Re: [PATCH] If interrupt injection is not possible do not scan IRR.

[Avi Kivity <avi@redhat.com>]

Gleb Natapov wrote:
> Forget to remove debug output before submitting. Resending.
>
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
> index 1ccb50c..d32ceac 100644
> --- a/arch/x86/kvm/i8259.c
> +++ b/arch/x86/kvm/i8259.c
> @@ -218,6 +218,11 @@ int kvm_pic_read_irq(struct kvm *kvm)
>  	struct kvm_pic *s = pic_irqchip(kvm);
>  
>  	pic_lock(s);
> +	if (!s->output) {
> +		pic_unlock(s);
> +		return -1;
> +	}
> +	s->output = 0;
>  	irq = pic_get_irq(&s->pics[0]);
>  	if (irq >= 0) {
>  		pic_intack(&s->pics[0], irq);
> diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c
> index 96dfbb6..e93405a 100644
> --- a/arch/x86/kvm/irq.c
> +++ b/arch/x86/kvm/irq.c
> @@ -78,7 +78,6 @@ int kvm_cpu_get_interrupt(struct kvm_vcpu *v)
>  	if (vector == -1) {
>  		if (kvm_apic_accept_pic_intr(v)) {
>  			s = pic_irqchip(v->kvm);
> -			s->output = 0;		/* PIC */
>  			vector = kvm_pic_read_irq(v->kvm);
>  		}
>  	}
>   

Please split into a different patch.  Even though it is a lot simpler, 
it contains non-local changes and is therefore relatively dangerous.

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 44e87a5..854e8c9 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3174,10 +3174,10 @@ static void inject_pending_irq(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>  			vcpu->arch.nmi_injected = true;
>  			kvm_x86_ops->set_nmi(vcpu);
>  		}
> -	} else if (kvm_cpu_has_interrupt(vcpu)) {
> -		if (kvm_x86_ops->interrupt_allowed(vcpu)) {
> -			kvm_queue_interrupt(vcpu, kvm_cpu_get_interrupt(vcpu),
> -					    false);
> +	} else if (kvm_x86_ops->interrupt_allowed(vcpu)) {
> +		int vec = kvm_cpu_get_interrupt(vcpu);
> +		if (vec != -1) {
> +			kvm_queue_interrupt(vcpu, vec, false);
>  			kvm_x86_ops->set_irq(vcpu);
>  		}
>  	}
>   

Again, I don't think this is a win.  Usually ->interrupts_allowed() == 
true so we'll execute the rest anyway.

Perhaps we could move the call to has_interrupt into get_interrupt.

-- 
error compiling committee.c: too many arguments to function