Messages in this thread | | | Date | Sun, 24 Jun 2012 18:49:38 +0300 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH 3/4] kvm: Extend irqfd to support level interrupts |
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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?
-- MST
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