Re: [PATCHv4 3/5] kvm: host side for eoi optimization

[Gleb Natapov <gleb@redhat.com>]

On Wed, May 16, 2012 at 10:07:58PM +0300, Michael S. Tsirkin wrote:
> > This code is reached from kvm_cpu_get_interrupt(), but this function will
> > not be called in above scenario.
> 
> I think I see. So this shall fix it also makes code cleaner
> (no -2 hack). Right? kvm_apic_has_interrupt is called correct?
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index b4f7013..5a38e34 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1273,8 +1273,12 @@ int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu)
>  	highest_irr = apic_find_highest_irr(apic);
>  	if (highest_irr == -1)
>  		return -1;
> -	if (((highest_irr & 0xF0) <= apic_get_reg(apic, APIC_PROCPRI)))
> -		return -2;
> +	/* Detect interrupt nesting and disable EOI optimization */
> +	if ((highest_irr & 0xF0) <= apic_get_reg(apic, APIC_PROCPRI)) {
> +		if (pv_eoi_enabled(vcpu))
> +			pv_eoi_clr_pending(vcpu);
> +		return -1;
> +	}
>  	return highest_irr;
>  }
>  
I do not like it. kvm_apic_has_interrupt() does not suppose to mutate
state.

> @@ -1306,10 +1310,6 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu)
>  	int vector = kvm_apic_has_interrupt(vcpu);
>  	struct kvm_lapic *apic = vcpu->arch.apic;
>  
> -	/* Detect interrupt nesting and disable EOI optimization */
> -	if (pv_eoi_enabled(vcpu) && vector == -2)
> -		pv_eoi_clr_pending(vcpu);
> -
>  	if (vector < 0)
>  		return -1;
>  

--
			Gleb.