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KVM: x86/pmu: preserve IA32_PERF_CAPABILITIES across CPUID refresh
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Once MSR_IA32_PERF_CAPABILITIES is changed via vmx_set_msr(), the
value should not be changed by cpuid(). To ensure that the new value
is kept, the default initialization path is moved to intel_pmu_init().
The effective value of the MSR will be 0 if PDCM is clear, however.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Paolo Bonzini committed Feb 4, 2021
1 parent 252e365 commit a755753
Showing 1 changed file with 10 additions and 6 deletions.
16 changes: 10 additions & 6 deletions arch/x86/kvm/vmx/pmu_intel.c
Original file line number Diff line number Diff line change
Expand Up @@ -152,12 +152,17 @@ static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
return &counters[array_index_nospec(idx, num_counters)];
}

static inline bool fw_writes_is_enabled(struct kvm_vcpu *vcpu)
static inline u64 vcpu_get_perf_capabilities(struct kvm_vcpu *vcpu)
{
if (!guest_cpuid_has(vcpu, X86_FEATURE_PDCM))
return false;
return 0;

return vcpu->arch.perf_capabilities & PMU_CAP_FW_WRITES;
return vcpu->arch.perf_capabilities;
}

static inline bool fw_writes_is_enabled(struct kvm_vcpu *vcpu)
{
return (vcpu_get_perf_capabilities(vcpu) & PMU_CAP_FW_WRITES) != 0;
}

static inline struct kvm_pmc *get_fw_gp_pmc(struct kvm_pmu *pmu, u32 msr)
Expand Down Expand Up @@ -327,7 +332,6 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
pmu->counter_bitmask[KVM_PMC_FIXED] = 0;
pmu->version = 0;
pmu->reserved_bits = 0xffffffff00200000ull;
vcpu->arch.perf_capabilities = 0;

entry = kvm_find_cpuid_entry(vcpu, 0xa, 0);
if (!entry)
Expand All @@ -340,8 +344,6 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
return;

perf_get_x86_pmu_capability(&x86_pmu);
if (guest_cpuid_has(vcpu, X86_FEATURE_PDCM))
vcpu->arch.perf_capabilities = vmx_get_perf_capabilities();

pmu->nr_arch_gp_counters = min_t(int, eax.split.num_counters,
x86_pmu.num_counters_gp);
Expand Down Expand Up @@ -405,6 +407,8 @@ static void intel_pmu_init(struct kvm_vcpu *vcpu)
pmu->fixed_counters[i].idx = i + INTEL_PMC_IDX_FIXED;
pmu->fixed_counters[i].current_config = 0;
}

vcpu->arch.perf_capabilities = vmx_get_perf_capabilities();
}

static void intel_pmu_reset(struct kvm_vcpu *vcpu)
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