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

Michael S. Tsirkin
2012-09-05T15:12:29Z

On Wed, Sep 05, 2012 at 05:59:46PM +0300, Avi Kivity wrote:
> 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.

I agree. All resample irqfds are deasserted at the same time,
tracking them separately gets us nothing.

> Plus I'd like to
> fix the theoretical bug even if it doesn't bite in practice.
>

I'm not sure what the bug is, for edge, and how a separate ID fixes it.
Could you clarify?

>
> --
> error compiling committee.c: too many arguments to function