Messages in this thread Patch in this message | | | From | Wanpeng Li <> | Subject | [PATCH] KVM: VMX: Micro-optimize vmexit time when not exposing PMU | Date | Thu, 12 Mar 2020 18:05:47 +0800 |
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From: Wanpeng Li <wanpengli@tencent.com>
PMU is not exposed to guest by most of 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.
~1.28% vmexit time reduced can be observed by kvm-unit-tests/vmexit.flat on my SKX server.
Before patch: vmcall 1559
After patch: vmcall 1539
Signed-off-by: Wanpeng Li <wanpengli@tencent.com> --- arch/x86/kvm/vmx/vmx.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 40b1e61..fd526c8 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -6441,6 +6441,9 @@ static void atomic_switch_perf_msrs(struct vcpu_vmx *vmx) int i, nr_msrs; struct perf_guest_switch_msr *msrs; + if (!vcpu_to_pmu(&vmx->vcpu)->version) + return; + msrs = perf_guest_get_msrs(&nr_msrs); if (!msrs) -- 2.7.4
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