From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753637AbdF1B3S (ORCPT ); Tue, 27 Jun 2017 21:29:18 -0400 Received: from mail-pf0-f196.google.com ([209.85.192.196]:33301 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753516AbdF1B3R (ORCPT ); Tue, 27 Jun 2017 21:29:17 -0400 From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= , Wanpeng Li Subject: [PATCH v3] KVM: LAPIC: Fix lapic timer injection delay Date: Tue, 27 Jun 2017 18:29:12 -0700 Message-Id: <1498613352-4651-1-git-send-email-wanpeng.li@hotmail.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li 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 --- v2 -> v3: * update the patch description arch/x86/kvm/lapic.c | 7 ++++++- arch/x86/kvm/vmx.c | 3 +++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index d24c874..08cf73d 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -1504,12 +1504,17 @@ static void cancel_hv_timer(struct kvm_lapic *apic) static bool start_hv_timer(struct kvm_lapic *apic) { u64 tscdeadline = apic->lapic_timer.tscdeadline; + int ret = 0; if ((atomic_read(&apic->lapic_timer.pending) && !apic_lvtt_period(apic)) || - kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline)) { + (ret = kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline))) { if (apic->lapic_timer.hv_timer_in_use) cancel_hv_timer(apic); + if (ret == 1) { + apic_timer_expired(apic); + return true; + } } else { apic->lapic_timer.hv_timer_in_use = true; hrtimer_cancel(&apic->lapic_timer.timer); diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 2e906cf..2008e9b 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -11149,6 +11149,9 @@ static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc) u64 guest_tscl = kvm_read_l1_tsc(vcpu, tscl); u64 delta_tsc = max(guest_deadline_tsc, guest_tscl) - guest_tscl; + if (delta_tsc == 0) + return 1; + /* Convert to host delta tsc if tsc scaling is enabled */ if (vcpu->arch.tsc_scaling_ratio != kvm_default_tsc_scaling_ratio && u64_shl_div_u64(delta_tsc, -- 2.7.4