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

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
+             * 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.


Julien Grall

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