From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752364AbdF2Hz0 (ORCPT ); Thu, 29 Jun 2017 03:55:26 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:34937 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751983AbdF2HzS (ORCPT ); Thu, 29 Jun 2017 03:55:18 -0400 Subject: Re: [PATCH v3] KVM: LAPIC: Fix lapic timer injection delay To: Wanpeng Li Cc: "linux-kernel@vger.kernel.org" , kvm , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Wanpeng Li 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> From: Paolo Bonzini Message-ID: <62c6b468-52c0-38c5-e15f-c770483188cd@redhat.com> Date: Thu, 29 Jun 2017 09:55:14 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; } Otherwise it looks good. Thanks for your persistence. :) Paolo > /* 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, >