP_ARM_USER_IRQ is supported, the KVM_CHECK_EXTENSION ioctl returns a
-number larger than 0 indicating the version of this capability is implemented
-and thereby which bits in in run->s.regs.device_irq_level can signal values.
-
-Currently the following bits are defined for the device_irq_level bitmap:
-
- KVM_CAP_ARM_USER_IRQ >= 1:
-
- KVM_ARM_DEV_EL1_VTIMER - EL1 virtual timer
- KVM_ARM_DEV_EL1_PTIMER - EL1 physical timer
- KVM_ARM_DEV_PMU - ARM PMU overflow interrupt signal
-
-Future versions of kvm may implement additional events. These will get
-indicated by returning a higher number from KVM_CHECK_EXTENSION and will be
-listed above.
-
-8.10 KVM_CAP_PPC_SMT_POSSIBLE
-
-Architectures: ppc
-
-Querying this capability returns a bitmap indicating the possible
-virtual SMT modes that can be set using KVM_CAP_PPC_SMT. If bit N
-(counting from the right) is set, then a virtual SMT mode of 2^N is
-available.
-
-8.11 KVM_CAP_HYPERV_SYNIC2
-
-Architectures: x86
-
-This capability enables a newer version of Hyper-V Synthetic interrupt
-controller (SynIC). The only difference with KVM_CAP_HYPERV_SYNIC is that KVM
-doesn't clear SynIC message and event flags pages when they are enabled by
-writing to the respective MSRs.
-
-8.12 KVM_CAP_HYPERV_VP_INDEX
-
-Architectures: x86
-
-This capability indicates that userspace can load HV_X64_MSR_VP_INDEX msr. Its
-value is used to denote the target vcpu for a SynIC interrupt. For
-compatibilty, KVM initializes this msr to KVM's internal vcpu index. When this
-capability is absent, userspace can still query this msr's value.
-
-8.13 KVM_CAP_S390_AIS_MIGRATION
-
-Architectures: s390
-Parameters: none
-
-This capability indicates if the flic device will be able to get/set the
-AIS states for migration via the KVM_DEV_FLIC_AISM_ALL attribute and allows
-to discover this without having to create a flic device.
-
-8.14 KVM_CAP_S390_PSW
-
-Architectures: s390
-
-This capability indicates that the PSW is exposed via the kvm_run structure.
-
-8.15 KVM_CAP_S390_GMAP
-
-Architectures: s390
-
-This capability indicates that the user space memory used as guest mapping can
-be anywhere in the user memory address space, as long as the memory slots are
-aligned and sized to a segment (1MB) boundary.
-
-8.16 KVM_CAP_S390_COW
-
-Architectures: s390
-
-This capability indicates that the user space memory used as guest mapping can
-use copy-on-write semantics as well as dirty pages tracking via read-only page
-tables.
-
-8.17 KVM_CAP_S390_BPB
-
-Architectures: s390
-
-This capability indicates that kvm will implement the interfaces to handle
-reset, migration and nested KVM for branch prediction blocking. The stfle
-facility 82 should not be provided to the guest without this capability.
-
-8.18 KVM_CAP_HYPERV_TLBFLUSH
-
-Architectures: x86
-
-This capability indicates that KVM supports paravirtualized Hyper-V TLB Flush
-hypercalls:
-HvFlushVirtualAddressSpace, HvFlushVirtualAddressSpaceEx,
-HvFlushVirtualAddressList, HvFlushVirtualAddressListEx.
-
-8.19 KVM_CAP_ARM_INJECT_SERROR_ESR
-
-Architectures: arm, arm64
-
-This capability indicates that userspace can specify (via the
-KVM_SET_VCPU_EVENTS ioctl) the syndrome value reported to the guest when it
-takes a virtual SError interrupt exception.
-If KVM advertises this capability, userspace can only specify the ISS field for
-the ESR syndrome. Other parts of the ESR, such as the EC are generated by the
-CPU when the exception is taken. If this virtual SError is taken to EL1 using
-AArch64, this value will be reported in the ISS field of ESR_ELx.
-
-See KVM_CAP_VCPU_EVENTS for more details.
-8.20 KVM_CAP_HYPERV_SEND_IPI
-
-Architectures: x86
-
-This capability indicates that KVM supports paravirtualized Hyper-V IPI send
-hypercalls:
-HvCallSendSyntheticClusterIpi, HvCallSendSyntheticClusterIpiEx.
+++ /dev/null
-* Internal ABI between the kernel and HYP
-
-This file documents the interaction between the Linux kernel and the
-hypervisor layer when running Linux as a hypervisor (for example
-KVM). It doesn't cover the interaction of the kernel with the
-hypervisor when running as a guest (under Xen, KVM or any other
-hypervisor), or any hypervisor-specific interaction when the kernel is
-used as a host.
-
-On arm and arm64 (without VHE), the kernel doesn't run in hypervisor
-mode, but still needs to interact with it, allowing a built-in
-hypervisor to be either installed or torn down.
-
-In order to achieve this, the kernel must be booted at HYP (arm) or
-EL2 (arm64), allowing it to install a set of stubs before dropping to
-SVC/EL1. These stubs are accessible by using a 'hvc #0' instruction,
-and only act on individual CPUs.
-
-Unless specified otherwise, any built-in hypervisor must implement
-these functions (see arch/arm{,64}/include/asm/virt.h):
-
-* r0/x0 = HVC_SET_VECTORS
- r1/x1 = vectors
-
- Set HVBAR/VBAR_EL2 to 'vectors' to enable a hypervisor. 'vectors'
- must be a physical address, and respect the alignment requirements
- of the architecture. Only implemented by the initial stubs, not by
- Linux hypervisors.
-
-* r0/x0 = HVC_RESET_VECTORS
-
- Turn HYP/EL2 MMU off, and reset HVBAR/VBAR_EL2 to the initials
- stubs' exception vector value. This effectively disables an existing
- hypervisor.
-
-* r0/x0 = HVC_SOFT_RESTART
- r1/x1 = restart address
- x2 = x0's value when entering the next payload (arm64)
- x3 = x1's value when entering the next payload (arm64)
- x4 = x2's value when entering the next payload (arm64)
-
- Mask all exceptions, disable the MMU, move the arguments into place
- (arm64 only), and jump to the restart address while at HYP/EL2. This
- hypercall is not expected to return to its caller.
-
-Any other value of r0/x0 triggers a hypervisor-specific handling,
-which is not documented here.
-
-The return value of a stub hypercall is held by r0/x0, and is 0 on
-success, and HVC_STUB_ERR on error. A stub hypercall is allowed to
-clobber any of the caller-saved registers (x0-x18 on arm64, r0-r3 and
-ip on arm). It is thus recommended to use a function call to perform
-the hypercall.
+++ /dev/null
-KVM implements the PSCI (Power State Coordination Interface)
-specification in order to provide services such as CPU on/off, reset
-and power-off to the guest.
-
-The PSCI specification is regularly updated to provide new features,
-and KVM implements these updates if they make sense from a virtualization
-point of view.
-
-This means that a guest booted on two different versions of KVM can
-observe two different "firmware" revisions. This could cause issues if
-a given guest is tied to a particular PSCI revision (unlikely), or if
-a migration causes a different PSCI version to be exposed out of the
-blue to an unsuspecting guest.
-
-In order to remedy this situation, KVM exposes a set of "firmware
-pseudo-registers" that can be manipulated using the GET/SET_ONE_REG
-interface. These registers can be saved/restored by userspace, and set
-to a convenient value if required.
-
-The following register is defined:
-
-* KVM_REG_ARM_PSCI_VERSION:
-
- - Only valid if the vcpu has the KVM_ARM_VCPU_PSCI_0_2 feature set
- (and thus has already been initialized)
- - Returns the current PSCI version on GET_ONE_REG (defaulting to the
- highest PSCI version implemented by KVM and compatible with v0.2)
- - Allows any PSCI version implemented by KVM and compatible with
- v0.2 to be set with SET_ONE_REG
- - Affects the whole VM (even if the register view is per-vcpu)
-
-* KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
- Holds the state of the firmware support to mitigate CVE-2017-5715, as
- offered by KVM to the guest via a HVC call. The workaround is described
- under SMCCC_ARCH_WORKAROUND_1 in [1].
- Accepted values are:
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL: KVM does not offer
- firmware support for the workaround. The mitigation status for the
- guest is unknown.
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL: The workaround HVC call is
- available to the guest and required for the mitigation.
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED: The workaround HVC call
- is available to the guest, but it is not needed on this VCPU.
-
-* KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
- Holds the state of the firmware support to mitigate CVE-2018-3639, as
- offered by KVM to the guest via a HVC call. The workaround is described
- under SMCCC_ARCH_WORKAROUND_2 in [1].
- Accepted values are:
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL: A workaround is not
- available. KVM does not offer firmware support for the workaround.
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN: The workaround state is
- unknown. KVM does not offer firmware support for the workaround.
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL: The workaround is available,
- and can be disabled by a vCPU. If
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED is set, it is active for
- this vCPU.
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED: The workaround is
- always active on this vCPU or it is not needed.
-
-[1] https://developer.arm.com/-/media/developer/pdf/ARM_DEN_0070A_Firmware_interfaces_for_mitigating_CVE-2017-5715.pdf
+++ /dev/null
-.. SPDX-License-Identifier: GPL-2.0
-
-==============
-KVM CPUID bits
-==============
-
-:Author: Glauber Costa <glommer@gmail.com>
-
-A guest running on a kvm host, can check some of its features using
-cpuid. This is not always guaranteed to work, since userspace can
-mask-out some, or even all KVM-related cpuid features before launching
-a guest.
-
-KVM cpuid functions are:
-
-function: KVM_CPUID_SIGNATURE (0x40000000)
-
-returns::
-
- eax = 0x40000001
- ebx = 0x4b4d564b
- ecx = 0x564b4d56
- edx = 0x4d
-
-Note that this value in ebx, ecx and edx corresponds to the string "KVMKVMKVM".
-The value in eax corresponds to the maximum cpuid function present in this leaf,
-and will be updated if more functions are added in the future.
-Note also that old hosts set eax value to 0x0. This should
-be interpreted as if the value was 0x40000001.
-This function queries the presence of KVM cpuid leafs.
-
-function: define KVM_CPUID_FEATURES (0x40000001)
-
-returns::
-
- ebx, ecx
- eax = an OR'ed group of (1 << flag)
-
-where ``flag`` is defined as below:
-
-================================= =========== ================================
-flag value meaning
-================================= =========== ================================
-KVM_FEATURE_CLOCKSOURCE 0 kvmclock available at msrs
- 0x11 and 0x12
-
-KVM_FEATURE_NOP_IO_DELAY 1 not necessary to perform delays
- on PIO operations
-
-KVM_FEATURE_MMU_OP 2 deprecated
-
-KVM_FEATURE_CLOCKSOURCE2 3 kvmclock available at msrs
-
- 0x4b564d00 and 0x4b564d01
-KVM_FEATURE_ASYNC_PF 4 async pf can be enabled by
- writing to msr 0x4b564d02
-
-KVM_FEATURE_STEAL_TIME 5 steal time can be enabled by
- writing to msr 0x4b564d03
-
-KVM_FEATURE_PV_EOI 6 paravirtualized end of interrupt
- handler can be enabled by
- writing to msr 0x4b564d04
-
-KVM_FEATURE_PV_UNHAULT 7 guest checks this feature bit
- before enabling paravirtualized
- spinlock support
-
-KVM_FEATURE_PV_TLB_FLUSH 9 guest checks this feature bit
- before enabling paravirtualized
- tlb flush
-
-KVM_FEATURE_ASYNC_PF_VMEXIT 10 paravirtualized async PF VM EXIT
- can be enabled by setting bit 2
- when writing to msr 0x4b564d02
-
-KVM_FEATURE_PV_SEND_IPI 11 guest checks this feature bit
- before enabling paravirtualized
- sebd IPIs
-
-KVM_FEATURE_PV_POLL_CONTROL 12 host-side polling on HLT can
- be disabled by writing
- to msr 0x4b564d05.
-
-KVM_FEATURE_PV_SCHED_YIELD 13 guest checks this feature bit
- before using paravirtualized
- sched yield.
-
-KVM_FEATURE_CLOCSOURCE_STABLE_BIT 24 host will warn if no guest-side
- per-cpu warps are expeced in
- kvmclock
-================================= =========== ================================
-
-::
-
- edx = an OR'ed group of (1 << flag)
-
-Where ``flag`` here is defined as below:
-
-================== ============ =================================
-flag value meaning
-================== ============ =================================
-KVM_HINTS_REALTIME 0 guest checks this feature bit to
- determine that vCPUs are never
- preempted for an unlimited time
- allowing optimizations
-================== ============ =================================
+++ /dev/null
-This directory contains specific device bindings for KVM_CAP_DEVICE_CTRL.
+++ /dev/null
-ARM Virtual Interrupt Translation Service (ITS)
-===============================================
-
-Device types supported:
- KVM_DEV_TYPE_ARM_VGIC_ITS ARM Interrupt Translation Service Controller
-
-The ITS allows MSI(-X) interrupts to be injected into guests. This extension is
-optional. Creating a virtual ITS controller also requires a host GICv3 (see
-arm-vgic-v3.txt), but does not depend on having physical ITS controllers.
-
-There can be multiple ITS controllers per guest, each of them has to have
-a separate, non-overlapping MMIO region.
-
-
-Groups:
- KVM_DEV_ARM_VGIC_GRP_ADDR
- Attributes:
- KVM_VGIC_ITS_ADDR_TYPE (rw, 64-bit)
- Base address in the guest physical address space of the GICv3 ITS
- control register frame.
- This address needs to be 64K aligned and the region covers 128K.
- Errors:
- -E2BIG: Address outside of addressable IPA range
- -EINVAL: Incorrectly aligned address
- -EEXIST: Address already configured
- -EFAULT: Invalid user pointer for attr->addr.
- -ENODEV: Incorrect attribute or the ITS is not supported.
-
-
- KVM_DEV_ARM_VGIC_GRP_CTRL
- Attributes:
- KVM_DEV_ARM_VGIC_CTRL_INIT
- request the initialization of the ITS, no additional parameter in
- kvm_device_attr.addr.
-
- KVM_DEV_ARM_ITS_CTRL_RESET
- reset the ITS, no additional parameter in kvm_device_attr.addr.
- See "ITS Reset State" section.
-
- KVM_DEV_ARM_ITS_SAVE_TABLES
- save the ITS table data into guest RAM, at the location provisioned
- by the guest in corresponding registers/table entries.
-
- The layout of the tables in guest memory defines an ABI. The entries
- are laid out in little endian format as described in the last paragraph.
-
- KVM_DEV_ARM_ITS_RESTORE_TABLES
- restore the ITS tables from guest RAM to ITS internal structures.
-
- The GICV3 must be restored before the ITS and all ITS registers but
- the GITS_CTLR must be restored before restoring the ITS tables.
-
- The GITS_IIDR read-only register must also be restored before
- calling KVM_DEV_ARM_ITS_RESTORE_TABLES as the IIDR revision field
- encodes the ABI revision.
-
- The expected ordering when restoring the GICv3/ITS is described in section
- "ITS Restore Sequence".
-
- Errors:
- -ENXIO: ITS not properly configured as required prior to setting
- this attribute
- -ENOMEM: Memory shortage when allocating ITS internal data
- -EINVAL: Inconsistent restored data
- -EFAULT: Invalid guest ram access
- -EBUSY: One or more VCPUS are running
- -EACCES: The virtual ITS is backed by a physical GICv4 ITS, and the
- state is not available
-
- KVM_DEV_ARM_VGIC_GRP_ITS_REGS
- Attributes:
- The attr field of kvm_device_attr encodes the offset of the
- ITS register, relative to the ITS control frame base address
- (ITS_base).
-
- kvm_device_attr.addr points to a __u64 value whatever the width
- of the addressed register (32/64 bits). 64 bit registers can only
- be accessed with full length.
-
- Writes to read-only registers are ignored by the kernel except for:
- - GITS_CREADR. It must be restored otherwise commands in the queue
- will be re-executed after restoring CWRITER. GITS_CREADR must be
- restored before restoring the GITS_CTLR which is likely to enable the
- ITS. Also it must be restored after GITS_CBASER since a write to
- GITS_CBASER resets GITS_CREADR.
- - GITS_IIDR. The Revision field encodes the table layout ABI revision.
- In the future we might implement direct injection of virtual LPIs.
- This will require an upgrade of the table layout and an evolution of
- the ABI. GITS_IIDR must be restored before calling
- KVM_DEV_ARM_ITS_RESTORE_TABLES.
-
- For other registers, getting or setting a register has the same
- effect as reading/writing the register on real hardware.
- Errors:
- -ENXIO: Offset does not correspond to any supported register
- -EFAULT: Invalid user pointer for attr->addr
- -EINVAL: Offset is not 64-bit aligned
- -EBUSY: one or more VCPUS are running
-
- ITS Restore Sequence:
- -------------------------
-
-The following ordering must be followed when restoring the GIC and the ITS:
-a) restore all guest memory and create vcpus
-b) restore all redistributors
-c) provide the ITS base address
- (KVM_DEV_ARM_VGIC_GRP_ADDR)
-d) restore the ITS in the following order:
- 1. Restore GITS_CBASER
- 2. Restore all other GITS_ registers, except GITS_CTLR!
- 3. Load the ITS table data (KVM_DEV_ARM_ITS_RESTORE_TABLES)
- 4. Restore GITS_CTLR
-
-Then vcpus can be started.
-
- ITS Table ABI REV0:
- -------------------
-
- Revision 0 of the ABI only supports the features of a virtual GICv3, and does
- not support a virtual GICv4 with support for direct injection of virtual
- interrupts for nested hypervisors.
-
- The device table and ITT are indexed by the DeviceID and EventID,
- respectively. The collection table is not indexed by CollectionID, and the
- entries in the collection are listed in no particular order.
- All entries are 8 bytes.
-
- Device Table Entry (DTE):
-
- bits: | 63| 62 ... 49 | 48 ... 5 | 4 ... 0 |
- values: | V | next | ITT_addr | Size |
-
- where;
- - V indicates whether the entry is valid. If not, other fields
- are not meaningful.
- - next: equals to 0 if this entry is the last one; otherwise it
- corresponds to the DeviceID offset to the next DTE, capped by
- 2^14 -1.
- - ITT_addr matches bits [51:8] of the ITT address (256 Byte aligned).
- - Size specifies the supported number of bits for the EventID,
- minus one
-
- Collection Table Entry (CTE):
-
- bits: | 63| 62 .. 52 | 51 ... 16 | 15 ... 0 |
- values: | V | RES0 | RDBase | ICID |
-
- where:
- - V indicates whether the entry is valid. If not, other fields are
- not meaningful.
- - RES0: reserved field with Should-Be-Zero-or-Preserved behavior.
- - RDBase is the PE number (GICR_TYPER.Processor_Number semantic),
- - ICID is the collection ID
-
- Interrupt Translation Entry (ITE):
-
- bits: | 63 ... 48 | 47 ... 16 | 15 ... 0 |
- values: | next | pINTID | ICID |
-
- where:
- - next: equals to 0 if this entry is the last one; otherwise it corresponds
- to the EventID offset to the next ITE capped by 2^16 -1.
- - pINTID is the physical LPI ID; if zero, it means the entry is not valid
- and other fields are not meaningful.
- - ICID is the collection ID
-
- ITS Reset State:
- ----------------
-
-RESET returns the ITS to the same state that it was when first created and
-initialized. When the RESET command returns, the following things are
-guaranteed:
-
-- The ITS is not enabled and quiescent
- GITS_CTLR.Enabled = 0 .Quiescent=1
-- There is no internally cached state
-- No collection or device table are used
- GITS_BASER<n>.Valid = 0
-- GITS_CBASER = 0, GITS_CREADR = 0, GITS_CWRITER = 0
-- The ABI version is unchanged and remains the one set when the ITS
- device was first created.
+++ /dev/null
-ARM Virtual Generic Interrupt Controller v3 and later (VGICv3)
-==============================================================
-
-
-Device types supported:
- KVM_DEV_TYPE_ARM_VGIC_V3 ARM Generic Interrupt Controller v3.0
-
-Only one VGIC instance may be instantiated through this API. The created VGIC
-will act as the VM interrupt controller, requiring emulated user-space devices
-to inject interrupts to the VGIC instead of directly to CPUs. It is not
-possible to create both a GICv3 and GICv2 on the same VM.
-
-Creating a guest GICv3 device requires a host GICv3 as well.
-
-
-Groups:
- KVM_DEV_ARM_VGIC_GRP_ADDR
- Attributes:
- KVM_VGIC_V3_ADDR_TYPE_DIST (rw, 64-bit)
- Base address in the guest physical address space of the GICv3 distributor
- register mappings. Only valid for KVM_DEV_TYPE_ARM_VGIC_V3.
- This address needs to be 64K aligned and the region covers 64 KByte.
-
- KVM_VGIC_V3_ADDR_TYPE_REDIST (rw, 64-bit)
- Base address in the guest physical address space of the GICv3
- redistributor register mappings. There are two 64K pages for each
- VCPU and all of the redistributor pages are contiguous.
- Only valid for KVM_DEV_TYPE_ARM_VGIC_V3.
- This address needs to be 64K aligned.
-
- KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION (rw, 64-bit)
- The attribute data pointed to by kvm_device_attr.addr is a __u64 value:
- bits: | 63 .... 52 | 51 .... 16 | 15 - 12 |11 - 0
- values: | count | base | flags | index
- - index encodes the unique redistributor region index
- - flags: reserved for future use, currently 0
- - base field encodes bits [51:16] of the guest physical base address
- of the first redistributor in the region.
- - count encodes the number of redistributors in the region. Must be
- greater than 0.
- There are two 64K pages for each redistributor in the region and
- redistributors are laid out contiguously within the region. Regions
- are filled with redistributors in the index order. The sum of all
- region count fields must be greater than or equal to the number of
- VCPUs. Redistributor regions must be registered in the incremental
- index order, starting from index 0.
- The characteristics of a specific redistributor region can be read
- by presetting the index field in the attr data.
- Only valid for KVM_DEV_TYPE_ARM_VGIC_V3.
-
- It is invalid to mix calls with KVM_VGIC_V3_ADDR_TYPE_REDIST and
- KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION attributes.
-
- Errors:
- -E2BIG: Address outside of addressable IPA range
- -EINVAL: Incorrectly aligned address, bad redistributor region
- count/index, mixed redistributor region attribute usage
- -EEXIST: Address already configured
- -ENOENT: Attempt to read the characteristics of a non existing
- redistributor region
- -ENXIO: The group or attribute is unknown/unsupported for this device
- or hardware support is missing.
- -EFAULT: Invalid user pointer for attr->addr.
-
-
- KVM_DEV_ARM_VGIC_GRP_DIST_REGS
- KVM_DEV_ARM_VGIC_GRP_REDIST_REGS
- Attributes:
- The attr field of kvm_device_attr encodes two values:
- bits: | 63 .... 32 | 31 .... 0 |
- values: | mpidr | offset |
-
- All distributor regs are (rw, 32-bit) and kvm_device_attr.addr points to a
- __u32 value. 64-bit registers must be accessed by separately accessing the
- lower and higher word.
-
- Writes to read-only registers are ignored by the kernel.
-
- KVM_DEV_ARM_VGIC_GRP_DIST_REGS accesses the main distributor registers.
- KVM_DEV_ARM_VGIC_GRP_REDIST_REGS accesses the redistributor of the CPU
- specified by the mpidr.
-
- The offset is relative to the "[Re]Distributor base address" as defined
- in the GICv3/4 specs. Getting or setting such a register has the same
- effect as reading or writing the register on real hardware, except for the
- following registers: GICD_STATUSR, GICR_STATUSR, GICD_ISPENDR,
- GICR_ISPENDR0, GICD_ICPENDR, and GICR_ICPENDR0. These registers behave
- differently when accessed via this interface compared to their
- architecturally defined behavior to allow software a full view of the
- VGIC's internal state.
-
- The mpidr field is used to specify which
- redistributor is accessed. The mpidr is ignored for the distributor.
-
- The mpidr encoding is based on the affinity information in the
- architecture defined MPIDR, and the field is encoded as follows:
- | 63 .... 56 | 55 .... 48 | 47 .... 40 | 39 .... 32 |
- | Aff3 | Aff2 | Aff1 | Aff0 |
-
- Note that distributor fields are not banked, but return the same value
- regardless of the mpidr used to access the register.
-
- GICD_IIDR.Revision is updated when the KVM implementation is changed in a
- way directly observable by the guest or userspace. Userspace should read
- GICD_IIDR from KVM and write back the read value to confirm its expected
- behavior is aligned with the KVM implementation. Userspace should set
- GICD_IIDR before setting any other registers to ensure the expected
- behavior.
-
-
- The GICD_STATUSR and GICR_STATUSR registers are architecturally defined such
- that a write of a clear bit has no effect, whereas a write with a set bit
- clears that value. To allow userspace to freely set the values of these two
- registers, setting the attributes with the register offsets for these two
- registers simply sets the non-reserved bits to the value written.
-
-
- Accesses (reads and writes) to the GICD_ISPENDR register region and
- GICR_ISPENDR0 registers get/set the value of the latched pending state for
- the interrupts.
-
- This is identical to the value returned by a guest read from ISPENDR for an
- edge triggered interrupt, but may differ for level triggered interrupts.
- For edge triggered interrupts, once an interrupt becomes pending (whether
- because of an edge detected on the input line or because of a guest write
- to ISPENDR) this state is "latched", and only cleared when either the
- interrupt is activated or when the guest writes to ICPENDR. A level
- triggered interrupt may be pending either because the level input is held
- high by a device, or because of a guest write to the ISPENDR register. Only
- ISPENDR writes are latched; if the device lowers the line level then the
- interrupt is no longer pending unless the guest also wrote to ISPENDR, and
- conversely writes to ICPENDR or activations of the interrupt do not clear
- the pending status if the line level is still being held high. (These
- rules are documented in the GICv3 specification descriptions of the ICPENDR
- and ISPENDR registers.) For a level triggered interrupt the value accessed
- here is that of the latch which is set by ISPENDR and cleared by ICPENDR or
- interrupt activation, whereas the value returned by a guest read from
- ISPENDR is the logical OR of the latch value and the input line level.
-
- Raw access to the latch state is provided to userspace so that it can save
- and restore the entire GIC internal state (which is defined by the
- combination of the current input line level and the latch state, and cannot
- be deduced from purely the line level and the value of the ISPENDR
- registers).
-
- Accesses to GICD_ICPENDR register region and GICR_ICPENDR0 registers have
- RAZ/WI semantics, meaning that reads always return 0 and writes are always
- ignored.
-
- Errors:
- -ENXIO: Getting or setting this register is not yet supported
- -EBUSY: One or more VCPUs are running
-
-
- KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS
- Attributes:
- The attr field of kvm_device_attr encodes two values:
- bits: | 63 .... 32 | 31 .... 16 | 15 .... 0 |
- values: | mpidr | RES | instr |
-
- The mpidr field encodes the CPU ID based on the affinity information in the
- architecture defined MPIDR, and the field is encoded as follows:
- | 63 .... 56 | 55 .... 48 | 47 .... 40 | 39 .... 32 |
- | Aff3 | Aff2 | Aff1 | Aff0 |
-
- The instr field encodes the system register to access based on the fields
- defined in the A64 instruction set encoding for system register access
- (RES means the bits are reserved for future use and should be zero):
-
- | 15 ... 14 | 13 ... 11 | 10 ... 7 | 6 ... 3 | 2 ... 0 |
- | Op 0 | Op1 | CRn | CRm | Op2 |
-
- All system regs accessed through this API are (rw, 64-bit) and
- kvm_device_attr.addr points to a __u64 value.
-
- KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS accesses the CPU interface registers for the
- CPU specified by the mpidr field.
-
- CPU interface registers access is not implemented for AArch32 mode.
- Error -ENXIO is returned when accessed in AArch32 mode.
- Errors:
- -ENXIO: Getting or setting this register is not yet supported
- -EBUSY: VCPU is running
- -EINVAL: Invalid mpidr or register value supplied
-
-
- KVM_DEV_ARM_VGIC_GRP_NR_IRQS
- Attributes:
- A value describing the number of interrupts (SGI, PPI and SPI) for
- this GIC instance, ranging from 64 to 1024, in increments of 32.
-
- kvm_device_attr.addr points to a __u32 value.
-
- Errors:
- -EINVAL: Value set is out of the expected range
- -EBUSY: Value has already be set.
-
-
- KVM_DEV_ARM_VGIC_GRP_CTRL
- Attributes:
- KVM_DEV_ARM_VGIC_CTRL_INIT
- request the initialization of the VGIC, no additional parameter in
- kvm_device_attr.addr.
- KVM_DEV_ARM_VGIC_SAVE_PENDING_TABLES
- save all LPI pending bits into guest RAM pending tables.
-
- The first kB of the pending table is not altered by this operation.
- Errors:
- -ENXIO: VGIC not properly configured as required prior to calling
- this attribute
- -ENODEV: no online VCPU
- -ENOMEM: memory shortage when allocating vgic internal data
- -EFAULT: Invalid guest ram access
- -EBUSY: One or more VCPUS are running
-
-
- KVM_DEV_ARM_VGIC_GRP_LEVEL_INFO
- Attributes:
- The attr field of kvm_device_attr encodes the following values:
- bits: | 63 .... 32 | 31 .... 10 | 9 .... 0 |
- values: | mpidr | info | vINTID |
-
- The vINTID specifies which set of IRQs is reported on.
-
- The info field specifies which information userspace wants to get or set
- using this interface. Currently we support the following info values:
-
- VGIC_LEVEL_INFO_LINE_LEVEL:
- Get/Set the input level of the IRQ line for a set of 32 contiguously
- numbered interrupts.
- vINTID must be a multiple of 32.
-
- kvm_device_attr.addr points to a __u32 value which will contain a
- bitmap where a set bit means the interrupt level is asserted.
-
- Bit[n] indicates the status for interrupt vINTID + n.
-
- SGIs and any interrupt with a higher ID than the number of interrupts
- supported, will be RAZ/WI. LPIs are always edge-triggered and are
- therefore not supported by this interface.
-
- PPIs are reported per VCPU as specified in the mpidr field, and SPIs are
- reported with the same value regardless of the mpidr specified.
-
- The mpidr field encodes the CPU ID based on the affinity information in the
- architecture defined MPIDR, and the field is encoded as follows:
- | 63 .... 56 | 55 .... 48 | 47 .... 40 | 39 .... 32 |
- | Aff3 | Aff2 | Aff1 | Aff0 |
- Errors:
- -EINVAL: vINTID is not multiple of 32 or
- info field is not VGIC_LEVEL_INFO_LINE_LEVEL
+++ /dev/null
-ARM Virtual Generic Interrupt Controller v2 (VGIC)
-==================================================
-
-Device types supported:
- KVM_DEV_TYPE_ARM_VGIC_V2 ARM Generic Interrupt Controller v2.0
-
-Only one VGIC instance may be instantiated through either this API or the
-legacy KVM_CREATE_IRQCHIP API. The created VGIC will act as the VM interrupt
-controller, requiring emulated user-space devices to inject interrupts to the
-VGIC instead of directly to CPUs.
-
-GICv3 implementations with hardware compatibility support allow creating a
-guest GICv2 through this interface. For information on creating a guest GICv3
-device and guest ITS devices, see arm-vgic-v3.txt. It is not possible to
-create both a GICv3 and GICv2 device on the same VM.
-
-
-Groups:
- KVM_DEV_ARM_VGIC_GRP_ADDR
- Attributes:
- KVM_VGIC_V2_ADDR_TYPE_DIST (rw, 64-bit)
- Base address in the guest physical address space of the GIC distributor
- register mappings. Only valid for KVM_DEV_TYPE_ARM_VGIC_V2.
- This address needs to be 4K aligned and the region covers 4 KByte.
-
- KVM_VGIC_V2_ADDR_TYPE_CPU (rw, 64-bit)
- Base address in the guest physical address space of the GIC virtual cpu
- interface register mappings. Only valid for KVM_DEV_TYPE_ARM_VGIC_V2.
- This address needs to be 4K aligned and the region covers 4 KByte.
- Errors:
- -E2BIG: Address outside of addressable IPA range
- -EINVAL: Incorrectly aligned address
- -EEXIST: Address already configured
- -ENXIO: The group or attribute is unknown/unsupported for this device
- or hardware support is missing.
- -EFAULT: Invalid user pointer for attr->addr.
-
- KVM_DEV_ARM_VGIC_GRP_DIST_REGS
- Attributes:
- The attr field of kvm_device_attr encodes two values:
- bits: | 63 .... 40 | 39 .. 32 | 31 .... 0 |
- values: | reserved | vcpu_index | offset |
-
- All distributor regs are (rw, 32-bit)
-
- The offset is relative to the "Distributor base address" as defined in the
- GICv2 specs. Getting or setting such a register has the same effect as
- reading or writing the register on the actual hardware from the cpu whose
- index is specified with the vcpu_index field. Note that most distributor
- fields are not banked, but return the same value regardless of the
- vcpu_index used to access the register.
-
- GICD_IIDR.Revision is updated when the KVM implementation of an emulated
- GICv2 is changed in a way directly observable by the guest or userspace.
- Userspace should read GICD_IIDR from KVM and write back the read value to
- confirm its expected behavior is aligned with the KVM implementation.
- Userspace should set GICD_IIDR before setting any other registers (both
- KVM_DEV_ARM_VGIC_GRP_DIST_REGS and KVM_DEV_ARM_VGIC_GRP_CPU_REGS) to ensure
- the expected behavior. Unless GICD_IIDR has been set from userspace, writes
- to the interrupt group registers (GICD_IGROUPR) are ignored.
- Errors:
- -ENXIO: Getting or setting this register is not yet supported
- -EBUSY: One or more VCPUs are running
- -EINVAL: Invalid vcpu_index supplied
-
- KVM_DEV_ARM_VGIC_GRP_CPU_REGS
- Attributes:
- The attr field of kvm_device_attr encodes two values:
- bits: | 63 .... 40 | 39 .. 32 | 31 .... 0 |
- values: | reserved | vcpu_index | offset |
-
- All CPU interface regs are (rw, 32-bit)
-
- The offset specifies the offset from the "CPU interface base address" as
- defined in the GICv2 specs. Getting or setting such a register has the
- same effect as reading or writing the register on the actual hardware.
-
- The Active Priorities Registers APRn are implementation defined, so we set a
- fixed format for our implementation that fits with the model of a "GICv2
- implementation without the security extensions" which we present to the
- guest. This interface always exposes four register APR[0-3] describing the
- maximum possible 128 preemption levels. The semantics of the register
- indicate if any interrupts in a given preemption level are in the active
- state by setting the corresponding bit.
-
- Thus, preemption level X has one or more active interrupts if and only if:
-
- APRn[X mod 32] == 0b1, where n = X / 32
-
- Bits for undefined preemption levels are RAZ/WI.
-
- Note that this differs from a CPU's view of the APRs on hardware in which
- a GIC without the security extensions expose group 0 and group 1 active
- priorities in separate register groups, whereas we show a combined view
- similar to GICv2's GICH_APR.
-
- For historical reasons and to provide ABI compatibility with userspace we
- export the GICC_PMR register in the format of the GICH_VMCR.VMPriMask
- field in the lower 5 bits of a word, meaning that userspace must always
- use the lower 5 bits to communicate with the KVM device and must shift the
- value left by 3 places to obtain the actual priority mask level.
-
- Errors:
- -ENXIO: Getting or setting this register is not yet supported
- -EBUSY: One or more VCPUs are running
- -EINVAL: Invalid vcpu_index supplied
-
- KVM_DEV_ARM_VGIC_GRP_NR_IRQS
- Attributes:
- A value describing the number of interrupts (SGI, PPI and SPI) for
- this GIC instance, ranging from 64 to 1024, in increments of 32.
-
- Errors:
- -EINVAL: Value set is out of the expected range
- -EBUSY: Value has already be set, or GIC has already been initialized
- with default values.
-
- KVM_DEV_ARM_VGIC_GRP_CTRL
- Attributes:
- KVM_DEV_ARM_VGIC_CTRL_INIT
- request the initialization of the VGIC or ITS, no additional parameter
- in kvm_device_attr.addr.
- Errors:
- -ENXIO: VGIC not properly configured as required prior to calling
- this attribute
- -ENODEV: no online VCPU
- -ENOMEM: memory shortage when allocating vgic internal data
+++ /dev/null
-MPIC interrupt controller
-=========================
-
-Device types supported:
- KVM_DEV_TYPE_FSL_MPIC_20 Freescale MPIC v2.0
- KVM_DEV_TYPE_FSL_MPIC_42 Freescale MPIC v4.2
-
-Only one MPIC instance, of any type, may be instantiated. The created
-MPIC will act as the system interrupt controller, connecting to each
-vcpu's interrupt inputs.
-
-Groups:
- KVM_DEV_MPIC_GRP_MISC
- Attributes:
- KVM_DEV_MPIC_BASE_ADDR (rw, 64-bit)
- Base address of the 256 KiB MPIC register space. Must be
- naturally aligned. A value of zero disables the mapping.
- Reset value is zero.
-
- KVM_DEV_MPIC_GRP_REGISTER (rw, 32-bit)
- Access an MPIC register, as if the access were made from the guest.
- "attr" is the byte offset into the MPIC register space. Accesses
- must be 4-byte aligned.
-
- MSIs may be signaled by using this attribute group to write
- to the relevant MSIIR.
-
- KVM_DEV_MPIC_GRP_IRQ_ACTIVE (rw, 32-bit)
- IRQ input line for each standard openpic source. 0 is inactive and 1
- is active, regardless of interrupt sense.
-
- For edge-triggered interrupts: Writing 1 is considered an activating
- edge, and writing 0 is ignored. Reading returns 1 if a previously
- signaled edge has not been acknowledged, and 0 otherwise.
-
- "attr" is the IRQ number. IRQ numbers for standard sources are the
- byte offset of the relevant IVPR from EIVPR0, divided by 32.
-
-IRQ Routing:
-
- The MPIC emulation supports IRQ routing. Only a single MPIC device can
- be instantiated. Once that device has been created, it's available as
- irqchip id 0.
-
- This irqchip 0 has 256 interrupt pins, which expose the interrupts in
- the main array of interrupt sources (a.k.a. "SRC" interrupts).
-
- The numbering is the same as the MPIC device tree binding -- based on
- the register offset from the beginning of the sources array, without
- regard to any subdivisions in chip documentation such as "internal"
- or "external" interrupts.
-
- Access to non-SRC interrupts is not implemented through IRQ routing mechanisms.
+++ /dev/null
-FLIC (floating interrupt controller)
-====================================
-
-FLIC handles floating (non per-cpu) interrupts, i.e. I/O, service and some
-machine check interruptions. All interrupts are stored in a per-vm list of
-pending interrupts. FLIC performs operations on this list.
-
-Only one FLIC instance may be instantiated.
-
-FLIC provides support to
-- add interrupts (KVM_DEV_FLIC_ENQUEUE)
-- inspect currently pending interrupts (KVM_FLIC_GET_ALL_IRQS)
-- purge all pending floating interrupts (KVM_DEV_FLIC_CLEAR_IRQS)
-- purge one pending floating I/O interrupt (KVM_DEV_FLIC_CLEAR_IO_IRQ)
-- enable/disable for the guest transparent async page faults
-- register and modify adapter interrupt sources (KVM_DEV_FLIC_ADAPTER_*)
-- modify AIS (adapter-interruption-suppression) mode state (KVM_DEV_FLIC_AISM)
-- inject adapter interrupts on a specified adapter (KVM_DEV_FLIC_AIRQ_INJECT)
-- get/set all AIS mode states (KVM_DEV_FLIC_AISM_ALL)
-
-Groups:
- KVM_DEV_FLIC_ENQUEUE
- Passes a buffer and length into the kernel which are then injected into
- the list of pending interrupts.
- attr->addr contains the pointer to the buffer and attr->attr contains
- the length of the buffer.
- The format of the data structure kvm_s390_irq as it is copied from userspace
- is defined in usr/include/linux/kvm.h.
-
- KVM_DEV_FLIC_GET_ALL_IRQS
- Copies all floating interrupts into a buffer provided by userspace.
- When the buffer is too small it returns -ENOMEM, which is the indication
- for userspace to try again with a bigger buffer.
- -ENOBUFS is returned when the allocation of a kernelspace buffer has
- failed.
- -EFAULT is returned when copying data to userspace failed.
- All interrupts remain pending, i.e. are not deleted from the list of
- currently pending interrupts.
- attr->addr contains the userspace address of the buffer into which all
- interrupt data will be copied.
- attr->attr contains the size of the buffer in bytes.
-
- KVM_DEV_FLIC_CLEAR_IRQS
- Simply deletes all elements from the list of currently pending floating
- interrupts. No interrupts are injected into the guest.
-
- KVM_DEV_FLIC_CLEAR_IO_IRQ
- Deletes one (if any) I/O interrupt for a subchannel identified by the
- subsystem identification word passed via the buffer specified by
- attr->addr (address) and attr->attr (length).
-
- KVM_DEV_FLIC_APF_ENABLE
- Enables async page faults for the guest. So in case of a major page fault
- the host is allowed to handle this async and continues the guest.
-
- KVM_DEV_FLIC_APF_DISABLE_WAIT
- Disables async page faults for the guest and waits until already pending
- async page faults are done. This is necessary to trigger a completion interrupt
- for every init interrupt before migrating the interrupt list.
-
- KVM_DEV_FLIC_ADAPTER_REGISTER
- Register an I/O adapter interrupt source. Takes a kvm_s390_io_adapter
- describing the adapter to register:
-
-struct kvm_s390_io_adapter {
- __u32 id;
- __u8 isc;
- __u8 maskable;
- __u8 swap;
- __u8 flags;
-};
-
- id contains the unique id for the adapter, isc the I/O interruption subclass
- to use, maskable whether this adapter may be masked (interrupts turned off),
- swap whether the indicators need to be byte swapped, and flags contains
- further characteristics of the adapter.
- Currently defined values for 'flags' are:
- - KVM_S390_ADAPTER_SUPPRESSIBLE: adapter is subject to AIS
- (adapter-interrupt-suppression) facility. This flag only has an effect if
- the AIS capability is enabled.
- Unknown flag values are ignored.
-
-
- KVM_DEV_FLIC_ADAPTER_MODIFY
- Modifies attributes of an existing I/O adapter interrupt source. Takes
- a kvm_s390_io_adapter_req specifying the adapter and the operation:
-
-struct kvm_s390_io_adapter_req {
- __u32 id;
- __u8 type;
- __u8 mask;
- __u16 pad0;
- __u64 addr;
-};
-
- id specifies the adapter and type the operation. The supported operations
- are:
-
- KVM_S390_IO_ADAPTER_MASK
- mask or unmask the adapter, as specified in mask
-
- KVM_S390_IO_ADAPTER_MAP
- perform a gmap translation for the guest address provided in addr,
- pin a userspace page for the translated address and add it to the
- list of mappings
- Note: A new mapping will be created unconditionally; therefore,
- the calling code should avoid making duplicate mappings.
-
- KVM_S390_IO_ADAPTER_UNMAP
- release a userspace page for the translated address specified in addr
- from the list of mappings
-
- KVM_DEV_FLIC_AISM
- modify the adapter-interruption-suppression mode for a given isc if the
- AIS capability is enabled. Takes a kvm_s390_ais_req describing:
-
-struct kvm_s390_ais_req {
- __u8 isc;
- __u16 mode;
-};
-
- isc contains the target I/O interruption subclass, mode the target
- adapter-interruption-suppression mode. The following modes are
- currently supported:
- - KVM_S390_AIS_MODE_ALL: ALL-Interruptions Mode, i.e. airq injection
- is always allowed;
- - KVM_S390_AIS_MODE_SINGLE: SINGLE-Interruption Mode, i.e. airq
- injection is only allowed once and the following adapter interrupts
- will be suppressed until the mode is set again to ALL-Interruptions
- or SINGLE-Interruption mode.
-
- KVM_DEV_FLIC_AIRQ_INJECT
- Inject adapter interrupts on a specified adapter.
- attr->attr contains the unique id for the adapter, which allows for
- adapter-specific checks and actions.
- For adapters subject to AIS, handle the airq injection suppression for
- an isc according to the adapter-interruption-suppression mode on condition
- that the AIS capability is enabled.
-
- KVM_DEV_FLIC_AISM_ALL
- Gets or sets the adapter-interruption-suppression mode for all ISCs. Takes
- a kvm_s390_ais_all describing:
-
-struct kvm_s390_ais_all {
- __u8 simm; /* Single-Interruption-Mode mask */
- __u8 nimm; /* No-Interruption-Mode mask *
-};
-
- simm contains Single-Interruption-Mode mask for all ISCs, nimm contains
- No-Interruption-Mode mask for all ISCs. Each bit in simm and nimm corresponds
- to an ISC (MSB0 bit 0 to ISC 0 and so on). The combination of simm bit and
- nimm bit presents AIS mode for a ISC.
-
- KVM_DEV_FLIC_AISM_ALL is indicated by KVM_CAP_S390_AIS_MIGRATION.
-
-Note: The KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR device ioctls executed on
-FLIC with an unknown group or attribute gives the error code EINVAL (instead of
-ENXIO, as specified in the API documentation). It is not possible to conclude
-that a FLIC operation is unavailable based on the error code resulting from a
-usage attempt.
-
-Note: The KVM_DEV_FLIC_CLEAR_IO_IRQ ioctl will return EINVAL in case a zero
-schid is specified.
+++ /dev/null
-Generic vcpu interface
-====================================
-
-The virtual cpu "device" also accepts the ioctls KVM_SET_DEVICE_ATTR,
-KVM_GET_DEVICE_ATTR, and KVM_HAS_DEVICE_ATTR. The interface uses the same struct
-kvm_device_attr as other devices, but targets VCPU-wide settings and controls.
-
-The groups and attributes per virtual cpu, if any, are architecture specific.
-
-1. GROUP: KVM_ARM_VCPU_PMU_V3_CTRL
-Architectures: ARM64
-
-1.1. ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_IRQ
-Parameters: in kvm_device_attr.addr the address for PMU overflow interrupt is a
- pointer to an int
-Returns: -EBUSY: The PMU overflow interrupt is already set
- -ENXIO: The overflow interrupt not set when attempting to get it
- -ENODEV: PMUv3 not supported
- -EINVAL: Invalid PMU overflow interrupt number supplied or
- trying to set the IRQ number without using an in-kernel
- irqchip.
-
-A value describing the PMUv3 (Performance Monitor Unit v3) overflow interrupt
-number for this vcpu. This interrupt could be a PPI or SPI, but the interrupt
-type must be same for each vcpu. As a PPI, the interrupt number is the same for
-all vcpus, while as an SPI it must be a separate number per vcpu.
-
-1.2 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_INIT
-Parameters: no additional parameter in kvm_device_attr.addr
-Returns: -ENODEV: PMUv3 not supported or GIC not initialized
- -ENXIO: PMUv3 not properly configured or in-kernel irqchip not
- configured as required prior to calling this attribute
- -EBUSY: PMUv3 already initialized
-
-Request the initialization of the PMUv3. If using the PMUv3 with an in-kernel
-virtual GIC implementation, this must be done after initializing the in-kernel
-irqchip.
-
-
-2. GROUP: KVM_ARM_VCPU_TIMER_CTRL
-Architectures: ARM,ARM64
-
-2.1. ATTRIBUTE: KVM_ARM_VCPU_TIMER_IRQ_VTIMER
-2.2. ATTRIBUTE: KVM_ARM_VCPU_TIMER_IRQ_PTIMER
-Parameters: in kvm_device_attr.addr the address for the timer interrupt is a
- pointer to an int
-Returns: -EINVAL: Invalid timer interrupt number
- -EBUSY: One or more VCPUs has already run
-
-A value describing the architected timer interrupt number when connected to an
-in-kernel virtual GIC. These must be a PPI (16 <= intid < 32). Setting the
-attribute overrides the default values (see below).
-
-KVM_ARM_VCPU_TIMER_IRQ_VTIMER: The EL1 virtual timer intid (default: 27)
-KVM_ARM_VCPU_TIMER_IRQ_PTIMER: The EL1 physical timer intid (default: 30)
-
-Setting the same PPI for different timers will prevent the VCPUs from running.
-Setting the interrupt number on a VCPU configures all VCPUs created at that
-time to use the number provided for a given timer, overwriting any previously
-configured values on other VCPUs. Userspace should configure the interrupt
-numbers on at least one VCPU after creating all VCPUs and before running any
-VCPUs.
+++ /dev/null
-VFIO virtual device
-===================
-
-Device types supported:
- KVM_DEV_TYPE_VFIO
-
-Only one VFIO instance may be created per VM. The created device
-tracks VFIO groups in use by the VM and features of those groups
-important to the correctness and acceleration of the VM. As groups
-are enabled and disabled for use by the VM, KVM should be updated
-about their presence. When registered with KVM, a reference to the
-VFIO-group is held by KVM.
-
-Groups:
- KVM_DEV_VFIO_GROUP
-
-KVM_DEV_VFIO_GROUP attributes:
- KVM_DEV_VFIO_GROUP_ADD: Add a VFIO group to VFIO-KVM device tracking
- kvm_device_attr.addr points to an int32_t file descriptor
- for the VFIO group.
- KVM_DEV_VFIO_GROUP_DEL: Remove a VFIO group from VFIO-KVM device tracking
- kvm_device_attr.addr points to an int32_t file descriptor
- for the VFIO group.
- KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table
- allocated by sPAPR KVM.
- kvm_device_attr.addr points to a struct:
-
- struct kvm_vfio_spapr_tce {
- __s32 groupfd;
- __s32 tablefd;
- };
-
- where
- @groupfd is a file descriptor for a VFIO group;
- @tablefd is a file descriptor for a TCE table allocated via
- KVM_CREATE_SPAPR_TCE.
+++ /dev/null
-Generic vm interface
-====================================
-
-The virtual machine "device" also accepts the ioctls KVM_SET_DEVICE_ATTR,
-KVM_GET_DEVICE_ATTR, and KVM_HAS_DEVICE_ATTR. The interface uses the same
-struct kvm_device_attr as other devices, but targets VM-wide settings
-and controls.
-
-The groups and attributes per virtual machine, if any, are architecture
-specific.
-
-1. GROUP: KVM_S390_VM_MEM_CTRL
-Architectures: s390
-
-1.1. ATTRIBUTE: KVM_S390_VM_MEM_ENABLE_CMMA
-Parameters: none
-Returns: -EBUSY if a vcpu is already defined, otherwise 0
-
-Enables Collaborative Memory Management Assist (CMMA) for the virtual machine.
-
-1.2. ATTRIBUTE: KVM_S390_VM_MEM_CLR_CMMA
-Parameters: none
-Returns: -EINVAL if CMMA was not enabled
- 0 otherwise
-
-Clear the CMMA status for all guest pages, so any pages the guest marked
-as unused are again used any may not be reclaimed by the host.
-
-1.3. ATTRIBUTE KVM_S390_VM_MEM_LIMIT_SIZE
-Parameters: in attr->addr the address for the new limit of guest memory
-Returns: -EFAULT if the given address is not accessible
- -EINVAL if the virtual machine is of type UCONTROL
- -E2BIG if the given guest memory is to big for that machine
- -EBUSY if a vcpu is already defined
- -ENOMEM if not enough memory is available for a new shadow guest mapping
- 0 otherwise
-
-Allows userspace to query the actual limit and set a new limit for
-the maximum guest memory size. The limit will be rounded up to
-2048 MB, 4096 GB, 8192 TB respectively, as this limit is governed by
-the number of page table levels. In the case that there is no limit we will set
-the limit to KVM_S390_NO_MEM_LIMIT (U64_MAX).
-
-2. GROUP: KVM_S390_VM_CPU_MODEL
-Architectures: s390
-
-2.1. ATTRIBUTE: KVM_S390_VM_CPU_MACHINE (r/o)
-
-Allows user space to retrieve machine and kvm specific cpu related information:
-
-struct kvm_s390_vm_cpu_machine {
- __u64 cpuid; # CPUID of host
- __u32 ibc; # IBC level range offered by host
- __u8 pad[4];
- __u64 fac_mask[256]; # set of cpu facilities enabled by KVM
- __u64 fac_list[256]; # set of cpu facilities offered by host
-}
-
-Parameters: address of buffer to store the machine related cpu data
- of type struct kvm_s390_vm_cpu_machine*
-Returns: -EFAULT if the given address is not accessible from kernel space
- -ENOMEM if not enough memory is available to process the ioctl
- 0 in case of success
-
-2.2. ATTRIBUTE: KVM_S390_VM_CPU_PROCESSOR (r/w)
-
-Allows user space to retrieve or request to change cpu related information for a vcpu:
-
-struct kvm_s390_vm_cpu_processor {
- __u64 cpuid; # CPUID currently (to be) used by this vcpu
- __u16 ibc; # IBC level currently (to be) used by this vcpu
- __u8 pad[6];
- __u64 fac_list[256]; # set of cpu facilities currently (to be) used
- # by this vcpu
-}
-
-KVM does not enforce or limit the cpu model data in any form. Take the information
-retrieved by means of KVM_S390_VM_CPU_MACHINE as hint for reasonable configuration
-setups. Instruction interceptions triggered by additionally set facility bits that
-are not handled by KVM need to by imlemented in the VM driver code.
-
-Parameters: address of buffer to store/set the processor related cpu
- data of type struct kvm_s390_vm_cpu_processor*.
-Returns: -EBUSY in case 1 or more vcpus are already activated (only in write case)
- -EFAULT if the given address is not accessible from kernel space
- -ENOMEM if not enough memory is available to process the ioctl
- 0 in case of success
-
-2.3. ATTRIBUTE: KVM_S390_VM_CPU_MACHINE_FEAT (r/o)
-
-Allows user space to retrieve available cpu features. A feature is available if
-provided by the hardware and supported by kvm. In theory, cpu features could
-even be completely emulated by kvm.
-
-struct kvm_s390_vm_cpu_feat {
- __u64 feat[16]; # Bitmap (1 = feature available), MSB 0 bit numbering
-};
-
-Parameters: address of a buffer to load the feature list from.
-Returns: -EFAULT if the given address is not accessible from kernel space.
- 0 in case of success.
-
-2.4. ATTRIBUTE: KVM_S390_VM_CPU_PROCESSOR_FEAT (r/w)
-
-Allows user space to retrieve or change enabled cpu features for all VCPUs of a
-VM. Features that are not available cannot be enabled.
-
-See 2.3. for a description of the parameter struct.
-
-Parameters: address of a buffer to store/load the feature list from.
-Returns: -EFAULT if the given address is not accessible from kernel space.
- -EINVAL if a cpu feature that is not available is to be enabled.
- -EBUSY if at least one VCPU has already been defined.
- 0 in case of success.
-
-2.5. ATTRIBUTE: KVM_S390_VM_CPU_MACHINE_SUBFUNC (r/o)
-
-Allows user space to retrieve available cpu subfunctions without any filtering
-done by a set IBC. These subfunctions are indicated to the guest VCPU via
-query or "test bit" subfunctions and used e.g. by cpacf functions, plo and ptff.
-
-A subfunction block is only valid if KVM_S390_VM_CPU_MACHINE contains the
-STFL(E) bit introducing the affected instruction. If the affected instruction
-indicates subfunctions via a "query subfunction", the response block is
-contained in the returned struct. If the affected instruction
-indicates subfunctions via a "test bit" mechanism, the subfunction codes are
-contained in the returned struct in MSB 0 bit numbering.
-
-struct kvm_s390_vm_cpu_subfunc {
- u8 plo[32]; # always valid (ESA/390 feature)
- u8 ptff[16]; # valid with TOD-clock steering
- u8 kmac[16]; # valid with Message-Security-Assist
- u8 kmc[16]; # valid with Message-Security-Assist
- u8 km[16]; # valid with Message-Security-Assist
- u8 kimd[16]; # valid with Message-Security-Assist
- u8 klmd[16]; # valid with Message-Security-Assist
- u8 pckmo[16]; # valid with Message-Security-Assist-Extension 3
- u8 kmctr[16]; # valid with Message-Security-Assist-Extension 4
- u8 kmf[16]; # valid with Message-Security-Assist-Extension 4
- u8 kmo[16]; # valid with Message-Security-Assist-Extension 4
- u8 pcc[16]; # valid with Message-Security-Assist-Extension 4
- u8 ppno[16]; # valid with Message-Security-Assist-Extension 5
- u8 kma[16]; # valid with Message-Security-Assist-Extension 8
- u8 kdsa[16]; # valid with Message-Security-Assist-Extension 9
- u8 reserved[1792]; # reserved for future instructions
-};
-
-Parameters: address of a buffer to load the subfunction blocks from.
-Returns: -EFAULT if the given address is not accessible from kernel space.
- 0 in case of success.
-
-2.6. ATTRIBUTE: KVM_S390_VM_CPU_PROCESSOR_SUBFUNC (r/w)
-
-Allows user space to retrieve or change cpu subfunctions to be indicated for
-all VCPUs of a VM. This attribute will only be available if kernel and
-hardware support are in place.
-
-The kernel uses the configured subfunction blocks for indication to
-the guest. A subfunction block will only be used if the associated STFL(E) bit
-has not been disabled by user space (so the instruction to be queried is
-actually available for the guest).
-
-As long as no data has been written, a read will fail. The IBC will be used
-to determine available subfunctions in this case, this will guarantee backward
-compatibility.
-
-See 2.5. for a description of the parameter struct.
-
-Parameters: address of a buffer to store/load the subfunction blocks from.
-Returns: -EFAULT if the given address is not accessible from kernel space.
- -EINVAL when reading, if there was no write yet.
- -EBUSY if at least one VCPU has already been defined.
- 0 in case of success.
-
-3. GROUP: KVM_S390_VM_TOD
-Architectures: s390
-
-3.1. ATTRIBUTE: KVM_S390_VM_TOD_HIGH
-
-Allows user space to set/get the TOD clock extension (u8) (superseded by
-KVM_S390_VM_TOD_EXT).
-
-Parameters: address of a buffer in user space to store the data (u8) to
-Returns: -EFAULT if the given address is not accessible from kernel space
- -EINVAL if setting the TOD clock extension to != 0 is not supported
-
-3.2. ATTRIBUTE: KVM_S390_VM_TOD_LOW
-
-Allows user space to set/get bits 0-63 of the TOD clock register as defined in
-the POP (u64).
-
-Parameters: address of a buffer in user space to store the data (u64) to
-Returns: -EFAULT if the given address is not accessible from kernel space
-
-3.3. ATTRIBUTE: KVM_S390_VM_TOD_EXT
-Allows user space to set/get bits 0-63 of the TOD clock register as defined in
-the POP (u64). If the guest CPU model supports the TOD clock extension (u8), it
-also allows user space to get/set it. If the guest CPU model does not support
-it, it is stored as 0 and not allowed to be set to a value != 0.
-
-Parameters: address of a buffer in user space to store the data
- (kvm_s390_vm_tod_clock) to
-Returns: -EFAULT if the given address is not accessible from kernel space
- -EINVAL if setting the TOD clock extension to != 0 is not supported
-
-4. GROUP: KVM_S390_VM_CRYPTO
-Architectures: s390
-
-4.1. ATTRIBUTE: KVM_S390_VM_CRYPTO_ENABLE_AES_KW (w/o)
-
-Allows user space to enable aes key wrapping, including generating a new
-wrapping key.
-
-Parameters: none
-Returns: 0
-
-4.2. ATTRIBUTE: KVM_S390_VM_CRYPTO_ENABLE_DEA_KW (w/o)
-
-Allows user space to enable dea key wrapping, including generating a new
-wrapping key.
-
-Parameters: none
-Returns: 0
-
-4.3. ATTRIBUTE: KVM_S390_VM_CRYPTO_DISABLE_AES_KW (w/o)
-
-Allows user space to disable aes key wrapping, clearing the wrapping key.
-
-Parameters: none
-Returns: 0
-
-4.4. ATTRIBUTE: KVM_S390_VM_CRYPTO_DISABLE_DEA_KW (w/o)
-
-Allows user space to disable dea key wrapping, clearing the wrapping key.
-
-Parameters: none
-Returns: 0
-
-5. GROUP: KVM_S390_VM_MIGRATION
-Architectures: s390
-
-5.1. ATTRIBUTE: KVM_S390_VM_MIGRATION_STOP (w/o)
-
-Allows userspace to stop migration mode, needed for PGSTE migration.
-Setting this attribute when migration mode is not active will have no
-effects.
-
-Parameters: none
-Returns: 0
-
-5.2. ATTRIBUTE: KVM_S390_VM_MIGRATION_START (w/o)
-
-Allows userspace to start migration mode, needed for PGSTE migration.
-Setting this attribute when migration mode is already active will have
-no effects.
-
-Parameters: none
-Returns: -ENOMEM if there is not enough free memory to start migration mode
- -EINVAL if the state of the VM is invalid (e.g. no memory defined)
- 0 in case of success.
-
-5.3. ATTRIBUTE: KVM_S390_VM_MIGRATION_STATUS (r/o)
-
-Allows userspace to query the status of migration mode.
-
-Parameters: address of a buffer in user space to store the data (u64) to;
- the data itself is either 0 if migration mode is disabled or 1
- if it is enabled
-Returns: -EFAULT if the given address is not accessible from kernel space
- 0 in case of success.
+++ /dev/null
-XICS interrupt controller
-
-Device type supported: KVM_DEV_TYPE_XICS
-
-Groups:
- KVM_DEV_XICS_SOURCES
- Attributes: One per interrupt source, indexed by the source number.
-
-This device emulates the XICS (eXternal Interrupt Controller
-Specification) defined in PAPR. The XICS has a set of interrupt
-sources, each identified by a 20-bit source number, and a set of
-Interrupt Control Presentation (ICP) entities, also called "servers",
-each associated with a virtual CPU.
-
-The ICP entities are created by enabling the KVM_CAP_IRQ_ARCH
-capability for each vcpu, specifying KVM_CAP_IRQ_XICS in args[0] and
-the interrupt server number (i.e. the vcpu number from the XICS's
-point of view) in args[1] of the kvm_enable_cap struct. Each ICP has
-64 bits of state which can be read and written using the
-KVM_GET_ONE_REG and KVM_SET_ONE_REG ioctls on the vcpu. The 64 bit
-state word has the following bitfields, starting at the
-least-significant end of the word:
-
-* Unused, 16 bits
-
-* Pending interrupt priority, 8 bits
- Zero is the highest priority, 255 means no interrupt is pending.
-
-* Pending IPI (inter-processor interrupt) priority, 8 bits
- Zero is the highest priority, 255 means no IPI is pending.
-
-* Pending interrupt source number, 24 bits
- Zero means no interrupt pending, 2 means an IPI is pending
-
-* Current processor priority, 8 bits
- Zero is the highest priority, meaning no interrupts can be
- delivered, and 255 is the lowest priority.
-
-Each source has 64 bits of state that can be read and written using
-the KVM_GET_DEVICE_ATTR and KVM_SET_DEVICE_ATTR ioctls, specifying the
-KVM_DEV_XICS_SOURCES attribute group, with the attribute number being
-the interrupt source number. The 64 bit state word has the following
-bitfields, starting from the least-significant end of the word:
-
-* Destination (server number), 32 bits
- This specifies where the interrupt should be sent, and is the
- interrupt server number specified for the destination vcpu.
-
-* Priority, 8 bits
- This is the priority specified for this interrupt source, where 0 is
- the highest priority and 255 is the lowest. An interrupt with a
- priority of 255 will never be delivered.
-
-* Level sensitive flag, 1 bit
- This bit is 1 for a level-sensitive interrupt source, or 0 for
- edge-sensitive (or MSI).
-
-* Masked flag, 1 bit
- This bit is set to 1 if the interrupt is masked (cannot be delivered
- regardless of its priority), for example by the ibm,int-off RTAS
- call, or 0 if it is not masked.
-
-* Pending flag, 1 bit
- This bit is 1 if the source has a pending interrupt, otherwise 0.
-
-Only one XICS instance may be created per VM.
+++ /dev/null
-POWER9 eXternal Interrupt Virtualization Engine (XIVE Gen1)
-==========================================================
-
-Device types supported:
- KVM_DEV_TYPE_XIVE POWER9 XIVE Interrupt Controller generation 1
-
-This device acts as a VM interrupt controller. It provides the KVM
-interface to configure the interrupt sources of a VM in the underlying
-POWER9 XIVE interrupt controller.
-
-Only one XIVE instance may be instantiated. A guest XIVE device
-requires a POWER9 host and the guest OS should have support for the
-XIVE native exploitation interrupt mode. If not, it should run using
-the legacy interrupt mode, referred as XICS (POWER7/8).
-
-* Device Mappings
-
- The KVM device exposes different MMIO ranges of the XIVE HW which
- are required for interrupt management. These are exposed to the
- guest in VMAs populated with a custom VM fault handler.
-
- 1. Thread Interrupt Management Area (TIMA)
-
- Each thread has an associated Thread Interrupt Management context
- composed of a set of registers. These registers let the thread
- handle priority management and interrupt acknowledgment. The most
- important are :
-
- - Interrupt Pending Buffer (IPB)
- - Current Processor Priority (CPPR)
- - Notification Source Register (NSR)
-
- They are exposed to software in four different pages each proposing
- a view with a different privilege. The first page is for the
- physical thread context and the second for the hypervisor. Only the
- third (operating system) and the fourth (user level) are exposed the
- guest.
-
- 2. Event State Buffer (ESB)
-
- Each source is associated with an Event State Buffer (ESB) with
- either a pair of even/odd pair of pages which provides commands to
- manage the source: to trigger, to EOI, to turn off the source for
- instance.
-
- 3. Device pass-through
-
- When a device is passed-through into the guest, the source
- interrupts are from a different HW controller (PHB4) and the ESB
- pages exposed to the guest should accommadate this change.
-
- The passthru_irq helpers, kvmppc_xive_set_mapped() and
- kvmppc_xive_clr_mapped() are called when the device HW irqs are
- mapped into or unmapped from the guest IRQ number space. The KVM
- device extends these helpers to clear the ESB pages of the guest IRQ
- number being mapped and then lets the VM fault handler repopulate.
- The handler will insert the ESB page corresponding to the HW
- interrupt of the device being passed-through or the initial IPI ESB
- page if the device has being removed.
-
- The ESB remapping is fully transparent to the guest and the OS
- device driver. All handling is done within VFIO and the above
- helpers in KVM-PPC.
-
-* Groups:
-
- 1. KVM_DEV_XIVE_GRP_CTRL
- Provides global controls on the device
- Attributes:
- 1.1 KVM_DEV_XIVE_RESET (write only)
- Resets the interrupt controller configuration for sources and event
- queues. To be used by kexec and kdump.
- Errors: none
-
- 1.2 KVM_DEV_XIVE_EQ_SYNC (write only)
- Sync all the sources and queues and mark the EQ pages dirty. This
- to make sure that a consistent memory state is captured when
- migrating the VM.
- Errors: none
-
- 2. KVM_DEV_XIVE_GRP_SOURCE (write only)
- Initializes a new source in the XIVE device and mask it.
- Attributes:
- Interrupt source number (64-bit)
- The kvm_device_attr.addr points to a __u64 value:
- bits: | 63 .... 2 | 1 | 0
- values: | unused | level | type
- - type: 0:MSI 1:LSI
- - level: assertion level in case of an LSI.
- Errors:
- -E2BIG: Interrupt source number is out of range
- -ENOMEM: Could not create a new source block
- -EFAULT: Invalid user pointer for attr->addr.
- -ENXIO: Could not allocate underlying HW interrupt
-
- 3. KVM_DEV_XIVE_GRP_SOURCE_CONFIG (write only)
- Configures source targeting
- Attributes:
- Interrupt source number (64-bit)
- The kvm_device_attr.addr points to a __u64 value:
- bits: | 63 .... 33 | 32 | 31 .. 3 | 2 .. 0
- values: | eisn | mask | server | priority
- - priority: 0-7 interrupt priority level
- - server: CPU number chosen to handle the interrupt
- - mask: mask flag (unused)
- - eisn: Effective Interrupt Source Number
- Errors:
- -ENOENT: Unknown source number
- -EINVAL: Not initialized source number
- -EINVAL: Invalid priority
- -EINVAL: Invalid CPU number.
- -EFAULT: Invalid user pointer for attr->addr.
- -ENXIO: CPU event queues not configured or configuration of the
- underlying HW interrupt failed
- -EBUSY: No CPU available to serve interrupt
-
- 4. KVM_DEV_XIVE_GRP_EQ_CONFIG (read-write)
- Configures an event queue of a CPU
- Attributes:
- EQ descriptor identifier (64-bit)
- The EQ descriptor identifier is a tuple (server, priority) :
- bits: | 63 .... 32 | 31 .. 3 | 2 .. 0
- values: | unused | server | priority
- The kvm_device_attr.addr points to :
- struct kvm_ppc_xive_eq {
- __u32 flags;
- __u32 qshift;
- __u64 qaddr;
- __u32 qtoggle;
- __u32 qindex;
- __u8 pad[40];
- };
- - flags: queue flags
- KVM_XIVE_EQ_ALWAYS_NOTIFY (required)
- forces notification without using the coalescing mechanism
- provided by the XIVE END ESBs.
- - qshift: queue size (power of 2)
- - qaddr: real address of queue
- - qtoggle: current queue toggle bit
- - qindex: current queue index
- - pad: reserved for future use
- Errors:
- -ENOENT: Invalid CPU number
- -EINVAL: Invalid priority
- -EINVAL: Invalid flags
- -EINVAL: Invalid queue size
- -EINVAL: Invalid queue address
- -EFAULT: Invalid user pointer for attr->addr.
- -EIO: Configuration of the underlying HW failed
-
- 5. KVM_DEV_XIVE_GRP_SOURCE_SYNC (write only)
- Synchronize the source to flush event notifications
- Attributes:
- Interrupt source number (64-bit)
- Errors:
- -ENOENT: Unknown source number
- -EINVAL: Not initialized source number
-
-* VCPU state
-
- The XIVE IC maintains VP interrupt state in an internal structure
- called the NVT. When a VP is not dispatched on a HW processor
- thread, this structure can be updated by HW if the VP is the target
- of an event notification.
-
- It is important for migration to capture the cached IPB from the NVT
- as it synthesizes the priorities of the pending interrupts. We
- capture a bit more to report debug information.
-
- KVM_REG_PPC_VP_STATE (2 * 64bits)
- bits: | 63 .... 32 | 31 .... 0 |
- values: | TIMA word0 | TIMA word1 |
- bits: | 127 .......... 64 |
- values: | unused |
-
-* Migration:
-
- Saving the state of a VM using the XIVE native exploitation mode
- should follow a specific sequence. When the VM is stopped :
-
- 1. Mask all sources (PQ=01) to stop the flow of events.
-
- 2. Sync the XIVE device with the KVM control KVM_DEV_XIVE_EQ_SYNC to
- flush any in-flight event notification and to stabilize the EQs. At
- this stage, the EQ pages are marked dirty to make sure they are
- transferred in the migration sequence.
-
- 3. Capture the state of the source targeting, the EQs configuration
- and the state of thread interrupt context registers.
-
- Restore is similar :
-
- 1. Restore the EQ configuration. As targeting depends on it.
- 2. Restore targeting
- 3. Restore the thread interrupt contexts
- 4. Restore the source states
- 5. Let the vCPU run
+++ /dev/null
-The KVM halt polling system
-===========================
-
-The KVM halt polling system provides a feature within KVM whereby the latency
-of a guest can, under some circumstances, be reduced by polling in the host
-for some time period after the guest has elected to no longer run by cedeing.
-That is, when a guest vcpu has ceded, or in the case of powerpc when all of the
-vcpus of a single vcore have ceded, the host kernel polls for wakeup conditions
-before giving up the cpu to the scheduler in order to let something else run.
-
-Polling provides a latency advantage in cases where the guest can be run again
-very quickly by at least saving us a trip through the scheduler, normally on
-the order of a few micro-seconds, although performance benefits are workload
-dependant. In the event that no wakeup source arrives during the polling
-interval or some other task on the runqueue is runnable the scheduler is
-invoked. Thus halt polling is especially useful on workloads with very short
-wakeup periods where the time spent halt polling is minimised and the time
-savings of not invoking the scheduler are distinguishable.
-
-The generic halt polling code is implemented in:
-
- virt/kvm/kvm_main.c: kvm_vcpu_block()
-
-The powerpc kvm-hv specific case is implemented in:
-
- arch/powerpc/kvm/book3s_hv.c: kvmppc_vcore_blocked()
-
-Halt Polling Interval
-=====================
-
-The maximum time for which to poll before invoking the scheduler, referred to
-as the halt polling interval, is increased and decreased based on the perceived
-effectiveness of the polling in an attempt to limit pointless polling.
-This value is stored in either the vcpu struct:
-
- kvm_vcpu->halt_poll_ns
-
-or in the case of powerpc kvm-hv, in the vcore struct:
-
- kvmppc_vcore->halt_poll_ns
-
-Thus this is a per vcpu (or vcore) value.
-
-During polling if a wakeup source is received within the halt polling interval,
-the interval is left unchanged. In the event that a wakeup source isn't
-received during the polling interval (and thus schedule is invoked) there are
-two options, either the polling interval and total block time[0] were less than
-the global max polling interval (see module params below), or the total block
-time was greater than the global max polling interval.
-
-In the event that both the polling interval and total block time were less than
-the global max polling interval then the polling interval can be increased in
-the hope that next time during the longer polling interval the wake up source
-will be received while the host is polling and the latency benefits will be
-received. The polling interval is grown in the function grow_halt_poll_ns() and
-is multiplied by the module parameters halt_poll_ns_grow and
-halt_poll_ns_grow_start.
-
-In the event that the total block time was greater than the global max polling
-interval then the host will never poll for long enough (limited by the global
-max) to wakeup during the polling interval so it may as well be shrunk in order
-to avoid pointless polling. The polling interval is shrunk in the function
-shrink_halt_poll_ns() and is divided by the module parameter
-halt_poll_ns_shrink, or set to 0 iff halt_poll_ns_shrink == 0.
-
-It is worth noting that this adjustment process attempts to hone in on some
-steady state polling interval but will only really do a good job for wakeups
-which come at an approximately constant rate, otherwise there will be constant
-adjustment of the polling interval.
-
-[0] total block time: the time between when the halt polling function is
- invoked and a wakeup source received (irrespective of
- whether the scheduler is invoked within that function).
-
-Module Parameters
-=================
-
-The kvm module has 3 tuneable module parameters to adjust the global max
-polling interval as well as the rate at which the polling interval is grown and
-shrunk. These variables are defined in include/linux/kvm_host.h and as module
-parameters in virt/kvm/kvm_main.c, or arch/powerpc/kvm/book3s_hv.c in the
-powerpc kvm-hv case.
-
-Module Parameter | Description | Default Value
---------------------------------------------------------------------------------
-halt_poll_ns | The global max polling | KVM_HALT_POLL_NS_DEFAULT
- | interval which defines |
- | the ceiling value of the |
- | polling interval for | (per arch value)
- | each vcpu. |
---------------------------------------------------------------------------------
-halt_poll_ns_grow | The value by which the | 2
- | halt polling interval is |
- | multiplied in the |
- | grow_halt_poll_ns() |
- | function. |
---------------------------------------------------------------------------------
-halt_poll_ns_grow_start | The initial value to grow | 10000
- | to from zero in the |
- | grow_halt_poll_ns() |
- | function. |
---------------------------------------------------------------------------------
-halt_poll_ns_shrink | The value by which the | 0
- | halt polling interval is |
- | divided in the |
- | shrink_halt_poll_ns() |
- | function. |
---------------------------------------------------------------------------------
-
-These module parameters can be set from the debugfs files in:
-
- /sys/module/kvm/parameters/
-
-Note: that these module parameters are system wide values and are not able to
- be tuned on a per vm basis.
-
-Further Notes
-=============
-
-- Care should be taken when setting the halt_poll_ns module parameter as a
-large value has the potential to drive the cpu usage to 100% on a machine which
-would be almost entirely idle otherwise. This is because even if a guest has
-wakeups during which very little work is done and which are quite far apart, if
-the period is shorter than the global max polling interval (halt_poll_ns) then
-the host will always poll for the entire block time and thus cpu utilisation
-will go to 100%.
-
-- Halt polling essentially presents a trade off between power usage and latency
-and the module parameters should be used to tune the affinity for this. Idle
-cpu time is essentially converted to host kernel time with the aim of decreasing
-latency when entering the guest.
-
-- Halt polling will only be conducted by the host when no other tasks are
-runnable on that cpu, otherwise the polling will cease immediately and
-schedule will be invoked to allow that other task to run. Thus this doesn't
-allow a guest to denial of service the cpu.
+++ /dev/null
-Linux KVM Hypercall:
-===================
-X86:
- KVM Hypercalls have a three-byte sequence of either the vmcall or the vmmcall
- instruction. The hypervisor can replace it with instructions that are
- guaranteed to be supported.
-
- Up to four arguments may be passed in rbx, rcx, rdx, and rsi respectively.
- The hypercall number should be placed in rax and the return value will be
- placed in rax. No other registers will be clobbered unless explicitly stated
- by the particular hypercall.
-
-S390:
- R2-R7 are used for parameters 1-6. In addition, R1 is used for hypercall
- number. The return value is written to R2.
-
- S390 uses diagnose instruction as hypercall (0x500) along with hypercall
- number in R1.
-
- For further information on the S390 diagnose call as supported by KVM,
- refer to Documentation/virtual/kvm/s390-diag.txt.
-
- PowerPC:
- It uses R3-R10 and hypercall number in R11. R4-R11 are used as output registers.
- Return value is placed in R3.
-
- KVM hypercalls uses 4 byte opcode, that are patched with 'hypercall-instructions'
- property inside the device tree's /hypervisor node.
- For more information refer to Documentation/virtual/kvm/ppc-pv.txt
-
-MIPS:
- KVM hypercalls use the HYPCALL instruction with code 0 and the hypercall
- number in $2 (v0). Up to four arguments may be placed in $4-$7 (a0-a3) and
- the return value is placed in $2 (v0).
-
-KVM Hypercalls Documentation
-===========================
-The template for each hypercall is:
-1. Hypercall name.
-2. Architecture(s)
-3. Status (deprecated, obsolete, active)
-4. Purpose
-
-1. KVM_HC_VAPIC_POLL_IRQ
-------------------------
-Architecture: x86
-Status: active
-Purpose: Trigger guest exit so that the host can check for pending
-interrupts on reentry.
-
-2. KVM_HC_MMU_OP
-------------------------
-Architecture: x86
-Status: deprecated.
-Purpose: Support MMU operations such as writing to PTE,
-flushing TLB, release PT.
-
-3. KVM_HC_FEATURES
-------------------------
-Architecture: PPC
-Status: active
-Purpose: Expose hypercall availability to the guest. On x86 platforms, cpuid
-used to enumerate which hypercalls are available. On PPC, either device tree
-based lookup ( which is also what EPAPR dictates) OR KVM specific enumeration
-mechanism (which is this hypercall) can be used.
-
-4. KVM_HC_PPC_MAP_MAGIC_PAGE
-------------------------
-Architecture: PPC
-Status: active
-Purpose: To enable communication between the hypervisor and guest there is a
-shared page that contains parts of supervisor visible register state.
-The guest can map this shared page to access its supervisor register through
-memory using this hypercall.
-
-5. KVM_HC_KICK_CPU
-------------------------
-Architecture: x86
-Status: active
-Purpose: Hypercall used to wakeup a vcpu from HLT state
-Usage example : A vcpu of a paravirtualized guest that is busywaiting in guest
-kernel mode for an event to occur (ex: a spinlock to become available) can
-execute HLT instruction once it has busy-waited for more than a threshold
-time-interval. Execution of HLT instruction would cause the hypervisor to put
-the vcpu to sleep until occurrence of an appropriate event. Another vcpu of the
-same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
-specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
-is used in the hypercall for future use.
-
-
-6. KVM_HC_CLOCK_PAIRING
-------------------------
-Architecture: x86
-Status: active
-Purpose: Hypercall used to synchronize host and guest clocks.
-Usage:
-
-a0: guest physical address where host copies
-"struct kvm_clock_offset" structure.
-
-a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
-is supported (corresponding to the host's CLOCK_REALTIME clock).
-
- struct kvm_clock_pairing {
- __s64 sec;
- __s64 nsec;
- __u64 tsc;
- __u32 flags;
- __u32 pad[9];
- };
-
- Where:
- * sec: seconds from clock_type clock.
- * nsec: nanoseconds from clock_type clock.
- * tsc: guest TSC value used to calculate sec/nsec pair
- * flags: flags, unused (0) at the moment.
-
-The hypercall lets a guest compute a precise timestamp across
-host and guest. The guest can use the returned TSC value to
-compute the CLOCK_REALTIME for its clock, at the same instant.
-
-Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
-or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
-
-6. KVM_HC_SEND_IPI
-------------------------
-Architecture: x86
-Status: active
-Purpose: Send IPIs to multiple vCPUs.
-
-a0: lower part of the bitmap of destination APIC IDs
-a1: higher part of the bitmap of destination APIC IDs
-a2: the lowest APIC ID in bitmap
-a3: APIC ICR
-
-The hypercall lets a guest send multicast IPIs, with at most 128
-128 destinations per hypercall in 64-bit mode and 64 vCPUs per
-hypercall in 32-bit mode. The destinations are represented by a
-bitmap contained in the first two arguments (a0 and a1). Bit 0 of
-a0 corresponds to the APIC ID in the third argument (a2), bit 1
-corresponds to the APIC ID a2+1, and so on.
-
-Returns the number of CPUs to which the IPIs were delivered successfully.
-
-7. KVM_HC_SCHED_YIELD
-------------------------
-Architecture: x86
-Status: active
-Purpose: Hypercall used to yield if the IPI target vCPU is preempted
-
-a0: destination APIC ID
-
-Usage example: When sending a call-function IPI-many to vCPUs, yield if
-any of the IPI target vCPUs was preempted.
+++ /dev/null
-.. SPDX-License-Identifier: GPL-2.0
-
-===
-KVM
-===
-
-.. toctree::
- :maxdepth: 2
-
- amd-memory-encryption
- cpuid
+++ /dev/null
-KVM Lock Overview
-=================
-
-1. Acquisition Orders
----------------------
-
-The acquisition orders for mutexes are as follows:
-
-- kvm->lock is taken outside vcpu->mutex
-
-- kvm->lock is taken outside kvm->slots_lock and kvm->irq_lock
-
-- kvm->slots_lock is taken outside kvm->irq_lock, though acquiring
- them together is quite rare.
-
-On x86, vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock.
-
-Everything else is a leaf: no other lock is taken inside the critical
-sections.
-
-2: Exception
-------------
-
-Fast page fault:
-
-Fast page fault is the fast path which fixes the guest page fault out of
-the mmu-lock on x86. Currently, the page fault can be fast in one of the
-following two cases:
-
-1. Access Tracking: The SPTE is not present, but it is marked for access
-tracking i.e. the SPTE_SPECIAL_MASK is set. That means we need to
-restore the saved R/X bits. This is described in more detail later below.
-
-2. Write-Protection: The SPTE is present and the fault is
-caused by write-protect. That means we just need to change the W bit of the
-spte.
-
-What we use to avoid all the race is the SPTE_HOST_WRITEABLE bit and
-SPTE_MMU_WRITEABLE bit on the spte:
-- SPTE_HOST_WRITEABLE means the gfn is writable on host.
-- SPTE_MMU_WRITEABLE means the gfn is writable on mmu. The bit is set when
- the gfn is writable on guest mmu and it is not write-protected by shadow
- page write-protection.
-
-On fast page fault path, we will use cmpxchg to atomically set the spte W
-bit if spte.SPTE_HOST_WRITEABLE = 1 and spte.SPTE_WRITE_PROTECT = 1, or
-restore the saved R/X bits if VMX_EPT_TRACK_ACCESS mask is set, or both. This
-is safe because whenever changing these bits can be detected by cmpxchg.
-
-But we need carefully check these cases:
-1): The mapping from gfn to pfn
-The mapping from gfn to pfn may be changed since we can only ensure the pfn
-is not changed during cmpxchg. This is a ABA problem, for example, below case
-will happen:
-
-At the beginning:
-gpte = gfn1
-gfn1 is mapped to pfn1 on host
-spte is the shadow page table entry corresponding with gpte and
-spte = pfn1
-
- VCPU 0 VCPU0
-on fast page fault path:
-
- old_spte = *spte;
- pfn1 is swapped out:
- spte = 0;
-
- pfn1 is re-alloced for gfn2.
-
- gpte is changed to point to
- gfn2 by the guest:
- spte = pfn1;
-
- if (cmpxchg(spte, old_spte, old_spte+W)
- mark_page_dirty(vcpu->kvm, gfn1)
- OOPS!!!
-
-We dirty-log for gfn1, that means gfn2 is lost in dirty-bitmap.
-
-For direct sp, we can easily avoid it since the spte of direct sp is fixed
-to gfn. For indirect sp, before we do cmpxchg, we call gfn_to_pfn_atomic()
-to pin gfn to pfn, because after gfn_to_pfn_atomic():
-- We have held the refcount of pfn that means the pfn can not be freed and
- be reused for another gfn.
-- The pfn is writable that means it can not be shared between different gfns
- by KSM.
-
-Then, we can ensure the dirty bitmaps is correctly set for a gfn.
-
-Currently, to simplify the whole things, we disable fast page fault for
-indirect shadow page.
-
-2): Dirty bit tracking
-In the origin code, the spte can be fast updated (non-atomically) if the
-spte is read-only and the Accessed bit has already been set since the
-Accessed bit and Dirty bit can not be lost.
-
-But it is not true after fast page fault since the spte can be marked
-writable between reading spte and updating spte. Like below case:
-
-At the beginning:
-spte.W = 0
-spte.Accessed = 1
-
- VCPU 0 VCPU0
-In mmu_spte_clear_track_bits():
-
- old_spte = *spte;
-
- /* 'if' condition is satisfied. */
- if (old_spte.Accessed == 1 &&
- old_spte.W == 0)
- spte = 0ull;
- on fast page fault path:
- spte.W = 1
- memory write on the spte:
- spte.Dirty = 1
-
-
- else
- old_spte = xchg(spte, 0ull)
-
-
- if (old_spte.Accessed == 1)
- kvm_set_pfn_accessed(spte.pfn);
- if (old_spte.Dirty == 1)
- kvm_set_pfn_dirty(spte.pfn);
- OOPS!!!
-
-The Dirty bit is lost in this case.
-
-In order to avoid this kind of issue, we always treat the spte as "volatile"
-if it can be updated out of mmu-lock, see spte_has_volatile_bits(), it means,
-the spte is always atomically updated in this case.
-
-3): flush tlbs due to spte updated
-If the spte is updated from writable to readonly, we should flush all TLBs,
-otherwise rmap_write_protect will find a read-only spte, even though the
-writable spte might be cached on a CPU's TLB.
-
-As mentioned before, the spte can be updated to writable out of mmu-lock on
-fast page fault path, in order to easily audit the path, we see if TLBs need
-be flushed caused by this reason in mmu_spte_update() since this is a common
-function to update spte (present -> present).
-
-Since the spte is "volatile" if it can be updated out of mmu-lock, we always
-atomically update the spte, the race caused by fast page fault can be avoided,
-See the comments in spte_has_volatile_bits() and mmu_spte_update().
-
-Lockless Access Tracking:
-
-This is used for Intel CPUs that are using EPT but do not support the EPT A/D
-bits. In this case, when the KVM MMU notifier is called to track accesses to a
-page (via kvm_mmu_notifier_clear_flush_young), it marks the PTE as not-present
-by clearing the RWX bits in the PTE and storing the original R & X bits in
-some unused/ignored bits. In addition, the SPTE_SPECIAL_MASK is also set on the
-PTE (using the ignored bit 62). When the VM tries to access the page later on,
-a fault is generated and the fast page fault mechanism described above is used
-to atomically restore the PTE to a Present state. The W bit is not saved when
-the PTE is marked for access tracking and during restoration to the Present
-state, the W bit is set depending on whether or not it was a write access. If
-it wasn't, then the W bit will remain clear until a write access happens, at
-which time it will be set using the Dirty tracking mechanism described above.
-
-3. Reference
-------------
-
-Name: kvm_lock
-Type: mutex
-Arch: any
-Protects: - vm_list
-
-Name: kvm_count_lock
-Type: raw_spinlock_t
-Arch: any
-Protects: - hardware virtualization enable/disable
-Comment: 'raw' because hardware enabling/disabling must be atomic /wrt
- migration.
-
-Name: kvm_arch::tsc_write_lock
-Type: raw_spinlock
-Arch: x86
-Protects: - kvm_arch::{last_tsc_write,last_tsc_nsec,last_tsc_offset}
- - tsc offset in vmcb
-Comment: 'raw' because updating the tsc offsets must not be preempted.
-
-Name: kvm->mmu_lock
-Type: spinlock_t
-Arch: any
-Protects: -shadow page/shadow tlb entry
-Comment: it is a spinlock since it is used in mmu notifier.
-
-Name: kvm->srcu
-Type: srcu lock
-Arch: any
-Protects: - kvm->memslots
- - kvm->buses
-Comment: The srcu read lock must be held while accessing memslots (e.g.
- when using gfn_to_* functions) and while accessing in-kernel
- MMIO/PIO address->device structure mapping (kvm->buses).
- The srcu index can be stored in kvm_vcpu->srcu_idx per vcpu
- if it is needed by multiple functions.
-
-Name: blocked_vcpu_on_cpu_lock
-Type: spinlock_t
-Arch: x86
-Protects: blocked_vcpu_on_cpu
-Comment: This is a per-CPU lock and it is used for VT-d posted-interrupts.
- When VT-d posted-interrupts is supported and the VM has assigned
- devices, we put the blocked vCPU on the list blocked_vcpu_on_cpu
- protected by blocked_vcpu_on_cpu_lock, when VT-d hardware issues
- wakeup notification event since external interrupts from the
- assigned devices happens, we will find the vCPU on the list to
- wakeup.
+++ /dev/null
-The x86 kvm shadow mmu
-======================
-
-The mmu (in arch/x86/kvm, files mmu.[ch] and paging_tmpl.h) is responsible
-for presenting a standard x86 mmu to the guest, while translating guest
-physical addresses to host physical addresses.
-
-The mmu code attempts to satisfy the following requirements:
-
-- correctness: the guest should not be able to determine that it is running
- on an emulated mmu except for timing (we attempt to comply
- with the specification, not emulate the characteristics of
- a particular implementation such as tlb size)
-- security: the guest must not be able to touch host memory not assigned
- to it
-- performance: minimize the performance penalty imposed by the mmu
-- scaling: need to scale to large memory and large vcpu guests
-- hardware: support the full range of x86 virtualization hardware
-- integration: Linux memory management code must be in control of guest memory
- so that swapping, page migration, page merging, transparent
- hugepages, and similar features work without change
-- dirty tracking: report writes to guest memory to enable live migration
- and framebuffer-based displays
-- footprint: keep the amount of pinned kernel memory low (most memory
- should be shrinkable)
-- reliability: avoid multipage or GFP_ATOMIC allocations
-
-Acronyms
-========
-
-pfn host page frame number
-hpa host physical address
-hva host virtual address
-gfn guest frame number
-gpa guest physical address
-gva guest virtual address
-ngpa nested guest physical address
-ngva nested guest virtual address
-pte page table entry (used also to refer generically to paging structure
- entries)
-gpte guest pte (referring to gfns)
-spte shadow pte (referring to pfns)
-tdp two dimensional paging (vendor neutral term for NPT and EPT)
-
-Virtual and real hardware supported
-===================================
-
-The mmu supports first-generation mmu hardware, which allows an atomic switch
-of the current paging mode and cr3 during guest entry, as well as
-two-dimensional paging (AMD's NPT and Intel's EPT). The emulated hardware
-it exposes is the traditional 2/3/4 level x86 mmu, with support for global
-pages, pae, pse, pse36, cr0.wp, and 1GB pages. Emulated hardware also
-able to expose NPT capable hardware on NPT capable hosts.
-
-Translation
-===========
-
-The primary job of the mmu is to program the processor's mmu to translate
-addresses for the guest. Different translations are required at different
-times:
-
-- when guest paging is disabled, we translate guest physical addresses to
- host physical addresses (gpa->hpa)
-- when guest paging is enabled, we translate guest virtual addresses, to
- guest physical addresses, to host physical addresses (gva->gpa->hpa)
-- when the guest launches a guest of its own, we translate nested guest
- virtual addresses, to nested guest physical addresses, to guest physical
- addresses, to host physical addresses (ngva->ngpa->gpa->hpa)
-
-The primary challenge is to encode between 1 and 3 translations into hardware
-that support only 1 (traditional) and 2 (tdp) translations. When the
-number of required translations matches the hardware, the mmu operates in
-direct mode; otherwise it operates in shadow mode (see below).
-
-Memory
-======
-
-Guest memory (gpa) is part of the user address space of the process that is
-using kvm. Userspace defines the translation between guest addresses and user
-addresses (gpa->hva); note that two gpas may alias to the same hva, but not
-vice versa.
-
-These hvas may be backed using any method available to the host: anonymous
-memory, file backed memory, and device memory. Memory might be paged by the
-host at any time.
-
-Events
-======
-
-The mmu is driven by events, some from the guest, some from the host.
-
-Guest generated events:
-- writes to control registers (especially cr3)
-- invlpg/invlpga instruction execution
-- access to missing or protected translations
-
-Host generated events:
-- changes in the gpa->hpa translation (either through gpa->hva changes or
- through hva->hpa changes)
-- memory pressure (the shrinker)
-
-Shadow pages
-============
-
-The principal data structure is the shadow page, 'struct kvm_mmu_page'. A
-shadow page contains 512 sptes, which can be either leaf or nonleaf sptes. A
-shadow page may contain a mix of leaf and nonleaf sptes.
-
-A nonleaf spte allows the hardware mmu to reach the leaf pages and
-is not related to a translation directly. It points to other shadow pages.
-
-A leaf spte corresponds to either one or two translations encoded into
-one paging structure entry. These are always the lowest level of the
-translation stack, with optional higher level translations left to NPT/EPT.
-Leaf ptes point at guest pages.
-
-The following table shows translations encoded by leaf ptes, with higher-level
-translations in parentheses:
-
- Non-nested guests:
- nonpaging: gpa->hpa
- paging: gva->gpa->hpa
- paging, tdp: (gva->)gpa->hpa
- Nested guests:
- non-tdp: ngva->gpa->hpa (*)
- tdp: (ngva->)ngpa->gpa->hpa
-
-(*) the guest hypervisor will encode the ngva->gpa translation into its page
- tables if npt is not present
-
-Shadow pages contain the following information:
- role.level:
- The level in the shadow paging hierarchy that this shadow page belongs to.
- 1=4k sptes, 2=2M sptes, 3=1G sptes, etc.
- role.direct:
- If set, leaf sptes reachable from this page are for a linear range.
- Examples include real mode translation, large guest pages backed by small
- host pages, and gpa->hpa translations when NPT or EPT is active.
- The linear range starts at (gfn << PAGE_SHIFT) and its size is determined
- by role.level (2MB for first level, 1GB for second level, 0.5TB for third
- level, 256TB for fourth level)
- If clear, this page corresponds to a guest page table denoted by the gfn
- field.
- role.quadrant:
- When role.gpte_is_8_bytes=0, the guest uses 32-bit gptes while the host uses 64-bit
- sptes. That means a guest page table contains more ptes than the host,
- so multiple shadow pages are needed to shadow one guest page.
- For first-level shadow pages, role.quadrant can be 0 or 1 and denotes the
- first or second 512-gpte block in the guest page table. For second-level
- page tables, each 32-bit gpte is converted to two 64-bit sptes
- (since each first-level guest page is shadowed by two first-level
- shadow pages) so role.quadrant takes values in the range 0..3. Each
- quadrant maps 1GB virtual address space.
- role.access:
- Inherited guest access permissions in the form uwx. Note execute
- permission is positive, not negative.
- role.invalid:
- The page is invalid and should not be used. It is a root page that is
- currently pinned (by a cpu hardware register pointing to it); once it is
- unpinned it will be destroyed.
- role.gpte_is_8_bytes:
- Reflects the size of the guest PTE for which the page is valid, i.e. '1'
- if 64-bit gptes are in use, '0' if 32-bit gptes are in use.
- role.nxe:
- Contains the value of efer.nxe for which the page is valid.
- role.cr0_wp:
- Contains the value of cr0.wp for which the page is valid.
- role.smep_andnot_wp:
- Contains the value of cr4.smep && !cr0.wp for which the page is valid
- (pages for which this is true are different from other pages; see the
- treatment of cr0.wp=0 below).
- role.smap_andnot_wp:
- Contains the value of cr4.smap && !cr0.wp for which the page is valid
- (pages for which this is true are different from other pages; see the
- treatment of cr0.wp=0 below).
- role.ept_sp:
- This is a virtual flag to denote a shadowed nested EPT page. ept_sp
- is true if "cr0_wp && smap_andnot_wp", an otherwise invalid combination.
- role.smm:
- Is 1 if the page is valid in system management mode. This field
- determines which of the kvm_memslots array was used to build this
- shadow page; it is also used to go back from a struct kvm_mmu_page
- to a memslot, through the kvm_memslots_for_spte_role macro and
- __gfn_to_memslot.
- role.ad_disabled:
- Is 1 if the MMU instance cannot use A/D bits. EPT did not have A/D
- bits before Haswell; shadow EPT page tables also cannot use A/D bits
- if the L1 hypervisor does not enable them.
- gfn:
- Either the guest page table containing the translations shadowed by this
- page, or the base page frame for linear translations. See role.direct.
- spt:
- A pageful of 64-bit sptes containing the translations for this page.
- Accessed by both kvm and hardware.
- The page pointed to by spt will have its page->private pointing back
- at the shadow page structure.
- sptes in spt point either at guest pages, or at lower-level shadow pages.
- Specifically, if sp1 and sp2 are shadow pages, then sp1->spt[n] may point
- at __pa(sp2->spt). sp2 will point back at sp1 through parent_pte.
- The spt array forms a DAG structure with the shadow page as a node, and
- guest pages as leaves.
- gfns:
- An array of 512 guest frame numbers, one for each present pte. Used to
- perform a reverse map from a pte to a gfn. When role.direct is set, any
- element of this array can be calculated from the gfn field when used, in
- this case, the array of gfns is not allocated. See role.direct and gfn.
- root_count:
- A counter keeping track of how many hardware registers (guest cr3 or
- pdptrs) are now pointing at the page. While this counter is nonzero, the
- page cannot be destroyed. See role.invalid.
- parent_ptes:
- The reverse mapping for the pte/ptes pointing at this page's spt. If
- parent_ptes bit 0 is zero, only one spte points at this page and
- parent_ptes points at this single spte, otherwise, there exists multiple
- sptes pointing at this page and (parent_ptes & ~0x1) points at a data
- structure with a list of parent sptes.
- unsync:
- If true, then the translations in this page may not match the guest's
- translation. This is equivalent to the state of the tlb when a pte is
- changed but before the tlb entry is flushed. Accordingly, unsync ptes
- are synchronized when the guest executes invlpg or flushes its tlb by
- other means. Valid for leaf pages.
- unsync_children:
- How many sptes in the page point at pages that are unsync (or have
- unsynchronized children).
- unsync_child_bitmap:
- A bitmap indicating which sptes in spt point (directly or indirectly) at
- pages that may be unsynchronized. Used to quickly locate all unsychronized
- pages reachable from a given page.
- clear_spte_count:
- Only present on 32-bit hosts, where a 64-bit spte cannot be written
- atomically. The reader uses this while running out of the MMU lock
- to detect in-progress updates and retry them until the writer has
- finished the write.
- write_flooding_count:
- A guest may write to a page table many times, causing a lot of
- emulations if the page needs to be write-protected (see "Synchronized
- and unsynchronized pages" below). Leaf pages can be unsynchronized
- so that they do not trigger frequent emulation, but this is not
- possible for non-leafs. This field counts the number of emulations
- since the last time the page table was actually used; if emulation
- is triggered too frequently on this page, KVM will unmap the page
- to avoid emulation in the future.
-
-Reverse map
-===========
-
-The mmu maintains a reverse mapping whereby all ptes mapping a page can be
-reached given its gfn. This is used, for example, when swapping out a page.
-
-Synchronized and unsynchronized pages
-=====================================
-
-The guest uses two events to synchronize its tlb and page tables: tlb flushes
-and page invalidations (invlpg).
-
-A tlb flush means that we need to synchronize all sptes reachable from the
-guest's cr3. This is expensive, so we keep all guest page tables write
-protected, and synchronize sptes to gptes when a gpte is written.
-
-A special case is when a guest page table is reachable from the current
-guest cr3. In this case, the guest is obliged to issue an invlpg instruction
-before using the translation. We take advantage of that by removing write
-protection from the guest page, and allowing the guest to modify it freely.
-We synchronize modified gptes when the guest invokes invlpg. This reduces
-the amount of emulation we have to do when the guest modifies multiple gptes,
-or when the a guest page is no longer used as a page table and is used for
-random guest data.
-
-As a side effect we have to resynchronize all reachable unsynchronized shadow
-pages on a tlb flush.
-
-
-Reaction to events
-==================
-
-- guest page fault (or npt page fault, or ept violation)
-
-This is the most complicated event. The cause of a page fault can be:
-
- - a true guest fault (the guest translation won't allow the access) (*)
- - access to a missing translation
- - access to a protected translation
- - when logging dirty pages, memory is write protected
- - synchronized shadow pages are write protected (*)
- - access to untranslatable memory (mmio)
-
- (*) not applicable in direct mode
-
-Handling a page fault is performed as follows:
-
- - if the RSV bit of the error code is set, the page fault is caused by guest
- accessing MMIO and cached MMIO information is available.
- - walk shadow page table
- - check for valid generation number in the spte (see "Fast invalidation of
- MMIO sptes" below)
- - cache the information to vcpu->arch.mmio_gva, vcpu->arch.access and
- vcpu->arch.mmio_gfn, and call the emulator
- - If both P bit and R/W bit of error code are set, this could possibly
- be handled as a "fast page fault" (fixed without taking the MMU lock). See
- the description in Documentation/virtual/kvm/locking.txt.
- - if needed, walk the guest page tables to determine the guest translation
- (gva->gpa or ngpa->gpa)
- - if permissions are insufficient, reflect the fault back to the guest
- - determine the host page
- - if this is an mmio request, there is no host page; cache the info to
- vcpu->arch.mmio_gva, vcpu->arch.access and vcpu->arch.mmio_gfn
- - walk the shadow page table to find the spte for the translation,
- instantiating missing intermediate page tables as necessary
- - If this is an mmio request, cache the mmio info to the spte and set some
- reserved bit on the spte (see callers of kvm_mmu_set_mmio_spte_mask)
- - try to unsynchronize the page
- - if successful, we can let the guest continue and modify the gpte
- - emulate the instruction
- - if failed, unshadow the page and let the guest continue
- - update any translations that were modified by the instruction
-
-invlpg handling:
-
- - walk the shadow page hierarchy and drop affected translations
- - try to reinstantiate the indicated translation in the hope that the
- guest will use it in the near future
-
-Guest control register updates:
-
-- mov to cr3
- - look up new shadow roots
- - synchronize newly reachable shadow pages
-
-- mov to cr0/cr4/efer
- - set up mmu context for new paging mode
- - look up new shadow roots
- - synchronize newly reachable shadow pages
-
-Host translation updates:
-
- - mmu notifier called with updated hva
- - look up affected sptes through reverse map
- - drop (or update) translations
-
-Emulating cr0.wp
-================
-
-If tdp is not enabled, the host must keep cr0.wp=1 so page write protection
-works for the guest kernel, not guest guest userspace. When the guest
-cr0.wp=1, this does not present a problem. However when the guest cr0.wp=0,
-we cannot map the permissions for gpte.u=1, gpte.w=0 to any spte (the
-semantics require allowing any guest kernel access plus user read access).
-
-We handle this by mapping the permissions to two possible sptes, depending
-on fault type:
-
-- kernel write fault: spte.u=0, spte.w=1 (allows full kernel access,
- disallows user access)
-- read fault: spte.u=1, spte.w=0 (allows full read access, disallows kernel
- write access)
-
-(user write faults generate a #PF)
-
-In the first case there are two additional complications:
-- if CR4.SMEP is enabled: since we've turned the page into a kernel page,
- the kernel may now execute it. We handle this by also setting spte.nx.
- If we get a user fetch or read fault, we'll change spte.u=1 and
- spte.nx=gpte.nx back. For this to work, KVM forces EFER.NX to 1 when
- shadow paging is in use.
-- if CR4.SMAP is disabled: since the page has been changed to a kernel
- page, it can not be reused when CR4.SMAP is enabled. We set
- CR4.SMAP && !CR0.WP into shadow page's role to avoid this case. Note,
- here we do not care the case that CR4.SMAP is enabled since KVM will
- directly inject #PF to guest due to failed permission check.
-
-To prevent an spte that was converted into a kernel page with cr0.wp=0
-from being written by the kernel after cr0.wp has changed to 1, we make
-the value of cr0.wp part of the page role. This means that an spte created
-with one value of cr0.wp cannot be used when cr0.wp has a different value -
-it will simply be missed by the shadow page lookup code. A similar issue
-exists when an spte created with cr0.wp=0 and cr4.smep=0 is used after
-changing cr4.smep to 1. To avoid this, the value of !cr0.wp && cr4.smep
-is also made a part of the page role.
-
-Large pages
-===========
-
-The mmu supports all combinations of large and small guest and host pages.
-Supported page sizes include 4k, 2M, 4M, and 1G. 4M pages are treated as
-two separate 2M pages, on both guest and host, since the mmu always uses PAE
-paging.
-
-To instantiate a large spte, four constraints must be satisfied:
-
-- the spte must point to a large host page
-- the guest pte must be a large pte of at least equivalent size (if tdp is
- enabled, there is no guest pte and this condition is satisfied)
-- if the spte will be writeable, the large page frame may not overlap any
- write-protected pages
-- the guest page must be wholly contained by a single memory slot
-
-To check the last two conditions, the mmu maintains a ->disallow_lpage set of
-arrays for each memory slot and large page size. Every write protected page
-causes its disallow_lpage to be incremented, thus preventing instantiation of
-a large spte. The frames at the end of an unaligned memory slot have
-artificially inflated ->disallow_lpages so they can never be instantiated.
-
-Fast invalidation of MMIO sptes
-===============================
-
-As mentioned in "Reaction to events" above, kvm will cache MMIO
-information in leaf sptes. When a new memslot is added or an existing
-memslot is changed, this information may become stale and needs to be
-invalidated. This also needs to hold the MMU lock while walking all
-shadow pages, and is made more scalable with a similar technique.
-
-MMIO sptes have a few spare bits, which are used to store a
-generation number. The global generation number is stored in
-kvm_memslots(kvm)->generation, and increased whenever guest memory info
-changes.
-
-When KVM finds an MMIO spte, it checks the generation number of the spte.
-If the generation number of the spte does not equal the global generation
-number, it will ignore the cached MMIO information and handle the page
-fault through the slow path.
-
-Since only 19 bits are used to store generation-number on mmio spte, all
-pages are zapped when there is an overflow.
-
-Unfortunately, a single memory access might access kvm_memslots(kvm) multiple
-times, the last one happening when the generation number is retrieved and
-stored into the MMIO spte. Thus, the MMIO spte might be created based on
-out-of-date information, but with an up-to-date generation number.
-
-To avoid this, the generation number is incremented again after synchronize_srcu
-returns; thus, bit 63 of kvm_memslots(kvm)->generation set to 1 only during a
-memslot update, while some SRCU readers might be using the old copy. We do not
-want to use an MMIO sptes created with an odd generation number, and we can do
-this without losing a bit in the MMIO spte. The "update in-progress" bit of the
-generation is not stored in MMIO spte, and is so is implicitly zero when the
-generation is extracted out of the spte. If KVM is unlucky and creates an MMIO
-spte while an update is in-progress, the next access to the spte will always be
-a cache miss. For example, a subsequent access during the update window will
-miss due to the in-progress flag diverging, while an access after the update
-window closes will have a higher generation number (as compared to the spte).
-
-
-Further reading
-===============
-
-- NPT presentation from KVM Forum 2008
- http://www.linux-kvm.org/images/c/c8/KvmForum2008%24kdf2008_21.pdf
-
+++ /dev/null
-KVM-specific MSRs.
-Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010
-=====================================================
-
-KVM makes use of some custom MSRs to service some requests.
-
-Custom MSRs have a range reserved for them, that goes from
-0x4b564d00 to 0x4b564dff. There are MSRs outside this area,
-but they are deprecated and their use is discouraged.
-
-Custom MSR list
---------
-
-The current supported Custom MSR list is:
-
-MSR_KVM_WALL_CLOCK_NEW: 0x4b564d00
-
- data: 4-byte alignment physical address of a memory area which must be
- in guest RAM. This memory is expected to hold a copy of the following
- structure:
-
- struct pvclock_wall_clock {
- u32 version;
- u32 sec;
- u32 nsec;
- } __attribute__((__packed__));
-
- whose data will be filled in by the hypervisor. The hypervisor is only
- guaranteed to update this data at the moment of MSR write.
- Users that want to reliably query this information more than once have
- to write more than once to this MSR. Fields have the following meanings:
-
- version: guest has to check version before and after grabbing
- time information and check that they are both equal and even.
- An odd version indicates an in-progress update.
-
- sec: number of seconds for wallclock at time of boot.
-
- nsec: number of nanoseconds for wallclock at time of boot.
-
- In order to get the current wallclock time, the system_time from
- MSR_KVM_SYSTEM_TIME_NEW needs to be added.
-
- Note that although MSRs are per-CPU entities, the effect of this
- particular MSR is global.
-
- Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
- leaf prior to usage.
-
-MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
-
- data: 4-byte aligned physical address of a memory area which must be in
- guest RAM, plus an enable bit in bit 0. This memory is expected to hold
- a copy of the following structure:
-
- struct pvclock_vcpu_time_info {
- u32 version;
- u32 pad0;
- u64 tsc_timestamp;
- u64 system_time;
- u32 tsc_to_system_mul;
- s8 tsc_shift;
- u8 flags;
- u8 pad[2];
- } __attribute__((__packed__)); /* 32 bytes */
-
- whose data will be filled in by the hypervisor periodically. Only one
- write, or registration, is needed for each VCPU. The interval between
- updates of this structure is arbitrary and implementation-dependent.
- The hypervisor may update this structure at any time it sees fit until
- anything with bit0 == 0 is written to it.
-
- Fields have the following meanings:
-
- version: guest has to check version before and after grabbing
- time information and check that they are both equal and even.
- An odd version indicates an in-progress update.
-
- tsc_timestamp: the tsc value at the current VCPU at the time
- of the update of this structure. Guests can subtract this value
- from current tsc to derive a notion of elapsed time since the
- structure update.
-
- system_time: a host notion of monotonic time, including sleep
- time at the time this structure was last updated. Unit is
- nanoseconds.
-
- tsc_to_system_mul: multiplier to be used when converting
- tsc-related quantity to nanoseconds
-
- tsc_shift: shift to be used when converting tsc-related
- quantity to nanoseconds. This shift will ensure that
- multiplication with tsc_to_system_mul does not overflow.
- A positive value denotes a left shift, a negative value
- a right shift.
-
- The conversion from tsc to nanoseconds involves an additional
- right shift by 32 bits. With this information, guests can
- derive per-CPU time by doing:
-
- time = (current_tsc - tsc_timestamp)
- if (tsc_shift >= 0)
- time <<= tsc_shift;
- else
- time >>= -tsc_shift;
- time = (time * tsc_to_system_mul) >> 32
- time = time + system_time
-
- flags: bits in this field indicate extended capabilities
- coordinated between the guest and the hypervisor. Availability
- of specific flags has to be checked in 0x40000001 cpuid leaf.
- Current flags are:
-
- flag bit | cpuid bit | meaning
- -------------------------------------------------------------
- | | time measures taken across
- 0 | 24 | multiple cpus are guaranteed to
- | | be monotonic
- -------------------------------------------------------------
- | | guest vcpu has been paused by
- 1 | N/A | the host
- | | See 4.70 in api.txt
- -------------------------------------------------------------
-
- Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
- leaf prior to usage.
-
-
-MSR_KVM_WALL_CLOCK: 0x11
-
- data and functioning: same as MSR_KVM_WALL_CLOCK_NEW. Use that instead.
-
- This MSR falls outside the reserved KVM range and may be removed in the
- future. Its usage is deprecated.
-
- Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
- leaf prior to usage.
-
-MSR_KVM_SYSTEM_TIME: 0x12
-
- data and functioning: same as MSR_KVM_SYSTEM_TIME_NEW. Use that instead.
-
- This MSR falls outside the reserved KVM range and may be removed in the
- future. Its usage is deprecated.
-
- Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
- leaf prior to usage.
-
- The suggested algorithm for detecting kvmclock presence is then:
-
- if (!kvm_para_available()) /* refer to cpuid.txt */
- return NON_PRESENT;
-
- flags = cpuid_eax(0x40000001);
- if (flags & 3) {
- msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
- msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
- return PRESENT;
- } else if (flags & 0) {
- msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
- msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
- return PRESENT;
- } else
- return NON_PRESENT;
-
-MSR_KVM_ASYNC_PF_EN: 0x4b564d02
- data: Bits 63-6 hold 64-byte aligned physical address of a
- 64 byte memory area which must be in guest RAM and must be
- zeroed. Bits 5-3 are reserved and should be zero. Bit 0 is 1
- when asynchronous page faults are enabled on the vcpu 0 when
- disabled. Bit 1 is 1 if asynchronous page faults can be injected
- when vcpu is in cpl == 0. Bit 2 is 1 if asynchronous page faults
- are delivered to L1 as #PF vmexits. Bit 2 can be set only if
- KVM_FEATURE_ASYNC_PF_VMEXIT is present in CPUID.
-
- First 4 byte of 64 byte memory location will be written to by
- the hypervisor at the time of asynchronous page fault (APF)
- injection to indicate type of asynchronous page fault. Value
- of 1 means that the page referred to by the page fault is not
- present. Value 2 means that the page is now available. Disabling
- interrupt inhibits APFs. Guest must not enable interrupt
- before the reason is read, or it may be overwritten by another
- APF. Since APF uses the same exception vector as regular page
- fault guest must reset the reason to 0 before it does
- something that can generate normal page fault. If during page
- fault APF reason is 0 it means that this is regular page
- fault.
-
- During delivery of type 1 APF cr2 contains a token that will
- be used to notify a guest when missing page becomes
- available. When page becomes available type 2 APF is sent with
- cr2 set to the token associated with the page. There is special
- kind of token 0xffffffff which tells vcpu that it should wake
- up all processes waiting for APFs and no individual type 2 APFs
- will be sent.
-
- If APF is disabled while there are outstanding APFs, they will
- not be delivered.
-
- Currently type 2 APF will be always delivered on the same vcpu as
- type 1 was, but guest should not rely on that.
-
-MSR_KVM_STEAL_TIME: 0x4b564d03
-
- data: 64-byte alignment physical address of a memory area which must be
- in guest RAM, plus an enable bit in bit 0. This memory is expected to
- hold a copy of the following structure:
-
- struct kvm_steal_time {
- __u64 steal;
- __u32 version;
- __u32 flags;
- __u8 preempted;
- __u8 u8_pad[3];
- __u32 pad[11];
- }
-
- whose data will be filled in by the hypervisor periodically. Only one
- write, or registration, is needed for each VCPU. The interval between
- updates of this structure is arbitrary and implementation-dependent.
- The hypervisor may update this structure at any time it sees fit until
- anything with bit0 == 0 is written to it. Guest is required to make sure
- this structure is initialized to zero.
-
- Fields have the following meanings:
-
- version: a sequence counter. In other words, guest has to check
- this field before and after grabbing time information and make
- sure they are both equal and even. An odd version indicates an
- in-progress update.
-
- flags: At this point, always zero. May be used to indicate
- changes in this structure in the future.
-
- steal: the amount of time in which this vCPU did not run, in
- nanoseconds. Time during which the vcpu is idle, will not be
- reported as steal time.
-
- preempted: indicate the vCPU who owns this struct is running or
- not. Non-zero values mean the vCPU has been preempted. Zero
- means the vCPU is not preempted. NOTE, it is always zero if the
- the hypervisor doesn't support this field.
-
-MSR_KVM_EOI_EN: 0x4b564d04
- data: Bit 0 is 1 when PV end of interrupt is enabled on the vcpu; 0
- when disabled. Bit 1 is reserved and must be zero. When PV end of
- interrupt is enabled (bit 0 set), bits 63-2 hold a 4-byte aligned
- physical address of a 4 byte memory area which must be in guest RAM and
- must be zeroed.
-
- The first, least significant bit of 4 byte memory location will be
- written to by the hypervisor, typically at the time of interrupt
- injection. Value of 1 means that guest can skip writing EOI to the apic
- (using MSR or MMIO write); instead, it is sufficient to signal
- EOI by clearing the bit in guest memory - this location will
- later be polled by the hypervisor.
- Value of 0 means that the EOI write is required.
-
- It is always safe for the guest to ignore the optimization and perform
- the APIC EOI write anyway.
-
- Hypervisor is guaranteed to only modify this least
- significant bit while in the current VCPU context, this means that
- guest does not need to use either lock prefix or memory ordering
- primitives to synchronise with the hypervisor.
-
- However, hypervisor can set and clear this memory bit at any time:
- therefore to make sure hypervisor does not interrupt the
- guest and clear the least significant bit in the memory area
- in the window between guest testing it to detect
- whether it can skip EOI apic write and between guest
- clearing it to signal EOI to the hypervisor,
- guest must both read the least significant bit in the memory area and
- clear it using a single CPU instruction, such as test and clear, or
- compare and exchange.
-
-MSR_KVM_POLL_CONTROL: 0x4b564d05
- Control host-side polling.
-
- data: Bit 0 enables (1) or disables (0) host-side HLT polling logic.
-
- KVM guests can request the host not to poll on HLT, for example if
- they are performing polling themselves.
-
+++ /dev/null
-Nested VMX
-==========
-
-Overview
----------
-
-On Intel processors, KVM uses Intel's VMX (Virtual-Machine eXtensions)
-to easily and efficiently run guest operating systems. Normally, these guests
-*cannot* themselves be hypervisors running their own guests, because in VMX,
-guests cannot use VMX instructions.
-
-The "Nested VMX" feature adds this missing capability - of running guest
-hypervisors (which use VMX) with their own nested guests. It does so by
-allowing a guest to use VMX instructions, and correctly and efficiently
-emulating them using the single level of VMX available in the hardware.
-
-We describe in much greater detail the theory behind the nested VMX feature,
-its implementation and its performance characteristics, in the OSDI 2010 paper
-"The Turtles Project: Design and Implementation of Nested Virtualization",
-available at:
-
- http://www.usenix.org/events/osdi10/tech/full_papers/Ben-Yehuda.pdf
-
-
-Terminology
------------
-
-Single-level virtualization has two levels - the host (KVM) and the guests.
-In nested virtualization, we have three levels: The host (KVM), which we call
-L0, the guest hypervisor, which we call L1, and its nested guest, which we
-call L2.
-
-
-Running nested VMX
-------------------
-
-The nested VMX feature is disabled by default. It can be enabled by giving
-the "nested=1" option to the kvm-intel module.
-
-No modifications are required to user space (qemu). However, qemu's default
-emulated CPU type (qemu64) does not list the "VMX" CPU feature, so it must be
-explicitly enabled, by giving qemu one of the following options:
-
- -cpu host (emulated CPU has all features of the real CPU)
-
- -cpu qemu64,+vmx (add just the vmx feature to a named CPU type)
-
-
-ABIs
-----
-
-Nested VMX aims to present a standard and (eventually) fully-functional VMX
-implementation for the a guest hypervisor to use. As such, the official
-specification of the ABI that it provides is Intel's VMX specification,
-namely volume 3B of their "Intel 64 and IA-32 Architectures Software
-Developer's Manual". Not all of VMX's features are currently fully supported,
-but the goal is to eventually support them all, starting with the VMX features
-which are used in practice by popular hypervisors (KVM and others).
-
-As a VMX implementation, nested VMX presents a VMCS structure to L1.
-As mandated by the spec, other than the two fields revision_id and abort,
-this structure is *opaque* to its user, who is not supposed to know or care
-about its internal structure. Rather, the structure is accessed through the
-VMREAD and VMWRITE instructions.
-Still, for debugging purposes, KVM developers might be interested to know the
-internals of this structure; This is struct vmcs12 from arch/x86/kvm/vmx.c.
-
-The name "vmcs12" refers to the VMCS that L1 builds for L2. In the code we
-also have "vmcs01", the VMCS that L0 built for L1, and "vmcs02" is the VMCS
-which L0 builds to actually run L2 - how this is done is explained in the
-aforementioned paper.
-
-For convenience, we repeat the content of struct vmcs12 here. If the internals
-of this structure changes, this can break live migration across KVM versions.
-VMCS12_REVISION (from vmx.c) should be changed if struct vmcs12 or its inner
-struct shadow_vmcs is ever changed.
-
- typedef u64 natural_width;
- struct __packed vmcs12 {
- /* According to the Intel spec, a VMCS region must start with
- * these two user-visible fields */
- u32 revision_id;
- u32 abort;
-
- u32 launch_state; /* set to 0 by VMCLEAR, to 1 by VMLAUNCH */
- u32 padding[7]; /* room for future expansion */
-
- u64 io_bitmap_a;
- u64 io_bitmap_b;
- u64 msr_bitmap;
- u64 vm_exit_msr_store_addr;
- u64 vm_exit_msr_load_addr;
- u64 vm_entry_msr_load_addr;
- u64 tsc_offset;
- u64 virtual_apic_page_addr;
- u64 apic_access_addr;
- u64 ept_pointer;
- u64 guest_physical_address;
- u64 vmcs_link_pointer;
- u64 guest_ia32_debugctl;
- u64 guest_ia32_pat;
- u64 guest_ia32_efer;
- u64 guest_pdptr0;
- u64 guest_pdptr1;
- u64 guest_pdptr2;
- u64 guest_pdptr3;
- u64 host_ia32_pat;
- u64 host_ia32_efer;
- u64 padding64[8]; /* room for future expansion */
- natural_width cr0_guest_host_mask;
- natural_width cr4_guest_host_mask;
- natural_width cr0_read_shadow;
- natural_width cr4_read_shadow;
- natural_width cr3_target_value0;
- natural_width cr3_target_value1;
- natural_width cr3_target_value2;
- natural_width cr3_target_value3;
- natural_width exit_qualification;
- natural_width guest_linear_address;
- natural_width guest_cr0;
- natural_width guest_cr3;
- natural_width guest_cr4;
- natural_width guest_es_base;
- natural_width guest_cs_base;
- natural_width guest_ss_base;
- natural_width guest_ds_base;
- natural_width guest_fs_base;
- natural_width guest_gs_base;
- natural_width guest_ldtr_base;
- natural_width guest_tr_base;
- natural_width guest_gdtr_base;
- natural_width guest_idtr_base;
- natural_width guest_dr7;
- natural_width guest_rsp;
- natural_width guest_rip;
- natural_width guest_rflags;
- natural_width guest_pending_dbg_exceptions;
- natural_width guest_sysenter_esp;
- natural_width guest_sysenter_eip;
- natural_width host_cr0;
- natural_width host_cr3;
- natural_width host_cr4;
- natural_width host_fs_base;
- natural_width host_gs_base;
- natural_width host_tr_base;
- natural_width host_gdtr_base;
- natural_width host_idtr_base;
- natural_width host_ia32_sysenter_esp;
- natural_width host_ia32_sysenter_eip;
- natural_width host_rsp;
- natural_width host_rip;
- natural_width paddingl[8]; /* room for future expansion */
- u32 pin_based_vm_exec_control;
- u32 cpu_based_vm_exec_control;
- u32 exception_bitmap;
- u32 page_fault_error_code_mask;
- u32 page_fault_error_code_match;
- u32 cr3_target_count;
- u32 vm_exit_controls;
- u32 vm_exit_msr_store_count;
- u32 vm_exit_msr_load_count;
- u32 vm_entry_controls;
- u32 vm_entry_msr_load_count;
- u32 vm_entry_intr_info_field;
- u32 vm_entry_exception_error_code;
- u32 vm_entry_instruction_len;
- u32 tpr_threshold;
- u32 secondary_vm_exec_control;
- u32 vm_instruction_error;
- u32 vm_exit_reason;
- u32 vm_exit_intr_info;
- u32 vm_exit_intr_error_code;
- u32 idt_vectoring_info_field;
- u32 idt_vectoring_error_code;
- u32 vm_exit_instruction_len;
- u32 vmx_instruction_info;
- u32 guest_es_limit;
- u32 guest_cs_limit;
- u32 guest_ss_limit;
- u32 guest_ds_limit;
- u32 guest_fs_limit;
- u32 guest_gs_limit;
- u32 guest_ldtr_limit;
- u32 guest_tr_limit;
- u32 guest_gdtr_limit;
- u32 guest_idtr_limit;
- u32 guest_es_ar_bytes;
- u32 guest_cs_ar_bytes;
- u32 guest_ss_ar_bytes;
- u32 guest_ds_ar_bytes;
- u32 guest_fs_ar_bytes;
- u32 guest_gs_ar_bytes;
- u32 guest_ldtr_ar_bytes;
- u32 guest_tr_ar_bytes;
- u32 guest_interruptibility_info;
- u32 guest_activity_state;
- u32 guest_sysenter_cs;
- u32 host_ia32_sysenter_cs;
- u32 padding32[8]; /* room for future expansion */
- u16 virtual_processor_id;
- u16 guest_es_selector;
- u16 guest_cs_selector;
- u16 guest_ss_selector;
- u16 guest_ds_selector;
- u16 guest_fs_selector;
- u16 guest_gs_selector;
- u16 guest_ldtr_selector;
- u16 guest_tr_selector;
- u16 host_es_selector;
- u16 host_cs_selector;
- u16 host_ss_selector;
- u16 host_ds_selector;
- u16 host_fs_selector;
- u16 host_gs_selector;
- u16 host_tr_selector;
- };
-
-
-Authors
--------
-
-These patches were written by:
- Abel Gordon, abelg <at> il.ibm.com
- Nadav Har'El, nyh <at> il.ibm.com
- Orit Wasserman, oritw <at> il.ibm.com
- Ben-Ami Yassor, benami <at> il.ibm.com
- Muli Ben-Yehuda, muli <at> il.ibm.com
-
-With contributions by:
- Anthony Liguori, aliguori <at> us.ibm.com
- Mike Day, mdday <at> us.ibm.com
- Michael Factor, factor <at> il.ibm.com
- Zvi Dubitzky, dubi <at> il.ibm.com
-
-And valuable reviews by:
- Avi Kivity, avi <at> redhat.com
- Gleb Natapov, gleb <at> redhat.com
- Marcelo Tosatti, mtosatti <at> redhat.com
- Kevin Tian, kevin.tian <at> intel.com
- and others.
+++ /dev/null
-The PPC KVM paravirtual interface
-=================================
-
-The basic execution principle by which KVM on PowerPC works is to run all kernel
-space code in PR=1 which is user space. This way we trap all privileged
-instructions and can emulate them accordingly.
-
-Unfortunately that is also the downfall. There are quite some privileged
-instructions that needlessly return us to the hypervisor even though they
-could be handled differently.
-
-This is what the PPC PV interface helps with. It takes privileged instructions
-and transforms them into unprivileged ones with some help from the hypervisor.
-This cuts down virtualization costs by about 50% on some of my benchmarks.
-
-The code for that interface can be found in arch/powerpc/kernel/kvm*
-
-Querying for existence
-======================
-
-To find out if we're running on KVM or not, we leverage the device tree. When
-Linux is running on KVM, a node /hypervisor exists. That node contains a
-compatible property with the value "linux,kvm".
-
-Once you determined you're running under a PV capable KVM, you can now use
-hypercalls as described below.
-
-KVM hypercalls
-==============
-
-Inside the device tree's /hypervisor node there's a property called
-'hypercall-instructions'. This property contains at most 4 opcodes that make
-up the hypercall. To call a hypercall, just call these instructions.
-
-The parameters are as follows:
-
- Register IN OUT
-
- r0 - volatile
- r3 1st parameter Return code
- r4 2nd parameter 1st output value
- r5 3rd parameter 2nd output value
- r6 4th parameter 3rd output value
- r7 5th parameter 4th output value
- r8 6th parameter 5th output value
- r9 7th parameter 6th output value
- r10 8th parameter 7th output value
- r11 hypercall number 8th output value
- r12 - volatile
-
-Hypercall definitions are shared in generic code, so the same hypercall numbers
-apply for x86 and powerpc alike with the exception that each KVM hypercall
-also needs to be ORed with the KVM vendor code which is (42 << 16).
-
-Return codes can be as follows:
-
- Code Meaning
-
- 0 Success
- 12 Hypercall not implemented
- <0 Error
-
-The magic page
-==============
-
-To enable communication between the hypervisor and guest there is a new shared
-page that contains parts of supervisor visible register state. The guest can
-map this shared page using the KVM hypercall KVM_HC_PPC_MAP_MAGIC_PAGE.
-
-With this hypercall issued the guest always gets the magic page mapped at the
-desired location. The first parameter indicates the effective address when the
-MMU is enabled. The second parameter indicates the address in real mode, if
-applicable to the target. For now, we always map the page to -4096. This way we
-can access it using absolute load and store functions. The following
-instruction reads the first field of the magic page:
-
- ld rX, -4096(0)
-
-The interface is designed to be extensible should there be need later to add
-additional registers to the magic page. If you add fields to the magic page,
-also define a new hypercall feature to indicate that the host can give you more
-registers. Only if the host supports the additional features, make use of them.
-
-The magic page layout is described by struct kvm_vcpu_arch_shared
-in arch/powerpc/include/asm/kvm_para.h.
-
-Magic page features
-===================
-
-When mapping the magic page using the KVM hypercall KVM_HC_PPC_MAP_MAGIC_PAGE,
-a second return value is passed to the guest. This second return value contains
-a bitmap of available features inside the magic page.
-
-The following enhancements to the magic page are currently available:
-
- KVM_MAGIC_FEAT_SR Maps SR registers r/w in the magic page
- KVM_MAGIC_FEAT_MAS0_TO_SPRG7 Maps MASn, ESR, PIR and high SPRGs
-
-For enhanced features in the magic page, please check for the existence of the
-feature before using them!
-
-Magic page flags
-================
-
-In addition to features that indicate whether a host is capable of a particular
-feature we also have a channel for a guest to tell the guest whether it's capable
-of something. This is what we call "flags".
-
-Flags are passed to the host in the low 12 bits of the Effective Address.
-
-The following flags are currently available for a guest to expose:
-
- MAGIC_PAGE_FLAG_NOT_MAPPED_NX Guest handles NX bits correctly wrt magic page
-
-MSR bits
-========
-
-The MSR contains bits that require hypervisor intervention and bits that do
-not require direct hypervisor intervention because they only get interpreted
-when entering the guest or don't have any impact on the hypervisor's behavior.
-
-The following bits are safe to be set inside the guest:
-
- MSR_EE
- MSR_RI
-
-If any other bit changes in the MSR, please still use mtmsr(d).
-
-Patched instructions
-====================
-
-The "ld" and "std" instructions are transformed to "lwz" and "stw" instructions
-respectively on 32 bit systems with an added offset of 4 to accommodate for big
-endianness.
-
-The following is a list of mapping the Linux kernel performs when running as
-guest. Implementing any of those mappings is optional, as the instruction traps
-also act on the shared page. So calling privileged instructions still works as
-before.
-
-From To
-==== ==
-
-mfmsr rX ld rX, magic_page->msr
-mfsprg rX, 0 ld rX, magic_page->sprg0
-mfsprg rX, 1 ld rX, magic_page->sprg1
-mfsprg rX, 2 ld rX, magic_page->sprg2
-mfsprg rX, 3 ld rX, magic_page->sprg3
-mfsrr0 rX ld rX, magic_page->srr0
-mfsrr1 rX ld rX, magic_page->srr1
-mfdar rX ld rX, magic_page->dar
-mfdsisr rX lwz rX, magic_page->dsisr
-
-mtmsr rX std rX, magic_page->msr
-mtsprg 0, rX std rX, magic_page->sprg0
-mtsprg 1, rX std rX, magic_page->sprg1
-mtsprg 2, rX std rX, magic_page->sprg2
-mtsprg 3, rX std rX, magic_page->sprg3
-mtsrr0 rX std rX, magic_page->srr0
-mtsrr1 rX std rX, magic_page->srr1
-mtdar rX std rX, magic_page->dar
-mtdsisr rX stw rX, magic_page->dsisr
-
-tlbsync nop
-
-mtmsrd rX, 0 b <special mtmsr section>
-mtmsr rX b <special mtmsr section>
-
-mtmsrd rX, 1 b <special mtmsrd section>
-
-[Book3S only]
-mtsrin rX, rY b <special mtsrin section>
-
-[BookE only]
-wrteei [0|1] b <special wrteei section>
-
-
-Some instructions require more logic to determine what's going on than a load
-or store instruction can deliver. To enable patching of those, we keep some
-RAM around where we can live translate instructions to. What happens is the
-following:
-
- 1) copy emulation code to memory
- 2) patch that code to fit the emulated instruction
- 3) patch that code to return to the original pc + 4
- 4) patch the original instruction to branch to the new code
-
-That way we can inject an arbitrary amount of code as replacement for a single
-instruction. This allows us to check for pending interrupts when setting EE=1
-for example.
-
-Hypercall ABIs in KVM on PowerPC
-=================================
-1) KVM hypercalls (ePAPR)
-
-These are ePAPR compliant hypercall implementation (mentioned above). Even
-generic hypercalls are implemented here, like the ePAPR idle hcall. These are
-available on all targets.
-
-2) PAPR hypercalls
-
-PAPR hypercalls are needed to run server PowerPC PAPR guests (-M pseries in QEMU).
-These are the same hypercalls that pHyp, the POWER hypervisor implements. Some of
-them are handled in the kernel, some are handled in user space. This is only
-available on book3s_64.
-
-3) OSI hypercalls
-
-Mac-on-Linux is another user of KVM on PowerPC, which has its own hypercall (long
-before KVM). This is supported to maintain compatibility. All these hypercalls get
-forwarded to user space. This is only useful on book3s_32, but can be used with
-book3s_64 as well.
+++ /dev/null
-Review checklist for kvm patches
-================================
-
-1. The patch must follow Documentation/process/coding-style.rst and
- Documentation/process/submitting-patches.rst.
-
-2. Patches should be against kvm.git master branch.
-
-3. If the patch introduces or modifies a new userspace API:
- - the API must be documented in Documentation/virtual/kvm/api.txt
- - the API must be discoverable using KVM_CHECK_EXTENSION
-
-4. New state must include support for save/restore.
-
-5. New features must default to off (userspace should explicitly request them).
- Performance improvements can and should default to on.
-
-6. New cpu features should be exposed via KVM_GET_SUPPORTED_CPUID2
-
-7. Emulator changes should be accompanied by unit tests for qemu-kvm.git
- kvm/test directory.
-
-8. Changes should be vendor neutral when possible. Changes to common code
- are better than duplicating changes to vendor code.
-
-9. Similarly, prefer changes to arch independent code than to arch dependent
- code.
-
-10. User/kernel interfaces and guest/host interfaces must be 64-bit clean
- (all variables and sizes naturally aligned on 64-bit; use specific types
- only - u64 rather than ulong).
-
-11. New guest visible features must either be documented in a hardware manual
- or be accompanied by documentation.
-
-12. Features must be robust against reset and kexec - for example, shared
- host/guest memory must be unshared to prevent the host from writing to
- guest memory that the guest has not reserved for this purpose.
+++ /dev/null
-The s390 DIAGNOSE call on KVM
-=============================
-
-KVM on s390 supports the DIAGNOSE call for making hypercalls, both for
-native hypercalls and for selected hypercalls found on other s390
-hypervisors.
-
-Note that bits are numbered as by the usual s390 convention (most significant
-bit on the left).
-
-
-General remarks
----------------
-
-DIAGNOSE calls by the guest cause a mandatory intercept. This implies
-all supported DIAGNOSE calls need to be handled by either KVM or its
-userspace.
-
-All DIAGNOSE calls supported by KVM use the RS-a format:
-
---------------------------------------
-| '83' | R1 | R3 | B2 | D2 |
---------------------------------------
-0 8 12 16 20 31
-
-The second-operand address (obtained by the base/displacement calculation)
-is not used to address data. Instead, bits 48-63 of this address specify
-the function code, and bits 0-47 are ignored.
-
-The supported DIAGNOSE function codes vary by the userspace used. For
-DIAGNOSE function codes not specific to KVM, please refer to the
-documentation for the s390 hypervisors defining them.
-
-
-DIAGNOSE function code 'X'500' - KVM virtio functions
------------------------------------------------------
-
-If the function code specifies 0x500, various virtio-related functions
-are performed.
-
-General register 1 contains the virtio subfunction code. Supported
-virtio subfunctions depend on KVM's userspace. Generally, userspace
-provides either s390-virtio (subcodes 0-2) or virtio-ccw (subcode 3).
-
-Upon completion of the DIAGNOSE instruction, general register 2 contains
-the function's return code, which is either a return code or a subcode
-specific value.
-
-Subcode 0 - s390-virtio notification and early console printk
- Handled by userspace.
-
-Subcode 1 - s390-virtio reset
- Handled by userspace.
-
-Subcode 2 - s390-virtio set status
- Handled by userspace.
-
-Subcode 3 - virtio-ccw notification
- Handled by either userspace or KVM (ioeventfd case).
-
- General register 2 contains a subchannel-identification word denoting
- the subchannel of the virtio-ccw proxy device to be notified.
-
- General register 3 contains the number of the virtqueue to be notified.
-
- General register 4 contains a 64bit identifier for KVM usage (the
- kvm_io_bus cookie). If general register 4 does not contain a valid
- identifier, it is ignored.
-
- After completion of the DIAGNOSE call, general register 2 may contain
- a 64bit identifier (in the kvm_io_bus cookie case), or a negative
- error value, if an internal error occurred.
-
- See also the virtio standard for a discussion of this hypercall.
-
-
-DIAGNOSE function code 'X'501 - KVM breakpoint
-----------------------------------------------
-
-If the function code specifies 0x501, breakpoint functions may be performed.
-This function code is handled by userspace.
-
-This diagnose function code has no subfunctions and uses no parameters.
+++ /dev/null
-
- Timekeeping Virtualization for X86-Based Architectures
-
- Zachary Amsden <zamsden@redhat.com>
- Copyright (c) 2010, Red Hat. All rights reserved.
-
-1) Overview
-2) Timing Devices
-3) TSC Hardware
-4) Virtualization Problems
-
-=========================================================================
-
-1) Overview
-
-One of the most complicated parts of the X86 platform, and specifically,
-the virtualization of this platform is the plethora of timing devices available
-and the complexity of emulating those devices. In addition, virtualization of
-time introduces a new set of challenges because it introduces a multiplexed
-division of time beyond the control of the guest CPU.
-
-First, we will describe the various timekeeping hardware available, then
-present some of the problems which arise and solutions available, giving
-specific recommendations for certain classes of KVM guests.
-
-The purpose of this document is to collect data and information relevant to
-timekeeping which may be difficult to find elsewhere, specifically,
-information relevant to KVM and hardware-based virtualization.
-
-=========================================================================
-
-2) Timing Devices
-
-First we discuss the basic hardware devices available. TSC and the related
-KVM clock are special enough to warrant a full exposition and are described in
-the following section.
-
-2.1) i8254 - PIT
-
-One of the first timer devices available is the programmable interrupt timer,
-or PIT. The PIT has a fixed frequency 1.193182 MHz base clock and three
-channels which can be programmed to deliver periodic or one-shot interrupts.
-These three channels can be configured in different modes and have individual
-counters. Channel 1 and 2 were not available for general use in the original
-IBM PC, and historically were connected to control RAM refresh and the PC
-speaker. Now the PIT is typically integrated as part of an emulated chipset
-and a separate physical PIT is not used.
-
-The PIT uses I/O ports 0x40 - 0x43. Access to the 16-bit counters is done
-using single or multiple byte access to the I/O ports. There are 6 modes
-available, but not all modes are available to all timers, as only timer 2
-has a connected gate input, required for modes 1 and 5. The gate line is
-controlled by port 61h, bit 0, as illustrated in the following diagram.
-
- -------------- ----------------
-| | | |
-| 1.1932 MHz |---------->| CLOCK OUT | ---------> IRQ 0
-| Clock | | | |
- -------------- | +->| GATE TIMER 0 |
- | ----------------
- |
- | ----------------
- | | |
- |------>| CLOCK OUT | ---------> 66.3 KHZ DRAM
- | | | (aka /dev/null)
- | +->| GATE TIMER 1 |
- | ----------------
- |
- | ----------------
- | | |
- |------>| CLOCK OUT | ---------> Port 61h, bit 5
- | | |
-Port 61h, bit 0 ---------->| GATE TIMER 2 | \_.---- ____
- ---------------- _| )--|LPF|---Speaker
- / *---- \___/
-Port 61h, bit 1 -----------------------------------/
-
-The timer modes are now described.
-
-Mode 0: Single Timeout. This is a one-shot software timeout that counts down
- when the gate is high (always true for timers 0 and 1). When the count
- reaches zero, the output goes high.
-
-Mode 1: Triggered One-shot. The output is initially set high. When the gate
- line is set high, a countdown is initiated (which does not stop if the gate is
- lowered), during which the output is set low. When the count reaches zero,
- the output goes high.
-
-Mode 2: Rate Generator. The output is initially set high. When the countdown
- reaches 1, the output goes low for one count and then returns high. The value
- is reloaded and the countdown automatically resumes. If the gate line goes
- low, the count is halted. If the output is low when the gate is lowered, the
- output automatically goes high (this only affects timer 2).
-
-Mode 3: Square Wave. This generates a high / low square wave. The count
- determines the length of the pulse, which alternates between high and low
- when zero is reached. The count only proceeds when gate is high and is
- automatically reloaded on reaching zero. The count is decremented twice at
- each clock to generate a full high / low cycle at the full periodic rate.
- If the count is even, the clock remains high for N/2 counts and low for N/2
- counts; if the clock is odd, the clock is high for (N+1)/2 counts and low
- for (N-1)/2 counts. Only even values are latched by the counter, so odd
- values are not observed when reading. This is the intended mode for timer 2,
- which generates sine-like tones by low-pass filtering the square wave output.
-
-Mode 4: Software Strobe. After programming this mode and loading the counter,
- the output remains high until the counter reaches zero. Then the output
- goes low for 1 clock cycle and returns high. The counter is not reloaded.
- Counting only occurs when gate is high.
-
-Mode 5: Hardware Strobe. After programming and loading the counter, the
- output remains high. When the gate is raised, a countdown is initiated
- (which does not stop if the gate is lowered). When the counter reaches zero,
- the output goes low for 1 clock cycle and then returns high. The counter is
- not reloaded.
-
-In addition to normal binary counting, the PIT supports BCD counting. The
-command port, 0x43 is used to set the counter and mode for each of the three
-timers.
-
-PIT commands, issued to port 0x43, using the following bit encoding:
-
-Bit 7-4: Command (See table below)
-Bit 3-1: Mode (000 = Mode 0, 101 = Mode 5, 11X = undefined)
-Bit 0 : Binary (0) / BCD (1)
-
-Command table:
-
-0000 - Latch Timer 0 count for port 0x40
- sample and hold the count to be read in port 0x40;
- additional commands ignored until counter is read;
- mode bits ignored.
-
-0001 - Set Timer 0 LSB mode for port 0x40
- set timer to read LSB only and force MSB to zero;
- mode bits set timer mode
-
-0010 - Set Timer 0 MSB mode for port 0x40
- set timer to read MSB only and force LSB to zero;
- mode bits set timer mode
-
-0011 - Set Timer 0 16-bit mode for port 0x40
- set timer to read / write LSB first, then MSB;
- mode bits set timer mode
-
-0100 - Latch Timer 1 count for port 0x41 - as described above
-0101 - Set Timer 1 LSB mode for port 0x41 - as described above
-0110 - Set Timer 1 MSB mode for port 0x41 - as described above
-0111 - Set Timer 1 16-bit mode for port 0x41 - as described above
-
-1000 - Latch Timer 2 count for port 0x42 - as described above
-1001 - Set Timer 2 LSB mode for port 0x42 - as described above
-1010 - Set Timer 2 MSB mode for port 0x42 - as described above
-1011 - Set Timer 2 16-bit mode for port 0x42 as described above
-
-1101 - General counter latch
- Latch combination of counters into corresponding ports
- Bit 3 = Counter 2
- Bit 2 = Counter 1
- Bit 1 = Counter 0
- Bit 0 = Unused
-
-1110 - Latch timer status
- Latch combination of counter mode into corresponding ports
- Bit 3 = Counter 2
- Bit 2 = Counter 1
- Bit 1 = Counter 0
-
- The output of ports 0x40-0x42 following this command will be:
-
- Bit 7 = Output pin
- Bit 6 = Count loaded (0 if timer has expired)
- Bit 5-4 = Read / Write mode
- 01 = MSB only
- 10 = LSB only
- 11 = LSB / MSB (16-bit)
- Bit 3-1 = Mode
- Bit 0 = Binary (0) / BCD mode (1)
-
-2.2) RTC
-
-The second device which was available in the original PC was the MC146818 real
-time clock. The original device is now obsolete, and usually emulated by the
-system chipset, sometimes by an HPET and some frankenstein IRQ routing.
-
-The RTC is accessed through CMOS variables, which uses an index register to
-control which bytes are read. Since there is only one index register, read
-of the CMOS and read of the RTC require lock protection (in addition, it is
-dangerous to allow userspace utilities such as hwclock to have direct RTC
-access, as they could corrupt kernel reads and writes of CMOS memory).
-
-The RTC generates an interrupt which is usually routed to IRQ 8. The interrupt
-can function as a periodic timer, an additional once a day alarm, and can issue
-interrupts after an update of the CMOS registers by the MC146818 is complete.
-The type of interrupt is signalled in the RTC status registers.
-
-The RTC will update the current time fields by battery power even while the
-system is off. The current time fields should not be read while an update is
-in progress, as indicated in the status register.
-
-The clock uses a 32.768kHz crystal, so bits 6-4 of register A should be
-programmed to a 32kHz divider if the RTC is to count seconds.
-
-This is the RAM map originally used for the RTC/CMOS:
-
-Location Size Description
-------------------------------------------
-00h byte Current second (BCD)
-01h byte Seconds alarm (BCD)
-02h byte Current minute (BCD)
-03h byte Minutes alarm (BCD)
-04h byte Current hour (BCD)
-05h byte Hours alarm (BCD)
-06h byte Current day of week (BCD)
-07h byte Current day of month (BCD)
-08h byte Current month (BCD)
-09h byte Current year (BCD)
-0Ah byte Register A
- bit 7 = Update in progress
- bit 6-4 = Divider for clock
- 000 = 4.194 MHz
- 001 = 1.049 MHz
- 010 = 32 kHz
- 10X = test modes
- 110 = reset / disable
- 111 = reset / disable
- bit 3-0 = Rate selection for periodic interrupt
- 000 = periodic timer disabled
- 001 = 3.90625 uS
- 010 = 7.8125 uS
- 011 = .122070 mS
- 100 = .244141 mS
- ...
- 1101 = 125 mS
- 1110 = 250 mS
- 1111 = 500 mS
-0Bh byte Register B
- bit 7 = Run (0) / Halt (1)
- bit 6 = Periodic interrupt enable
- bit 5 = Alarm interrupt enable
- bit 4 = Update-ended interrupt enable
- bit 3 = Square wave interrupt enable
- bit 2 = BCD calendar (0) / Binary (1)
- bit 1 = 12-hour mode (0) / 24-hour mode (1)
- bit 0 = 0 (DST off) / 1 (DST enabled)
-OCh byte Register C (read only)
- bit 7 = interrupt request flag (IRQF)
- bit 6 = periodic interrupt flag (PF)
- bit 5 = alarm interrupt flag (AF)
- bit 4 = update interrupt flag (UF)
- bit 3-0 = reserved
-ODh byte Register D (read only)
- bit 7 = RTC has power
- bit 6-0 = reserved
-32h byte Current century BCD (*)
- (*) location vendor specific and now determined from ACPI global tables
-
-2.3) APIC
-
-On Pentium and later processors, an on-board timer is available to each CPU
-as part of the Advanced Programmable Interrupt Controller. The APIC is
-accessed through memory-mapped registers and provides interrupt service to each
-CPU, used for IPIs and local timer interrupts.
-
-Although in theory the APIC is a safe and stable source for local interrupts,
-in practice, many bugs and glitches have occurred due to the special nature of
-the APIC CPU-local memory-mapped hardware. Beware that CPU errata may affect
-the use of the APIC and that workarounds may be required. In addition, some of
-these workarounds pose unique constraints for virtualization - requiring either
-extra overhead incurred from extra reads of memory-mapped I/O or additional
-functionality that may be more computationally expensive to implement.
-
-Since the APIC is documented quite well in the Intel and AMD manuals, we will
-avoid repetition of the detail here. It should be pointed out that the APIC
-timer is programmed through the LVT (local vector timer) register, is capable
-of one-shot or periodic operation, and is based on the bus clock divided down
-by the programmable divider register.
-
-2.4) HPET
-
-HPET is quite complex, and was originally intended to replace the PIT / RTC
-support of the X86 PC. It remains to be seen whether that will be the case, as
-the de facto standard of PC hardware is to emulate these older devices. Some
-systems designated as legacy free may support only the HPET as a hardware timer
-device.
-
-The HPET spec is rather loose and vague, requiring at least 3 hardware timers,
-but allowing implementation freedom to support many more. It also imposes no
-fixed rate on the timer frequency, but does impose some extremal values on
-frequency, error and slew.
-
-In general, the HPET is recommended as a high precision (compared to PIT /RTC)
-time source which is independent of local variation (as there is only one HPET
-in any given system). The HPET is also memory-mapped, and its presence is
-indicated through ACPI tables by the BIOS.
-
-Detailed specification of the HPET is beyond the current scope of this
-document, as it is also very well documented elsewhere.
-
-2.5) Offboard Timers
-
-Several cards, both proprietary (watchdog boards) and commonplace (e1000) have
-timing chips built into the cards which may have registers which are accessible
-to kernel or user drivers. To the author's knowledge, using these to generate
-a clocksource for a Linux or other kernel has not yet been attempted and is in
-general frowned upon as not playing by the agreed rules of the game. Such a
-timer device would require additional support to be virtualized properly and is
-not considered important at this time as no known operating system does this.
-
-=========================================================================
-
-3) TSC Hardware
-
-The TSC or time stamp counter is relatively simple in theory; it counts
-instruction cycles issued by the processor, which can be used as a measure of
-time. In practice, due to a number of problems, it is the most complicated
-timekeeping device to use.
-
-The TSC is represented internally as a 64-bit MSR which can be read with the
-RDMSR, RDTSC, or RDTSCP (when available) instructions. In the past, hardware
-limitations made it possible to write the TSC, but generally on old hardware it
-was only possible to write the low 32-bits of the 64-bit counter, and the upper
-32-bits of the counter were cleared. Now, however, on Intel processors family
-0Fh, for models 3, 4 and 6, and family 06h, models e and f, this restriction
-has been lifted and all 64-bits are writable. On AMD systems, the ability to
-write the TSC MSR is not an architectural guarantee.
-
-The TSC is accessible from CPL-0 and conditionally, for CPL > 0 software by
-means of the CR4.TSD bit, which when enabled, disables CPL > 0 TSC access.
-
-Some vendors have implemented an additional instruction, RDTSCP, which returns
-atomically not just the TSC, but an indicator which corresponds to the
-processor number. This can be used to index into an array of TSC variables to
-determine offset information in SMP systems where TSCs are not synchronized.
-The presence of this instruction must be determined by consulting CPUID feature
-bits.
-
-Both VMX and SVM provide extension fields in the virtualization hardware which
-allows the guest visible TSC to be offset by a constant. Newer implementations
-promise to allow the TSC to additionally be scaled, but this hardware is not
-yet widely available.
-
-3.1) TSC synchronization
-
-The TSC is a CPU-local clock in most implementations. This means, on SMP
-platforms, the TSCs of different CPUs may start at different times depending
-on when the CPUs are powered on. Generally, CPUs on the same die will share
-the same clock, however, this is not always the case.
-
-The BIOS may attempt to resynchronize the TSCs during the poweron process and
-the operating system or other system software may attempt to do this as well.
-Several hardware limitations make the problem worse - if it is not possible to
-write the full 64-bits of the TSC, it may be impossible to match the TSC in
-newly arriving CPUs to that of the rest of the system, resulting in
-unsynchronized TSCs. This may be done by BIOS or system software, but in
-practice, getting a perfectly synchronized TSC will not be possible unless all
-values are read from the same clock, which generally only is possible on single
-socket systems or those with special hardware support.
-
-3.2) TSC and CPU hotplug
-
-As touched on already, CPUs which arrive later than the boot time of the system
-may not have a TSC value that is synchronized with the rest of the system.
-Either system software, BIOS, or SMM code may actually try to establish the TSC
-to a value matching the rest of the system, but a perfect match is usually not
-a guarantee. This can have the effect of bringing a system from a state where
-TSC is synchronized back to a state where TSC synchronization flaws, however
-small, may be exposed to the OS and any virtualization environment.
-
-3.3) TSC and multi-socket / NUMA
-
-Multi-socket systems, especially large multi-socket systems are likely to have
-individual clocksources rather than a single, universally distributed clock.
-Since these clocks are driven by different crystals, they will not have
-perfectly matched frequency, and temperature and electrical variations will
-cause the CPU clocks, and thus the TSCs to drift over time. Depending on the
-exact clock and bus design, the drift may or may not be fixed in absolute
-error, and may accumulate over time.
-
-In addition, very large systems may deliberately slew the clocks of individual
-cores. This technique, known as spread-spectrum clocking, reduces EMI at the
-clock frequency and harmonics of it, which may be required to pass FCC
-standards for telecommunications and computer equipment.
-
-It is recommended not to trust the TSCs to remain synchronized on NUMA or
-multiple socket systems for these reasons.
-
-3.4) TSC and C-states
-
-C-states, or idling states of the processor, especially C1E and deeper sleep
-states may be problematic for TSC as well. The TSC may stop advancing in such
-a state, resulting in a TSC which is behind that of other CPUs when execution
-is resumed. Such CPUs must be detected and flagged by the operating system
-based on CPU and chipset identifications.
-
-The TSC in such a case may be corrected by catching it up to a known external
-clocksource.
-
-3.5) TSC frequency change / P-states
-
-To make things slightly more interesting, some CPUs may change frequency. They
-may or may not run the TSC at the same rate, and because the frequency change
-may be staggered or slewed, at some points in time, the TSC rate may not be
-known other than falling within a range of values. In this case, the TSC will
-not be a stable time source, and must be calibrated against a known, stable,
-external clock to be a usable source of time.
-
-Whether the TSC runs at a constant rate or scales with the P-state is model
-dependent and must be determined by inspecting CPUID, chipset or vendor
-specific MSR fields.
-
-In addition, some vendors have known bugs where the P-state is actually
-compensated for properly during normal operation, but when the processor is
-inactive, the P-state may be raised temporarily to service cache misses from
-other processors. In such cases, the TSC on halted CPUs could advance faster
-than that of non-halted processors. AMD Turion processors are known to have
-this problem.
-
-3.6) TSC and STPCLK / T-states
-
-External signals given to the processor may also have the effect of stopping
-the TSC. This is typically done for thermal emergency power control to prevent
-an overheating condition, and typically, there is no way to detect that this
-condition has happened.
-
-3.7) TSC virtualization - VMX
-
-VMX provides conditional trapping of RDTSC, RDMSR, WRMSR and RDTSCP
-instructions, which is enough for full virtualization of TSC in any manner. In
-addition, VMX allows passing through the host TSC plus an additional TSC_OFFSET
-field specified in the VMCS. Special instructions must be used to read and
-write the VMCS field.
-
-3.8) TSC virtualization - SVM
-
-SVM provides conditional trapping of RDTSC, RDMSR, WRMSR and RDTSCP
-instructions, which is enough for full virtualization of TSC in any manner. In
-addition, SVM allows passing through the host TSC plus an additional offset
-field specified in the SVM control block.
-
-3.9) TSC feature bits in Linux
-
-In summary, there is no way to guarantee the TSC remains in perfect
-synchronization unless it is explicitly guaranteed by the architecture. Even
-if so, the TSCs in multi-sockets or NUMA systems may still run independently
-despite being locally consistent.
-
-The following feature bits are used by Linux to signal various TSC attributes,
-but they can only be taken to be meaningful for UP or single node systems.
-
-X86_FEATURE_TSC : The TSC is available in hardware
-X86_FEATURE_RDTSCP : The RDTSCP instruction is available
-X86_FEATURE_CONSTANT_TSC : The TSC rate is unchanged with P-states
-X86_FEATURE_NONSTOP_TSC : The TSC does not stop in C-states
-X86_FEATURE_TSC_RELIABLE : TSC sync checks are skipped (VMware)
-
-4) Virtualization Problems
-
-Timekeeping is especially problematic for virtualization because a number of
-challenges arise. The most obvious problem is that time is now shared between
-the host and, potentially, a number of virtual machines. Thus the virtual
-operating system does not run with 100% usage of the CPU, despite the fact that
-it may very well make that assumption. It may expect it to remain true to very
-exacting bounds when interrupt sources are disabled, but in reality only its
-virtual interrupt sources are disabled, and the machine may still be preempted
-at any time. This causes problems as the passage of real time, the injection
-of machine interrupts and the associated clock sources are no longer completely
-synchronized with real time.
-
-This same problem can occur on native hardware to a degree, as SMM mode may
-steal cycles from the naturally on X86 systems when SMM mode is used by the
-BIOS, but not in such an extreme fashion. However, the fact that SMM mode may
-cause similar problems to virtualization makes it a good justification for
-solving many of these problems on bare metal.
-
-4.1) Interrupt clocking
-
-One of the most immediate problems that occurs with legacy operating systems
-is that the system timekeeping routines are often designed to keep track of
-time by counting periodic interrupts. These interrupts may come from the PIT
-or the RTC, but the problem is the same: the host virtualization engine may not
-be able to deliver the proper number of interrupts per second, and so guest
-time may fall behind. This is especially problematic if a high interrupt rate
-is selected, such as 1000 HZ, which is unfortunately the default for many Linux
-guests.
-
-There are three approaches to solving this problem; first, it may be possible
-to simply ignore it. Guests which have a separate time source for tracking
-'wall clock' or 'real time' may not need any adjustment of their interrupts to
-maintain proper time. If this is not sufficient, it may be necessary to inject
-additional interrupts into the guest in order to increase the effective
-interrupt rate. This approach leads to complications in extreme conditions,
-where host load or guest lag is too much to compensate for, and thus another
-solution to the problem has risen: the guest may need to become aware of lost
-ticks and compensate for them internally. Although promising in theory, the
-implementation of this policy in Linux has been extremely error prone, and a
-number of buggy variants of lost tick compensation are distributed across
-commonly used Linux systems.
-
-Windows uses periodic RTC clocking as a means of keeping time internally, and
-thus requires interrupt slewing to keep proper time. It does use a low enough
-rate (ed: is it 18.2 Hz?) however that it has not yet been a problem in
-practice.
-
-4.2) TSC sampling and serialization
-
-As the highest precision time source available, the cycle counter of the CPU
-has aroused much interest from developers. As explained above, this timer has
-many problems unique to its nature as a local, potentially unstable and
-potentially unsynchronized source. One issue which is not unique to the TSC,
-but is highlighted because of its very precise nature is sampling delay. By
-definition, the counter, once read is already old. However, it is also
-possible for the counter to be read ahead of the actual use of the result.
-This is a consequence of the superscalar execution of the instruction stream,
-which may execute instructions out of order. Such execution is called
-non-serialized. Forcing serialized execution is necessary for precise
-measurement with the TSC, and requires a serializing instruction, such as CPUID
-or an MSR read.
-
-Since CPUID may actually be virtualized by a trap and emulate mechanism, this
-serialization can pose a performance issue for hardware virtualization. An
-accurate time stamp counter reading may therefore not always be available, and
-it may be necessary for an implementation to guard against "backwards" reads of
-the TSC as seen from other CPUs, even in an otherwise perfectly synchronized
-system.
-
-4.3) Timespec aliasing
-
-Additionally, this lack of serialization from the TSC poses another challenge
-when using results of the TSC when measured against another time source. As
-the TSC is much higher precision, many possible values of the TSC may be read
-while another clock is still expressing the same value.
-
-That is, you may read (T,T+10) while external clock C maintains the same value.
-Due to non-serialized reads, you may actually end up with a range which
-fluctuates - from (T-1.. T+10). Thus, any time calculated from a TSC, but
-calibrated against an external value may have a range of valid values.
-Re-calibrating this computation may actually cause time, as computed after the
-calibration, to go backwards, compared with time computed before the
-calibration.
-
-This problem is particularly pronounced with an internal time source in Linux,
-the kernel time, which is expressed in the theoretically high resolution
-timespec - but which advances in much larger granularity intervals, sometimes
-at the rate of jiffies, and possibly in catchup modes, at a much larger step.
-
-This aliasing requires care in the computation and recalibration of kvmclock
-and any other values derived from TSC computation (such as TSC virtualization
-itself).
-
-4.4) Migration
-
-Migration of a virtual machine raises problems for timekeeping in two ways.
-First, the migration itself may take time, during which interrupts cannot be
-delivered, and after which, the guest time may need to be caught up. NTP may
-be able to help to some degree here, as the clock correction required is
-typically small enough to fall in the NTP-correctable window.
-
-An additional concern is that timers based off the TSC (or HPET, if the raw bus
-clock is exposed) may now be running at different rates, requiring compensation
-in some way in the hypervisor by virtualizing these timers. In addition,
-migrating to a faster machine may preclude the use of a passthrough TSC, as a
-faster clock cannot be made visible to a guest without the potential of time
-advancing faster than usual. A slower clock is less of a problem, as it can
-always be caught up to the original rate. KVM clock avoids these problems by
-simply storing multipliers and offsets against the TSC for the guest to convert
-back into nanosecond resolution values.
-
-4.5) Scheduling
-
-Since scheduling may be based on precise timing and firing of interrupts, the
-scheduling algorithms of an operating system may be adversely affected by
-virtualization. In theory, the effect is random and should be universally
-distributed, but in contrived as well as real scenarios (guest device access,
-causes of virtualization exits, possible context switch), this may not always
-be the case. The effect of this has not been well studied.
-
-In an attempt to work around this, several implementations have provided a
-paravirtualized scheduler clock, which reveals the true amount of CPU time for
-which a virtual machine has been running.
-
-4.6) Watchdogs
-
-Watchdog timers, such as the lock detector in Linux may fire accidentally when
-running under hardware virtualization due to timer interrupts being delayed or
-misinterpretation of the passage of real time. Usually, these warnings are
-spurious and can be ignored, but in some circumstances it may be necessary to
-disable such detection.
-
-4.7) Delays and precision timing
-
-Precise timing and delays may not be possible in a virtualized system. This
-can happen if the system is controlling physical hardware, or issues delays to
-compensate for slower I/O to and from devices. The first issue is not solvable
-in general for a virtualized system; hardware control software can't be
-adequately virtualized without a full real-time operating system, which would
-require an RT aware virtualization platform.
-
-The second issue may cause performance problems, but this is unlikely to be a
-significant issue. In many cases these delays may be eliminated through
-configuration or paravirtualization.
-
-4.8) Covert channels and leaks
-
-In addition to the above problems, time information will inevitably leak to the
-guest about the host in anything but a perfect implementation of virtualized
-time. This may allow the guest to infer the presence of a hypervisor (as in a
-red-pill type detection), and it may allow information to leak between guests
-by using CPU utilization itself as a signalling channel. Preventing such
-problems would require completely isolated virtual time which may not track
-real time any longer. This may be useful in certain security or QA contexts,
-but in general isn't recommended for real-world deployment scenarios.
+++ /dev/null
-=================
-KVM VCPU Requests
-=================
-
-Overview
-========
-
-KVM supports an internal API enabling threads to request a VCPU thread to
-perform some activity. For example, a thread may request a VCPU to flush
-its TLB with a VCPU request. The API consists of the following functions::
-
- /* Check if any requests are pending for VCPU @vcpu. */
- bool kvm_request_pending(struct kvm_vcpu *vcpu);
-
- /* Check if VCPU @vcpu has request @req pending. */
- bool kvm_test_request(int req, struct kvm_vcpu *vcpu);
-
- /* Clear request @req for VCPU @vcpu. */
- void kvm_clear_request(int req, struct kvm_vcpu *vcpu);
-
- /*
- * Check if VCPU @vcpu has request @req pending. When the request is
- * pending it will be cleared and a memory barrier, which pairs with
- * another in kvm_make_request(), will be issued.
- */
- bool kvm_check_request(int req, struct kvm_vcpu *vcpu);
-
- /*
- * Make request @req of VCPU @vcpu. Issues a memory barrier, which pairs
- * with another in kvm_check_request(), prior to setting the request.
- */
- void kvm_make_request(int req, struct kvm_vcpu *vcpu);
-
- /* Make request @req of all VCPUs of the VM with struct kvm @kvm. */
- bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req);
-
-Typically a requester wants the VCPU to perform the activity as soon
-as possible after making the request. This means most requests
-(kvm_make_request() calls) are followed by a call to kvm_vcpu_kick(),
-and kvm_make_all_cpus_request() has the kicking of all VCPUs built
-into it.
-
-VCPU Kicks
-----------
-
-The goal of a VCPU kick is to bring a VCPU thread out of guest mode in
-order to perform some KVM maintenance. To do so, an IPI is sent, forcing
-a guest mode exit. However, a VCPU thread may not be in guest mode at the
-time of the kick. Therefore, depending on the mode and state of the VCPU
-thread, there are two other actions a kick may take. All three actions
-are listed below:
-
-1) Send an IPI. This forces a guest mode exit.
-2) Waking a sleeping VCPU. Sleeping VCPUs are VCPU threads outside guest
- mode that wait on waitqueues. Waking them removes the threads from
- the waitqueues, allowing the threads to run again. This behavior
- may be suppressed, see KVM_REQUEST_NO_WAKEUP below.
-3) Nothing. When the VCPU is not in guest mode and the VCPU thread is not
- sleeping, then there is nothing to do.
-
-VCPU Mode
----------
-
-VCPUs have a mode state, ``vcpu->mode``, that is used to track whether the
-guest is running in guest mode or not, as well as some specific
-outside guest mode states. The architecture may use ``vcpu->mode`` to
-ensure VCPU requests are seen by VCPUs (see "Ensuring Requests Are Seen"),
-as well as to avoid sending unnecessary IPIs (see "IPI Reduction"), and
-even to ensure IPI acknowledgements are waited upon (see "Waiting for
-Acknowledgements"). The following modes are defined:
-
-OUTSIDE_GUEST_MODE
-
- The VCPU thread is outside guest mode.
-
-IN_GUEST_MODE
-
- The VCPU thread is in guest mode.
-
-EXITING_GUEST_MODE
-
- The VCPU thread is transitioning from IN_GUEST_MODE to
- OUTSIDE_GUEST_MODE.
-
-READING_SHADOW_PAGE_TABLES
-
- The VCPU thread is outside guest mode, but it wants the sender of
- certain VCPU requests, namely KVM_REQ_TLB_FLUSH, to wait until the VCPU
- thread is done reading the page tables.
-
-VCPU Request Internals
-======================
-
-VCPU requests are simply bit indices of the ``vcpu->requests`` bitmap.
-This means general bitops, like those documented in [atomic-ops]_ could
-also be used, e.g. ::
-
- clear_bit(KVM_REQ_UNHALT & KVM_REQUEST_MASK, &vcpu->requests);
-
-However, VCPU request users should refrain from doing so, as it would
-break the abstraction. The first 8 bits are reserved for architecture
-independent requests, all additional bits are available for architecture
-dependent requests.
-
-Architecture Independent Requests
----------------------------------
-
-KVM_REQ_TLB_FLUSH
-
- KVM's common MMU notifier may need to flush all of a guest's TLB
- entries, calling kvm_flush_remote_tlbs() to do so. Architectures that
- choose to use the common kvm_flush_remote_tlbs() implementation will
- need to handle this VCPU request.
-
-KVM_REQ_MMU_RELOAD
-
- When shadow page tables are used and memory slots are removed it's
- necessary to inform each VCPU to completely refresh the tables. This
- request is used for that.
-
-KVM_REQ_PENDING_TIMER
-
- This request may be made from a timer handler run on the host on behalf
- of a VCPU. It informs the VCPU thread to inject a timer interrupt.
-
-KVM_REQ_UNHALT
-
- This request may be made from the KVM common function kvm_vcpu_block(),
- which is used to emulate an instruction that causes a CPU to halt until
- one of an architectural specific set of events and/or interrupts is
- received (determined by checking kvm_arch_vcpu_runnable()). When that
- event or interrupt arrives kvm_vcpu_block() makes the request. This is
- in contrast to when kvm_vcpu_block() returns due to any other reason,
- such as a pending signal, which does not indicate the VCPU's halt
- emulation should stop, and therefore does not make the request.
-
-KVM_REQUEST_MASK
-----------------
-
-VCPU requests should be masked by KVM_REQUEST_MASK before using them with
-bitops. This is because only the lower 8 bits are used to represent the
-request's number. The upper bits are used as flags. Currently only two
-flags are defined.
-
-VCPU Request Flags
-------------------
-
-KVM_REQUEST_NO_WAKEUP
-
- This flag is applied to requests that only need immediate attention
- from VCPUs running in guest mode. That is, sleeping VCPUs do not need
- to be awaken for these requests. Sleeping VCPUs will handle the
- requests when they are awaken later for some other reason.
-
-KVM_REQUEST_WAIT
-
- When requests with this flag are made with kvm_make_all_cpus_request(),
- then the caller will wait for each VCPU to acknowledge its IPI before
- proceeding. This flag only applies to VCPUs that would receive IPIs.
- If, for example, the VCPU is sleeping, so no IPI is necessary, then
- the requesting thread does not wait. This means that this flag may be
- safely combined with KVM_REQUEST_NO_WAKEUP. See "Waiting for
- Acknowledgements" for more information about requests with
- KVM_REQUEST_WAIT.
-
-VCPU Requests with Associated State
-===================================
-
-Requesters that want the receiving VCPU to handle new state need to ensure
-the newly written state is observable to the receiving VCPU thread's CPU
-by the time it observes the request. This means a write memory barrier
-must be inserted after writing the new state and before setting the VCPU
-request bit. Additionally, on the receiving VCPU thread's side, a
-corresponding read barrier must be inserted after reading the request bit
-and before proceeding to read the new state associated with it. See
-scenario 3, Message and Flag, of [lwn-mb]_ and the kernel documentation
-[memory-barriers]_.
-
-The pair of functions, kvm_check_request() and kvm_make_request(), provide
-the memory barriers, allowing this requirement to be handled internally by
-the API.
-
-Ensuring Requests Are Seen
-==========================
-
-When making requests to VCPUs, we want to avoid the receiving VCPU
-executing in guest mode for an arbitrary long time without handling the
-request. We can be sure this won't happen as long as we ensure the VCPU
-thread checks kvm_request_pending() before entering guest mode and that a
-kick will send an IPI to force an exit from guest mode when necessary.
-Extra care must be taken to cover the period after the VCPU thread's last
-kvm_request_pending() check and before it has entered guest mode, as kick
-IPIs will only trigger guest mode exits for VCPU threads that are in guest
-mode or at least have already disabled interrupts in order to prepare to
-enter guest mode. This means that an optimized implementation (see "IPI
-Reduction") must be certain when it's safe to not send the IPI. One
-solution, which all architectures except s390 apply, is to:
-
-- set ``vcpu->mode`` to IN_GUEST_MODE between disabling the interrupts and
- the last kvm_request_pending() check;
-- enable interrupts atomically when entering the guest.
-
-This solution also requires memory barriers to be placed carefully in both
-the requesting thread and the receiving VCPU. With the memory barriers we
-can exclude the possibility of a VCPU thread observing
-!kvm_request_pending() on its last check and then not receiving an IPI for
-the next request made of it, even if the request is made immediately after
-the check. This is done by way of the Dekker memory barrier pattern
-(scenario 10 of [lwn-mb]_). As the Dekker pattern requires two variables,
-this solution pairs ``vcpu->mode`` with ``vcpu->requests``. Substituting
-them into the pattern gives::
-
- CPU1 CPU2
- ================= =================
- local_irq_disable();
- WRITE_ONCE(vcpu->mode, IN_GUEST_MODE); kvm_make_request(REQ, vcpu);
- smp_mb(); smp_mb();
- if (kvm_request_pending(vcpu)) { if (READ_ONCE(vcpu->mode) ==
- IN_GUEST_MODE) {
- ...abort guest entry... ...send IPI...
- } }
-
-As stated above, the IPI is only useful for VCPU threads in guest mode or
-that have already disabled interrupts. This is why this specific case of
-the Dekker pattern has been extended to disable interrupts before setting
-``vcpu->mode`` to IN_GUEST_MODE. WRITE_ONCE() and READ_ONCE() are used to
-pedantically implement the memory barrier pattern, guaranteeing the
-compiler doesn't interfere with ``vcpu->mode``'s carefully planned
-accesses.
-
-IPI Reduction
--------------
-
-As only one IPI is needed to get a VCPU to check for any/all requests,
-then they may be coalesced. This is easily done by having the first IPI
-sending kick also change the VCPU mode to something !IN_GUEST_MODE. The
-transitional state, EXITING_GUEST_MODE, is used for this purpose.
-
-Waiting for Acknowledgements
-----------------------------
-
-Some requests, those with the KVM_REQUEST_WAIT flag set, require IPIs to
-be sent, and the acknowledgements to be waited upon, even when the target
-VCPU threads are in modes other than IN_GUEST_MODE. For example, one case
-is when a target VCPU thread is in READING_SHADOW_PAGE_TABLES mode, which
-is set after disabling interrupts. To support these cases, the
-KVM_REQUEST_WAIT flag changes the condition for sending an IPI from
-checking that the VCPU is IN_GUEST_MODE to checking that it is not
-OUTSIDE_GUEST_MODE.
-
-Request-less VCPU Kicks
------------------------
-
-As the determination of whether or not to send an IPI depends on the
-two-variable Dekker memory barrier pattern, then it's clear that
-request-less VCPU kicks are almost never correct. Without the assurance
-that a non-IPI generating kick will still result in an action by the
-receiving VCPU, as the final kvm_request_pending() check does for
-request-accompanying kicks, then the kick may not do anything useful at
-all. If, for instance, a request-less kick was made to a VCPU that was
-just about to set its mode to IN_GUEST_MODE, meaning no IPI is sent, then
-the VCPU thread may continue its entry without actually having done
-whatever it was the kick was meant to initiate.
-
-One exception is x86's posted interrupt mechanism. In this case, however,
-even the request-less VCPU kick is coupled with the same
-local_irq_disable() + smp_mb() pattern described above; the ON bit
-(Outstanding Notification) in the posted interrupt descriptor takes the
-role of ``vcpu->requests``. When sending a posted interrupt, PIR.ON is
-set before reading ``vcpu->mode``; dually, in the VCPU thread,
-vmx_sync_pir_to_irr() reads PIR after setting ``vcpu->mode`` to
-IN_GUEST_MODE.
-
-Additional Considerations
-=========================
-
-Sleeping VCPUs
---------------
-
-VCPU threads may need to consider requests before and/or after calling
-functions that may put them to sleep, e.g. kvm_vcpu_block(). Whether they
-do or not, and, if they do, which requests need consideration, is
-architecture dependent. kvm_vcpu_block() calls kvm_arch_vcpu_runnable()
-to check if it should awaken. One reason to do so is to provide
-architectures a function where requests may be checked if necessary.
-
-Clearing Requests
------------------
-
-Generally it only makes sense for the receiving VCPU thread to clear a
-request. However, in some circumstances, such as when the requesting
-thread and the receiving VCPU thread are executed serially, such as when
-they are the same thread, or when they are using some form of concurrency
-control to temporarily execute synchronously, then it's possible to know
-that the request may be cleared immediately, rather than waiting for the
-receiving VCPU thread to handle the request in VCPU RUN. The only current
-examples of this are kvm_vcpu_block() calls made by VCPUs to block
-themselves. A possible side-effect of that call is to make the
-KVM_REQ_UNHALT request, which may then be cleared immediately when the
-VCPU returns from the call.
-
-References
-==========
-
-.. [atomic-ops] Documentation/core-api/atomic_ops.rst
-.. [memory-barriers] Documentation/memory-barriers.txt
-.. [lwn-mb] https://lwn.net/Articles/573436/
+++ /dev/null
-.. SPDX-License-Identifier: GPL-2.0
-
-============
-Paravirt_ops
-============
-
-Linux provides support for different hypervisor virtualization technologies.
-Historically different binary kernels would be required in order to support
-different hypervisors, this restriction was removed with pv_ops.
-Linux pv_ops is a virtualization API which enables support for different
-hypervisors. It allows each hypervisor to override critical operations and
-allows a single kernel binary to run on all supported execution environments
-including native machine -- without any hypervisors.
-
-pv_ops provides a set of function pointers which represent operations
-corresponding to low level critical instructions and high level
-functionalities in various areas. pv-ops allows for optimizations at run
-time by enabling binary patching of the low-ops critical operations
-at boot time.
-
-pv_ops operations are classified into three categories:
-
-- simple indirect call
- These operations correspond to high level functionality where it is
- known that the overhead of indirect call isn't very important.
-
-- indirect call which allows optimization with binary patch
- Usually these operations correspond to low level critical instructions. They
- are called frequently and are performance critical. The overhead is
- very important.
-
-- a set of macros for hand written assembly code
- Hand written assembly codes (.S files) also need paravirtualization
- because they include sensitive instructions or some of code paths in
- them are very performance critical.
+++ /dev/null
- User Mode Linux HOWTO
- User Mode Linux Core Team
- Mon Nov 18 14:16:16 EST 2002
-
- This document describes the use and abuse of Jeff Dike's User Mode
- Linux: a port of the Linux kernel as a normal Intel Linux process.
- ______________________________________________________________________
-
- Table of Contents
-
- 1. Introduction
-
- 1.1 How is User Mode Linux Different?
- 1.2 Why Would I Want User Mode Linux?
-
- 2. Compiling the kernel and modules
-
- 2.1 Compiling the kernel
- 2.2 Compiling and installing kernel modules
- 2.3 Compiling and installing uml_utilities
-
- 3. Running UML and logging in
-
- 3.1 Running UML
- 3.2 Logging in
- 3.3 Examples
-
- 4. UML on 2G/2G hosts
-
- 4.1 Introduction
- 4.2 The problem
- 4.3 The solution
-
- 5. Setting up serial lines and consoles
-
- 5.1 Specifying the device
- 5.2 Specifying the channel
- 5.3 Examples
-
- 6. Setting up the network
-
- 6.1 General setup
- 6.2 Userspace daemons
- 6.3 Specifying ethernet addresses
- 6.4 UML interface setup
- 6.5 Multicast
- 6.6 TUN/TAP with the uml_net helper
- 6.7 TUN/TAP with a preconfigured tap device
- 6.8 Ethertap
- 6.9 The switch daemon
- 6.10 Slip
- 6.11 Slirp
- 6.12 pcap
- 6.13 Setting up the host yourself
-
- 7. Sharing Filesystems between Virtual Machines
-
- 7.1 A warning
- 7.2 Using layered block devices
- 7.3 Note!
- 7.4 Another warning
- 7.5 uml_moo : Merging a COW file with its backing file
-
- 8. Creating filesystems
-
- 8.1 Create the filesystem file
- 8.2 Assign the file to a UML device
- 8.3 Creating and mounting the filesystem
-
- 9. Host file access
-
- 9.1 Using hostfs
- 9.2 hostfs as the root filesystem
- 9.3 Building hostfs
-
- 10. The Management Console
- 10.1 version
- 10.2 halt and reboot
- 10.3 config
- 10.4 remove
- 10.5 sysrq
- 10.6 help
- 10.7 cad
- 10.8 stop
- 10.9 go
-
- 11. Kernel debugging
-
- 11.1 Starting the kernel under gdb
- 11.2 Examining sleeping processes
- 11.3 Running ddd on UML
- 11.4 Debugging modules
- 11.5 Attaching gdb to the kernel
- 11.6 Using alternate debuggers
-
- 12. Kernel debugging examples
-
- 12.1 The case of the hung fsck
- 12.2 Episode 2: The case of the hung fsck
-
- 13. What to do when UML doesn't work
-
- 13.1 Strange compilation errors when you build from source
- 13.2 (obsolete)
- 13.3 A variety of panics and hangs with /tmp on a reiserfs filesystem
- 13.4 The compile fails with errors about conflicting types for 'open', 'dup', and 'waitpid'
- 13.5 UML doesn't work when /tmp is an NFS filesystem
- 13.6 UML hangs on boot when compiled with gprof support
- 13.7 syslogd dies with a SIGTERM on startup
- 13.8 TUN/TAP networking doesn't work on a 2.4 host
- 13.9 You can network to the host but not to other machines on the net
- 13.10 I have no root and I want to scream
- 13.11 UML build conflict between ptrace.h and ucontext.h
- 13.12 The UML BogoMips is exactly half the host's BogoMips
- 13.13 When you run UML, it immediately segfaults
- 13.14 xterms appear, then immediately disappear
- 13.15 Any other panic, hang, or strange behavior
-
- 14. Diagnosing Problems
-
- 14.1 Case 1 : Normal kernel panics
- 14.2 Case 2 : Tracing thread panics
- 14.3 Case 3 : Tracing thread panics caused by other threads
- 14.4 Case 4 : Hangs
-
- 15. Thanks
-
- 15.1 Code and Documentation
- 15.2 Flushing out bugs
- 15.3 Buglets and clean-ups
- 15.4 Case Studies
- 15.5 Other contributions
-
-
- ______________________________________________________________________
-
- 1. Introduction
-
- Welcome to User Mode Linux. It's going to be fun.
-
-
-
- 1.1. How is User Mode Linux Different?
-
- Normally, the Linux Kernel talks straight to your hardware (video
- card, keyboard, hard drives, etc), and any programs which run ask the
- kernel to operate the hardware, like so:
-
-
-
- +-----------+-----------+----+
- | Process 1 | Process 2 | ...|
- +-----------+-----------+----+
- | Linux Kernel |
- +----------------------------+
- | Hardware |
- +----------------------------+
-
-
-
-
- The User Mode Linux Kernel is different; instead of talking to the
- hardware, it talks to a `real' Linux kernel (called the `host kernel'
- from now on), like any other program. Programs can then run inside
- User-Mode Linux as if they were running under a normal kernel, like
- so:
-
-
-
- +----------------+
- | Process 2 | ...|
- +-----------+----------------+
- | Process 1 | User-Mode Linux|
- +----------------------------+
- | Linux Kernel |
- +----------------------------+
- | Hardware |
- +----------------------------+
-
-
-
-
-
- 1.2. Why Would I Want User Mode Linux?
-
-
- 1. If User Mode Linux crashes, your host kernel is still fine.
-
- 2. You can run a usermode kernel as a non-root user.
-
- 3. You can debug the User Mode Linux like any normal process.
-
- 4. You can run gprof (profiling) and gcov (coverage testing).
-
- 5. You can play with your kernel without breaking things.
-
- 6. You can use it as a sandbox for testing new apps.
-
- 7. You can try new development kernels safely.
-
- 8. You can run different distributions simultaneously.
-
- 9. It's extremely fun.
-
-
-
-
-
- 2. Compiling the kernel and modules
-
-
-
-
- 2.1. Compiling the kernel
-
-
- Compiling the user mode kernel is just like compiling any other
- kernel. Let's go through the steps, using 2.4.0-prerelease (current
- as of this writing) as an example:
-
-
- 1. Download the latest UML patch from
-
- the download page <http://user-mode-linux.sourceforge.net/
-
- In this example, the file is uml-patch-2.4.0-prerelease.bz2.
-
-
- 2. Download the matching kernel from your favourite kernel mirror,
- such as:
-
- ftp://ftp.ca.kernel.org/pub/kernel/v2.4/linux-2.4.0-prerelease.tar.bz2
- <ftp://ftp.ca.kernel.org/pub/kernel/v2.4/linux-2.4.0-prerelease.tar.bz2>
- .
-
-
- 3. Make a directory and unpack the kernel into it.
-
-
-
- host%
- mkdir ~/uml
-
-
-
-
-
-
- host%
- cd ~/uml
-
-
-
-
-
-
- host%
- tar -xzvf linux-2.4.0-prerelease.tar.bz2
-
-
-
-
-
-
- 4. Apply the patch using
-
-
-
- host%
- cd ~/uml/linux
-
-
-
- host%
- bzcat uml-patch-2.4.0-prerelease.bz2 | patch -p1
-
-
-
-
-
-
- 5. Run your favorite config; `make xconfig ARCH=um' is the most
- convenient. `make config ARCH=um' and 'make menuconfig ARCH=um'
- will work as well. The defaults will give you a useful kernel. If
- you want to change something, go ahead, it probably won't hurt
- anything.
-
-
- Note: If the host is configured with a 2G/2G address space split
- rather than the usual 3G/1G split, then the packaged UML binaries
- will not run. They will immediately segfault. See ``UML on 2G/2G
- hosts'' for the scoop on running UML on your system.
-
-
-
- 6. Finish with `make linux ARCH=um': the result is a file called
- `linux' in the top directory of your source tree.
-
- Make sure that you don't build this kernel in /usr/src/linux. On some
- distributions, /usr/include/asm is a link into this pool. The user-
- mode build changes the other end of that link, and things that include
- <asm/anything.h> stop compiling.
-
- The sources are also available from cvs at the project's cvs page,
- which has directions on getting the sources. You can also browse the
- CVS pool from there.
-
- If you get the CVS sources, you will have to check them out into an
- empty directory. You will then have to copy each file into the
- corresponding directory in the appropriate kernel pool.
-
- If you don't have the latest kernel pool, you can get the
- corresponding user-mode sources with
-
-
- host% cvs co -r v_2_3_x linux
-
-
-
-
- where 'x' is the version in your pool. Note that you will not get the
- bug fixes and enhancements that have gone into subsequent releases.
-
-
- 2.2. Compiling and installing kernel modules
-
- UML modules are built in the same way as the native kernel (with the
- exception of the 'ARCH=um' that you always need for UML):
-
-
- host% make modules ARCH=um
-
-
-
-
- Any modules that you want to load into this kernel need to be built in
- the user-mode pool. Modules from the native kernel won't work.
-
- You can install them by using ftp or something to copy them into the
- virtual machine and dropping them into /lib/modules/`uname -r`.
-
- You can also get the kernel build process to install them as follows:
-
- 1. with the kernel not booted, mount the root filesystem in the top
- level of the kernel pool:
-
-
- host% mount root_fs mnt -o loop
-
-
-
-
-
-
- 2. run
-
-
- host%
- make modules_install INSTALL_MOD_PATH=`pwd`/mnt ARCH=um
-
-
-
-
-
-
- 3. unmount the filesystem
-
-
- host% umount mnt
-
-
-
-
-
-
- 4. boot the kernel on it
-
-
- When the system is booted, you can use insmod as usual to get the
- modules into the kernel. A number of things have been loaded into UML
- as modules, especially filesystems and network protocols and filters,
- so most symbols which need to be exported probably already are.
- However, if you do find symbols that need exporting, let us
- <http://user-mode-linux.sourceforge.net/> know, and
- they'll be "taken care of".
-
-
-
- 2.3. Compiling and installing uml_utilities
-
- Many features of the UML kernel require a user-space helper program,
- so a uml_utilities package is distributed separately from the kernel
- patch which provides these helpers. Included within this is:
-
- o port-helper - Used by consoles which connect to xterms or ports
-
- o tunctl - Configuration tool to create and delete tap devices
-
- o uml_net - Setuid binary for automatic tap device configuration
-
- o uml_switch - User-space virtual switch required for daemon
- transport
-
- The uml_utilities tree is compiled with:
-
-
- host#
- make && make install
-
-
-
-
- Note that UML kernel patches may require a specific version of the
- uml_utilities distribution. If you don't keep up with the mailing
- lists, ensure that you have the latest release of uml_utilities if you
- are experiencing problems with your UML kernel, particularly when
- dealing with consoles or command-line switches to the helper programs
-
-
-
-
-
-
-
-
- 3. Running UML and logging in
-
-
-
- 3.1. Running UML
-
- It runs on 2.2.15 or later, and all 2.4 kernels.
-
-
- Booting UML is straightforward. Simply run 'linux': it will try to
- mount the file `root_fs' in the current directory. You do not need to
- run it as root. If your root filesystem is not named `root_fs', then
- you need to put a `ubd0=root_fs_whatever' switch on the linux command
- line.
-
-
- You will need a filesystem to boot UML from. There are a number
- available for download from here <http://user-mode-
- linux.sourceforge.net/> . There are also several tools
- <http://user-mode-linux.sourceforge.net/> which can be
- used to generate UML-compatible filesystem images from media.
- The kernel will boot up and present you with a login prompt.
-
-
- Note: If the host is configured with a 2G/2G address space split
- rather than the usual 3G/1G split, then the packaged UML binaries will
- not run. They will immediately segfault. See ``UML on 2G/2G hosts''
- for the scoop on running UML on your system.
-
-
-
- 3.2. Logging in
-
-
-
- The prepackaged filesystems have a root account with password 'root'
- and a user account with password 'user'. The login banner will
- generally tell you how to log in. So, you log in and you will find
- yourself inside a little virtual machine. Our filesystems have a
- variety of commands and utilities installed (and it is fairly easy to
- add more), so you will have a lot of tools with which to poke around
- the system.
-
- There are a couple of other ways to log in:
-
- o On a virtual console
-
-
-
- Each virtual console that is configured (i.e. the device exists in
- /dev and /etc/inittab runs a getty on it) will come up in its own
- xterm. If you get tired of the xterms, read ``Setting up serial
- lines and consoles'' to see how to attach the consoles to
- something else, like host ptys.
-
-
-
- o Over the serial line
-
-
- In the boot output, find a line that looks like:
-
-
-
- serial line 0 assigned pty /dev/ptyp1
-
-
-
-
- Attach your favorite terminal program to the corresponding tty. I.e.
- for minicom, the command would be
-
-
- host% minicom -o -p /dev/ttyp1
-
-
-
-
-
-
- o Over the net
-
-
- If the network is running, then you can telnet to the virtual
- machine and log in to it. See ``Setting up the network'' to learn
- about setting up a virtual network.
-
- When you're done using it, run halt, and the kernel will bring itself
- down and the process will exit.
-
-
- 3.3. Examples
-
- Here are some examples of UML in action:
-
- o A login session <http://user-mode-linux.sourceforge.net/login.html>
-
- o A virtual network <http://user-mode-linux.sourceforge.net/net.html>
-
-
-
-
-
-
-
- 4. UML on 2G/2G hosts
-
-
-
-
- 4.1. Introduction
-
-
- Most Linux machines are configured so that the kernel occupies the
- upper 1G (0xc0000000 - 0xffffffff) of the 4G address space and
- processes use the lower 3G (0x00000000 - 0xbfffffff). However, some
- machine are configured with a 2G/2G split, with the kernel occupying
- the upper 2G (0x80000000 - 0xffffffff) and processes using the lower
- 2G (0x00000000 - 0x7fffffff).
-
-
-
-
- 4.2. The problem
-
-
- The prebuilt UML binaries on this site will not run on 2G/2G hosts
- because UML occupies the upper .5G of the 3G process address space
- (0xa0000000 - 0xbfffffff). Obviously, on 2G/2G hosts, this is right
- in the middle of the kernel address space, so UML won't even load - it
- will immediately segfault.
-
-
-
-
- 4.3. The solution
-
-
- The fix for this is to rebuild UML from source after enabling
- CONFIG_HOST_2G_2G (under 'General Setup'). This will cause UML to
- load itself in the top .5G of that smaller process address space,
- where it will run fine. See ``Compiling the kernel and modules'' if
- you need help building UML from source.
-
-
-
-
-
-
-
-
-
-
- 5. Setting up serial lines and consoles
-
-
- It is possible to attach UML serial lines and consoles to many types
- of host I/O channels by specifying them on the command line.
-
-
- You can attach them to host ptys, ttys, file descriptors, and ports.
- This allows you to do things like
-
- o have a UML console appear on an unused host console,
-
- o hook two virtual machines together by having one attach to a pty
- and having the other attach to the corresponding tty
-
- o make a virtual machine accessible from the net by attaching a
- console to a port on the host.
-
-
- The general format of the command line option is device=channel.
-
-
-
- 5.1. Specifying the device
-
- Devices are specified with "con" or "ssl" (console or serial line,
- respectively), optionally with a device number if you are talking
- about a specific device.
-
-
- Using just "con" or "ssl" describes all of the consoles or serial
- lines. If you want to talk about console #3 or serial line #10, they
- would be "con3" and "ssl10", respectively.
-
-
- A specific device name will override a less general "con=" or "ssl=".
- So, for example, you can assign a pty to each of the serial lines
- except for the first two like this:
-
-
- ssl=pty ssl0=tty:/dev/tty0 ssl1=tty:/dev/tty1
-
-
-
-
- The specificity of the device name is all that matters; order on the
- command line is irrelevant.
-
-
-
- 5.2. Specifying the channel
-
- There are a number of different types of channels to attach a UML
- device to, each with a different way of specifying exactly what to
- attach to.
-
- o pseudo-terminals - device=pty pts terminals - device=pts
-
-
- This will cause UML to allocate a free host pseudo-terminal for the
- device. The terminal that it got will be announced in the boot
- log. You access it by attaching a terminal program to the
- corresponding tty:
-
- o screen /dev/pts/n
-
- o screen /dev/ttyxx
-
- o minicom -o -p /dev/ttyxx - minicom seems not able to handle pts
- devices
-
- o kermit - start it up, 'open' the device, then 'connect'
-
-
-
-
-
- o terminals - device=tty:tty device file
-
-
- This will make UML attach the device to the specified tty (i.e
-
-
- con1=tty:/dev/tty3
-
-
-
-
- will attach UML's console 1 to the host's /dev/tty3). If the tty that
- you specify is the slave end of a tty/pty pair, something else must
- have already opened the corresponding pty in order for this to work.
-
-
-
-
-
- o xterms - device=xterm
-
-
- UML will run an xterm and the device will be attached to it.
-
-
-
-
-
- o Port - device=port:port number
-
-
- This will attach the UML devices to the specified host port.
- Attaching console 1 to the host's port 9000 would be done like
- this:
-
-
- con1=port:9000
-
-
-
-
- Attaching all the serial lines to that port would be done similarly:
-
-
- ssl=port:9000
-
-
-
-
- You access these devices by telnetting to that port. Each active tel-
- net session gets a different device. If there are more telnets to a
- port than UML devices attached to it, then the extra telnet sessions
- will block until an existing telnet detaches, or until another device
- becomes active (i.e. by being activated in /etc/inittab).
-
- This channel has the advantage that you can both attach multiple UML
- devices to it and know how to access them without reading the UML boot
- log. It is also unique in allowing access to a UML from remote
- machines without requiring that the UML be networked. This could be
- useful in allowing public access to UMLs because they would be
- accessible from the net, but wouldn't need any kind of network
- filtering or access control because they would have no network access.
-
-
- If you attach the main console to a portal, then the UML boot will
- appear to hang. In reality, it's waiting for a telnet to connect, at
- which point the boot will proceed.
-
-
-
-
-
- o already-existing file descriptors - device=file descriptor
-
-
- If you set up a file descriptor on the UML command line, you can
- attach a UML device to it. This is most commonly used to put the
- main console back on stdin and stdout after assigning all the other
- consoles to something else:
-
-
- con0=fd:0,fd:1 con=pts
-
-
-
-
-
-
-
-
- o Nothing - device=null
-
-
- This allows the device to be opened, in contrast to 'none', but
- reads will block, and writes will succeed and the data will be
- thrown out.
-
-
-
-
-
- o None - device=none
-
-
- This causes the device to disappear.
-
-
-
- You can also specify different input and output channels for a device
- by putting a comma between them:
-
-
- ssl3=tty:/dev/tty2,xterm
-
-
-
-
- will cause serial line 3 to accept input on the host's /dev/tty2 and
- display output on an xterm. That's a silly example - the most common
- use of this syntax is to reattach the main console to stdin and stdout
- as shown above.
-
-
- If you decide to move the main console away from stdin/stdout, the
- initial boot output will appear in the terminal that you're running
- UML in. However, once the console driver has been officially
- initialized, then the boot output will start appearing wherever you
- specified that console 0 should be. That device will receive all
- subsequent output.
-
-
-
- 5.3. Examples
-
- There are a number of interesting things you can do with this
- capability.
-
-
- First, this is how you get rid of those bleeding console xterms by
- attaching them to host ptys:
-
-
- con=pty con0=fd:0,fd:1
-
-
-
-
- This will make a UML console take over an unused host virtual console,
- so that when you switch to it, you will see the UML login prompt
- rather than the host login prompt:
-
-
- con1=tty:/dev/tty6
-
-
-
-
- You can attach two virtual machines together with what amounts to a
- serial line as follows:
-
- Run one UML with a serial line attached to a pty -
-
-
- ssl1=pty
-
-
-
-
- Look at the boot log to see what pty it got (this example will assume
- that it got /dev/ptyp1).
-
- Boot the other UML with a serial line attached to the corresponding
- tty -
-
-
- ssl1=tty:/dev/ttyp1
-
-
-
-
- Log in, make sure that it has no getty on that serial line, attach a
- terminal program like minicom to it, and you should see the login
- prompt of the other virtual machine.
-
-
- 6. Setting up the network
-
-
-
- This page describes how to set up the various transports and to
- provide a UML instance with network access to the host, other machines
- on the local net, and the rest of the net.
-
-
- As of 2.4.5, UML networking has been completely redone to make it much
- easier to set up, fix bugs, and add new features.
-
-
- There is a new helper, uml_net, which does the host setup that
- requires root privileges.
-
-
- There are currently five transport types available for a UML virtual
- machine to exchange packets with other hosts:
-
- o ethertap
-
- o TUN/TAP
-
- o Multicast
-
- o a switch daemon
-
- o slip
-
- o slirp
-
- o pcap
-
- The TUN/TAP, ethertap, slip, and slirp transports allow a UML
- instance to exchange packets with the host. They may be directed
- to the host or the host may just act as a router to provide access
- to other physical or virtual machines.
-
-
- The pcap transport is a synthetic read-only interface, using the
- libpcap binary to collect packets from interfaces on the host and
- filter them. This is useful for building preconfigured traffic
- monitors or sniffers.
-
-
- The daemon and multicast transports provide a completely virtual
- network to other virtual machines. This network is completely
- disconnected from the physical network unless one of the virtual
- machines on it is acting as a gateway.
-
-
- With so many host transports, which one should you use? Here's when
- you should use each one:
-
- o ethertap - if you want access to the host networking and it is
- running 2.2
-
- o TUN/TAP - if you want access to the host networking and it is
- running 2.4. Also, the TUN/TAP transport is able to use a
- preconfigured device, allowing it to avoid using the setuid uml_net
- helper, which is a security advantage.
-
- o Multicast - if you want a purely virtual network and you don't want
- to set up anything but the UML
-
- o a switch daemon - if you want a purely virtual network and you
- don't mind running the daemon in order to get somewhat better
- performance
-
- o slip - there is no particular reason to run the slip backend unless
- ethertap and TUN/TAP are just not available for some reason
-
- o slirp - if you don't have root access on the host to setup
- networking, or if you don't want to allocate an IP to your UML
-
- o pcap - not much use for actual network connectivity, but great for
- monitoring traffic on the host
-
- Ethertap is available on 2.4 and works fine. TUN/TAP is preferred
- to it because it has better performance and ethertap is officially
- considered obsolete in 2.4. Also, the root helper only needs to
- run occasionally for TUN/TAP, rather than handling every packet, as
- it does with ethertap. This is a slight security advantage since
- it provides fewer opportunities for a nasty UML user to somehow
- exploit the helper's root privileges.
-
-
- 6.1. General setup
-
- First, you must have the virtual network enabled in your UML. If are
- running a prebuilt kernel from this site, everything is already
- enabled. If you build the kernel yourself, under the "Network device
- support" menu, enable "Network device support", and then the three
- transports.
-
-
- The next step is to provide a network device to the virtual machine.
- This is done by describing it on the kernel command line.
-
- The general format is
-
-
- eth <n> = <transport> , <transport args>
-
-
-
-
- For example, a virtual ethernet device may be attached to a host
- ethertap device as follows:
-
-
- eth0=ethertap,tap0,fe:fd:0:0:0:1,192.168.0.254
-
-
-
-
- This sets up eth0 inside the virtual machine to attach itself to the
- host /dev/tap0, assigns it an ethernet address, and assigns the host
- tap0 interface an IP address.
-
-
-
- Note that the IP address you assign to the host end of the tap device
- must be different than the IP you assign to the eth device inside UML.
- If you are short on IPs and don't want to consume two per UML, then
- you can reuse the host's eth IP address for the host ends of the tap
- devices. Internally, the UMLs must still get unique IPs for their eth
- devices. You can also give the UMLs non-routable IPs (192.168.x.x or
- 10.x.x.x) and have the host masquerade them. This will let outgoing
- connections work, but incoming connections won't without more work,
- such as port forwarding from the host.
- Also note that when you configure the host side of an interface, it is
- only acting as a gateway. It will respond to pings sent to it
- locally, but is not useful to do that since it's a host interface.
- You are not talking to the UML when you ping that interface and get a
- response.
-
-
- You can also add devices to a UML and remove them at runtime. See the
- ``The Management Console'' page for details.
-
-
- The sections below describe this in more detail.
-
-
- Once you've decided how you're going to set up the devices, you boot
- UML, log in, configure the UML side of the devices, and set up routes
- to the outside world. At that point, you will be able to talk to any
- other machines, physical or virtual, on the net.
-
-
- If ifconfig inside UML fails and the network refuses to come up, run
- tell you what went wrong.
-
-
-
- 6.2. Userspace daemons
-
- You will likely need the setuid helper, or the switch daemon, or both.
- They are both installed with the RPM and deb, so if you've installed
- either, you can skip the rest of this section.
-
-
- If not, then you need to check them out of CVS, build them, and
- install them. The helper is uml_net, in CVS /tools/uml_net, and the
- daemon is uml_switch, in CVS /tools/uml_router. They are both built
- with a plain 'make'. Both need to be installed in a directory that's
- in your path - /usr/bin is recommend. On top of that, uml_net needs
- to be setuid root.
-
-
-
- 6.3. Specifying ethernet addresses
-
- Below, you will see that the TUN/TAP, ethertap, and daemon interfaces
- allow you to specify hardware addresses for the virtual ethernet
- devices. This is generally not necessary. If you don't have a
- specific reason to do it, you probably shouldn't. If one is not
- specified on the command line, the driver will assign one based on the
- device IP address. It will provide the address fe:fd:nn:nn:nn:nn
- where nn.nn.nn.nn is the device IP address. This is nearly always
- sufficient to guarantee a unique hardware address for the device. A
- couple of exceptions are:
-
- o Another set of virtual ethernet devices are on the same network and
- they are assigned hardware addresses using a different scheme which
- may conflict with the UML IP address-based scheme
-
- o You aren't going to use the device for IP networking, so you don't
- assign the device an IP address
-
- If you let the driver provide the hardware address, you should make
- sure that the device IP address is known before the interface is
- brought up. So, inside UML, this will guarantee that:
-
-
-
- UML#
- ifconfig eth0 192.168.0.250 up
-
-
-
-
- If you decide to assign the hardware address yourself, make sure that
- the first byte of the address is even. Addresses with an odd first
- byte are broadcast addresses, which you don't want assigned to a
- device.
-
-
-
- 6.4. UML interface setup
-
- Once the network devices have been described on the command line, you
- should boot UML and log in.
-
-
- The first thing to do is bring the interface up:
-
-
- UML# ifconfig ethn ip-address up
-
-
-
-
- You should be able to ping the host at this point.
-
-
- To reach the rest of the world, you should set a default route to the
- host:
-
-
- UML# route add default gw host ip
-
-
-
-
- Again, with host ip of 192.168.0.4:
-
-
- UML# route add default gw 192.168.0.4
-
-
-
-
- This page used to recommend setting a network route to your local net.
- This is wrong, because it will cause UML to try to figure out hardware
- addresses of the local machines by arping on the interface to the
- host. Since that interface is basically a single strand of ethernet
- with two nodes on it (UML and the host) and arp requests don't cross
- networks, they will fail to elicit any responses. So, what you want
- is for UML to just blindly throw all packets at the host and let it
- figure out what to do with them, which is what leaving out the network
- route and adding the default route does.
-
-
- Note: If you can't communicate with other hosts on your physical
- ethernet, it's probably because of a network route that's
- automatically set up. If you run 'route -n' and see a route that
- looks like this:
-
-
-
-
- Destination Gateway Genmask Flags Metric Ref Use Iface
- 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
-
-
-
-
- with a mask that's not 255.255.255.255, then replace it with a route
- to your host:
-
-
- UML#
- route del -net 192.168.0.0 dev eth0 netmask 255.255.255.0
-
-
-
-
-
-
- UML#
- route add -host 192.168.0.4 dev eth0
-
-
-
-
- This, plus the default route to the host, will allow UML to exchange
- packets with any machine on your ethernet.
-
-
-
- 6.5. Multicast
-
- The simplest way to set up a virtual network between multiple UMLs is
- to use the mcast transport. This was written by Harald Welte and is
- present in UML version 2.4.5-5um and later. Your system must have
- multicast enabled in the kernel and there must be a multicast-capable
- network device on the host. Normally, this is eth0, but if there is
- no ethernet card on the host, then you will likely get strange error
- messages when you bring the device up inside UML.
-
-
- To use it, run two UMLs with
-
-
- eth0=mcast
-
-
-
-
- on their command lines. Log in, configure the ethernet device in each
- machine with different IP addresses:
-
-
- UML1# ifconfig eth0 192.168.0.254
-
-
-
-
-
-
- UML2# ifconfig eth0 192.168.0.253
-
-
-
-
- and they should be able to talk to each other.
-
- The full set of command line options for this transport are
-
-
-
- ethn=mcast,ethernet address,multicast
- address,multicast port,ttl
-
-
-
-
- Harald's original README is here <http://user-mode-linux.source-
- forge.net/> and explains these in detail, as well as
- some other issues.
-
- There is also a related point-to-point only "ucast" transport.
- This is useful when your network does not support multicast, and
- all network connections are simple point to point links.
-
- The full set of command line options for this transport are
-
-
- ethn=ucast,ethernet address,remote address,listen port,remote port
-
-
-
-
- 6.6. TUN/TAP with the uml_net helper
-
- TUN/TAP is the preferred mechanism on 2.4 to exchange packets with the
- host. The TUN/TAP backend has been in UML since 2.4.9-3um.
-
-
- The easiest way to get up and running is to let the setuid uml_net
- helper do the host setup for you. This involves insmod-ing the tun.o
- module if necessary, configuring the device, and setting up IP
- forwarding, routing, and proxy arp. If you are new to UML networking,
- do this first. If you're concerned about the security implications of
- the setuid helper, use it to get up and running, then read the next
- section to see how to have UML use a preconfigured tap device, which
- avoids the use of uml_net.
-
-
- If you specify an IP address for the host side of the device, the
- uml_net helper will do all necessary setup on the host - the only
- requirement is that TUN/TAP be available, either built in to the host
- kernel or as the tun.o module.
-
- The format of the command line switch to attach a device to a TUN/TAP
- device is
-
-
- eth <n> =tuntap,,, <IP address>
-
-
-
-
- For example, this argument will attach the UML's eth0 to the next
- available tap device and assign an ethernet address to it based on its
- IP address
-
-
- eth0=tuntap,,,192.168.0.254
-
-
-
-
-
-
- Note that the IP address that must be used for the eth device inside
- UML is fixed by the routing and proxy arp that is set up on the
- TUN/TAP device on the host. You can use a different one, but it won't
- work because reply packets won't reach the UML. This is a feature.
- It prevents a nasty UML user from doing things like setting the UML IP
- to the same as the network's nameserver or mail server.
-
-
- There are a couple potential problems with running the TUN/TAP
- transport on a 2.4 host kernel
-
- o TUN/TAP seems not to work on 2.4.3 and earlier. Upgrade the host
- kernel or use the ethertap transport.
-
- o With an upgraded kernel, TUN/TAP may fail with
-
-
- File descriptor in bad state
-
-
-
-
- This is due to a header mismatch between the upgraded kernel and the
- kernel that was originally installed on the machine. The fix is to
- make sure that /usr/src/linux points to the headers for the running
- kernel.
-
- These were pointed out by Tim Robinson <timro at trkr dot net> in
- <http://www.geocrawler.com/> name="this uml-
- user post"> .
-
-
-
- 6.7. TUN/TAP with a preconfigured tap device
-
- If you prefer not to have UML use uml_net (which is somewhat
- insecure), with UML 2.4.17-11, you can set up a TUN/TAP device
- beforehand. The setup needs to be done as root, but once that's done,
- there is no need for root assistance. Setting up the device is done
- as follows:
-
- o Create the device with tunctl (available from the UML utilities
- tarball)
-
-
-
-
- host# tunctl -u uid
-
-
-
-
- where uid is the user id or username that UML will be run as. This
- will tell you what device was created.
-
- o Configure the device IP (change IP addresses and device name to
- suit)
-
-
-
-
- host# ifconfig tap0 192.168.0.254 up
-
-
-
-
-
- o Set up routing and arping if desired - this is my recipe, there are
- other ways of doing the same thing
-
-
- host#
- bash -c 'echo 1 > /proc/sys/net/ipv4/ip_forward'
-
- host#
- route add -host 192.168.0.253 dev tap0
-
-
-
-
-
-
- host#
- bash -c 'echo 1 > /proc/sys/net/ipv4/conf/tap0/proxy_arp'
-
-
-
-
-
-
- host#
- arp -Ds 192.168.0.253 eth0 pub
-
-
-
-
- Note that this must be done every time the host boots - this configu-
- ration is not stored across host reboots. So, it's probably a good
- idea to stick it in an rc file. An even better idea would be a little
- utility which reads the information from a config file and sets up
- devices at boot time.
-
- o Rather than using up two IPs and ARPing for one of them, you can
- also provide direct access to your LAN by the UML by using a
- bridge.
-
-
- host#
- brctl addbr br0
-
-
-
-
-
-
- host#
- ifconfig eth0 0.0.0.0 promisc up
-
-
-
-
-
-
- host#
- ifconfig tap0 0.0.0.0 promisc up
-
-
-
-
-
-
- host#
- ifconfig br0 192.168.0.1 netmask 255.255.255.0 up
-
-
-
-
-
-
-
- host#
- brctl stp br0 off
-
-
-
-
-
-
- host#
- brctl setfd br0 1
-
-
-
-
-
-
- host#
- brctl sethello br0 1
-
-
-
-
-
-
- host#
- brctl addif br0 eth0
-
-
-
-
-
-
- host#
- brctl addif br0 tap0
-
-
-
-
- Note that 'br0' should be setup using ifconfig with the existing IP
- address of eth0, as eth0 no longer has its own IP.
-
- o
-
-
- Also, the /dev/net/tun device must be writable by the user running
- UML in order for the UML to use the device that's been configured
- for it. The simplest thing to do is
-
-
- host# chmod 666 /dev/net/tun
-
-
-
-
- Making it world-writable looks bad, but it seems not to be
- exploitable as a security hole. However, it does allow anyone to cre-
- ate useless tap devices (useless because they can't configure them),
- which is a DOS attack. A somewhat more secure alternative would to be
- to create a group containing all the users who have preconfigured tap
- devices and chgrp /dev/net/tun to that group with mode 664 or 660.
-
-
- o Once the device is set up, run UML with 'eth0=tuntap,device name'
- (i.e. 'eth0=tuntap,tap0') on the command line (or do it with the
- mconsole config command).
-
- o Bring the eth device up in UML and you're in business.
-
- If you don't want that tap device any more, you can make it non-
- persistent with
-
-
- host# tunctl -d tap device
-
-
-
-
- Finally, tunctl has a -b (for brief mode) switch which causes it to
- output only the name of the tap device it created. This makes it
- suitable for capture by a script:
-
-
- host# TAP=`tunctl -u 1000 -b`
-
-
-
-
-
-
- 6.8. Ethertap
-
- Ethertap is the general mechanism on 2.2 for userspace processes to
- exchange packets with the kernel.
-
-
-
- To use this transport, you need to describe the virtual network device
- on the UML command line. The general format for this is
-
-
- eth <n> =ethertap, <device> , <ethernet address> , <tap IP address>
-
-
-
-
- So, the previous example
-
-
- eth0=ethertap,tap0,fe:fd:0:0:0:1,192.168.0.254
-
-
-
-
- attaches the UML eth0 device to the host /dev/tap0, assigns it the
- ethernet address fe:fd:0:0:0:1, and assigns the IP address
- 192.168.0.254 to the tap device.
-
-
-
- The tap device is mandatory, but the others are optional. If the
- ethernet address is omitted, one will be assigned to it.
-
-
- The presence of the tap IP address will cause the helper to run and do
- whatever host setup is needed to allow the virtual machine to
- communicate with the outside world. If you're not sure you know what
- you're doing, this is the way to go.
-
-
- If it is absent, then you must configure the tap device and whatever
- arping and routing you will need on the host. However, even in this
- case, the uml_net helper still needs to be in your path and it must be
- setuid root if you're not running UML as root. This is because the
- tap device doesn't support SIGIO, which UML needs in order to use
- something as a source of input. So, the helper is used as a
- convenient asynchronous IO thread.
-
- If you're using the uml_net helper, you can ignore the following host
- setup - uml_net will do it for you. You just need to make sure you
- have ethertap available, either built in to the host kernel or
- available as a module.
-
-
- If you want to set things up yourself, you need to make sure that the
- appropriate /dev entry exists. If it doesn't, become root and create
- it as follows:
-
-
- mknod /dev/tap <minor> c 36 <minor> + 16
-
-
-
-
- For example, this is how to create /dev/tap0:
-
-
- mknod /dev/tap0 c 36 0 + 16
-
-
-
-
- You also need to make sure that the host kernel has ethertap support.
- If ethertap is enabled as a module, you apparently need to insmod
- ethertap once for each ethertap device you want to enable. So,
-
-
- host#
- insmod ethertap
-
-
-
-
- will give you the tap0 interface. To get the tap1 interface, you need
- to run
-
-
- host#
- insmod ethertap unit=1 -o ethertap1
-
-
-
-
-
-
-
- 6.9. The switch daemon
-
- Note: This is the daemon formerly known as uml_router, but which was
- renamed so the network weenies of the world would stop growling at me.
-
-
- The switch daemon, uml_switch, provides a mechanism for creating a
- totally virtual network. By default, it provides no connection to the
- host network (but see -tap, below).
-
-
- The first thing you need to do is run the daemon. Running it with no
- arguments will make it listen on a default pair of unix domain
- sockets.
-
-
- If you want it to listen on a different pair of sockets, use
-
-
- -unix control socket data socket
-
-
-
-
-
- If you want it to act as a hub rather than a switch, use
-
-
- -hub
-
-
-
-
-
- If you want the switch to be connected to host networking (allowing
- the umls to get access to the outside world through the host), use
-
-
- -tap tap0
-
-
-
-
-
- Note that the tap device must be preconfigured (see "TUN/TAP with a
- preconfigured tap device", above). If you're using a different tap
- device than tap0, specify that instead of tap0.
-
-
- uml_switch can be backgrounded as follows
-
-
- host%
- uml_switch [ options ] < /dev/null > /dev/null
-
-
-
-
- The reason it doesn't background by default is that it listens to
- stdin for EOF. When it sees that, it exits.
-
-
- The general format of the kernel command line switch is
-
-
-
- ethn=daemon,ethernet address,socket
- type,control socket,data socket
-
-
-
-
- You can leave off everything except the 'daemon'. You only need to
- specify the ethernet address if the one that will be assigned to it
- isn't acceptable for some reason. The rest of the arguments describe
- how to communicate with the daemon. You should only specify them if
- you told the daemon to use different sockets than the default. So, if
- you ran the daemon with no arguments, running the UML on the same
- machine with
- eth0=daemon
-
-
-
-
- will cause the eth0 driver to attach itself to the daemon correctly.
-
-
-
- 6.10. Slip
-
- Slip is another, less general, mechanism for a process to communicate
- with the host networking. In contrast to the ethertap interface,
- which exchanges ethernet frames with the host and can be used to
- transport any higher-level protocol, it can only be used to transport
- IP.
-
-
- The general format of the command line switch is
-
-
-
- ethn=slip,slip IP
-
-
-
-
- The slip IP argument is the IP address that will be assigned to the
- host end of the slip device. If it is specified, the helper will run
- and will set up the host so that the virtual machine can reach it and
- the rest of the network.
-
-
- There are some oddities with this interface that you should be aware
- of. You should only specify one slip device on a given virtual
- machine, and its name inside UML will be 'umn', not 'eth0' or whatever
- you specified on the command line. These problems will be fixed at
- some point.
-
-
-
- 6.11. Slirp
-
- slirp uses an external program, usually /usr/bin/slirp, to provide IP
- only networking connectivity through the host. This is similar to IP
- masquerading with a firewall, although the translation is performed in
- user-space, rather than by the kernel. As slirp does not set up any
- interfaces on the host, or changes routing, slirp does not require
- root access or setuid binaries on the host.
-
-
- The general format of the command line switch for slirp is:
-
-
-
- ethn=slirp,ethernet address,slirp path
-
-
-
-
- The ethernet address is optional, as UML will set up the interface
- with an ethernet address based upon the initial IP address of the
- interface. The slirp path is generally /usr/bin/slirp, although it
- will depend on distribution.
-
-
- The slirp program can have a number of options passed to the command
- line and we can't add them to the UML command line, as they will be
- parsed incorrectly. Instead, a wrapper shell script can be written or
- the options inserted into the /.slirprc file. More information on
- all of the slirp options can be found in its man pages.
-
-
- The eth0 interface on UML should be set up with the IP 10.2.0.15,
- although you can use anything as long as it is not used by a network
- you will be connecting to. The default route on UML should be set to
- use
-
-
- UML#
- route add default dev eth0
-
-
-
-
- slirp provides a number of useful IP addresses which can be used by
- UML, such as 10.0.2.3 which is an alias for the DNS server specified
- in /etc/resolv.conf on the host or the IP given in the 'dns' option
- for slirp.
-
-
- Even with a baudrate setting higher than 115200, the slirp connection
- is limited to 115200. If you need it to go faster, the slirp binary
- needs to be compiled with FULL_BOLT defined in config.h.
-
-
-
- 6.12. pcap
-
- The pcap transport is attached to a UML ethernet device on the command
- line or with uml_mconsole with the following syntax:
-
-
-
- ethn=pcap,host interface,filter
- expression,option1,option2
-
-
-
-
- The expression and options are optional.
-
-
- The interface is whatever network device on the host you want to
- sniff. The expression is a pcap filter expression, which is also what
- tcpdump uses, so if you know how to specify tcpdump filters, you will
- use the same expressions here. The options are up to two of
- 'promisc', control whether pcap puts the host interface into
- promiscuous mode. 'optimize' and 'nooptimize' control whether the pcap
- expression optimizer is used.
-
-
- Example:
-
-
-
- eth0=pcap,eth0,tcp
-
- eth1=pcap,eth0,!tcp
-
-
-
- will cause the UML eth0 to emit all tcp packets on the host eth0 and
- the UML eth1 to emit all non-tcp packets on the host eth0.
-
-
-
- 6.13. Setting up the host yourself
-
- If you don't specify an address for the host side of the ethertap or
- slip device, UML won't do any setup on the host. So this is what is
- needed to get things working (the examples use a host-side IP of
- 192.168.0.251 and a UML-side IP of 192.168.0.250 - adjust to suit your
- own network):
-
- o The device needs to be configured with its IP address. Tap devices
- are also configured with an mtu of 1484. Slip devices are
- configured with a point-to-point address pointing at the UML ip
- address.
-
-
- host# ifconfig tap0 arp mtu 1484 192.168.0.251 up
-
-
-
-
-
-
- host#
- ifconfig sl0 192.168.0.251 pointopoint 192.168.0.250 up
-
-
-
-
-
- o If a tap device is being set up, a route is set to the UML IP.
-
-
- UML# route add -host 192.168.0.250 gw 192.168.0.251
-
-
-
-
-
- o To allow other hosts on your network to see the virtual machine,
- proxy arp is set up for it.
-
-
- host# arp -Ds 192.168.0.250 eth0 pub
-
-
-
-
-
- o Finally, the host is set up to route packets.
-
-
- host# echo 1 > /proc/sys/net/ipv4/ip_forward
-
-
-
-
-
-
-
-
-
-
- 7. Sharing Filesystems between Virtual Machines
-
-
-
-
- 7.1. A warning
-
- Don't attempt to share filesystems simply by booting two UMLs from the
- same file. That's the same thing as booting two physical machines
- from a shared disk. It will result in filesystem corruption.
-
-
-
- 7.2. Using layered block devices
-
- The way to share a filesystem between two virtual machines is to use
- the copy-on-write (COW) layering capability of the ubd block driver.
- As of 2.4.6-2um, the driver supports layering a read-write private
- device over a read-only shared device. A machine's writes are stored
- in the private device, while reads come from either device - the
- private one if the requested block is valid in it, the shared one if
- not. Using this scheme, the majority of data which is unchanged is
- shared between an arbitrary number of virtual machines, each of which
- has a much smaller file containing the changes that it has made. With
- a large number of UMLs booting from a large root filesystem, this
- leads to a huge disk space saving. It will also help performance,
- since the host will be able to cache the shared data using a much
- smaller amount of memory, so UML disk requests will be served from the
- host's memory rather than its disks.
-
-
-
-
- To add a copy-on-write layer to an existing block device file, simply
- add the name of the COW file to the appropriate ubd switch:
-
-
- ubd0=root_fs_cow,root_fs_debian_22
-
-
-
-
- where 'root_fs_cow' is the private COW file and 'root_fs_debian_22' is
- the existing shared filesystem. The COW file need not exist. If it
- doesn't, the driver will create and initialize it. Once the COW file
- has been initialized, it can be used on its own on the command line:
-
-
- ubd0=root_fs_cow
-
-
-
-
- The name of the backing file is stored in the COW file header, so it
- would be redundant to continue specifying it on the command line.
-
-
-
- 7.3. Note!
-
- When checking the size of the COW file in order to see the gobs of
- space that you're saving, make sure you use 'ls -ls' to see the actual
- disk consumption rather than the length of the file. The COW file is
- sparse, so the length will be very different from the disk usage.
- Here is a 'ls -l' of a COW file and backing file from one boot and
- shutdown:
- host% ls -l cow.debian debian2.2
- -rw-r--r-- 1 jdike jdike 492504064 Aug 6 21:16 cow.debian
- -rwxrw-rw- 1 jdike jdike 537919488 Aug 6 20:42 debian2.2
-
-
-
-
- Doesn't look like much saved space, does it? Well, here's 'ls -ls':
-
-
- host% ls -ls cow.debian debian2.2
- 880 -rw-r--r-- 1 jdike jdike 492504064 Aug 6 21:16 cow.debian
- 525832 -rwxrw-rw- 1 jdike jdike 537919488 Aug 6 20:42 debian2.2
-
-
-
-
- Now, you can see that the COW file has less than a meg of disk, rather
- than 492 meg.
-
-
-
- 7.4. Another warning
-
- Once a filesystem is being used as a readonly backing file for a COW
- file, do not boot directly from it or modify it in any way. Doing so
- will invalidate any COW files that are using it. The mtime and size
- of the backing file are stored in the COW file header at its creation,
- and they must continue to match. If they don't, the driver will
- refuse to use the COW file.
-
-
-
-
- If you attempt to evade this restriction by changing either the
- backing file or the COW header by hand, you will get a corrupted
- filesystem.
-
-
-
-
- Among other things, this means that upgrading the distribution in a
- backing file and expecting that all of the COW files using it will see
- the upgrade will not work.
-
-
-
-
- 7.5. uml_moo : Merging a COW file with its backing file
-
- Depending on how you use UML and COW devices, it may be advisable to
- merge the changes in the COW file into the backing file every once in
- a while.
-
-
-
-
- The utility that does this is uml_moo. Its usage is
-
-
- host% uml_moo COW file new backing file
-
-
-
-
- There's no need to specify the backing file since that information is
- already in the COW file header. If you're paranoid, boot the new
- merged file, and if you're happy with it, move it over the old backing
- file.
-
-
-
-
- uml_moo creates a new backing file by default as a safety measure. It
- also has a destructive merge option which will merge the COW file
- directly into its current backing file. This is really only usable
- when the backing file only has one COW file associated with it. If
- there are multiple COWs associated with a backing file, a -d merge of
- one of them will invalidate all of the others. However, it is
- convenient if you're short of disk space, and it should also be
- noticeably faster than a non-destructive merge.
-
-
-
-
- uml_moo is installed with the UML deb and RPM. If you didn't install
- UML from one of those packages, you can also get it from the UML
- utilities <http://user-mode-linux.sourceforge.net/
- utilities> tar file in tools/moo.
-
-
-
-
-
-
-
-
- 8. Creating filesystems
-
-
- You may want to create and mount new UML filesystems, either because
- your root filesystem isn't large enough or because you want to use a
- filesystem other than ext2.
-
-
- This was written on the occasion of reiserfs being included in the
- 2.4.1 kernel pool, and therefore the 2.4.1 UML, so the examples will
- talk about reiserfs. This information is generic, and the examples
- should be easy to translate to the filesystem of your choice.
-
-
- 8.1. Create the filesystem file
-
- dd is your friend. All you need to do is tell dd to create an empty
- file of the appropriate size. I usually make it sparse to save time
- and to avoid allocating disk space until it's actually used. For
- example, the following command will create a sparse 100 meg file full
- of zeroes.
-
-
- host%
- dd if=/dev/zero of=new_filesystem seek=100 count=1 bs=1M
-
-
-
-
-
-
- 8.2. Assign the file to a UML device
-
- Add an argument like the following to the UML command line:
-
- ubd4=new_filesystem
-
-
-
-
- making sure that you use an unassigned ubd device number.
-
-
-
- 8.3. Creating and mounting the filesystem
-
- Make sure that the filesystem is available, either by being built into
- the kernel, or available as a module, then boot up UML and log in. If
- the root filesystem doesn't have the filesystem utilities (mkfs, fsck,
- etc), then get them into UML by way of the net or hostfs.
-
-
- Make the new filesystem on the device assigned to the new file:
-
-
- host# mkreiserfs /dev/ubd/4
-
-
- <----------- MKREISERFSv2 ----------->
-
- ReiserFS version 3.6.25
- Block size 4096 bytes
- Block count 25856
- Used blocks 8212
- Journal - 8192 blocks (18-8209), journal header is in block 8210
- Bitmaps: 17
- Root block 8211
- Hash function "r5"
- ATTENTION: ALL DATA WILL BE LOST ON '/dev/ubd/4'! (y/n)y
- journal size 8192 (from 18)
- Initializing journal - 0%....20%....40%....60%....80%....100%
- Syncing..done.
-
-
-
-
- Now, mount it:
-
-
- UML#
- mount /dev/ubd/4 /mnt
-
-
-
-
- and you're in business.
-
-
-
-
-
-
-
-
-
- 9. Host file access
-
-
- If you want to access files on the host machine from inside UML, you
- can treat it as a separate machine and either nfs mount directories
- from the host or copy files into the virtual machine with scp or rcp.
- However, since UML is running on the host, it can access those
- files just like any other process and make them available inside the
- virtual machine without needing to use the network.
-
-
- This is now possible with the hostfs virtual filesystem. With it, you
- can mount a host directory into the UML filesystem and access the
- files contained in it just as you would on the host.
-
-
- 9.1. Using hostfs
-
- To begin with, make sure that hostfs is available inside the virtual
- machine with
-
-
- UML# cat /proc/filesystems
-
-
-
- . hostfs should be listed. If it's not, either rebuild the kernel
- with hostfs configured into it or make sure that hostfs is built as a
- module and available inside the virtual machine, and insmod it.
-
-
- Now all you need to do is run mount:
-
-
- UML# mount none /mnt/host -t hostfs
-
-
-
-
- will mount the host's / on the virtual machine's /mnt/host.
-
-
- If you don't want to mount the host root directory, then you can
- specify a subdirectory to mount with the -o switch to mount:
-
-
- UML# mount none /mnt/home -t hostfs -o /home
-
-
-
-
- will mount the hosts's /home on the virtual machine's /mnt/home.
-
-
-
- 9.2. hostfs as the root filesystem
-
- It's possible to boot from a directory hierarchy on the host using
- hostfs rather than using the standard filesystem in a file.
-
- To start, you need that hierarchy. The easiest way is to loop mount
- an existing root_fs file:
-
-
- host# mount root_fs uml_root_dir -o loop
-
-
-
-
- You need to change the filesystem type of / in etc/fstab to be
- 'hostfs', so that line looks like this:
-
- /dev/ubd/0 / hostfs defaults 1 1
-
-
-
-
- Then you need to chown to yourself all the files in that directory
- that are owned by root. This worked for me:
-
-
- host# find . -uid 0 -exec chown jdike {} \;
-
-
-
-
- Next, make sure that your UML kernel has hostfs compiled in, not as a
- module. Then run UML with the boot device pointing at that directory:
-
-
- ubd0=/path/to/uml/root/directory
-
-
-
-
- UML should then boot as it does normally.
-
-
- 9.3. Building hostfs
-
- If you need to build hostfs because it's not in your kernel, you have
- two choices:
-
-
-
- o Compiling hostfs into the kernel:
-
-
- Reconfigure the kernel and set the 'Host filesystem' option under
-
-
- o Compiling hostfs as a module:
-
-
- Reconfigure the kernel and set the 'Host filesystem' option under
- be in arch/um/fs/hostfs/hostfs.o. Install that in
- /lib/modules/`uname -r`/fs in the virtual machine, boot it up, and
-
-
- UML# insmod hostfs
-
-
-
-
-
-
-
-
-
-
-
-
- 10. The Management Console
-
-
-
- The UML management console is a low-level interface to the kernel,
- somewhat like the i386 SysRq interface. Since there is a full-blown
- operating system under UML, there is much greater flexibility possible
- than with the SysRq mechanism.
-
-
- There are a number of things you can do with the mconsole interface:
-
- o get the kernel version
-
- o add and remove devices
-
- o halt or reboot the machine
-
- o Send SysRq commands
-
- o Pause and resume the UML
-
-
- You need the mconsole client (uml_mconsole) which is present in CVS
- (/tools/mconsole) in 2.4.5-9um and later, and will be in the RPM in
- 2.4.6.
-
-
- You also need CONFIG_MCONSOLE (under 'General Setup') enabled in UML.
- When you boot UML, you'll see a line like:
-
-
- mconsole initialized on /home/jdike/.uml/umlNJ32yL/mconsole
-
-
-
-
- If you specify a unique machine id one the UML command line, i.e.
-
-
- umid=debian
-
-
-
-
- you'll see this
-
-
- mconsole initialized on /home/jdike/.uml/debian/mconsole
-
-
-
-
- That file is the socket that uml_mconsole will use to communicate with
- UML. Run it with either the umid or the full path as its argument:
-
-
- host% uml_mconsole debian
-
-
-
-
- or
-
-
- host% uml_mconsole /home/jdike/.uml/debian/mconsole
-
-
-
-
- You'll get a prompt, at which you can run one of these commands:
-
- o version
-
- o halt
-
- o reboot
-
- o config
-
- o remove
-
- o sysrq
-
- o help
-
- o cad
-
- o stop
-
- o go
-
-
- 10.1. version
-
- This takes no arguments. It prints the UML version.
-
-
- (mconsole) version
- OK Linux usermode 2.4.5-9um #1 Wed Jun 20 22:47:08 EDT 2001 i686
-
-
-
-
- There are a couple actual uses for this. It's a simple no-op which
- can be used to check that a UML is running. It's also a way of
- sending an interrupt to the UML. This is sometimes useful on SMP
- hosts, where there's a bug which causes signals to UML to be lost,
- often causing it to appear to hang. Sending such a UML the mconsole
- version command is a good way to 'wake it up' before networking has
- been enabled, as it does not do anything to the function of the UML.
-
-
-
- 10.2. halt and reboot
-
- These take no arguments. They shut the machine down immediately, with
- no syncing of disks and no clean shutdown of userspace. So, they are
- pretty close to crashing the machine.
-
-
- (mconsole) halt
- OK
-
-
-
-
-
-
- 10.3. config
-
- "config" adds a new device to the virtual machine. Currently the ubd
- and network drivers support this. It takes one argument, which is the
- device to add, with the same syntax as the kernel command line.
-
-
-
-
- (mconsole)
- config ubd3=/home/jdike/incoming/roots/root_fs_debian22
-
- OK
- (mconsole) config eth1=mcast
- OK
-
-
-
-
-
-
- 10.4. remove
-
- "remove" deletes a device from the system. Its argument is just the
- name of the device to be removed. The device must be idle in whatever
- sense the driver considers necessary. In the case of the ubd driver,
- the removed block device must not be mounted, swapped on, or otherwise
- open, and in the case of the network driver, the device must be down.
-
-
- (mconsole) remove ubd3
- OK
- (mconsole) remove eth1
- OK
-
-
-
-
-
-
- 10.5. sysrq
-
- This takes one argument, which is a single letter. It calls the
- generic kernel's SysRq driver, which does whatever is called for by
- that argument. See the SysRq documentation in
- Documentation/admin-guide/sysrq.rst in your favorite kernel tree to
- see what letters are valid and what they do.
-
-
-
- 10.6. help
-
- "help" returns a string listing the valid commands and what each one
- does.
-
-
-
- 10.7. cad
-
- This invokes the Ctl-Alt-Del action on init. What exactly this ends
- up doing is up to /etc/inittab. Normally, it reboots the machine.
- With UML, this is usually not desired, so if a halt would be better,
- then find the section of inittab that looks like this
-
-
- # What to do when CTRL-ALT-DEL is pressed.
- ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now
-
-
-
-
- and change the command to halt.
-
-
-
- 10.8. stop
-
- This puts the UML in a loop reading mconsole requests until a 'go'
- mconsole command is received. This is very useful for making backups
- of UML filesystems, as the UML can be stopped, then synced via 'sysrq
- s', so that everything is written to the filesystem. You can then copy
- the filesystem and then send the UML 'go' via mconsole.
-
-
- Note that a UML running with more than one CPU will have problems
- after you send the 'stop' command, as only one CPU will be held in a
- mconsole loop and all others will continue as normal. This is a bug,
- and will be fixed.
-
-
-
- 10.9. go
-
- This resumes a UML after being paused by a 'stop' command. Note that
- when the UML has resumed, TCP connections may have timed out and if
- the UML is paused for a long period of time, crond might go a little
- crazy, running all the jobs it didn't do earlier.
-
-
-
-
-
-
-
-
- 11. Kernel debugging
-
-
- Note: The interface that makes debugging, as described here, possible
- is present in 2.4.0-test6 kernels and later.
-
-
- Since the user-mode kernel runs as a normal Linux process, it is
- possible to debug it with gdb almost like any other process. It is
- slightly different because the kernel's threads are already being
- ptraced for system call interception, so gdb can't ptrace them.
- However, a mechanism has been added to work around that problem.
-
-
- In order to debug the kernel, you need build it from source. See
- ``Compiling the kernel and modules'' for information on doing that.
- Make sure that you enable CONFIG_DEBUGSYM and CONFIG_PT_PROXY during
- the config. These will compile the kernel with -g, and enable the
- ptrace proxy so that gdb works with UML, respectively.
-
-
-
-
- 11.1. Starting the kernel under gdb
-
- You can have the kernel running under the control of gdb from the
- beginning by putting 'debug' on the command line. You will get an
- xterm with gdb running inside it. The kernel will send some commands
- to gdb which will leave it stopped at the beginning of start_kernel.
- At this point, you can get things going with 'next', 'step', or
- 'cont'.
-
-
- There is a transcript of a debugging session here <debug-
- session.html> , with breakpoints being set in the scheduler and in an
- interrupt handler.
- 11.2. Examining sleeping processes
-
- Not every bug is evident in the currently running process. Sometimes,
- processes hang in the kernel when they shouldn't because they've
- deadlocked on a semaphore or something similar. In this case, when
- you ^C gdb and get a backtrace, you will see the idle thread, which
- isn't very relevant.
-
-
- What you want is the stack of whatever process is sleeping when it
- shouldn't be. You need to figure out which process that is, which is
- generally fairly easy. Then you need to get its host process id,
- which you can do either by looking at ps on the host or at
- task.thread.extern_pid in gdb.
-
-
- Now what you do is this:
-
- o detach from the current thread
-
-
- (UML gdb) det
-
-
-
-
-
- o attach to the thread you are interested in
-
-
- (UML gdb) att <host pid>
-
-
-
-
-
- o look at its stack and anything else of interest
-
-
- (UML gdb) bt
-
-
-
-
- Note that you can't do anything at this point that requires that a
- process execute, e.g. calling a function
-
- o when you're done looking at that process, reattach to the current
- thread and continue it
-
-
- (UML gdb)
- att 1
-
-
-
-
-
-
- (UML gdb)
- c
-
-
-
-
- Here, specifying any pid which is not the process id of a UML thread
- will cause gdb to reattach to the current thread. I commonly use 1,
- but any other invalid pid would work.
-
-
-
- 11.3. Running ddd on UML
-
- ddd works on UML, but requires a special kludge. The process goes
- like this:
-
- o Start ddd
-
-
- host% ddd linux
-
-
-
-
-
- o With ps, get the pid of the gdb that ddd started. You can ask the
- gdb to tell you, but for some reason that confuses things and
- causes a hang.
-
- o run UML with 'debug=parent gdb-pid=<pid>' added to the command line
- - it will just sit there after you hit return
-
- o type 'att 1' to the ddd gdb and you will see something like
-
-
- 0xa013dc51 in __kill ()
-
-
- (gdb)
-
-
-
-
-
- o At this point, type 'c', UML will boot up, and you can use ddd just
- as you do on any other process.
-
-
-
- 11.4. Debugging modules
-
- gdb has support for debugging code which is dynamically loaded into
- the process. This support is what is needed to debug kernel modules
- under UML.
-
-
- Using that support is somewhat complicated. You have to tell gdb what
- object file you just loaded into UML and where in memory it is. Then,
- it can read the symbol table, and figure out where all the symbols are
- from the load address that you provided. It gets more interesting
- when you load the module again (i.e. after an rmmod). You have to
- tell gdb to forget about all its symbols, including the main UML ones
- for some reason, then load then all back in again.
-
-
- There's an easy way and a hard way to do this. The easy way is to use
- the umlgdb expect script written by Chandan Kudige. It basically
- automates the process for you.
-
-
- First, you must tell it where your modules are. There is a list in
- the script that looks like this:
- set MODULE_PATHS {
- "fat" "/usr/src/uml/linux-2.4.18/fs/fat/fat.o"
- "isofs" "/usr/src/uml/linux-2.4.18/fs/isofs/isofs.o"
- "minix" "/usr/src/uml/linux-2.4.18/fs/minix/minix.o"
- }
-
-
-
-
- You change that to list the names and paths of the modules that you
- are going to debug. Then you run it from the toplevel directory of
- your UML pool and it basically tells you what to do:
-
-
-
-
- ******** GDB pid is 21903 ********
- Start UML as: ./linux <kernel switches> debug gdb-pid=21903
-
-
-
- GNU gdb 5.0rh-5 Red Hat Linux 7.1
- Copyright 2001 Free Software Foundation, Inc.
- GDB is free software, covered by the GNU General Public License, and you are
- welcome to change it and/or distribute copies of it under certain conditions.
- Type "show copying" to see the conditions.
- There is absolutely no warranty for GDB. Type "show warranty" for details.
- This GDB was configured as "i386-redhat-linux"...
- (gdb) b sys_init_module
- Breakpoint 1 at 0xa0011923: file module.c, line 349.
- (gdb) att 1
-
-
-
-
- After you run UML and it sits there doing nothing, you hit return at
- the 'att 1' and continue it:
-
-
- Attaching to program: /home/jdike/linux/2.4/um/./linux, process 1
- 0xa00f4221 in __kill ()
- (UML gdb) c
- Continuing.
-
-
-
-
- At this point, you debug normally. When you insmod something, the
- expect magic will kick in and you'll see something like:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- *** Module hostfs loaded ***
- Breakpoint 1, sys_init_module (name_user=0x805abb0 "hostfs",
- mod_user=0x8070e00) at module.c:349
- 349 char *name, *n_name, *name_tmp = NULL;
- (UML gdb) finish
- Run till exit from #0 sys_init_module (name_user=0x805abb0 "hostfs",
- mod_user=0x8070e00) at module.c:349
- 0xa00e2e23 in execute_syscall (r=0xa8140284) at syscall_kern.c:411
- 411 else res = EXECUTE_SYSCALL(syscall, regs);
- Value returned is $1 = 0
- (UML gdb)
- p/x (int)module_list + module_list->size_of_struct
-
- $2 = 0xa9021054
- (UML gdb) symbol-file ./linux
- Load new symbol table from "./linux"? (y or n) y
- Reading symbols from ./linux...
- done.
- (UML gdb)
- add-symbol-file /home/jdike/linux/2.4/um/arch/um/fs/hostfs/hostfs.o 0xa9021054
-
- add symbol table from file "/home/jdike/linux/2.4/um/arch/um/fs/hostfs/hostfs.o" at
- .text_addr = 0xa9021054
- (y or n) y
-
- Reading symbols from /home/jdike/linux/2.4/um/arch/um/fs/hostfs/hostfs.o...
- done.
- (UML gdb) p *module_list
- $1 = {size_of_struct = 84, next = 0xa0178720, name = 0xa9022de0 "hostfs",
- size = 9016, uc = {usecount = {counter = 0}, pad = 0}, flags = 1,
- nsyms = 57, ndeps = 0, syms = 0xa9023170, deps = 0x0, refs = 0x0,
- init = 0xa90221f0 <init_hostfs>, cleanup = 0xa902222c <exit_hostfs>,
- ex_table_start = 0x0, ex_table_end = 0x0, persist_start = 0x0,
- persist_end = 0x0, can_unload = 0, runsize = 0, kallsyms_start = 0x0,
- kallsyms_end = 0x0,
- archdata_start = 0x1b855 <Address 0x1b855 out of bounds>,
- archdata_end = 0xe5890000 <Address 0xe5890000 out of bounds>,
- kernel_data = 0xf689c35d <Address 0xf689c35d out of bounds>}
- >> Finished loading symbols for hostfs ...
-
-
-
-
- That's the easy way. It's highly recommended. The hard way is
- described below in case you're interested in what's going on.
-
-
- Boot the kernel under the debugger and load the module with insmod or
- modprobe. With gdb, do:
-
-
- (UML gdb) p module_list
-
-
-
-
- This is a list of modules that have been loaded into the kernel, with
- the most recently loaded module first. Normally, the module you want
- is at module_list. If it's not, walk down the next links, looking at
- the name fields until find the module you want to debug. Take the
- address of that structure, and add module.size_of_struct (which in
- 2.4.10 kernels is 96 (0x60)) to it. Gdb can make this hard addition
- for you :-):
-
-
-
- (UML gdb)
- printf "%#x\n", (int)module_list module_list->size_of_struct
-
-
-
-
- The offset from the module start occasionally changes (before 2.4.0,
- it was module.size_of_struct + 4), so it's a good idea to check the
- init and cleanup addresses once in a while, as describe below. Now
- do:
-
-
- (UML gdb)
- add-symbol-file /path/to/module/on/host that_address
-
-
-
-
- Tell gdb you really want to do it, and you're in business.
-
-
- If there's any doubt that you got the offset right, like breakpoints
- appear not to work, or they're appearing in the wrong place, you can
- check it by looking at the module structure. The init and cleanup
- fields should look like:
-
-
- init = 0x588066b0 <init_hostfs>, cleanup = 0x588066c0 <exit_hostfs>
-
-
-
-
- with no offsets on the symbol names. If the names are right, but they
- are offset, then the offset tells you how much you need to add to the
- address you gave to add-symbol-file.
-
-
- When you want to load in a new version of the module, you need to get
- gdb to forget about the old one. The only way I've found to do that
- is to tell gdb to forget about all symbols that it knows about:
-
-
- (UML gdb) symbol-file
-
-
-
-
- Then reload the symbols from the kernel binary:
-
-
- (UML gdb) symbol-file /path/to/kernel
-
-
-
-
- and repeat the process above. You'll also need to re-enable break-
- points. They were disabled when you dumped all the symbols because
- gdb couldn't figure out where they should go.
-
-
-
- 11.5. Attaching gdb to the kernel
-
- If you don't have the kernel running under gdb, you can attach gdb to
- it later by sending the tracing thread a SIGUSR1. The first line of
- the console output identifies its pid:
- tracing thread pid = 20093
-
-
-
-
- When you send it the signal:
-
-
- host% kill -USR1 20093
-
-
-
-
- you will get an xterm with gdb running in it.
-
-
- If you have the mconsole compiled into UML, then the mconsole client
- can be used to start gdb:
-
-
- (mconsole) (mconsole) config gdb=xterm
-
-
-
-
- will fire up an xterm with gdb running in it.
-
-
-
- 11.6. Using alternate debuggers
-
- UML has support for attaching to an already running debugger rather
- than starting gdb itself. This is present in CVS as of 17 Apr 2001.
- I sent it to Alan for inclusion in the ac tree, and it will be in my
- 2.4.4 release.
-
-
- This is useful when gdb is a subprocess of some UI, such as emacs or
- ddd. It can also be used to run debuggers other than gdb on UML.
- Below is an example of using strace as an alternate debugger.
-
-
- To do this, you need to get the pid of the debugger and pass it in
- with the
-
-
- If you are using gdb under some UI, then tell it to 'att 1', and
- you'll find yourself attached to UML.
-
-
- If you are using something other than gdb as your debugger, then
- you'll need to get it to do the equivalent of 'att 1' if it doesn't do
- it automatically.
-
-
- An example of an alternate debugger is strace. You can strace the
- actual kernel as follows:
-
- o Run the following in a shell
-
-
- host%
- sh -c 'echo pid=$$; echo -n hit return; read x; exec strace -p 1 -o strace.out'
-
-
-
- o Run UML with 'debug' and 'gdb-pid=<pid>' with the pid printed out
- by the previous command
-
- o Hit return in the shell, and UML will start running, and strace
- output will start accumulating in the output file.
-
- Note that this is different from running
-
-
- host% strace ./linux
-
-
-
-
- That will strace only the main UML thread, the tracing thread, which
- doesn't do any of the actual kernel work. It just oversees the vir-
- tual machine. In contrast, using strace as described above will show
- you the low-level activity of the virtual machine.
-
-
-
-
-
- 12. Kernel debugging examples
-
- 12.1. The case of the hung fsck
-
- When booting up the kernel, fsck failed, and dropped me into a shell
- to fix things up. I ran fsck -y, which hung:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Setting hostname uml [ OK ]
- Checking root filesystem
- /dev/fhd0 was not cleanly unmounted, check forced.
- Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780.
-
- /dev/fhd0: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.
- (i.e., without -a or -p options)
- [ FAILED ]
-
- *** An error occurred during the file system check.
- *** Dropping you to a shell; the system will reboot
- *** when you leave the shell.
- Give root password for maintenance
- (or type Control-D for normal startup):
-
- [root@uml /root]# fsck -y /dev/fhd0
- fsck -y /dev/fhd0
- Parallelizing fsck version 1.14 (9-Jan-1999)
- e2fsck 1.14, 9-Jan-1999 for EXT2 FS 0.5b, 95/08/09
- /dev/fhd0 contains a file system with errors, check forced.
- Pass 1: Checking inodes, blocks, and sizes
- Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780. Ignore error? yes
-
- Inode 19780, i_blocks is 1548, should be 540. Fix? yes
-
- Pass 2: Checking directory structure
- Error reading block 49405 (Attempt to read block from filesystem resulted in short read). Ignore error? yes
-
- Directory inode 11858, block 0, offset 0: directory corrupted
- Salvage? yes
-
- Missing '.' in directory inode 11858.
- Fix? yes
-
- Missing '..' in directory inode 11858.
- Fix? yes
-
-
-
-
-
- The standard drill in this sort of situation is to fire up gdb on the
- signal thread, which, in this case, was pid 1935. In another window,
- I run gdb and attach pid 1935.
-
-
-
-
- ~/linux/2.3.26/um 1016: gdb linux
- GNU gdb 4.17.0.11 with Linux support
- Copyright 1998 Free Software Foundation, Inc.
- GDB is free software, covered by the GNU General Public License, and you are
- welcome to change it and/or distribute copies of it under certain conditions.
- Type "show copying" to see the conditions.
- There is absolutely no warranty for GDB. Type "show warranty" for details.
- This GDB was configured as "i386-redhat-linux"...
-
- (gdb) att 1935
- Attaching to program `/home/dike/linux/2.3.26/um/linux', Pid 1935
- 0x100756d9 in __wait4 ()
-
-
-
-
-
-
- Let's see what's currently running:
-
-
-
- (gdb) p current_task.pid
- $1 = 0
-
-
-
-
-
- It's the idle thread, which means that fsck went to sleep for some
- reason and never woke up.
-
-
- Let's guess that the last process in the process list is fsck:
-
-
-
- (gdb) p current_task.prev_task.comm
- $13 = "fsck.ext2\000\000\000\000\000\000"
-
-
-
-
-
- It is, so let's see what it thinks it's up to:
-
-
-
- (gdb) p current_task.prev_task.thread
- $14 = {extern_pid = 1980, tracing = 0, want_tracing = 0, forking = 0,
- kernel_stack_page = 0, signal_stack = 1342627840, syscall = {id = 4, args = {
- 3, 134973440, 1024, 0, 1024}, have_result = 0, result = 50590720},
- request = {op = 2, u = {exec = {ip = 1350467584, sp = 2952789424}, fork = {
- regs = {1350467584, 2952789424, 0 <repeats 15 times>}, sigstack = 0,
- pid = 0}, switch_to = 0x507e8000, thread = {proc = 0x507e8000,
- arg = 0xaffffdb0, flags = 0, new_pid = 0}, input_request = {
- op = 1350467584, fd = -1342177872, proc = 0, pid = 0}}}}
-
-
-
-
-
- The interesting things here are the fact that its .thread.syscall.id
- is __NR_write (see the big switch in arch/um/kernel/syscall_kern.c or
- the defines in include/asm-um/arch/unistd.h), and that it never
- returned. Also, its .request.op is OP_SWITCH (see
- arch/um/include/user_util.h). These mean that it went into a write,
- and, for some reason, called schedule().
-
-
- The fact that it never returned from write means that its stack should
- be fairly interesting. Its pid is 1980 (.thread.extern_pid). That
- process is being ptraced by the signal thread, so it must be detached
- before gdb can attach it:
-
-
-
-
-
-
-
-
-
-
- (gdb) call detach(1980)
-
- Program received signal SIGSEGV, Segmentation fault.
- <function called from gdb>
- The program being debugged stopped while in a function called from GDB.
- When the function (detach) is done executing, GDB will silently
- stop (instead of continuing to evaluate the expression containing
- the function call).
- (gdb) call detach(1980)
- $15 = 0
-
-
-
-
-
- The first detach segfaults for some reason, and the second one
- succeeds.
-
-
- Now I detach from the signal thread, attach to the fsck thread, and
- look at its stack:
-
-
- (gdb) det
- Detaching from program: /home/dike/linux/2.3.26/um/linux Pid 1935
- (gdb) att 1980
- Attaching to program `/home/dike/linux/2.3.26/um/linux', Pid 1980
- 0x10070451 in __kill ()
- (gdb) bt
- #0 0x10070451 in __kill ()
- #1 0x10068ccd in usr1_pid (pid=1980) at process.c:30
- #2 0x1006a03f in _switch_to (prev=0x50072000, next=0x507e8000)
- at process_kern.c:156
- #3 0x1006a052 in switch_to (prev=0x50072000, next=0x507e8000, last=0x50072000)
- at process_kern.c:161
- #4 0x10001d12 in schedule () at core.c:777
- #5 0x1006a744 in __down (sem=0x507d241c) at semaphore.c:71
- #6 0x1006aa10 in __down_failed () at semaphore.c:157
- #7 0x1006c5d8 in segv_handler (sc=0x5006e940) at trap_user.c:174
- #8 0x1006c5ec in kern_segv_handler (sig=11) at trap_user.c:182
- #9 <signal handler called>
- #10 0x10155404 in errno ()
- #11 0x1006c0aa in segv (address=1342179328, is_write=2) at trap_kern.c:50
- #12 0x1006c5d8 in segv_handler (sc=0x5006eaf8) at trap_user.c:174
- #13 0x1006c5ec in kern_segv_handler (sig=11) at trap_user.c:182
- #14 <signal handler called>
- #15 0xc0fd in ?? ()
- #16 0x10016647 in sys_write (fd=3,
- buf=0x80b8800 <Address 0x80b8800 out of bounds>, count=1024)
- at read_write.c:159
- #17 0x1006d5b3 in execute_syscall (syscall=4, args=0x5006ef08)
- at syscall_kern.c:254
- #18 0x1006af87 in really_do_syscall (sig=12) at syscall_user.c:35
- #19 <signal handler called>
- #20 0x400dc8b0 in ?? ()
-
-
-
-
-
- The interesting things here are :
-
- o There are two segfaults on this stack (frames 9 and 14)
-
- o The first faulting address (frame 11) is 0x50000800
-
- (gdb) p (void *)1342179328
- $16 = (void *) 0x50000800
-
-
-
-
-
- The initial faulting address is interesting because it is on the idle
- thread's stack. I had been seeing the idle thread segfault for no
- apparent reason, and the cause looked like stack corruption. In hopes
- of catching the culprit in the act, I had turned off all protections
- to that stack while the idle thread wasn't running. This apparently
- tripped that trap.
-
-
- However, the more immediate problem is that second segfault and I'm
- going to concentrate on that. First, I want to see where the fault
- happened, so I have to go look at the sigcontent struct in frame 8:
-
-
-
- (gdb) up
- #1 0x10068ccd in usr1_pid (pid=1980) at process.c:30
- 30 kill(pid, SIGUSR1);
- (gdb)
- #2 0x1006a03f in _switch_to (prev=0x50072000, next=0x507e8000)
- at process_kern.c:156
- 156 usr1_pid(getpid());
- (gdb)
- #3 0x1006a052 in switch_to (prev=0x50072000, next=0x507e8000, last=0x50072000)
- at process_kern.c:161
- 161 _switch_to(prev, next);
- (gdb)
- #4 0x10001d12 in schedule () at core.c:777
- 777 switch_to(prev, next, prev);
- (gdb)
- #5 0x1006a744 in __down (sem=0x507d241c) at semaphore.c:71
- 71 schedule();
- (gdb)
- #6 0x1006aa10 in __down_failed () at semaphore.c:157
- 157 }
- (gdb)
- #7 0x1006c5d8 in segv_handler (sc=0x5006e940) at trap_user.c:174
- 174 segv(sc->cr2, sc->err & 2);
- (gdb)
- #8 0x1006c5ec in kern_segv_handler (sig=11) at trap_user.c:182
- 182 segv_handler(sc);
- (gdb) p *sc
- Cannot access memory at address 0x0.
-
-
-
-
- That's not very useful, so I'll try a more manual method:
-
-
- (gdb) p *((struct sigcontext *) (&sig + 1))
- $19 = {gs = 0, __gsh = 0, fs = 0, __fsh = 0, es = 43, __esh = 0, ds = 43,
- __dsh = 0, edi = 1342179328, esi = 1350378548, ebp = 1342630440,
- esp = 1342630420, ebx = 1348150624, edx = 1280, ecx = 0, eax = 0,
- trapno = 14, err = 4, eip = 268480945, cs = 35, __csh = 0, eflags = 66118,
- esp_at_signal = 1342630420, ss = 43, __ssh = 0, fpstate = 0x0, oldmask = 0,
- cr2 = 1280}
-
-
-
- The ip is in handle_mm_fault:
-
-
- (gdb) p (void *)268480945
- $20 = (void *) 0x1000b1b1
- (gdb) i sym $20
- handle_mm_fault + 57 in section .text
-
-
-
-
-
- Specifically, it's in pte_alloc:
-
-
- (gdb) i line *$20
- Line 124 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b1b1 <handle_mm_fault+57>
- and ends at 0x1000b1b7 <handle_mm_fault+63>.
-
-
-
-
-
- To find where in handle_mm_fault this is, I'll jump forward in the
- code until I see an address in that procedure:
-
-
-
- (gdb) i line *0x1000b1c0
- Line 126 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b1b7 <handle_mm_fault+63>
- and ends at 0x1000b1c3 <handle_mm_fault+75>.
- (gdb) i line *0x1000b1d0
- Line 131 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b1d0 <handle_mm_fault+88>
- and ends at 0x1000b1da <handle_mm_fault+98>.
- (gdb) i line *0x1000b1e0
- Line 61 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b1da <handle_mm_fault+98>
- and ends at 0x1000b1e1 <handle_mm_fault+105>.
- (gdb) i line *0x1000b1f0
- Line 134 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b1f0 <handle_mm_fault+120>
- and ends at 0x1000b200 <handle_mm_fault+136>.
- (gdb) i line *0x1000b200
- Line 135 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b200 <handle_mm_fault+136>
- and ends at 0x1000b208 <handle_mm_fault+144>.
- (gdb) i line *0x1000b210
- Line 139 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b210 <handle_mm_fault+152>
- and ends at 0x1000b219 <handle_mm_fault+161>.
- (gdb) i line *0x1000b220
- Line 1168 of "memory.c" starts at address 0x1000b21e <handle_mm_fault+166>
- and ends at 0x1000b222 <handle_mm_fault+170>.
-
-
-
-
-
- Something is apparently wrong with the page tables or vma_structs, so
- lets go back to frame 11 and have a look at them:
-
-
-
- #11 0x1006c0aa in segv (address=1342179328, is_write=2) at trap_kern.c:50
- 50 handle_mm_fault(current, vma, address, is_write);
- (gdb) call pgd_offset_proc(vma->vm_mm, address)
- $22 = (pgd_t *) 0x80a548c
-
-
-
-
-
- That's pretty bogus. Page tables aren't supposed to be in process
- text or data areas. Let's see what's in the vma:
-
-
- (gdb) p *vma
- $23 = {vm_mm = 0x507d2434, vm_start = 0, vm_end = 134512640,
- vm_next = 0x80a4f8c, vm_page_prot = {pgprot = 0}, vm_flags = 31200,
- vm_avl_height = 2058, vm_avl_left = 0x80a8c94, vm_avl_right = 0x80d1000,
- vm_next_share = 0xaffffdb0, vm_pprev_share = 0xaffffe63,
- vm_ops = 0xaffffe7a, vm_pgoff = 2952789626, vm_file = 0xafffffec,
- vm_private_data = 0x62}
- (gdb) p *vma.vm_mm
- $24 = {mmap = 0x507d2434, mmap_avl = 0x0, mmap_cache = 0x8048000,
- pgd = 0x80a4f8c, mm_users = {counter = 0}, mm_count = {counter = 134904288},
- map_count = 134909076, mmap_sem = {count = {counter = 135073792},
- sleepers = -1342177872, wait = {lock = <optimized out or zero length>,
- task_list = {next = 0xaffffe63, prev = 0xaffffe7a},
- __magic = -1342177670, __creator = -1342177300}, __magic = 98},
- page_table_lock = {}, context = 138, start_code = 0, end_code = 0,
- start_data = 0, end_data = 0, start_brk = 0, brk = 0, start_stack = 0,
- arg_start = 0, arg_end = 0, env_start = 0, env_end = 0, rss = 1350381536,
- total_vm = 0, locked_vm = 0, def_flags = 0, cpu_vm_mask = 0, swap_cnt = 0,
- swap_address = 0, segments = 0x0}
-
-
-
-
-
- This also pretty bogus. With all of the 0x80xxxxx and 0xaffffxxx
- addresses, this is looking like a stack was plonked down on top of
- these structures. Maybe it's a stack overflow from the next page:
-
-
-
- (gdb) p vma
- $25 = (struct vm_area_struct *) 0x507d2434
-
-
-
-
-
- That's towards the lower quarter of the page, so that would have to
- have been pretty heavy stack overflow:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- (gdb) x/100x $25
- 0x507d2434: 0x507d2434 0x00000000 0x08048000 0x080a4f8c
- 0x507d2444: 0x00000000 0x080a79e0 0x080a8c94 0x080d1000
- 0x507d2454: 0xaffffdb0 0xaffffe63 0xaffffe7a 0xaffffe7a
- 0x507d2464: 0xafffffec 0x00000062 0x0000008a 0x00000000
- 0x507d2474: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2484: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2494: 0x00000000 0x00000000 0x507d2fe0 0x00000000
- 0x507d24a4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d24b4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d24c4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d24d4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d24e4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d24f4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2504: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2514: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2524: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2534: 0x00000000 0x00000000 0x507d25dc 0x00000000
- 0x507d2544: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2554: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2564: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2574: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2584: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2594: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d25a4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d25b4: 0x00000000 0x00000000 0x00000000 0x00000000
-
-
-
-
-
- It's not stack overflow. The only "stack-like" piece of this data is
- the vma_struct itself.
-
-
- At this point, I don't see any avenues to pursue, so I just have to
- admit that I have no idea what's going on. What I will do, though, is
- stick a trap on the segfault handler which will stop if it sees any
- writes to the idle thread's stack. That was the thing that happened
- first, and it may be that if I can catch it immediately, what's going
- on will be somewhat clearer.
-
-
- 12.2. Episode 2: The case of the hung fsck
-
- After setting a trap in the SEGV handler for accesses to the signal
- thread's stack, I reran the kernel.
-
-
- fsck hung again, this time by hitting the trap:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Setting hostname uml [ OK ]
- Checking root filesystem
- /dev/fhd0 contains a file system with errors, check forced.
- Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780.
-
- /dev/fhd0: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.
- (i.e., without -a or -p options)
- [ FAILED ]
-
- *** An error occurred during the file system check.
- *** Dropping you to a shell; the system will reboot
- *** when you leave the shell.
- Give root password for maintenance
- (or type Control-D for normal startup):
-
- [root@uml /root]# fsck -y /dev/fhd0
- fsck -y /dev/fhd0
- Parallelizing fsck version 1.14 (9-Jan-1999)
- e2fsck 1.14, 9-Jan-1999 for EXT2 FS 0.5b, 95/08/09
- /dev/fhd0 contains a file system with errors, check forced.
- Pass 1: Checking inodes, blocks, and sizes
- Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780. Ignore error? yes
-
- Pass 2: Checking directory structure
- Error reading block 49405 (Attempt to read block from filesystem resulted in short read). Ignore error? yes
-
- Directory inode 11858, block 0, offset 0: directory corrupted
- Salvage? yes
-
- Missing '.' in directory inode 11858.
- Fix? yes
-
- Missing '..' in directory inode 11858.
- Fix? yes
-
- Untested (4127) [100fe44c]: trap_kern.c line 31
-
-
-
-
-
- I need to get the signal thread to detach from pid 4127 so that I can
- attach to it with gdb. This is done by sending it a SIGUSR1, which is
- caught by the signal thread, which detaches the process:
-
-
- kill -USR1 4127
-
-
-
-
-
- Now I can run gdb on it:
-
-
-
-
-
-
-
-
-
-
-
-
-
- ~/linux/2.3.26/um 1034: gdb linux
- GNU gdb 4.17.0.11 with Linux support
- Copyright 1998 Free Software Foundation, Inc.
- GDB is free software, covered by the GNU General Public License, and you are
- welcome to change it and/or distribute copies of it under certain conditions.
- Type "show copying" to see the conditions.
- There is absolutely no warranty for GDB. Type "show warranty" for details.
- This GDB was configured as "i386-redhat-linux"...
- (gdb) att 4127
- Attaching to program `/home/dike/linux/2.3.26/um/linux', Pid 4127
- 0x10075891 in __libc_nanosleep ()
-
-
-
-
-
- The backtrace shows that it was in a write and that the fault address
- (address in frame 3) is 0x50000800, which is right in the middle of
- the signal thread's stack page:
-
-
- (gdb) bt
- #0 0x10075891 in __libc_nanosleep ()
- #1 0x1007584d in __sleep (seconds=1000000)
- at ../sysdeps/unix/sysv/linux/sleep.c:78
- #2 0x1006ce9a in stop () at user_util.c:191
- #3 0x1006bf88 in segv (address=1342179328, is_write=2) at trap_kern.c:31
- #4 0x1006c628 in segv_handler (sc=0x5006eaf8) at trap_user.c:174
- #5 0x1006c63c in kern_segv_handler (sig=11) at trap_user.c:182
- #6 <signal handler called>
- #7 0xc0fd in ?? ()
- #8 0x10016647 in sys_write (fd=3, buf=0x80b8800 "R.", count=1024)
- at read_write.c:159
- #9 0x1006d603 in execute_syscall (syscall=4, args=0x5006ef08)
- at syscall_kern.c:254
- #10 0x1006af87 in really_do_syscall (sig=12) at syscall_user.c:35
- #11 <signal handler called>
- #12 0x400dc8b0 in ?? ()
- #13 <signal handler called>
- #14 0x400dc8b0 in ?? ()
- #15 0x80545fd in ?? ()
- #16 0x804daae in ?? ()
- #17 0x8054334 in ?? ()
- #18 0x804d23e in ?? ()
- #19 0x8049632 in ?? ()
- #20 0x80491d2 in ?? ()
- #21 0x80596b5 in ?? ()
- (gdb) p (void *)1342179328
- $3 = (void *) 0x50000800
-
-
-
-
-
- Going up the stack to the segv_handler frame and looking at where in
- the code the access happened shows that it happened near line 110 of
- block_dev.c:
-
-
-
-
-
-
-
-
-
- (gdb) up
- #1 0x1007584d in __sleep (seconds=1000000)
- at ../sysdeps/unix/sysv/linux/sleep.c:78
- ../sysdeps/unix/sysv/linux/sleep.c:78: No such file or directory.
- (gdb)
- #2 0x1006ce9a in stop () at user_util.c:191
- 191 while(1) sleep(1000000);
- (gdb)
- #3 0x1006bf88 in segv (address=1342179328, is_write=2) at trap_kern.c:31
- 31 KERN_UNTESTED();
- (gdb)
- #4 0x1006c628 in segv_handler (sc=0x5006eaf8) at trap_user.c:174
- 174 segv(sc->cr2, sc->err & 2);
- (gdb) p *sc
- $1 = {gs = 0, __gsh = 0, fs = 0, __fsh = 0, es = 43, __esh = 0, ds = 43,
- __dsh = 0, edi = 1342179328, esi = 134973440, ebp = 1342631484,
- esp = 1342630864, ebx = 256, edx = 0, ecx = 256, eax = 1024, trapno = 14,
- err = 6, eip = 268550834, cs = 35, __csh = 0, eflags = 66070,
- esp_at_signal = 1342630864, ss = 43, __ssh = 0, fpstate = 0x0, oldmask = 0,
- cr2 = 1342179328}
- (gdb) p (void *)268550834
- $2 = (void *) 0x1001c2b2
- (gdb) i sym $2
- block_write + 1090 in section .text
- (gdb) i line *$2
- Line 209 of "/home/dike/linux/2.3.26/um/include/asm/arch/string.h"
- starts at address 0x1001c2a1 <block_write+1073>
- and ends at 0x1001c2bf <block_write+1103>.
- (gdb) i line *0x1001c2c0
- Line 110 of "block_dev.c" starts at address 0x1001c2bf <block_write+1103>
- and ends at 0x1001c2e3 <block_write+1139>.
-
-
-
-
-
- Looking at the source shows that the fault happened during a call to
- copy_from_user to copy the data into the kernel:
-
-
- 107 count -= chars;
- 108 copy_from_user(p,buf,chars);
- 109 p += chars;
- 110 buf += chars;
-
-
-
-
-
- p is the pointer which must contain 0x50000800, since buf contains
- 0x80b8800 (frame 8 above). It is defined as:
-
-
- p = offset + bh->b_data;
-
-
-
-
-
- I need to figure out what bh is, and it just so happens that bh is
- passed as an argument to mark_buffer_uptodate and mark_buffer_dirty a
- few lines later, so I do a little disassembly:
-
-
-
-
- (gdb) disas 0x1001c2bf 0x1001c2e0
- Dump of assembler code from 0x1001c2bf to 0x1001c2d0:
- 0x1001c2bf <block_write+1103>: addl %eax,0xc(%ebp)
- 0x1001c2c2 <block_write+1106>: movl 0xfffffdd4(%ebp),%edx
- 0x1001c2c8 <block_write+1112>: btsl $0x0,0x18(%edx)
- 0x1001c2cd <block_write+1117>: btsl $0x1,0x18(%edx)
- 0x1001c2d2 <block_write+1122>: sbbl %ecx,%ecx
- 0x1001c2d4 <block_write+1124>: testl %ecx,%ecx
- 0x1001c2d6 <block_write+1126>: jne 0x1001c2e3 <block_write+1139>
- 0x1001c2d8 <block_write+1128>: pushl $0x0
- 0x1001c2da <block_write+1130>: pushl %edx
- 0x1001c2db <block_write+1131>: call 0x1001819c <__mark_buffer_dirty>
- End of assembler dump.
-
-
-
-
-
- At that point, bh is in %edx (address 0x1001c2da), which is calculated
- at 0x1001c2c2 as %ebp + 0xfffffdd4, so I figure exactly what that is,
- taking %ebp from the sigcontext_struct above:
-
-
- (gdb) p (void *)1342631484
- $5 = (void *) 0x5006ee3c
- (gdb) p 0x5006ee3c+0xfffffdd4
- $6 = 1342630928
- (gdb) p (void *)$6
- $7 = (void *) 0x5006ec10
- (gdb) p *((void **)$7)
- $8 = (void *) 0x50100200
-
-
-
-
-
- Now, I look at the structure to see what's in it, and particularly,
- what its b_data field contains:
-
-
- (gdb) p *((struct buffer_head *)0x50100200)
- $13 = {b_next = 0x50289380, b_blocknr = 49405, b_size = 1024, b_list = 0,
- b_dev = 15872, b_count = {counter = 1}, b_rdev = 15872, b_state = 24,
- b_flushtime = 0, b_next_free = 0x501001a0, b_prev_free = 0x50100260,
- b_this_page = 0x501001a0, b_reqnext = 0x0, b_pprev = 0x507fcf58,
- b_data = 0x50000800 "", b_page = 0x50004000,
- b_end_io = 0x10017f60 <end_buffer_io_sync>, b_dev_id = 0x0,
- b_rsector = 98810, b_wait = {lock = <optimized out or zero length>,
- task_list = {next = 0x50100248, prev = 0x50100248}, __magic = 1343226448,
- __creator = 0}, b_kiobuf = 0x0}
-
-
-
-
-
- The b_data field is indeed 0x50000800, so the question becomes how
- that happened. The rest of the structure looks fine, so this probably
- is not a case of data corruption. It happened on purpose somehow.
-
-
- The b_page field is a pointer to the page_struct representing the
- 0x50000000 page. Looking at it shows the kernel's idea of the state
- of that page:
-
-
-
- (gdb) p *$13.b_page
- $17 = {list = {next = 0x50004a5c, prev = 0x100c5174}, mapping = 0x0,
- index = 0, next_hash = 0x0, count = {counter = 1}, flags = 132, lru = {
- next = 0x50008460, prev = 0x50019350}, wait = {
- lock = <optimized out or zero length>, task_list = {next = 0x50004024,
- prev = 0x50004024}, __magic = 1342193708, __creator = 0},
- pprev_hash = 0x0, buffers = 0x501002c0, virtual = 1342177280,
- zone = 0x100c5160}
-
-
-
-
-
- Some sanity-checking: the virtual field shows the "virtual" address of
- this page, which in this kernel is the same as its "physical" address,
- and the page_struct itself should be mem_map[0], since it represents
- the first page of memory:
-
-
-
- (gdb) p (void *)1342177280
- $18 = (void *) 0x50000000
- (gdb) p mem_map
- $19 = (mem_map_t *) 0x50004000
-
-
-
-
-
- These check out fine.
-
-
- Now to check out the page_struct itself. In particular, the flags
- field shows whether the page is considered free or not:
-
-
- (gdb) p (void *)132
- $21 = (void *) 0x84
-
-
-
-
-
- The "reserved" bit is the high bit, which is definitely not set, so
- the kernel considers the signal stack page to be free and available to
- be used.
-
-
- At this point, I jump to conclusions and start looking at my early
- boot code, because that's where that page is supposed to be reserved.
-
-
- In my setup_arch procedure, I have the following code which looks just
- fine:
-
-
-
- bootmap_size = init_bootmem(start_pfn, end_pfn - start_pfn);
- free_bootmem(__pa(low_physmem) + bootmap_size, high_physmem - low_physmem);
-
-
-
-
-
- Two stack pages have already been allocated, and low_physmem points to
- the third page, which is the beginning of free memory.
- The init_bootmem call declares the entire memory to the boot memory
- manager, which marks it all reserved. The free_bootmem call frees up
- all of it, except for the first two pages. This looks correct to me.
-
-
- So, I decide to see init_bootmem run and make sure that it is marking
- those first two pages as reserved. I never get that far.
-
-
- Stepping into init_bootmem, and looking at bootmem_map before looking
- at what it contains shows the following:
-
-
-
- (gdb) p bootmem_map
- $3 = (void *) 0x50000000
-
-
-
-
-
- Aha! The light dawns. That first page is doing double duty as a
- stack and as the boot memory map. The last thing that the boot memory
- manager does is to free the pages used by its memory map, so this page
- is getting freed even its marked as reserved.
-
-
- The fix was to initialize the boot memory manager before allocating
- those two stack pages, and then allocate them through the boot memory
- manager. After doing this, and fixing a couple of subsequent buglets,
- the stack corruption problem disappeared.
-
-
-
-
-
- 13. What to do when UML doesn't work
-
-
-
-
- 13.1. Strange compilation errors when you build from source
-
- As of test11, it is necessary to have "ARCH=um" in the environment or
- on the make command line for all steps in building UML, including
- clean, distclean, or mrproper, config, menuconfig, or xconfig, dep,
- and linux. If you forget for any of them, the i386 build seems to
- contaminate the UML build. If this happens, start from scratch with
-
-
- host%
- make mrproper ARCH=um
-
-
-
-
- and repeat the build process with ARCH=um on all the steps.
-
-
- See ``Compiling the kernel and modules'' for more details.
-
-
- Another cause of strange compilation errors is building UML in
- /usr/src/linux. If you do this, the first thing you need to do is
- clean up the mess you made. The /usr/src/linux/asm link will now
- point to /usr/src/linux/asm-um. Make it point back to
- /usr/src/linux/asm-i386. Then, move your UML pool someplace else and
- build it there. Also see below, where a more specific set of symptoms
- is described.
-
-
-
- 13.3. A variety of panics and hangs with /tmp on a reiserfs filesys-
- tem
-
- I saw this on reiserfs 3.5.21 and it seems to be fixed in 3.5.27.
- Panics preceded by
-
-
- Detaching pid nnnn
-
-
-
- are diagnostic of this problem. This is a reiserfs bug which causes a
- thread to occasionally read stale data from a mmapped page shared with
- another thread. The fix is to upgrade the filesystem or to have /tmp
- be an ext2 filesystem.
-
-
-
- 13.4. The compile fails with errors about conflicting types for
- 'open', 'dup', and 'waitpid'
-
- This happens when you build in /usr/src/linux. The UML build makes
- the include/asm link point to include/asm-um. /usr/include/asm points
- to /usr/src/linux/include/asm, so when that link gets moved, files
- which need to include the asm-i386 versions of headers get the
- incompatible asm-um versions. The fix is to move the include/asm link
- back to include/asm-i386 and to do UML builds someplace else.
-
-
-
- 13.5. UML doesn't work when /tmp is an NFS filesystem
-
- This seems to be a similar situation with the ReiserFS problem above.
- Some versions of NFS seems not to handle mmap correctly, which UML
- depends on. The workaround is have /tmp be a non-NFS directory.
-
-
- 13.6. UML hangs on boot when compiled with gprof support
-
- If you build UML with gprof support and, early in the boot, it does
- this
-
-
- kernel BUG at page_alloc.c:100!
-
-
-
-
- you have a buggy gcc. You can work around the problem by removing
- UM_FASTCALL from CFLAGS in arch/um/Makefile-i386. This will open up
- another bug, but that one is fairly hard to reproduce.
-
-
-
- 13.7. syslogd dies with a SIGTERM on startup
-
- The exact boot error depends on the distribution that you're booting,
- but Debian produces this:
-
-
- /etc/rc2.d/S10sysklogd: line 49: 93 Terminated
- start-stop-daemon --start --quiet --exec /sbin/syslogd -- $SYSLOGD
-
-
-
-
- This is a syslogd bug. There's a race between a parent process
- installing a signal handler and its child sending the signal. See
- this uml-devel post <http://www.geocrawler.com/lists/3/Source-
- Forge/709/0/6612801> for the details.
-
-
-
- 13.8. TUN/TAP networking doesn't work on a 2.4 host
-
- There are a couple of problems which were
- <http://www.geocrawler.com/lists/3/SourceForge/597/0/> name="pointed
- out"> by Tim Robinson <timro at trkr dot net>
-
- o It doesn't work on hosts running 2.4.7 (or thereabouts) or earlier.
- The fix is to upgrade to something more recent and then read the
- next item.
-
- o If you see
-
-
- File descriptor in bad state
-
-
-
- when you bring up the device inside UML, you have a header mismatch
- between the original kernel and the upgraded one. Make /usr/src/linux
- point at the new headers. This will only be a problem if you build
- uml_net yourself.
-
-
-
- 13.9. You can network to the host but not to other machines on the
- net
-
- If you can connect to the host, and the host can connect to UML, but
- you cannot connect to any other machines, then you may need to enable
- IP Masquerading on the host. Usually this is only experienced when
- using private IP addresses (192.168.x.x or 10.x.x.x) for host/UML
- networking, rather than the public address space that your host is
- connected to. UML does not enable IP Masquerading, so you will need
- to create a static rule to enable it:
-
-
- host%
- iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
-
-
-
-
- Replace eth0 with the interface that you use to talk to the rest of
- the world.
-
-
- Documentation on IP Masquerading, and SNAT, can be found at
- www.netfilter.org <http://www.netfilter.org> .
-
-
- If you can reach the local net, but not the outside Internet, then
- that is usually a routing problem. The UML needs a default route:
-
-
- UML#
- route add default gw gateway IP
-
-
-
-
- The gateway IP can be any machine on the local net that knows how to
- reach the outside world. Usually, this is the host or the local net-
- work's gateway.
-
-
- Occasionally, we hear from someone who can reach some machines, but
- not others on the same net, or who can reach some ports on other
- machines, but not others. These are usually caused by strange
- firewalling somewhere between the UML and the other box. You track
- this down by running tcpdump on every interface the packets travel
- over and see where they disappear. When you find a machine that takes
- the packets in, but does not send them onward, that's the culprit.
-
-
-
- 13.10. I have no root and I want to scream
-
- Thanks to Birgit Wahlich for telling me about this strange one. It
- turns out that there's a limit of six environment variables on the
- kernel command line. When that limit is reached or exceeded, argument
- processing stops, which means that the 'root=' argument that UML
- usually adds is not seen. So, the filesystem has no idea what the
- root device is, so it panics.
-
-
- The fix is to put less stuff on the command line. Glomming all your
- setup variables into one is probably the best way to go.
-
-
-
- 13.11. UML build conflict between ptrace.h and ucontext.h
-
- On some older systems, /usr/include/asm/ptrace.h and
- /usr/include/sys/ucontext.h define the same names. So, when they're
- included together, the defines from one completely mess up the parsing
- of the other, producing errors like:
- /usr/include/sys/ucontext.h:47: parse error before
- `10'
-
-
-
-
- plus a pile of warnings.
-
-
- This is a libc botch, which has since been fixed, and I don't see any
- way around it besides upgrading.
-
-
-
- 13.12. The UML BogoMips is exactly half the host's BogoMips
-
- On i386 kernels, there are two ways of running the loop that is used
- to calculate the BogoMips rating, using the TSC if it's there or using
- a one-instruction loop. The TSC produces twice the BogoMips as the
- loop. UML uses the loop, since it has nothing resembling a TSC, and
- will get almost exactly the same BogoMips as a host using the loop.
- However, on a host with a TSC, its BogoMips will be double the loop
- BogoMips, and therefore double the UML BogoMips.
-
-
-
- 13.13. When you run UML, it immediately segfaults
-
- If the host is configured with the 2G/2G address space split, that's
- why. See ``UML on 2G/2G hosts'' for the details on getting UML to
- run on your host.
-
-
-
- 13.14. xterms appear, then immediately disappear
-
- If you're running an up to date kernel with an old release of
- uml_utilities, the port-helper program will not work properly, so
- xterms will exit straight after they appear. The solution is to
- upgrade to the latest release of uml_utilities. Usually this problem
- occurs when you have installed a packaged release of UML then compiled
- your own development kernel without upgrading the uml_utilities from
- the source distribution.
-
-
-
- 13.15. Any other panic, hang, or strange behavior
-
- If you're seeing truly strange behavior, such as hangs or panics that
- happen in random places, or you try running the debugger to see what's
- happening and it acts strangely, then it could be a problem in the
- host kernel. If you're not running a stock Linus or -ac kernel, then
- try that. An early version of the preemption patch and a 2.4.10 SuSE
- kernel have caused very strange problems in UML.
-
-
- Otherwise, let me know about it. Send a message to one of the UML
- mailing lists - either the developer list - user-mode-linux-devel at
- lists dot sourceforge dot net (subscription info) or the user list -
- user-mode-linux-user at lists dot sourceforge do net (subscription
- info), whichever you prefer. Don't assume that everyone knows about
- it and that a fix is imminent.
-
-
- If you want to be super-helpful, read ``Diagnosing Problems'' and
- follow the instructions contained therein.
- 14. Diagnosing Problems
-
-
- If you get UML to crash, hang, or otherwise misbehave, you should
- report this on one of the project mailing lists, either the developer
- list - user-mode-linux-devel at lists dot sourceforge dot net
- (subscription info) or the user list - user-mode-linux-user at lists
- dot sourceforge dot net (subscription info). When you do, it is
- likely that I will want more information. So, it would be helpful to
- read the stuff below, do whatever is applicable in your case, and
- report the results to the list.
-
-
- For any diagnosis, you're going to need to build a debugging kernel.
- The binaries from this site aren't debuggable. If you haven't done
- this before, read about ``Compiling the kernel and modules'' and
- ``Kernel debugging'' UML first.
-
-
- 14.1. Case 1 : Normal kernel panics
-
- The most common case is for a normal thread to panic. To debug this,
- you will need to run it under the debugger (add 'debug' to the command
- line). An xterm will start up with gdb running inside it. Continue
- it when it stops in start_kernel and make it crash. Now ^C gdb and
-
-
- If the panic was a "Kernel mode fault", then there will be a segv
- frame on the stack and I'm going to want some more information. The
- stack might look something like this:
-
-
- (UML gdb) backtrace
- #0 0x1009bf76 in __sigprocmask (how=1, set=0x5f347940, oset=0x0)
- at ../sysdeps/unix/sysv/linux/sigprocmask.c:49
- #1 0x10091411 in change_sig (signal=10, on=1) at process.c:218
- #2 0x10094785 in timer_handler (sig=26) at time_kern.c:32
- #3 0x1009bf38 in __restore ()
- at ../sysdeps/unix/sysv/linux/i386/sigaction.c:125
- #4 0x1009534c in segv (address=8, ip=268849158, is_write=2, is_user=0)
- at trap_kern.c:66
- #5 0x10095c04 in segv_handler (sig=11) at trap_user.c:285
- #6 0x1009bf38 in __restore ()
-
-
-
-
- I'm going to want to see the symbol and line information for the value
- of ip in the segv frame. In this case, you would do the following:
-
-
- (UML gdb) i sym 268849158
-
-
-
-
- and
-
-
- (UML gdb) i line *268849158
-
-
-
-
- The reason for this is the __restore frame right above the segv_han-
- dler frame is hiding the frame that actually segfaulted. So, I have
- to get that information from the faulting ip.
-
-
- 14.2. Case 2 : Tracing thread panics
-
- The less common and more painful case is when the tracing thread
- panics. In this case, the kernel debugger will be useless because it
- needs a healthy tracing thread in order to work. The first thing to
- do is get a backtrace from the tracing thread. This is done by
- figuring out what its pid is, firing up gdb, and attaching it to that
- pid. You can figure out the tracing thread pid by looking at the
- first line of the console output, which will look like this:
-
-
- tracing thread pid = 15851
-
-
-
-
- or by running ps on the host and finding the line that looks like
- this:
-
-
- jdike 15851 4.5 0.4 132568 1104 pts/0 S 21:34 0:05 ./linux [(tracing thread)]
-
-
-
-
- If the panic was 'segfault in signals', then follow the instructions
- above for collecting information about the location of the seg fault.
-
-
- If the tracing thread flaked out all by itself, then send that
- backtrace in and wait for our crack debugging team to fix the problem.
-
-
- 14.3. Case 3 : Tracing thread panics caused by other threads
-
- However, there are cases where the misbehavior of another thread
- caused the problem. The most common panic of this type is:
-
-
- wait_for_stop failed to wait for <pid> to stop with <signal number>
-
-
-
-
- In this case, you'll need to get a backtrace from the process men-
- tioned in the panic, which is complicated by the fact that the kernel
- debugger is defunct and without some fancy footwork, another gdb can't
- attach to it. So, this is how the fancy footwork goes:
-
- In a shell:
-
-
- host% kill -STOP pid
-
-
-
-
- Run gdb on the tracing thread as described in case 2 and do:
-
-
- (host gdb) call detach(pid)
-
-
- If you get a segfault, do it again. It always works the second time.
-
- Detach from the tracing thread and attach to that other thread:
-
-
- (host gdb) detach
-
-
-
-
-
-
- (host gdb) attach pid
-
-
-
-
- If gdb hangs when attaching to that process, go back to a shell and
- do:
-
-
- host%
- kill -CONT pid
-
-
-
-
- And then get the backtrace:
-
-
- (host gdb) backtrace
-
-
-
-
-
- 14.4. Case 4 : Hangs
-
- Hangs seem to be fairly rare, but they sometimes happen. When a hang
- happens, we need a backtrace from the offending process. Run the
- kernel debugger as described in case 1 and get a backtrace. If the
- current process is not the idle thread, then send in the backtrace.
- You can tell that it's the idle thread if the stack looks like this:
-
-
- #0 0x100b1401 in __libc_nanosleep ()
- #1 0x100a2885 in idle_sleep (secs=10) at time.c:122
- #2 0x100a546f in do_idle () at process_kern.c:445
- #3 0x100a5508 in cpu_idle () at process_kern.c:471
- #4 0x100ec18f in start_kernel () at init/main.c:592
- #5 0x100a3e10 in start_kernel_proc (unused=0x0) at um_arch.c:71
- #6 0x100a383f in signal_tramp (arg=0x100a3dd8) at trap_user.c:50
-
-
-
-
- If this is the case, then some other process is at fault, and went to
- sleep when it shouldn't have. Run ps on the host and figure out which
- process should not have gone to sleep and stayed asleep. Then attach
- to it with gdb and get a backtrace as described in case 3.
-
-
-
-
-
-
- 15. Thanks
-
-
- A number of people have helped this project in various ways, and this
- page gives recognition where recognition is due.
-
-
- If you're listed here and you would prefer a real link on your name,
- or no link at all, instead of the despammed email address pseudo-link,
- let me know.
-
-
- If you're not listed here and you think maybe you should be, please
- let me know that as well. I try to get everyone, but sometimes my
- bookkeeping lapses and I forget about contributions.
-
-
- 15.1. Code and Documentation
-
- Rusty Russell <rusty at linuxcare.com.au> -
-
- o wrote the HOWTO <http://user-mode-
- linux.sourceforge.net/UserModeLinux-HOWTO.html>
-
- o prodded me into making this project official and putting it on
- SourceForge
-
- o came up with the way cool UML logo <http://user-mode-
- linux.sourceforge.net/uml-small.png>
-
- o redid the config process
-
-
- Peter Moulder <reiter at netspace.net.au> - Fixed my config and build
- processes, and added some useful code to the block driver
-
-
- Bill Stearns <wstearns at pobox.com> -
-
- o HOWTO updates
-
- o lots of bug reports
-
- o lots of testing
-
- o dedicated a box (uml.ists.dartmouth.edu) to support UML development
-
- o wrote the mkrootfs script, which allows bootable filesystems of
- RPM-based distributions to be cranked out
-
- o cranked out a large number of filesystems with said script
-
-
- Jim Leu <jleu at mindspring.com> - Wrote the virtual ethernet driver
- and associated usermode tools
-
- Lars Brinkhoff <http://lars.nocrew.org/> - Contributed the ptrace
- proxy from his own project <http://a386.nocrew.org/> to allow easier
- kernel debugging
-
-
- Andrea Arcangeli <andrea at suse.de> - Redid some of the early boot
- code so that it would work on machines with Large File Support
-
-
- Chris Emerson <http://www.chiark.greenend.org.uk/~cemerson/> - Did
- the first UML port to Linux/ppc
-
-
- Harald Welte <laforge at gnumonks.org> - Wrote the multicast
- transport for the network driver
-
-
- Jorgen Cederlof - Added special file support to hostfs
-
-
- Greg Lonnon <glonnon at ridgerun dot com> - Changed the ubd driver
- to allow it to layer a COW file on a shared read-only filesystem and
- wrote the iomem emulation support
-
-
- Henrik Nordstrom <http://hem.passagen.se/hno/> - Provided a variety
- of patches, fixes, and clues
-
-
- Lennert Buytenhek - Contributed various patches, a rewrite of the
- network driver, the first implementation of the mconsole driver, and
- did the bulk of the work needed to get SMP working again.
-
-
- Yon Uriarte - Fixed the TUN/TAP network backend while I slept.
-
-
- Adam Heath - Made a bunch of nice cleanups to the initialization code,
- plus various other small patches.
-
-
- Matt Zimmerman - Matt volunteered to be the UML Debian maintainer and
- is doing a real nice job of it. He also noticed and fixed a number of
- actually and potentially exploitable security holes in uml_net. Plus
- the occasional patch. I like patches.
-
-
- James McMechan - James seems to have taken over maintenance of the ubd
- driver and is doing a nice job of it.
-
-
- Chandan Kudige - wrote the umlgdb script which automates the reloading
- of module symbols.
-
-
- Steve Schmidtke - wrote the UML slirp transport and hostaudio drivers,
- enabling UML processes to access audio devices on the host. He also
- submitted patches for the slip transport and lots of other things.
-
-
- David Coulson <http://davidcoulson.net> -
-
- o Set up the usermodelinux.org <http://usermodelinux.org> site,
- which is a great way of keeping the UML user community on top of
- UML goings-on.
-
- o Site documentation and updates
-
- o Nifty little UML management daemon UMLd
- <http://uml.openconsultancy.com/umld/>
-
- o Lots of testing and bug reports
-
-
-
-
- 15.2. Flushing out bugs
-
-
-
- o Yuri Pudgorodsky
-
- o Gerald Britton
-
- o Ian Wehrman
-
- o Gord Lamb
-
- o Eugene Koontz
-
- o John H. Hartman
-
- o Anders Karlsson
-
- o Daniel Phillips
-
- o John Fremlin
-
- o Rainer Burgstaller
-
- o James Stevenson
-
- o Matt Clay
-
- o Cliff Jefferies
-
- o Geoff Hoff
-
- o Lennert Buytenhek
-
- o Al Viro
-
- o Frank Klingenhoefer
-
- o Livio Baldini Soares
-
- o Jon Burgess
-
- o Petru Paler
-
- o Paul
-
- o Chris Reahard
-
- o Sverker Nilsson
-
- o Gong Su
-
- o johan verrept
-
- o Bjorn Eriksson
-
- o Lorenzo Allegrucci
-
- o Muli Ben-Yehuda
-
- o David Mansfield
-
- o Howard Goff
-
- o Mike Anderson
-
- o John Byrne
-
- o Sapan J. Batia
-
- o Iris Huang
-
- o Jan Hudec
-
- o Voluspa
-
-
-
-
- 15.3. Buglets and clean-ups
-
-
-
- o Dave Zarzycki
-
- o Adam Lazur
-
- o Boria Feigin
-
- o Brian J. Murrell
-
- o JS
-
- o Roman Zippel
-
- o Wil Cooley
-
- o Ayelet Shemesh
-
- o Will Dyson
-
- o Sverker Nilsson
-
- o dvorak
-
- o v.naga srinivas
-
- o Shlomi Fish
-
- o Roger Binns
-
- o johan verrept
-
- o MrChuoi
-
- o Peter Cleve
-
- o Vincent Guffens
-
- o Nathan Scott
-
- o Patrick Caulfield
-
- o jbearce
-
- o Catalin Marinas
-
- o Shane Spencer
-
- o Zou Min
-
-
- o Ryan Boder
-
- o Lorenzo Colitti
-
- o Gwendal Grignou
-
- o Andre' Breiler
-
- o Tsutomu Yasuda
-
-
-
- 15.4. Case Studies
-
-
- o Jon Wright
-
- o William McEwan
-
- o Michael Richardson
-
-
-
- 15.5. Other contributions
-
-
- Bill Carr <Bill.Carr at compaq.com> made the Red Hat mkrootfs script
- work with RH 6.2.
-
- Michael Jennings <mikejen at hevanet.com> sent in some material which
- is now gracing the top of the index page <http://user-mode-
- linux.sourceforge.net/> of this site.
-
- SGI <http://www.sgi.com> (and more specifically Ralf Baechle <ralf at
- uni-koblenz.de> ) gave me an account on oss.sgi.com
- <http://www.oss.sgi.com> . The bandwidth there made it possible to
- produce most of the filesystems available on the project download
- page.
-
- Laurent Bonnaud <Laurent.Bonnaud at inpg.fr> took the old grotty
- Debian filesystem that I've been distributing and updated it to 2.2.
- It is now available by itself here.
-
- Rik van Riel gave me some ftp space on ftp.nl.linux.org so I can make
- releases even when Sourceforge is broken.
-
- Rodrigo de Castro looked at my broken pte code and told me what was
- wrong with it, letting me fix a long-standing (several weeks) and
- serious set of bugs.
-
- Chris Reahard built a specialized root filesystem for running a DNS
- server jailed inside UML. It's available from the download
- <http://user-mode-linux.sourceforge.net/dl-sf.html> page in the Jail
- Filesystems section.
-
-
-
-
-
-
-
-
-
-
-
-
W: http://www.linux-kvm.org
T: git git://git.kernel.org/pub/scm/virt/kvm/kvm.git
S: Supported
-F: Documentation/virtual/kvm/
+F: Documentation/virt/kvm/
F: include/trace/events/kvm.h
F: include/uapi/asm-generic/kvm*
F: include/uapi/linux/kvm*
M: Alok Kataria <akataria@vmware.com>
L: virtualization@lists.linux-foundation.org
S: Supported
-F: Documentation/virtual/paravirt_ops.txt
+F: Documentation/virt/paravirt_ops.txt
F: arch/*/kernel/paravirt*
F: arch/*/include/asm/paravirt*.h
F: include/linux/hypervisor.h
Q: https://patchwork.ozlabs.org/project/linux-um/list/
T: git git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml.git
S: Maintained
-F: Documentation/virtual/uml/
+F: Documentation/virt/uml/
F: arch/um/
F: arch/x86/um/
F: fs/hostfs/
* Struct fields are always 32 or 64 bit aligned, depending on them being 32
* or 64 bit wide respectively.
*
- * See Documentation/virtual/kvm/ppc-pv.txt
+ * See Documentation/virt/kvm/ppc-pv.txt
*/
struct kvm_vcpu_arch_shared {
__u64 scratch1;
/*
* Currently, fast page fault only works for direct mapping
* since the gfn is not stable for indirect shadow page. See
- * Documentation/virtual/kvm/locking.txt to get more detail.
+ * Documentation/virt/kvm/locking.txt to get more detail.
*/
fault_handled = fast_pf_fix_direct_spte(vcpu, sp,
iterator.sptep, spte,
* ACPI gsi notion of irq.
* For IA-64 (APIC model) IOAPIC0: irq 0-23; IOAPIC1: irq 24-47..
* For X86 (standard AT mode) PIC0/1: irq 0-15. IOAPIC0: 0-23..
- * For ARM: See Documentation/virtual/kvm/api.txt
+ * For ARM: See Documentation/virt/kvm/api.txt
*/
union {
__u32 irq;
*
* KVM_IRQFD_FLAG_RESAMPLE indicates resamplefd is valid and specifies
* the irqfd to operate in resampling mode for level triggered interrupt
- * emulation. See Documentation/virtual/kvm/api.txt.
+ * emulation. See Documentation/virt/kvm/api.txt.
*/
#define KVM_IRQFD_FLAG_RESAMPLE (1 << 1)
* ACPI gsi notion of irq.
* For IA-64 (APIC model) IOAPIC0: irq 0-23; IOAPIC1: irq 24-47..
* For X86 (standard AT mode) PIC0/1: irq 0-15. IOAPIC0: 0-23..
- * For ARM: See Documentation/virtual/kvm/api.txt
+ * For ARM: See Documentation/virt/kvm/api.txt
*/
union {
__u32 irq;
*
* KVM_IRQFD_FLAG_RESAMPLE indicates resamplefd is valid and specifies
* the irqfd to operate in resampling mode for level triggered interrupt
- * emulation. See Documentation/virtual/kvm/api.txt.
+ * emulation. See Documentation/virt/kvm/api.txt.
*/
#define KVM_IRQFD_FLAG_RESAMPLE (1 << 1)
* Ensure we set mode to IN_GUEST_MODE after we disable
* interrupts and before the final VCPU requests check.
* See the comment in kvm_vcpu_exiting_guest_mode() and
- * Documentation/virtual/kvm/vcpu-requests.rst
+ * Documentation/virt/kvm/vcpu-requests.rst
*/
smp_store_mb(vcpu->mode, IN_GUEST_MODE);
* pending state of interrupt is latched in pending_latch variable.
* Userspace will save and restore pending state and line_level
* separately.
- * Refer to Documentation/virtual/kvm/devices/arm-vgic-v3.txt
+ * Refer to Documentation/virt/kvm/devices/arm-vgic-v3.txt
* for handling of ISPENDR and ICPENDR.
*/
for (i = 0; i < len * 8; i++) {
VGIC_AFFINITY_LEVEL(val, 3))
/*
- * As per Documentation/virtual/kvm/devices/arm-vgic-v3.txt,
+ * As per Documentation/virt/kvm/devices/arm-vgic-v3.txt,
* below macros are defined for CPUREG encoding.
*/
#define KVM_REG_ARM_VGIC_SYSREG_OP0_MASK 0x000000000000c000
KVM_REG_ARM_VGIC_SYSREG_OP2_MASK)
/*
- * As per Documentation/virtual/kvm/devices/arm-vgic-its.txt,
+ * As per Documentation/virt/kvm/devices/arm-vgic-its.txt,
* below macros are defined for ITS table entry encoding.
*/
#define KVM_ITS_CTE_VALID_SHIFT 63
projects / openwrt / staging / blogic.git / commitdiff