Re: [PATCH v9 1/2] kvm: Use a reserved IRQ source ID for irqfd

Avi Kivity
2012-09-05T14:59:50Z

On 09/05/2012 05:51 PM, Michael S. Tsirkin wrote:
> On Wed, Sep 05, 2012 at 05:35:43PM +0300, Avi Kivity wrote:
>> On 08/22/2012 03:41 AM, Michael S. Tsirkin wrote:
>> >>
>> >> I assumed you were pointing out the level vs edge interaction. If we
>> >> call that a userspace bug, I can just drop this. Thanks,
>> >>
>> >> Alex
>> >
>> > level is userspace bug I think :)
>>
>> I don't see how it's a bug. Suppose we have a vfio device that shares a
>> gsi with an emulated device. The emulated device naturally uses
>> KVM_IRQ_LINE (it has no need to re-sample on ADN), while vfio naturally
>> has to use irqfd.
>
> Absolutely. But vfio needs to use irqfd with the new flag.
> Using existing irqfd for level is a bug.

I see we're not reusing this irq source id for level irqfd. But I think
we should, there's no need for per-gsi irq source id. Plus I'd like to
fix the theoretical bug even if it doesn't bite in practice.

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