From: Like Xu <likexu@xxxxxxxxxxx>
On Intel platforms, the software can use the IA32_MISC_ENABLE[7] bit to
detect whether the processor supports performance monitoring facility.
It depends on the PMU is enabled for the guest, and a software write
operation to this available bit will be ignored. The proposal to ignore
the toggle in KVM is the way to go and that behavior matches bare metal.
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
arch/x86/kvm/vmx/pmu_intel.c | 1 +
arch/x86/kvm/x86.c | 15 +++++++++++++--
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 4e5b1eeeb77c..61de7b07489c 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -496,6 +496,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
if (!pmu->version)
return;
+ vcpu->arch.ia32_misc_enable_msr |= MSR_IA32_MISC_ENABLE_EMON;
perf_get_x86_pmu_capability(&x86_pmu);
pmu->nr_arch_gp_counters = min_t(int, eax.split.num_counters,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cf17af4d6904..3c7a51468216 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3515,9 +3515,19 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
vcpu->arch.ia32_tsc_adjust_msr = data;
}
break;
- case MSR_IA32_MISC_ENABLE:
+ case MSR_IA32_MISC_ENABLE: {
+ u64 old_val = vcpu->arch.ia32_misc_enable_msr;
+ u64 pmu_mask = MSR_IA32_MISC_ENABLE_EMON;
+
+ /*
+ * For a dummy user space, the order of setting vPMU capabilities and
+ * initialising MSR_IA32_MISC_ENABLE is not strictly guaranteed, so to
+ * avoid inconsistent functionality we keep the vPMU bits unchanged here.
+ */
+ data &= ~pmu_mask;
+ data |= old_val & pmu_mask;
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)) {
+ ((old_val ^ data) & MSR_IA32_MISC_ENABLE_MWAIT)) {
if (!guest_cpuid_has(vcpu, X86_FEATURE_XMM3))
return 1;
vcpu->arch.ia32_misc_enable_msr = data;
@@ -3526,6 +3536,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
vcpu->arch.ia32_misc_enable_msr = data;
}
break;
+ }
case MSR_IA32_SMBASE:
if (!msr_info->host_initiated)
return 1;
--
2.35.1
