Re: [Xen-devel] irq_guest_eoi_timer interaction with MSI

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 14.11.08 10:42 >>>
>On 14/11/08 09:28, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:
>
>>> So we'd add a pirq-indexed bitmap to mitigate that. Whether we use
>>> PHYSDEVOP_irq_eoi or EVTCHNOP_unmask, we need a new shared-memory bitmap,
>>> right? Might as well use irq_eoi and index by pirq, I'd say.
>> 
>> Hmm, I'm still not convinced: With what you propose, it's unclear to me who
>> would when clear the bit in that bitmap for the 'temporarily masked' case.
>> Anyway, unless you get to implement your version earlier (and thus
>> convince me that things will work out correctly), I'll try to get implemented
>> what I would think should be appropriate here once I find time to do so.
>
>Perhaps if we go your route we can make PHYSDEVOP_irq_eoi obsolete? It's
>only really called where we also do an unmask, and it's pointless to have
>two hypercalls where one will do. So a guest that detects the new bitmap
>could then know it only needs to unmask-by-hypercall, rather than use
>PHYSDEVOP_irq_eoi at all.

Yes, folding the potentially two hypercalls into one was a parallel idea.

Jan


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