From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=47614 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PmQIM-0001R9-2G for qemu-devel@nongnu.org; Mon, 07 Feb 2011 07:34:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PmQIH-0006xV-HF for qemu-devel@nongnu.org; Mon, 07 Feb 2011 07:34:17 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58731) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PmQIH-0006xG-Ag for qemu-devel@nongnu.org; Mon, 07 Feb 2011 07:34:13 -0500 From: Juan Quintela In-Reply-To: <20110207123026.GA18830@redhat.com> (Michael S. Tsirkin's message of "Mon, 7 Feb 2011 14:30:26 +0200") References: <20110207123026.GA18830@redhat.com> Date: Mon, 07 Feb 2011 13:32:53 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] Re: [PATCH] e1000: clear EOP for multi-buffer descriptors Reply-To: quintela@redhat.com List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: qemu-devel@nongnu.org, Jes.Sorensen@redhat.com, Alex Williamson , agraf@suse.de, stefanha@linux.vnet.ibm.com "Michael S. Tsirkin" 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=E2=80=93= 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 > Reported-by: Juan Quintela reviewed-by: Juan Quintela