Re: [Xen-devel] [PATCH v4 11/17] xen/arm: ITS: Add GICR register emulation

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Sat, 2015-07-11 at 20:25 +0200, Julien Grall wrote:
> Hi,
> 
> On 10/07/2015 17:10, Ian Campbell wrote:
> > Extra space after the &.
> >> @@ -694,6 +755,14 @@ static int vgic_v3_distr_mmio_read(struct vcpu *v, 
> >> mmio_info_t *info)
> >>           *r = ((ncpus - 1) << GICD_TYPE_CPUS_SHIFT |
> >>                 DIV_ROUND_UP(v->domain->arch.vgic.nr_spis, 32));
> >>
> >> +        if ( gic_lpi_supported() )
> >> +        {
> >> +            irq_bits = gic_nr_id_bits();
> >> +            *r |= GICD_TYPE_LPIS;
> >> +        }
> >> +        else
> >> +            irq_bits = get_count_order(vgic_num_irqs(v->domain));
> >
> > I think gic_nr_id_bits should return the correct thing whether or not
> > LPIs are supported, i.e.
> >
> >          if ( gic_lpi_supported() )
> >              *r |= GICD_TYPE_LPIS;
> >          irq_bits = gic_nr_id_bits();
> >
> > should be sufficient.
> 
> Well no. The field GICD_TYPER.IDbits represents the number of bits 
> supported for the interrupt identifier.
> 
> The guest may have a different number of IDbits than the hardware which 
> could be higher (for instance a guest where emulated SPI is supported).

Yes, I really meant vgic_nr_id_bits(), which might for the dom0 case end
up returning something related to the h/w value from the appropriate
vgic hw cfg struct.



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