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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Sun, 25 May 2014, Julien Grall wrote:
> 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?

done


> With this change:
> 
> Acked-by: Julien Grall <julien.grall@xxxxxxxxxx>
> 
> Regards,
> 
> -- 
> Julien Grall
> 

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