On 28/7/2022 7:34 am, Sean Christopherson wrote:
guest_cpuid_has() is expensive due to the linear search of guest CPUID entries, intel_pmu_lbr_is_enabled() is checked on every VM-Enter,_and_ simply enumerating the same "Model" as the host causes KVM to set the number of LBR records to a non-zero value.
Before reconsidering vcpu->arch.perf_capabilities to reach a conclusion, how about this minor inline change help reduce my sins ? diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 0ecbbae42976..06a21d66be13 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7039,7 +7039,8 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu) pt_guest_enter(vmx); atomic_switch_perf_msrs(vmx); - if (intel_pmu_lbr_is_enabled(vcpu)) + if (vmx->lbr_desc.records.nr && + (vcpu->arch.perf_capabilities & PMU_CAP_LBR_FMT)) vmx_passthrough_lbr_msrs(vcpu); if (enable_preemption_timer)
