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Re: [Xen-devel] [PATCH v3 13/24] xen/arm: Implement hypercall PHYSDEVOP_{, un}map_pirq

On 23/02/15 16:04, Ian Campbell wrote:
> On Mon, 2015-02-23 at 15:53 +0000, Julien Grall wrote:
>> Hi Ian,
>> On 23/02/15 15:28, Ian Campbell wrote:
>>> On Mon, 2015-02-23 at 09:33 +0000, Jan Beulich wrote:
>>>>>>> On 20.02.15 at 17:53, <ian.campbell@xxxxxxxxxx> wrote:
>>>>> Jan, do you have any feeling for how this is going to play out on x86
>>>>> with the vapic stuff?
>>>> The vapic logic shouldn't require any physdevop involvement, so if
>>>> I read right what you propose (not having such a requirement /
>>>> connection on ARM) either, I agree that a new domctl should be all
>>>> that's needed (if XEN_DOMCTL_{,un}bind_pt_irq can't be re-used).
>>> Actually, I think bind_pt_irq with a new PT_IRQ_TYPE_* would be a good
>>> option.
>>> An ARM SPI is a bit like an ISA IRQ, but not close enough to reuse IMHO
>>> (and the datatype would need widening).
>> We have to think about MSI and other type too...
>> In any case a DOMCTL is not suitable here because a guest kernel may
>> need to map/unmap IRQ too (think about ACPI or device passthrough).
> I don't follow, setting up device passthrough is very much a toolstack
> operation, isn't it? Where does the guest kernel get involved?

Sorry I meant the DOM0 kernel.

Not really. On platform device pass-through there is no way to know the
IRQ, so for now the routing is done by the toolstack.

But we could decide to implement a driver in DOM0 which will
unbind/bind/reset device. In this case it will require to
assign/deassign the IRQ from DOM0.

There is also the case of MSI.

> As for ACPI, I think dom0 propagating ACPI derived platform info to Xen
> should be handled differently (at the hypercall interface at least)
> separate from passthrough.

There is no difference between routing because of ACPI and/or because
pass-through. So this should be done the same way.


Julien Grall

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