Re: [Xen-devel] [PATCH v5 3/6] xen/arm: observe itargets setting in vgic_enable_irqs and vgic_disable_irqs

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 12 Jun 2014, Julien Grall wrote:
> Hi Stefano,
> 
> On 11/06/14 17:27, Stefano Stabellini wrote:
> > +static struct vcpu *_vgic_get_target_vcpu(struct vcpu *v, unsigned int irq)
> 
> [..]
> 
> > +struct vcpu *vgic_get_target_vcpu(struct vcpu *v, unsigned int irq)
> 
> Can you add comment explaining what are the differences between these 2
> functions?
> 
> AFAIU, the first one is assuming the rank lock is taken. If so, I would add an
> ASSERT in it. I would avoid people misuse the 2 functions.

OK


> >       case GICD_ISPENDR ... GICD_ISPENDRN:
> > @@ -589,12 +625,23 @@ static int vgic_distr_mmio_write(struct vcpu *v,
> > mmio_info_t *info)
> >           if ( dabt.size != 0 && dabt.size != 2 ) goto bad_width;
> >           rank = vgic_rank_offset(v, 8, gicd_reg - GICD_ITARGETSR);
> >           if ( rank == NULL) goto write_ignore;
> > +        /* 8-bit vcpu mask for this domain */
> 
> BUG_ON(v->domain->max_vcpus > 8)? Just for enforcement.

OK


> > +        tr = (1 << v->domain->max_vcpus) - 1;
> > +        tr = tr | (tr << 8) | (tr << 16) | (tr << 24);
> > +        tr &= *r;
> > +        /* ignore zero writes */
> > +        if ( !tr )
> > +            goto write_ignore;
> > +        if ( dabt.size == 2 &&
> > +            !((tr & 0xff) && (tr & (0xff << 8)) &&
> > +             (tr & (0xff << 16)) && (tr & (0xff << 24))))
> > +            goto write_ignore;
> 
> I quite difficult to understand this check. Does this check is only for
> word-access?

The previous test covers byte-access after the change of the following
patch. I should move it to this patch to make it clearer.


> AFAIU, with byte-access it's possible to write 0 in itargets. For this case,
> the register may contain some 1 out of the byte offset.



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