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Re: [Xen-devel] [PATCH for-4.6 3/4] xen/arm: vgic: notice if the vIRQ is not allocated when the guest enable it

Hi Ian,

On 14/01/15 12:42, Julien Grall wrote:
> On 14/01/15 12:28, Ian Campbell wrote:
>> On Tue, 2015-01-13 at 20:33 +0000, Julien Grall wrote:
>>> On 13/01/15 15:55, Ian Campbell wrote:
>>>> On Fri, 2014-12-12 at 14:43 +0000, Julien Grall wrote:
>>>>> This help for guest interrupts debugging. If the vIRQ is not allocate,
>>>>> this means that nothing is wired to it.
>>>> Should we short circuit the rest of the enable operation for this IRQ
>>>> then? i.e. implement such writes as ignored, e.g. not reflect it in
>>>> reads of ISENABLER etc.
>>>> What (if anything) does the GIC spec have to say on the subject?
>>> "A register bit corresponding to an unimplemented interrupt is RAZ/WI."
>>> The goal of this print was mostly for debugging physical IRQ routed to a
>>> guest.
>>> I could extend to ignore write to any register that should be RAZ/WI for
>>> this specific interrupt.
>> Since those are the defined semantics I think that is the best thing to
>> do.
> Ok. I will look at it to see how we can implement it.

So I looked to the code. It may need some rework to effectively
implement most of registers bits RAZ/WI when the interrupt doesn't exist.

As this series is required for the ACPI series, I suggest to defer this
work in a follow-up series.


Julien Grall

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