From: Alex Williamson <alex.williamson@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: avi@redhat.com, gleb@redhat.com, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 6/6] kvm: Add de-assert option to KVM_IRQ_ACKFD
Date: Wed, 15 Aug 2012 11:24:03 -0600 [thread overview]
Message-ID: <1345051443.4683.425.camel@ul30vt.home> (raw)
In-Reply-To: <20120815141113.GE3068@redhat.com>
On Wed, 2012-08-15 at 17:11 +0300, Michael S. Tsirkin wrote:
> On Fri, Aug 10, 2012 at 04:37:56PM -0600, Alex Williamson wrote:
> > It's likely (vfio) that one of the reasons to watch for an IRQ ACK
> > is to de-assert and re-enable an interrupt. As the IRQ ACK notfier
> > is already watching a GSI for an IRQ source ID we can easily couple
> > these together.
> >
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
>
> This source id is required the only way to assert
> in the 1st place is with irqfd.
ioctl(fd, KVM_IRQ_ACKFD, kvm_irq_ackfd.{flags = 0, fd = eventfd, gsi = $GSI});
ioctl(fd, KVM_IRQ_LINE, kvm_irq_level.{irq = $GSI, level = 1);
/* eventfd notification */
ioctl(fd, KVM_IRQ_LINE, kvm_irq_level.{irq = $GSI, level = 0);
> So why is this an ackfd flag and not an irqfd flag?
> I am guessing because this way you do not need
> an extra ack notifier, but isn't this an internal
> optimization leaking out to userspace?
If irqfd were to setup it's own irq ack notifier for de-assert, we can
guarantee the ordering of de-assert vs eventfd trigger. So, whoever
does one, needs to do both. Thanks,
Alex
next prev parent reply other threads:[~2012-08-15 17:24 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 [this message]
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
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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