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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: Vlad Zolotarov <vladz@cloudius-systems.com>, kvm@vger.kernel.org
Subject: Re: virtio specification: OOO completion of the xmit buffers in the networking device
Date: Wed, 4 Jun 2014 21:54:17 +0300	[thread overview]
Message-ID: <20140604185417.GD11756@redhat.com> (raw)
In-Reply-To: <871tv549gu.fsf@rustcorp.com.au>

On Wed, Jun 04, 2014 at 01:22:49PM +0930, Rusty Russell wrote:
> Vlad Zolotarov <vladz@cloudius-systems.com> writes:
> > Rusty, hi!
> > I'd like to ask for a small clarification about the virtio spec.
> > The virtio specification is put the way that it allows the out-of-order 
> > completions in general. Although it states that it's mostly relevant to 
> > the virtio-blk it doesn't explicitly bans it for virtio networking 
> > devices (for generality?).
> 
> Indeed.
> 
> > (AFAICS the current virtio HV implementations make sure there is no OOO 
> > Tx buffers completions).
> >
> > I wonder if this feature (OOO Tx buffers completions) seems practical to 
> > u and if not can I hope that it could be clearly stated in the future 
> > virtio specification releases that it's forbidden?
> 
> Are you sure that vhost-net doesn't allow async completion already?
> I can't immediately see why it can't happen, but MST is CC'd.
> 
> Cheers,
> Rusty.

vhost-net completes in order but this is just an implementation detail:
this allows keeping a couple of indexes for head/tail instead
of tracking requests individually.

We can change this in the future and
guest must allow out of order completions.

-- 
MST

      reply	other threads:[~2014-06-04 18:53 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-02 13:33 virtio specification: OOO completion of the xmit buffers in the networking device Vlad Zolotarov
2014-06-04  3:52 ` Rusty Russell
2014-06-04 18:54   ` Michael S. Tsirkin [this message]

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