[PATCH v2 09/17] KVM: x86: Set PEBS_UNAVAIL in IA32_MISC_ENABLE when PEBS is enabled

[Like Xu]

The bit 12 represents "Processor Event Based Sampling Unavailable (RO)" :
	1 = PEBS is not supported.
	0 = PEBS is supported.

A write to this PEBS_UNAVL available bit will bring #GP(0) when guest PEBS
is enabled. Some PEBS drivers in guest may care about this bit.

Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/vmx/pmu_intel.c | 2 ++
 arch/x86/kvm/x86.c           | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index c04e12812797..99d9453e0176 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -426,6 +426,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 		INTEL_PMC_MAX_GENERIC, pmu->nr_arch_fixed_counters);
 
 	if (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_FORMAT) {
+		vcpu->arch.ia32_misc_enable_msr &= ~MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
 		if (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_BASELINE) {
 			pmu->pebs_enable_mask = ~pmu->global_ctrl;
 			pmu->reserved_bits &= ~ICL_EVENTSEL_ADAPTIVE;
@@ -436,6 +437,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 		} else
 			pmu->pebs_enable_mask = ~((1ull << pmu->nr_arch_gp_counters) - 1);
 	} else {
+		vcpu->arch.ia32_misc_enable_msr |= MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL;
 		vcpu->arch.perf_capabilities &= ~PERF_CAP_PEBS_MASK;
 	}
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e1280bb18152..b5963a36bf6b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3087,6 +3087,10 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		break;
 	case MSR_IA32_MISC_ENABLE:
 		data &= ~MSR_IA32_MISC_ENABLE_EMON;
+		if (!msr_info->host_initiated &&
+		    (vcpu->arch.perf_capabilities & PERF_CAP_PEBS_FORMAT) &&
+		    (data & MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL))
+			return 1;
 		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))
-- 
2.21.3