On Sun, Jun 24, 2012 at 09:18:38AM -0600, Alex Williamson wrote:
> > > @@ -242,7 +299,8 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd
> > > *args)
> > >
> > > ret = 0;
> > > list_for_each_entry(tmp, &kvm->irqfds.items, list) {
> > > - if (irqfd->eventfd != tmp->eventfd)
> > > + if (irqfd->eventfd != tmp->eventfd &&
> > > + irqfd->eventfd != tmp->eoi_eventfd)
> > > continue;
> >
> > So we allow duplicate irqfd with differing eoifd (or edge-triggered and
> > level-triggered irqfd on the same context).
> >
> > (why the check in the first place? just so we can have a reliable
> > deassign or is it avoiding a deeper problem?)
>
> I really wasn't sure to what extent we wanted to prevent duplicates. My
> guess was that we don't want to have an irqfd trigger more than one
> thing. That seems to be what the current code does. I don't see any
> problems with multiple irqfds triggering the same eventfd though. I
> only added a test that a new irqfd can't be triggered by an existing
> eoi_eventfd as that could make a nasty loop.
How would that make a loop? You can have the same thing
with e.g. ioeventfd - why isn't it a problem there?
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