Re: [Xen-devel] [PATCH v8 09/13] xen/arm: second irq injection while the first irq is still inflight

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 23/05/14 18:24, Stefano Stabellini wrote:
> On Fri, 23 May 2014, Julien Grall wrote:
> > On 05/23/2014 03:50 PM, Stefano Stabellini wrote:
> > > The following change works:
> > >
> > > diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
> > > index 33141e3..2a8456f 100644
> > > --- a/xen/arch/arm/domain.c
> > > +++ b/xen/arch/arm/domain.c
> > > @@ -644,6 +644,8 @@ int arch_set_info_guest(
> > >       else
> > >           set_bit(_VPF_down, &v->pause_flags);
> > >
> > > +    vgic_vcpu_inject_irq(v, v->domain->arch.evtchn_irq);
> > > +
> > This is racy, we may not clear the _VPF_down bit in this function
> > (depending if VGCF_online is set or not).
> >
> > Hopefully for ARM, libxc is setting this flags by default but it's not
> > always true.
> I could change the code to call vgic_vcpu_inject_irq only if VGCF_online
> is set, but on second thought, would the code actually be more readable?
> Or less error prone?
>
> I think that the original patch is better. At least the hack is present
> in a single very obvious place (vgic_enable_irqs).
Hmmm ... right. I know that this code will likely change (with GICv3 
support). Can you add a comment in the code explain this issue?
With this change:

Acked-by: Julien Grall <julien.grall@xxxxxxxxxx>

Regards,

--
Julien Grall

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