Re: [Xen-devel] [PATCH v2] xen/arm: gicv2: Export GICv2m register frames to domain0 by device tree

[Julien Grall <julien.grall@xxxxxxx>]

On 27/04/2016 07:05, Wei Chen wrote:
> Hi Julien,
Hi Wei,

> On 26 April 2016 at 18:49, Julien Grall <julien.grall@xxxxxxx> wrote:
> > On 25/04/2016 10:39, Wei Chen wrote:
> > > +                   d->domain_id);
> > > +            return ret;
> > > +        }
> > > +
> > > +        /*
> > > +         * Map all SPIs that are allocated to MSIs for the frame to the
> > > +         * domain.
> > > +         */
> > > +        for ( spi = v2m_data->spi_start;
> > > +              spi < (v2m_data->spi_start + v2m_data->nr_spis); spi++ )
> > > +        {
> > > +            /*
> > > +             * MSIs are always edge-triggered. Configure the associated
> > > SPIs
> > > +             * to be edge-rising.
> >
> > How did you find that SPIs should be configured edge-rising?
> Before route_irq_to_guest, the SPI must be configured. I found Linux
> v2m driver set
> the SPI type to edge-rising, so I set edge-rising as v2m SPI default
> type here too.
Well, Linux did it for a good reason (i.e based on a spec). We are 
trying in Xen to document piece of code which may not be 
straight-forward to deduce.
In this case, the IRQ is configured edge-rising because this is the only 
edge type supported by SPIs. I would expand the second sentence of the 
comment to explain that.
Regards,

--
Julien Grall

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