Re: [Xen-devel] [GSoC-2019] About the crossbar and xen

[Julien Grall <julien.grall@xxxxxxx>]

On 7/11/19 1:50 PM, Denis Obrezkov wrote:
> Hi,
Hi,

> > > I am interested whether we should do something with omap5-wugen-mpu. I
> > > found that crossbar is connected to GIC. And on some schemes in trm it
> > > is connected via omap5-wugen-mpu. So, it is not clear for me whether it
> > > should be handled in xen.
I don't know much about omap5-wugen-mpu, so I will leave Hunyue and Iain 
to provide feedback here.

> >
> Also, I am interested in how to add the crossbar. I can see two options
> as we discussed earlier. The first option is to remove the crossbar but
> for me it might cause some problems since a guest might want to use it.
> The second option is to expose the crossbar and intercept all the calls
> to it. But the problem is that now xen supports only one
> interrupt-controller. And at the same time most of the SPI IRQs are
> mapped to the crossbar. So, when xen checks whether the main
> interrupt-controller is the same as the one to who external interrupts
> are mapped it fails.
> (xen/common/device_tree.c:dt_irq_translate()).
> And I don't think that I should change interrupt-parent option of
> devices to map them to the GIC because it is essentially the first
> option mentioned above. So, it seems that probably interrupt-parent
> finding decision logic should be changed a bit? Like to find a GIC node
> not in a direct interrupt-parent but transitively in one of ancestors:
>
> UART -> crossbar -> wugen -> GIC
>
> What do you think?
Have you looked at the series I pointed out earlier on? It extends Xen 
to support other interrupt controller parent.
Cheers,

--
Julien Grall

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