Re: [Xen-devel] [XenARM] XEN tools for ARM with Virtualization Extensions

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 10 July 2013 20:38, Eric Trudeau <etrudeau@xxxxxxxxxxxx> wrote:
>> > What functions should I call to implement  XEN_DOMCTL_bind_pt_irq on
>> ARM?
>>
>> There's a function like route_irq_to_guest which we use to route IRQs to
>> dom0 during boot. In principal that could also be used to reroute an IRQ
>> to a guest, but I'm not sure how it will interact with the reassignment,
>> since in your case the IRQ starts off bound to dom0. Hopefully it's just
>> a small change to make it work for this case.
>>
>
> In gic_route_irq_to_guest(), there is this call:
>     gic_set_irq_properties(irq->irq, level, 1u << smp_processor_id(), 0xa0);
>
> I believe this will mean all IRQs will be routed on the current processor.
> I believe this is PCPU0 when the dom0 device tree is being parsed.
> When the PHYSDEVOP_map_pirq call is handled by the Hypervisor, the PCPU
> may be any of the processors.
> Is there a reason when we only route the IRQs for Dom0 to one PCPU?
> If only one is allowed, should it be PCPU0?

I don't see any particular reason to route the PIRQs on only PCPU0.
I think it's because Xen only routes SPIs to VCPU0, which is mostly
running on PCPU0.

The best solution is routing the PIRQ on the PCPU which is running the VCPU.

--
Julien Grall

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