Messages in this thread Patch in this message | | | Date | Fri, 29 Jul 2022 18:10:11 +0800 | Subject | Re: [PATCH 3/3] KVM: VMX: Adjust number of LBR records for PERF_CAPABILITIES at refresh | From | Like Xu <> |
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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)
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