arm/arm64: KVM: Add PSCI version selection API

Although we've implemented PSCI 0.1, 0.2 and 1.0, we expose either 0.1
or 1.0 to a guest, defaulting to the latest version of the PSCI
implementation that is compatible with the requested version. This is
no different from doing a firmware upgrade on KVM.

But in order to give a chance to hypothetical badly implemented guests
that would have a fit by discovering something other than PSCI 0.2,
let's provide a new API that allows userspace to pick one particular
version of the API.

This is implemented as a new class of "firmware" registers, where
we expose the PSCI version. This allows the PSCI version to be
save/restored as part of a guest migration, and also set to
any supported version if the guest requires it.

Cc: stable@vger.kernel.org #4.16
Reviewed-by: Christoffer Dall <cdall@kernel.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 1c7958b57fe9fd52d337862fa9b6b5d46ca2e9f8..758bf403a169dac0db8ec259bc611986aea69cfd 100644 (file)
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1960,6 +1960,9 @@ ARM 32-bit VFP control registers have the following id bit patterns:
 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:
@@ -1976,6 +1979,9 @@ arm64 CCSIDR registers are demultiplexed by CSSELR value:
 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>
+
 
 MIPS registers are mapped using the lower 32 bits.  The upper 16 of that is
 the register group type:
@@ -2510,7 +2516,8 @@ Possible features:
          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 for the CPU.
+       - 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.

diff --git a/Documentation/virtual/kvm/arm/psci.txt b/Documentation/virtual/kvm/arm/psci.txt
new file mode 100644 (file)
index 0000000..aafdab8
--- /dev/null
+++ b/Documentation/virtual/kvm/arm/psci.txt
@@ -0,0 +1,30 @@
+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)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index c6a749568dd6c413603ef3b7554561f356b33cc9..c7c28c885a1946de9a012311cbca7861d93a67da 100644 (file)
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -77,6 +77,9 @@ struct kvm_arch {
        /* Interrupt controller */
        struct vgic_dist        vgic;
        int max_vcpus;
+
+       /* Mandated version of PSCI */
+       u32 psci_version;
 };
 
 #define KVM_NR_MEM_OBJS     40

diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
index 2ba95d6fe852d7bed7460b022f1ed5b8409caacd..caae4843cb7001fbee1fa9b222850df7006850fb 100644 (file)
--- a/arch/arm/include/uapi/asm/kvm.h
+++ b/arch/arm/include/uapi/asm/kvm.h
@@ -195,6 +195,12 @@ struct kvm_arch_memory_slot {
 #define KVM_REG_ARM_VFP_FPINST         0x1009
 #define KVM_REG_ARM_VFP_FPINST2                0x100A
 
+/* KVM-as-firmware specific pseudo-registers */
+#define KVM_REG_ARM_FW                 (0x0014 << KVM_REG_ARM_COPROC_SHIFT)
+#define KVM_REG_ARM_FW_REG(r)          (KVM_REG_ARM | KVM_REG_SIZE_U64 | \
+                                        KVM_REG_ARM_FW | ((r) & 0xffff))
+#define KVM_REG_ARM_PSCI_VERSION       KVM_REG_ARM_FW_REG(0)
+
 /* Device Control API: ARM VGIC */
 #define KVM_DEV_ARM_VGIC_GRP_ADDR      0
 #define KVM_DEV_ARM_VGIC_GRP_DIST_REGS 1

diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
index 1e0784ebbfd6db77595652961ad3c48c41fceabe..a18f33edc471a92fcf6194dbe6601bc4b94f1988 100644 (file)
--- a/arch/arm/kvm/guest.c
+++ b/arch/arm/kvm/guest.c
@@ -22,6 +22,7 @@
 #include <linux/module.h>
 #include <linux/vmalloc.h>
 #include <linux/fs.h>
+#include <kvm/arm_psci.h>
 #include <asm/cputype.h>
 #include <linux/uaccess.h>
 #include <asm/kvm.h>
@@ -176,6 +177,7 @@ static unsigned long num_core_regs(void)
 unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu)
 {
        return num_core_regs() + kvm_arm_num_coproc_regs(vcpu)
+               + kvm_arm_get_fw_num_regs(vcpu)
                + NUM_TIMER_REGS;
 }
 
@@ -196,6 +198,11 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
                uindices++;
        }
 
+       ret = kvm_arm_copy_fw_reg_indices(vcpu, uindices);
+       if (ret)
+               return ret;
+       uindices += kvm_arm_get_fw_num_regs(vcpu);
+
        ret = copy_timer_indices(vcpu, uindices);
        if (ret)
                return ret;
@@ -214,6 +221,9 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
        if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
                return get_core_reg(vcpu, reg);
 
+       if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_FW)
+               return kvm_arm_get_fw_reg(vcpu, reg);
+
        if (is_timer_reg(reg->id))
                return get_timer_reg(vcpu, reg);
 
@@ -230,6 +240,9 @@ int kvm_arm_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
        if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
                return set_core_reg(vcpu, reg);
 
+       if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_FW)
+               return kvm_arm_set_fw_reg(vcpu, reg);
+
        if (is_timer_reg(reg->id))
                return set_timer_reg(vcpu, reg);
 

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index ab46bc70add636e0793f32083f800ff06bf80353..469de8acd06f5fa4103d9f55d0fb4c4c97d853a9 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -75,6 +75,9 @@ struct kvm_arch {
 
        /* Interrupt controller */
        struct vgic_dist        vgic;
+
+       /* Mandated version of PSCI */
+       u32 psci_version;
 };
 
 #define KVM_NR_MEM_OBJS     40

diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index 9abbf30446545a0668083b0891461f015563bcb1..04b3256f8e6d5f8e3e368b043f0fdcfeb7c23164 100644 (file)
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -206,6 +206,12 @@ struct kvm_arch_memory_slot {
 #define KVM_REG_ARM_TIMER_CNT          ARM64_SYS_REG(3, 3, 14, 3, 2)
 #define KVM_REG_ARM_TIMER_CVAL         ARM64_SYS_REG(3, 3, 14, 0, 2)
 
+/* KVM-as-firmware specific pseudo-registers */
+#define KVM_REG_ARM_FW                 (0x0014 << KVM_REG_ARM_COPROC_SHIFT)
+#define KVM_REG_ARM_FW_REG(r)          (KVM_REG_ARM64 | KVM_REG_SIZE_U64 | \
+                                        KVM_REG_ARM_FW | ((r) & 0xffff))
+#define KVM_REG_ARM_PSCI_VERSION       KVM_REG_ARM_FW_REG(0)
+
 /* Device Control API: ARM VGIC */
 #define KVM_DEV_ARM_VGIC_GRP_ADDR      0
 #define KVM_DEV_ARM_VGIC_GRP_DIST_REGS 1

diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 959e50d2588c0f14b9eb9230522c3f12c3f7daf9..56a0260ceb11a95258099f0f19356b8989ff6afa 100644 (file)
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -25,6 +25,7 @@
 #include <linux/module.h>
 #include <linux/vmalloc.h>
 #include <linux/fs.h>
+#include <kvm/arm_psci.h>
 #include <asm/cputype.h>
 #include <linux/uaccess.h>
 #include <asm/kvm.h>
@@ -205,7 +206,7 @@ static int get_timer_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu)
 {
        return num_core_regs() + kvm_arm_num_sys_reg_descs(vcpu)
-                + NUM_TIMER_REGS;
+               + kvm_arm_get_fw_num_regs(vcpu) + NUM_TIMER_REGS;
 }
 
 /**
@@ -225,6 +226,11 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
                uindices++;
        }
 
+       ret = kvm_arm_copy_fw_reg_indices(vcpu, uindices);
+       if (ret)
+               return ret;
+       uindices += kvm_arm_get_fw_num_regs(vcpu);
+
        ret = copy_timer_indices(vcpu, uindices);
        if (ret)
                return ret;
@@ -243,6 +249,9 @@ int kvm_arm_get_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
        if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
                return get_core_reg(vcpu, reg);
 
+       if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_FW)
+               return kvm_arm_get_fw_reg(vcpu, reg);
+
        if (is_timer_reg(reg->id))
                return get_timer_reg(vcpu, reg);
 
@@ -259,6 +268,9 @@ int kvm_arm_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
        if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_CORE)
                return set_core_reg(vcpu, reg);
 
+       if ((reg->id & KVM_REG_ARM_COPROC_MASK) == KVM_REG_ARM_FW)
+               return kvm_arm_set_fw_reg(vcpu, reg);
+
        if (is_timer_reg(reg->id))
                return set_timer_reg(vcpu, reg);
 

diff --git a/include/kvm/arm_psci.h b/include/kvm/arm_psci.h
index e518e4e3dfb50a83520a3b8100c3c27899c15bdf..4b1548129fa2b3e2b87565ec02d9dd5adb80ccb2 100644 (file)
--- a/include/kvm/arm_psci.h
+++ b/include/kvm/arm_psci.h
@@ -37,10 +37,15 @@ static inline int kvm_psci_version(struct kvm_vcpu *vcpu, struct kvm *kvm)
         * Our PSCI implementation stays the same across versions from
         * v0.2 onward, only adding the few mandatory functions (such
         * as FEATURES with 1.0) that are required by newer
-        * revisions. It is thus safe to return the latest.
+        * revisions. It is thus safe to return the latest, unless
+        * userspace has instructed us otherwise.
         */
-       if (test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features))
+       if (test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features)) {
+               if (vcpu->kvm->arch.psci_version)
+                       return vcpu->kvm->arch.psci_version;
+
                return KVM_ARM_PSCI_LATEST;
+       }
 
        return KVM_ARM_PSCI_0_1;
 }
@@ -48,4 +53,11 @@ static inline int kvm_psci_version(struct kvm_vcpu *vcpu, struct kvm *kvm)
 
 int kvm_hvc_call_handler(struct kvm_vcpu *vcpu);
 
+struct kvm_one_reg;
+
+int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu);
+int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices);
+int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
+int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg);
+
 #endif /* __KVM_ARM_PSCI_H__ */

diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
index 6919352cbf15e8d50b3742e32acfd152be4b18a8..c4762bef13c6d389ff0c1e4f656322d66bb167b0 100644 (file)
--- a/virt/kvm/arm/psci.c
+++ b/virt/kvm/arm/psci.c
@@ -18,6 +18,7 @@
 #include <linux/arm-smccc.h>
 #include <linux/preempt.h>
 #include <linux/kvm_host.h>
+#include <linux/uaccess.h>
 #include <linux/wait.h>
 
 #include <asm/cputype.h>
@@ -427,3 +428,62 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
        smccc_set_retval(vcpu, val, 0, 0, 0);
        return 1;
 }
+
+int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
+{
+       return 1;               /* PSCI version */
+}
+
+int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
+{
+       if (put_user(KVM_REG_ARM_PSCI_VERSION, uindices))
+               return -EFAULT;
+
+       return 0;
+}
+
+int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
+{
+       if (reg->id == KVM_REG_ARM_PSCI_VERSION) {
+               void __user *uaddr = (void __user *)(long)reg->addr;
+               u64 val;
+
+               val = kvm_psci_version(vcpu, vcpu->kvm);
+               if (copy_to_user(uaddr, &val, KVM_REG_SIZE(reg->id)))
+                       return -EFAULT;
+
+               return 0;
+       }
+
+       return -EINVAL;
+}
+
+int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
+{
+       if (reg->id == KVM_REG_ARM_PSCI_VERSION) {
+               void __user *uaddr = (void __user *)(long)reg->addr;
+               bool wants_02;
+               u64 val;
+
+               if (copy_from_user(&val, uaddr, KVM_REG_SIZE(reg->id)))
+                       return -EFAULT;
+
+               wants_02 = test_bit(KVM_ARM_VCPU_PSCI_0_2, vcpu->arch.features);
+
+               switch (val) {
+               case KVM_ARM_PSCI_0_1:
+                       if (wants_02)
+                               return -EINVAL;
+                       vcpu->kvm->arch.psci_version = val;
+                       return 0;
+               case KVM_ARM_PSCI_0_2:
+               case KVM_ARM_PSCI_1_0:
+                       if (!wants_02)
+                               return -EINVAL;
+                       vcpu->kvm->arch.psci_version = val;
+                       return 0;
+               }
+       }
+
+       return -EINVAL;
+}