From c853354429f7ec88f9cdde4e46e69a2c0e3c8310 Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Thu, 29 Jun 2017 06:28:09 -0700 Subject: [PATCH] KVM: LAPIC: Fix lapic timer injection delay MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit If the TSC deadline timer is programmed really close to the deadline or even in the past, the computation in vmx_set_hv_timer will program the absolute target tsc value to vmcs preemption timer field w/ delta == 0, then plays a vmentry and an upcoming vmx preemption timer fire vmexit dance, the lapic timer injection is delayed due to this duration. Actually the lapic timer which is emulated by hrtimer can handle this correctly. This patch fixes it by firing the lapic timer and injecting a timer interrupt immediately during the next vmentry if the TSC deadline timer is programmed really close to the deadline or even in the past. This saves ~300 cycles on the tsc_deadline_timer test of apic.flat. Cc: Paolo Bonzini Cc: Radim Krčmář Signed-off-by: Wanpeng Li Signed-off-by: Paolo Bonzini --- arch/x86/kvm/lapic.c | 5 ++++- arch/x86/kvm/vmx.c | 3 ++- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index a80e5a5d6f2f..2819d4c123eb 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -1525,8 +1525,11 @@ static bool start_hv_timer(struct kvm_lapic *apic) * the window. For periodic timer, leave the hv timer running for * simplicity, and the deadline will be recomputed on the next vmexit. */ - if (!apic_lvtt_period(apic) && atomic_read(&ktimer->pending)) + if (!apic_lvtt_period(apic) && (r || atomic_read(&ktimer->pending))) { + if (r) + apic_timer_expired(apic); return false; + } trace_kvm_hv_timer_state(apic->vcpu->vcpu_id, true); return true; diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index e8b61ad84a8e..92ddea08f999 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -11147,7 +11147,8 @@ static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc) vmx->hv_deadline_tsc = tscl + delta_tsc; vmcs_set_bits(PIN_BASED_VM_EXEC_CONTROL, PIN_BASED_VMX_PREEMPTION_TIMER); - return 0; + + return delta_tsc == 0; } static void vmx_cancel_hv_timer(struct kvm_vcpu *vcpu) -- 2.20.1