On 28/7/2022 7:34 am, Sean Christopherson wrote:
-bool intel_pmu_lbr_is_enabled(struct kvm_vcpu *vcpu)
-{
- struct x86_pmu_lbr *lbr = vcpu_to_lbr_records(vcpu);
-
- return lbr->nr && (vcpu_get_perf_capabilities(vcpu) & PMU_CAP_LBR_FMT);
-}
-
static bool intel_pmu_is_valid_lbr_msr(struct kvm_vcpu *vcpu, u32 index)
{
struct x86_pmu_lbr *records = vcpu_to_lbr_records(vcpu);
@@ -590,7 +583,9 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
bitmap_set(pmu->all_valid_pmc_idx,
INTEL_PMC_MAX_GENERIC, pmu->nr_arch_fixed_counters);
- if (cpuid_model_is_consistent(vcpu))
+ perf_capabilities = vcpu_get_perf_capabilities(vcpu);
+ if (cpuid_model_is_consistent(vcpu) &&
+ (perf_capabilities & PMU_CAP_LBR_FMT))
x86_perf_get_lbr(&lbr_desc->records);
As one of evil source to add CPUID walk in the critical path:
The x86_perf_get_lbr() is one of the perf interfaces, KVM cannot always trust
that the number of returned lbr_desc->records.nr is always > 0, and if not,
we have to tweak perf_capabilities inside KVM which violates user input again.
Do you have more inputs to address this issue ?
else
lbr_desc->records.nr = 0;
