From: "Michael S. Tsirkin" <mst@redhat.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: avi@redhat.com, gleb@redhat.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 0/6] kvm: level irqfd support
Date: Thu, 16 Aug 2012 15:53:37 +0300 [thread overview]
Message-ID: <20120816125337.GA21526@redhat.com> (raw)
In-Reply-To: <1345120492.4683.467.camel@ul30vt.home>
On Thu, Aug 16, 2012 at 06:34:52AM -0600, Alex Williamson wrote:
> > > > So I'm inclined to say source IDs are a requirement for shared
> > > > interrupts.
> > >
> > > Can yo show a specific example that breaks?
> > > I don't think it can exist.
> >
> > Only the edge vs level interaction if we define the policy above for
> > de-assert.
>
> Hmm, there is still a race w/ level. If we have a number of
> level-deassert-irqfds making use of the same gsi and sourceid and we
> individually de-assert and notify, a re-assert could get lost if it
> happens before all of the de-asserts have finished.
> We either need
> separate sourceids or we need to do a single de-assert followed by
> multiple notifies. Right? Thanks,
>
> Alex
Good catch, I agree, we need a single deassert.
I think I see how to implement this without reference counting and
stuff. So we chain all auto-deassert irqfds for a given GSI together,
and have a single ack notifier. When list becomes empty, remove the ack
notifier.
It's actually a good thing to do anyway, too many ack notifiers
would slow unrelated GSIs down.
--
MST
next prev parent reply other threads:[~2012-08-16 12:52 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-10 22:37 [PATCH v8 0/6] kvm: level irqfd support Alex Williamson
2012-08-10 22:37 ` [PATCH v8 1/6] kvm: Allow filtering of acked irqs Alex Williamson
2012-08-15 12:27 ` Michael S. Tsirkin
2012-08-15 16:47 ` Alex Williamson
2012-08-15 19:24 ` Michael S. Tsirkin
2012-08-10 22:37 ` [PATCH v8 2/6] kvm: Expose IRQ source IDs to userspace Alex Williamson
2012-08-15 12:59 ` Michael S. Tsirkin
2012-08-15 17:05 ` Alex Williamson
2012-08-10 22:37 ` [PATCH v8 3/6] kvm: Add IRQ source ID option to KVM_IRQFD Alex Williamson
2012-08-15 13:49 ` Michael S. Tsirkin
2012-08-15 17:08 ` Alex Williamson
2012-08-10 22:37 ` [PATCH v8 4/6] kvm: Add assert-only " Alex Williamson
2012-08-10 22:37 ` [PATCH v8 5/6] kvm: KVM_IRQ_ACKFD Alex Williamson
2012-08-15 14:05 ` Michael S. Tsirkin
2012-08-15 17:17 ` Alex Williamson
2012-08-10 22:37 ` [PATCH v8 6/6] kvm: Add de-assert option to KVM_IRQ_ACKFD Alex Williamson
2012-08-15 14:11 ` Michael S. Tsirkin
2012-08-15 17:24 ` Alex Williamson
2012-08-15 14:28 ` [PATCH v8 0/6] kvm: level irqfd support Michael S. Tsirkin
2012-08-15 17:36 ` Alex Williamson
2012-08-15 19:22 ` Michael S. Tsirkin
2012-08-15 19:59 ` Alex Williamson
2012-08-16 12:34 ` Alex Williamson
2012-08-16 12:53 ` Michael S. Tsirkin [this message]
2012-08-16 16:29 ` Avi Kivity
2012-08-16 16:36 ` Michael S. Tsirkin
2012-08-16 16:39 ` Avi Kivity
2012-08-16 16:54 ` Michael S. Tsirkin
2012-08-16 16:54 ` Avi Kivity
2012-08-16 17:01 ` Michael S. Tsirkin
2012-08-16 16:37 ` Alex Williamson
2012-08-16 16:32 ` Avi Kivity
2012-08-16 16:45 ` Alex Williamson
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