Commit 041bc42c authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini
Browse files

KVM: VMX: Micro-optimize vmexit time when not exposing PMU



PMU is not exposed to guest by most of products from cloud providers since the
bad performance of PMU emulation and security concern. However, it calls
perf_guest_switch_get_msrs() and clear_atomic_switch_msr() unconditionally
even if PMU is not exposed to the guest before each vmentry.

~2% vmexit time reduced can be observed by kvm-unit-tests/vmexit.flat on my
SKX server.

Before patch:
vmcall 1559

After patch:
vmcall 1529
Signed-off-by: default avatarWanpeng Li <wanpengli@tencent.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 331b4de9
......@@ -6549,7 +6549,8 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
pt_guest_enter(vmx);
atomic_switch_perf_msrs(vmx);
if (vcpu_to_pmu(vcpu)->version)
atomic_switch_perf_msrs(vmx);
atomic_switch_umwait_control_msr(vmx);
if (enable_preemption_timer)
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment