From 26efe2fd92e50822674acce1dbc4f2ac6fc1788f Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Wed, 6 May 2020 11:44:01 -0400 Subject: [PATCH] KVM: VMX: Handle preemption timer fastpath This patch implements a fastpath for the preemption timer vmexit. The vmexit can be handled quickly so it can be performed with interrupts off and going back directly to the guest. Testing on SKX Server. cyclictest in guest(w/o mwait exposed, adaptive advance lapic timer is default -1): 5540.5ns -> 4602ns 17% kvm-unit-test/vmexit.flat: w/o avanced timer: tscdeadline_immed: 3028.5 -> 2494.75 17.6% tscdeadline: 5765.7 -> 5285 8.3% w/ adaptive advance timer default -1: tscdeadline_immed: 3123.75 -> 2583 17.3% tscdeadline: 4663.75 -> 4537 2.7% Tested-by: Haiwei Li Cc: Haiwei Li Signed-off-by: Wanpeng Li Message-Id: <1588055009-12677-8-git-send-email-wanpengli@tencent.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/vmx.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index d267807..5fa162f 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -5601,14 +5601,22 @@ static int handle_pml_full(struct kvm_vcpu *vcpu) return 1; } -static int handle_preemption_timer(struct kvm_vcpu *vcpu) +static fastpath_t handle_fastpath_preemption_timer(struct kvm_vcpu *vcpu) { struct vcpu_vmx *vmx = to_vmx(vcpu); if (!vmx->req_immediate_exit && - !unlikely(vmx->loaded_vmcs->hv_timer_soft_disabled)) + !unlikely(vmx->loaded_vmcs->hv_timer_soft_disabled)) { kvm_lapic_expired_hv_timer(vcpu); + return EXIT_FASTPATH_REENTER_GUEST; + } + + return EXIT_FASTPATH_NONE; +} +static int handle_preemption_timer(struct kvm_vcpu *vcpu) +{ + handle_fastpath_preemption_timer(vcpu); return 1; } @@ -6631,6 +6639,8 @@ static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu) switch (to_vmx(vcpu)->exit_reason) { case EXIT_REASON_MSR_WRITE: return handle_fastpath_set_msr_irqoff(vcpu); + case EXIT_REASON_PREEMPTION_TIMER: + return handle_fastpath_preemption_timer(vcpu); default: return EXIT_FASTPATH_NONE; } -- 2.7.4