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([2001:b07:6468:f312:e943:5a4e:e068:244a]) by smtp.gmail.com with ESMTPSA id y7sm3656457wmm.19.2019.07.05.06.26.02 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Fri, 05 Jul 2019 06:26:03 -0700 (PDT) Subject: Re: [PATCH v5 4/4] KVM: LAPIC: Don't inject already-expired timer via posted interrupt To: Wanpeng Li , Wanpeng Li , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Marcelo Tosatti References: <1561110002-4438-1-git-send-email-wanpengli@tencent.com> <1561110002-4438-5-git-send-email-wanpengli@tencent.com> <67fad01b-8a77-5892-d963-77a3d321bb65@redhat.com> From: Paolo Bonzini Message-ID: <847fc9bd-c0b9-0f7b-f029-9a5499f2c74e@redhat.com> Date: Fri, 5 Jul 2019 15:26:02 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/07/19 15:11, Wanpeng Li wrote: > On 7/5/19 8:40 PM, Paolo Bonzini wrote: > >> On 21/06/19 11:40, Wanpeng Li wrote: >>> From: Wanpeng Li >>> >>> already-expired timer interrupt can be injected to guest when vCPU who >>> arms the lapic timer re-vmentry, don't posted inject in this case. >>> >>> Cc: Paolo Bonzini >>> Cc: Radim Krčmář >>> Cc: Marcelo Tosatti >>> Signed-off-by: Wanpeng Li >>> --- >>> arch/x86/kvm/lapic.c | 14 +++++++------- >>> 1 file changed, 7 insertions(+), 7 deletions(-) >>> >>> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c >>> index ae575c0..7cd95ea 100644 >>> --- a/arch/x86/kvm/lapic.c >>> +++ b/arch/x86/kvm/lapic.c >>> @@ -1452,7 +1452,7 @@ static void kvm_apic_inject_pending_timer_irqs(struct kvm_lapic *apic) >>> } >>> } >>> >>> -static void apic_timer_expired(struct kvm_lapic *apic) >>> +static void apic_timer_expired(struct kvm_lapic *apic, bool can_pi_inject) >>> { >>> struct kvm_vcpu *vcpu = apic->vcpu; >>> struct swait_queue_head *q = &vcpu->wq; >>> @@ -1464,7 +1464,7 @@ static void apic_timer_expired(struct kvm_lapic *apic) >>> if (apic_lvtt_tscdeadline(apic) || ktimer->hv_timer_in_use) >>> ktimer->expired_tscdeadline = ktimer->tscdeadline; >>> >>> - if (posted_interrupt_inject_timer(apic->vcpu)) { >>> + if (can_pi_inject && posted_interrupt_inject_timer(apic->vcpu)) { >> Perhaps it should use a posted interrupt if kvm_arch_should_kick(vcpu), >> i.e. just add kvm_arch_vcpu_should_kick(apic->vcpu) to >> posted_interrupt_inject_timer? > > So do you mean not nohz_full setup? An external interrupt is incurred > here and preemption timer is better. No, I mean instead of adding can_pi_inject, just test kvm_arch_should_kick in posted_interrupt_inject_timer, skipping the PI if the vCPU is not running. Instead just go down the normal path and the guest will get the interrupt by checking the timer-pending flag. Paolo