From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752769AbdF2MGL (ORCPT ); Thu, 29 Jun 2017 08:06:11 -0400 Received: from mail-oi0-f66.google.com ([209.85.218.66]:35808 "EHLO mail-oi0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752990AbdF2MFy (ORCPT ); Thu, 29 Jun 2017 08:05:54 -0400 MIME-Version: 1.0 In-Reply-To: <62c6b468-52c0-38c5-e15f-c770483188cd@redhat.com> References: <1498613352-4651-1-git-send-email-wanpeng.li@hotmail.com> <68c0d7f8-683f-c7fa-b328-e90e8dd9a789@redhat.com> <6fc8f133-15b8-3ee2-1483-614642deffa0@redhat.com> <62c6b468-52c0-38c5-e15f-c770483188cd@redhat.com> From: Wanpeng Li Date: Thu, 29 Jun 2017 20:05:48 +0800 Message-ID: Subject: Re: [PATCH v3] KVM: LAPIC: Fix lapic timer injection delay To: Paolo Bonzini Cc: "linux-kernel@vger.kernel.org" , kvm , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2017-06-29 15:55 GMT+08:00 Paolo Bonzini : > > > On 29/06/2017 05:42, Wanpeng Li wrote: >> So how about something like this? >> >> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c >> index d24c874..900ce86 100644 >> --- a/arch/x86/kvm/lapic.c >> +++ b/arch/x86/kvm/lapic.c >> @@ -1504,21 +1504,26 @@ static void cancel_hv_timer(struct kvm_lapic *apic) >> static bool start_hv_timer(struct kvm_lapic *apic) >> { >> u64 tscdeadline = apic->lapic_timer.tscdeadline; >> + bool need_cancel = apic->lapic_timer.hv_timer_in_use; >> + if (!atomic_read(&apic->lapic_timer.pending) || apic_lvtt_period(apic)) { >> + int r = kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline); >> + if (r >= 0) { >> + need_cancel = false; >> + apic->lapic_timer.hv_timer_in_use = true; >> + hrtimer_cancel(&apic->lapic_timer.timer); >> + >> + /* In case the sw timer triggered in the window */ >> + if (atomic_read(&apic->lapic_timer.pending) && >> + !apic_lvtt_period(apic)) >> + need_cancel = true; >> + else if (r && (apic_lvtt_oneshot(apic) || >> apic_lvtt_tscdeadline(apic))) >> + apic_timer_expired(apic); >> + } >> + } >> >> - if ((atomic_read(&apic->lapic_timer.pending) && >> - !apic_lvtt_period(apic)) || >> - kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline)) { >> - if (apic->lapic_timer.hv_timer_in_use) >> - cancel_hv_timer(apic); >> - } else { >> - apic->lapic_timer.hv_timer_in_use = true; >> - hrtimer_cancel(&apic->lapic_timer.timer); >> + if (need_cancel) >> + cancel_hv_timer(apic); >> >> - /* In case the sw timer triggered in the window */ >> - if (atomic_read(&apic->lapic_timer.pending) && >> - !apic_lvtt_period(apic)) >> - cancel_hv_timer(apic); >> - } >> trace_kvm_hv_timer_state(apic->vcpu->vcpu_id, >> apic->lapic_timer.hv_timer_in_use); >> return apic->lapic_timer.hv_timer_in_use; >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> index 4f616db..0a0e696 100644 >> --- a/arch/x86/kvm/vmx.c >> +++ b/arch/x86/kvm/vmx.c >> @@ -11125,6 +11125,9 @@ 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; > > You still need to enable the preemption timer even if you return 1, so > in lapic.c it becomes > > if (!apic_lvtt_period(apic)) { > if (r) > apic_timer_expired(apic); > if (atomic_read(&apic->lapic_timer.pending)) > need_cancel = true; > } As you point out, we should cancel the preemption timer if it returns 1 and the APIC timer's mode is oneshot/tscdeadline. How about something like this: diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index d24c874..b801385 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -1504,21 +1504,28 @@ static void cancel_hv_timer(struct kvm_lapic *apic) static bool start_hv_timer(struct kvm_lapic *apic) { u64 tscdeadline = apic->lapic_timer.tscdeadline; + bool need_cancel = apic->lapic_timer.hv_timer_in_use; + if (!atomic_read(&apic->lapic_timer.pending) || apic_lvtt_period(apic)) { + int r = kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline); + if (r >= 0) { + need_cancel = false; + apic->lapic_timer.hv_timer_in_use = true; + hrtimer_cancel(&apic->lapic_timer.timer); + + /* In case the sw timer triggered in the window */ + if (!apic_lvtt_period(apic)) { + if (r || atomic_read(&apic->lapic_timer.pending)) { + need_cancel = true; + if (r) + apic_timer_expired(apic); + } + } + } + } - if ((atomic_read(&apic->lapic_timer.pending) && - !apic_lvtt_period(apic)) || - kvm_x86_ops->set_hv_timer(apic->vcpu, tscdeadline)) { - if (apic->lapic_timer.hv_timer_in_use) - cancel_hv_timer(apic); - } else { - apic->lapic_timer.hv_timer_in_use = true; - hrtimer_cancel(&apic->lapic_timer.timer); + if (need_cancel) + cancel_hv_timer(apic); - /* In case the sw timer triggered in the window */ - if (atomic_read(&apic->lapic_timer.pending) && - !apic_lvtt_period(apic)) - cancel_hv_timer(apic); - } trace_kvm_hv_timer_state(apic->vcpu->vcpu_id, apic->lapic_timer.hv_timer_in_use); return apic->lapic_timer.hv_timer_in_use; diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index ca5d2b9..b8bde13 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -11134,7 +11134,11 @@ 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; + + if (delta_tsc == 0) + return 1; + else + return 0; } static void vmx_cancel_hv_timer(struct kvm_vcpu *vcpu) Regards, Wanpeng Li