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, 6 Jun 2014, Ian Campbell wrote:
> On Thu, 2014-05-22 at 13:32 +0100, Stefano Stabellini wrote:
> > @@ -626,19 +644,36 @@ static void gic_update_one_lr(struct vcpu *v, int i)
> >      ASSERT(spin_is_locked(&v->arch.vgic.lock));
> >  
> >      lr = GICH[GICH_LR + i];
> > -    if ( !(lr & (GICH_LR_PENDING|GICH_LR_ACTIVE)) )
> > +    irq = (lr >> GICH_LR_VIRTUAL_SHIFT) & GICH_LR_VIRTUAL_MASK;
> > +    p = irq_to_pending(v, irq);
> > +    if ( lr & GICH_LR_ACTIVE )
> >      {
> > +        if ( test_bit(GIC_IRQ_GUEST_ENABLED, &p->status) &&
> > +             test_and_clear_bit(GIC_IRQ_GUEST_QUEUED, &p->status) )
> > +        {
> > +            if ( p->desc == NULL )
> > +                GICH[GICH_LR + i] = lr | GICH_LR_PENDING;
> > +            else
> > +                gdprintk(XENLOG_WARNING, "unable to inject hw irq=%d into 
> > d%dv%d: already active in LR%d\n",
> > +                         irq, v->domain->domain_id, v->vcpu_id, i);
> 
> How common is this? Or should it never actually happen in reality?

It should never happen


> > +        }
> > +    } else if ( lr & GICH_LR_PENDING ) {
> > +        int q __attribute__ ((unused)) = 
> > test_and_clear_bit(GIC_IRQ_GUEST_QUEUED, &p->status);
> > +#ifdef GIC_DEBUG
> > +        if ( q )
> 
>          if ( test_and_clear_bit(GIC_IRQ_GUEST_QUEUED, &p->status) ) 
> #ifdef GIC_DEBUG
> > +            gdprintk(XENLOG_DEBUG, "trying to inject irq=%d into d%dv%d, 
> > when it is already pending in LR%d\n",
> > +                    irq, v->domain->domain_id, v->vcpu_id, i);
> #else
>                ; /* Nothing to do */
> #endif
> 
> would be nicer than attribute unused IMHO.
> 
> As it's a XENLOG_DEBUG this wouldn't be all that bad by default BTW,
> given that the already active case isn't even conditional.

This case can actually happen though

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