Re: [Xen-devel] [PATCH v3 08/24] xen/arm: Allow virq != irq

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Tue, 2015-01-13 at 14:25 +0000, Julien Grall wrote:
> Actually Xen is assuming that the virtual IRQ will always be the same as IRQ.

s/Actually/Currently/?

> Modify route_guest_irq to take the virtual IRQ in parameter and let Xen
> assign a different IRQ number.

I think I must be misunderstanding this, but if route_guest_irq is
taking the vIRQ as a parameter then why does it then need to assign a
different IRQ number?

Oh, did you mean allowing the *caller* to setup a non-1:1 mapping
perhaps? I think s/and let Xen assign/which allows Xen to.../ might be
closer to that meaning if that's the intention?

>  Also store the vIRQ in the desc action to
> easily retrieve easily the IRQ target when we need to inject the interrupt.

-ETooManyEasilys ;-)

(I think you want to drop the second one)

> As DOM0 will get most the devices, the vIRQ is equal to the IRQ in that case.

Am I correct that after this patch all callers still pass irq==virq to
the new function?

> At the same time modify the behavior of irq_get_domain. The function now
> assumes that the irq_desc belongs to an IRQ assigned to a guest.

s/assumes/requires/?

>  
>      action = xmalloc(struct irqaction);
> -    if (!action)
> +    if ( !action )
> +        return -ENOMEM;
> +
> +    info = xmalloc(struct irq_guest);

FWIW you might (subject to sizing/alignment needs) be able to do
        action = _xmalloc(sizeof(struct irqaction) + sizeof(struct irq_guest);
        info = (sturct irq_guest *)(action + 1);

which would save some memory overhead for free pointers etc and allow
you to avoid manually managing the info.

You probably won't like that though, so feel free to ignore.

Ian.


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