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 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).


> >      return 0;
> >  }
> >  
> > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> > index af5cd6c..d597f63 100644
> > --- a/xen/arch/arm/domain_build.c
> > +++ b/xen/arch/arm/domain_build.c
> > @@ -1087,6 +1087,8 @@ int construct_dom0(struct domain *d)
> >      }
> >  #endif
> >  
> > +    vgic_vcpu_inject_irq(v, v->domain->arch.evtchn_irq);
> > +
> 
> I think it needs a comment in code.
> 
> Regards,
> 
> -- 
> Julien Grall
> 

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