Re: [PATCH stable] KVM: x86: Fix lost interrupt on irr_pending race

[Paolo Bonzini <pbonzini@redhat.com>]

On 28/04/2015 18:24, Saso Slavicic wrote:
> This will probably end up in RHEL6 sooner or later (but probably not before
> 6.7)?
> As I like to experiment a bit, would this patch do for -2.6.32-504.12.2.el6
> kernel? The code in that function is somewhat different...
> 
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -230,8 +230,13 @@
>  
>  static inline int apic_test_and_set_irr(int vec, struct kvm_lapic *apic)
>  {
> +	int ret = apic_test_and_set_vector(vec, apic->regs + APIC_IRR);
> +	/*
> +	 * irr_pending must be true if any interrupt is pending; set it
> after
> +	 * APIC_IRR to avoid race with apic_clear_irr
> +	 */
>  	apic->irr_pending = true;
> -	return apic_test_and_set_vector(vec, apic->regs + APIC_IRR);
> +	return ret;
>  }
>  
>  static inline int apic_search_irr(struct kvm_lapic *apic)
> 
> 
> Regards,

Yes, this exact same patch is brewing in the RHEL6.7 internal trees...

See https://bugzilla.redhat.com/show_bug.cgi?id=1213741

Paolo