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Subject: Re: [PATCH v5 4/4] KVM: LAPIC: Don't inject already-expired timer via
 posted interrupt
To:     Wanpeng Li <kernellwp@gmail.com>, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Marcelo Tosatti <mtosatti@redhat.com>
References: <1561110002-4438-1-git-send-email-wanpengli@tencent.com>
 <1561110002-4438-5-git-send-email-wanpengli@tencent.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <67fad01b-8a77-5892-d963-77a3d321bb65@redhat.com>
Date:   Fri, 5 Jul 2019 14:40:27 +0200
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On 21/06/19 11:40, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
> 
> 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 <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
>  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?

Paolo

>  		if (apic->lapic_timer.timer_advance_ns)
>  			kvm_wait_lapic_expire(vcpu, true);
>  		kvm_apic_inject_pending_timer_irqs(apic);
> @@ -1607,7 +1607,7 @@ static void start_sw_tscdeadline(struct kvm_lapic *apic)
>  		expire = ktime_sub_ns(expire, ktimer->timer_advance_ns);
>  		hrtimer_start(&ktimer->timer, expire, HRTIMER_MODE_ABS);
>  	} else
> -		apic_timer_expired(apic);
> +		apic_timer_expired(apic, false);
>  
>  	local_irq_restore(flags);
>  }
> @@ -1697,7 +1697,7 @@ static void start_sw_period(struct kvm_lapic *apic)
>  
>  	if (ktime_after(ktime_get(),
>  			apic->lapic_timer.target_expiration)) {
> -		apic_timer_expired(apic);
> +		apic_timer_expired(apic, false);
>  
>  		if (apic_lvtt_oneshot(apic))
>  			return;
> @@ -1759,7 +1759,7 @@ static bool start_hv_timer(struct kvm_lapic *apic)
>  		if (atomic_read(&ktimer->pending)) {
>  			cancel_hv_timer(apic);
>  		} else if (expired) {
> -			apic_timer_expired(apic);
> +			apic_timer_expired(apic, false);
>  			cancel_hv_timer(apic);
>  		}
>  	}
> @@ -1809,7 +1809,7 @@ void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu)
>  		goto out;
>  	WARN_ON(swait_active(&vcpu->wq));
>  	cancel_hv_timer(apic);
> -	apic_timer_expired(apic);
> +	apic_timer_expired(apic, false);
>  
>  	if (apic_lvtt_period(apic) && apic->lapic_timer.period) {
>  		advance_periodic_target_expiration(apic);
> @@ -2312,7 +2312,7 @@ static enum hrtimer_restart apic_timer_fn(struct hrtimer *data)
>  	struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
>  	struct kvm_lapic *apic = container_of(ktimer, struct kvm_lapic, lapic_timer);
>  
> -	apic_timer_expired(apic);
> +	apic_timer_expired(apic, true);
>  
>  	if (lapic_is_periodic(apic)) {
>  		advance_periodic_target_expiration(apic);
>