From: Juan Quintela <quintela@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org, Jes.Sorensen@redhat.com,
Alex Williamson <alex.williamson@redhat.com>,
agraf@suse.de, stefanha@linux.vnet.ibm.com
Subject: [Qemu-devel] Re: [PATCH] e1000: clear EOP for multi-buffer descriptors
Date: Mon, 07 Feb 2011 13:32:53 +0100 [thread overview]
Message-ID: <m3hbcgautm.fsf@trasno.org> (raw)
In-Reply-To: <20110207123026.GA18830@redhat.com> (Michael S. Tsirkin's message of "Mon, 7 Feb 2011 14:30:26 +0200")
"Michael S. Tsirkin" <mst@redhat.com> wrote:
> The e1000 spec says: if software statically allocates
> buffers, and uses memory read to check for completed descriptors, it
> simply has to zero the status byte in the descriptor to make it ready
> for reuse by hardware. This is not a hardware requirement (moving the
> hardware tail pointer is), but is necessary for performing an in–memory
> scan.
>
> Thus the guest does not have to clear the status byte. In case it
> doesn't we need to clear EOP for all descriptors
> except the last. While I don't know of any such guests,
> it's probably a good idea to stick to the spec.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Reported-by: Juan Quintela <quintela@redhat.com>
reviewed-by: Juan Quintela <quintela@redhat.com>
next prev parent reply other threads:[~2011-02-07 12:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-07 12:30 [Qemu-devel] [PATCH] e1000: clear EOP for multi-buffer descriptors Michael S. Tsirkin
2011-02-07 12:32 ` Juan Quintela [this message]
2011-02-07 13:36 ` [Qemu-devel] " Stefan Hajnoczi
2011-02-07 15:37 ` Alex Williamson
2011-02-07 17:59 ` Alex Williamson
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