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SubjectRe: [PATCH v2 6/6] kvm: Level IRQ de-assert for KVM_IRQFD
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On Thu, 2012-06-28 at 15:59 +0300, Avi Kivity wrote:
> On 06/27/2012 08:10 AM, Alex Williamson wrote:
> > This is an alternate level irqfd de-assert mode that's potentially
> > useful for emulated drivers. It's included here to show how easy it
> > is to implement with the new level irqfd and eoifd support. It's
> > possible this mode might also prove interesting for device-assignment
> > where we inject via level irqfd, receive an EOI (w/o de-assert), and
> > use the level de-assert irqfd here.
>
> This use case is racy. The guest driver will have shut down the
> interrupt before EOI, but with what you describe, it will fire again
> until the eoifd/deassertfd sequence completes.

Hmm, that's a good point. We'll continue asserting the interrupt in the
indeterminate gap between eoifd and de-assert-irqfd which could fire
enough times for the guest to disable it. Oh well. Thanks,

Alex



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