From: Anthony Liguori <anthony@codemonkey.ws>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
virtualization@lists.linux-foundation.org, qemu-devel@nongnu.org,
kvm@vger.kernel.org
Subject: Re: question on virtio
Date: Wed, 05 May 2010 14:40:15 -0500 [thread overview]
Message-ID: <4BE1C99F.6050205@codemonkey.ws> (raw)
In-Reply-To: <20100505110947.GA27872@redhat.com>
On 05/05/2010 06:09 AM, Michael S. Tsirkin wrote:
> Hi!
> I see this in virtio_ring.c:
>
> /* Put entry in available array (but don't update avail->idx *
> until they do sync). */
>
> Why is it done this way?
> It seems that updating the index straight away would be simpler, while
> this might allow the host to specilatively look up the buffer and handle
> it, without waiting for the kick.
>
It should be okay as long as you don't update idx for partial vectors.
Regards,
Anthony Liguori
WARNING: multiple messages have this Message-ID (diff)
From: Anthony Liguori <anthony@codemonkey.ws>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
qemu-devel@nongnu.org, kvm@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: [Qemu-devel] Re: question on virtio
Date: Wed, 05 May 2010 14:40:15 -0500 [thread overview]
Message-ID: <4BE1C99F.6050205@codemonkey.ws> (raw)
In-Reply-To: <20100505110947.GA27872@redhat.com>
On 05/05/2010 06:09 AM, Michael S. Tsirkin wrote:
> Hi!
> I see this in virtio_ring.c:
>
> /* Put entry in available array (but don't update avail->idx *
> until they do sync). */
>
> Why is it done this way?
> It seems that updating the index straight away would be simpler, while
> this might allow the host to specilatively look up the buffer and handle
> it, without waiting for the kick.
>
It should be okay as long as you don't update idx for partial vectors.
Regards,
Anthony Liguori
next prev parent reply other threads:[~2010-05-05 19:40 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-05 11:09 question on virtio Michael S. Tsirkin
2010-05-05 11:09 ` [Qemu-devel] " Michael S. Tsirkin
2010-05-05 19:40 ` Anthony Liguori [this message]
2010-05-05 19:40 ` [Qemu-devel] " Anthony Liguori
2010-05-05 20:59 ` Michael S. Tsirkin
2010-05-05 20:59 ` Michael S. Tsirkin
2010-05-05 20:59 ` [Qemu-devel] " Michael S. Tsirkin
2010-05-05 19:40 ` Anthony Liguori
2010-05-06 1:32 ` Rusty Russell
2010-05-06 1:32 ` [Qemu-devel] " Rusty Russell
2010-05-06 1:32 ` Rusty Russell
2010-05-06 16:43 ` [Qemu-devel] " Jamie Lokier
2010-05-06 16:43 ` Jamie Lokier
2010-05-06 16:43 ` Jamie Lokier
-- strict thread matches above, loose matches on Subject: below --
2010-05-05 11:09 Michael S. Tsirkin
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