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    SubjectRe: [PATCH v2 0/6] kvm: level triggered irqfd support
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    On Wed, 2012-06-27 at 12:58 +0300, Michael S. Tsirkin wrote:
    > On Tue, Jun 26, 2012 at 11:08:52PM -0600, Alex Williamson wrote:
    > > Ok, let's see how this flies. I actually quite like this, so be
    > > gentle tearing it apart ;)
    > >
    > > I just couldn't bring myself to contort KVM_IRQFD into something
    > > that either sets up an irqfd or specifies a nearly unrelated EOI
    > > eventfd. The solution I've come up with, that also avoids exposing
    > > irq_source_ids to userspace, is to work through the irqfd. If we
    > > setup a level irqfd, we can optionally associate an eoifd with
    > > the same irq_source_id, by passing the irqfd. To do this, we just
    > > need to create a new reference counted object for the source ID
    > > so we don't run into problems ordering release. This means we
    > > end up with a KVM_EOIFD ioctl that has both general usefulness and
    > > can still tie into an irqfd.
    >
    > I like this API.

    Yay! I'll work on the bugs you've spotted.

    > > In patch 6/6 I also include an alternate de-assert mechanism via an
    > > irqfd with the opposite polarity. I don't currently use this, but
    > > it's pretty trivial and at least available in archives now.
    >
    > The nasty bit about that is that if you assert twice then
    > deassert once it's not clear what should happen.
    > But yea, it does not hurt to put them in the archives.

    It's no different that KVM_IRQ_LINE in that sense. It's not an
    accumulator, it's a set state. Thanks,

    Alex



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