KVM: X86: Emulate MSR_IA32_MISC_ENABLE MWAIT bit

MSR IA32_MISC_ENABLE bit 18, according to SDM:

| When this bit is set to 0, the MONITOR feature flag is not set (CPUID.01H:ECX[bit 3] = 0).
| This indicates that MONITOR/MWAIT are not supported.
|
| Software attempts to execute MONITOR/MWAIT will cause #UD when this bit is 0.
|
| When this bit is set to 1 (default), MONITOR/MWAIT are supported (CPUID.01H:ECX[bit 3] = 1).

The CPUID.01H:ECX[bit 3] ought to mirror the value of the MSR bit,
CPUID.01H:ECX[bit 3] is a better guard than kvm_mwait_in_guest().
kvm_mwait_in_guest() affects the behavior of MONITOR/MWAIT, not its
guest visibility.

This patch implements toggling of the CPUID bit based on guest writes
to the MSR.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Liran Alon <liran.alon@oracle.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
[Fixes for backwards compatibility - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 7a0e64ccd6ff5d02108a4424fc72a36f49018987..f9b021e16ebc8221ec1579b8500c8defae363952 100644 (file)
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -378,10 +378,11 @@ struct kvm_sync_regs {
        struct kvm_vcpu_events events;
 };
 
-#define KVM_X86_QUIRK_LINT0_REENABLED  (1 << 0)
-#define KVM_X86_QUIRK_CD_NW_CLEARED    (1 << 1)
-#define KVM_X86_QUIRK_LAPIC_MMIO_HOLE  (1 << 2)
-#define KVM_X86_QUIRK_OUT_7E_INC_RIP   (1 << 3)
+#define KVM_X86_QUIRK_LINT0_REENABLED     (1 << 0)
+#define KVM_X86_QUIRK_CD_NW_CLEARED       (1 << 1)
+#define KVM_X86_QUIRK_LAPIC_MMIO_HOLE     (1 << 2)
+#define KVM_X86_QUIRK_OUT_7E_INC_RIP      (1 << 3)
+#define KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT (1 << 4)
 
 #define KVM_STATE_NESTED_GUEST_MODE    0x00000001
 #define KVM_STATE_NESTED_RUN_PENDING   0x00000002

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index e18a9f9f65b546c15c4781a4573f5009c3805dec..60f87ba2ccca785b67b0e0edbc45e5d9b341ad56 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -137,6 +137,16 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
                (best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
                best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
 
+       if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT)) {
+               best = kvm_find_cpuid_entry(vcpu, 0x1, 0);
+               if (best) {
+                       if (vcpu->arch.ia32_misc_enable_msr & MSR_IA32_MISC_ENABLE_MWAIT)
+                               best->ecx |= F(MWAIT);
+                       else
+                               best->ecx &= ~F(MWAIT);
+               }
+       }
+
        /* Update physical-address width */
        vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
        kvm_mmu_reset_context(vcpu);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 17e9533f51eb3d6aa1d5e68ea03a643eb0083f1b..10feed6a01eb8fd83ba6a4f89cbde5073d31d565 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2547,7 +2547,15 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                }
                break;
        case MSR_IA32_MISC_ENABLE:
-               vcpu->arch.ia32_misc_enable_msr = data;
+               if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT) &&
+                   ((vcpu->arch.ia32_misc_enable_msr ^ data) & MSR_IA32_MISC_ENABLE_MWAIT)) {
+                       if (!guest_cpuid_has(vcpu, X86_FEATURE_XMM3))
+                               return 1;
+                       vcpu->arch.ia32_misc_enable_msr = data;
+                       kvm_update_cpuid(vcpu);
+               } else {
+                       vcpu->arch.ia32_misc_enable_msr = data;
+               }
                break;
        case MSR_IA32_SMBASE:
                if (!msr_info->host_initiated)