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, jan.kiszka@siemens.com
Subject: Re: [PATCH v7 2/2] kvm: KVM_EOIFD, an eventfd for EOIs
Date: Thu, 2 Aug 2012 11:42:52 +0300 [thread overview]
Message-ID: <20120802084252.GC24929@redhat.com> (raw)
In-Reply-To: <1343697135.8073.245.camel@ul30vt>
On Mon, Jul 30, 2012 at 07:12:15PM -0600, Alex Williamson wrote:
> > > > > > > kvm_eoifd.fd specifies the eventfd used for
> > > > > > > +notification. KVM_EOIFD_FLAG_DEASSIGN is used to de-assign an eoifd
> > > > > > > +once assigned. KVM_EOIFD also requires additional bits set in
> > > > > > > +kvm_eoifd.flags to bind to the proper interrupt line. The
> > > > > > > +KVM_EOIFD_FLAG_LEVEL_IRQFD indicates that kvm_eoifd.key is provided
> > > > > > > +and is a key from a level triggered interrupt (configured from
> > > > > > > +KVM_IRQFD using KVM_IRQFD_FLAG_LEVEL). The EOI notification is bound
> > > > > > > +to the same GSI and irqchip input as the irqfd. Both kvm_eoifd.key
> > > > > > > +and KVM_EOIFD_FLAG_LEVEL_IRQFD must be specified on assignment and
> > > > > > > +de-assignment of KVM_EOIFD. A level irqfd may only be bound to a
> > > > > > > +single eoifd. KVM_CAP_EOIFD_LEVEL_IRQFD indicates support of
> > > > > > > +KVM_EOIFD_FLAG_LEVEL_IRQFD.
> > > > > > >
> > > > > >
> > > > > > Hmm returning the key means we'll need to keep refcounting for source
> > > > > > IDs around forever. I liked passing the fd better: make implementation
> > > > > > match interface and not the other way around.
> > > > >
> > > > > False, a source ID has a finite lifecycle. The fd approach was broken.
> > > > > Holding the irqfd context imposed too many dependencies between eoifd
> > > > > and irqfd necessitating things like one interface disabling another. I
> > > > > thoroughly disagree with that approach.
> > > >
> > > > You keep saying this but it is still true: once irqfd
> > > > is closed eoifd does not get any more interrupts.
> > >
> > > How does that matter?
> >
> > Well if it does not get events it is disabled.
> > so you have one ifc disabling another, anyway.
>
> And a level irqfd without an eoifd can never be de-asserted. Either we
> make modular components, assemble them to do useful work, and
> disassemble them independently so they can be used by future interfaces
> or we bundle eoifd as just an option of irqfd. Which is it gonna be?
I'm fine just making it an option. I think Gleb wanted a separate
EOIFD to handle timedrift but it later seemed that eventfd is not
suitable for that?
--
MST
next prev parent reply other threads:[~2012-08-02 8:42 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-24 20:43 [PATCH v7 0/2] kvm: level irqfd and new eoifd Alex Williamson
2012-07-24 20:43 ` [PATCH v7 1/2] kvm: Extend irqfd to support level interrupts Alex Williamson
2012-07-29 15:01 ` Michael S. Tsirkin
2012-07-30 16:06 ` Alex Williamson
2012-07-24 20:43 ` [PATCH v7 2/2] kvm: KVM_EOIFD, an eventfd for EOIs Alex Williamson
2012-07-29 14:54 ` Michael S. Tsirkin
2012-07-30 16:22 ` Alex Williamson
2012-07-31 0:01 ` Michael S. Tsirkin
2012-07-31 0:26 ` Alex Williamson
2012-07-31 0:36 ` Michael S. Tsirkin
2012-07-31 1:12 ` Alex Williamson
2012-08-01 19:06 ` Alex Williamson
2012-08-12 7:49 ` Michael S. Tsirkin
2012-08-13 16:48 ` Alex Williamson
2012-08-13 16:59 ` Michael S. Tsirkin
2012-08-13 18:17 ` Alex Williamson
2012-08-13 19:50 ` Michael S. Tsirkin
2012-08-13 20:48 ` Alex Williamson
2012-08-13 21:50 ` Michael S. Tsirkin
2012-08-13 22:22 ` Alex Williamson
2012-08-13 22:52 ` Michael S. Tsirkin
2012-08-14 10:10 ` Gleb Natapov
2012-08-14 10:13 ` Gleb Natapov
2012-08-02 8:42 ` Michael S. Tsirkin [this message]
2012-08-06 10:17 ` Avi Kivity
2012-08-06 10:38 ` Avi Kivity
2012-08-06 10:40 ` Avi Kivity
2012-08-09 19:26 ` Alex Williamson
2012-08-12 8:36 ` Avi Kivity
2012-08-13 21:34 ` Alex Williamson
2012-08-13 22:06 ` Michael S. Tsirkin
2012-08-13 22:41 ` Alex Williamson
2012-08-13 23:00 ` Michael S. Tsirkin
2012-08-14 3:09 ` Alex Williamson
2012-08-14 8:35 ` Michael S. Tsirkin
2012-08-14 21:28 ` Alex Williamson
2012-08-12 9:33 ` Michael S. Tsirkin
2012-08-13 21:23 ` Alex Williamson
2012-08-13 22:00 ` Michael S. Tsirkin
2012-08-14 12:35 ` Avi Kivity
2012-08-14 14:50 ` Michael S. Tsirkin
2012-08-14 22:01 ` Alex Williamson
2012-08-14 23:04 ` Michael S. Tsirkin
2012-08-14 23:26 ` Alex Williamson
2012-08-15 13:09 ` Avi Kivity
2012-08-12 7:53 ` Michael S. Tsirkin
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