From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1LrwuS-0002kE-Qq
	for qemu-devel@nongnu.org; Thu, 09 Apr 2009 12:15:24 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1LrwuO-0002fR-Qi
	for qemu-devel@nongnu.org; Thu, 09 Apr 2009 12:15:24 -0400
Received: from [199.232.76.173] (port=44757 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1LrwuO-0002f9-Lq
	for qemu-devel@nongnu.org; Thu, 09 Apr 2009 12:15:20 -0400
Received: from mail1-relais-roc.national.inria.fr ([192.134.164.82]:13430)
	by monty-python.gnu.org with esmtps (TLS-1.0:RSA_ARCFOUR_SHA1:16)
	(Exim 4.60) (envelope-from <samuel.thibault@labri.fr>)
	id 1LrwuO-0000hN-9M
	for qemu-devel@nongnu.org; Thu, 09 Apr 2009 12:15:20 -0400
Received: from samy by const with local (Exim 4.69)
	(envelope-from <samuel.thibault@labri.fr>) id 1LrwuK-0004ya-GP
	for qemu-devel@nongnu.org; Thu, 09 Apr 2009 18:15:17 +0200
Date: Thu, 9 Apr 2009 18:15:16 +0200
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Subject: Re: [Qemu-devel] buffer alignment for block backends
Message-ID: <20090409161516.GL5457@const.bordeaux.inria.fr>
References: <49DCA80A.1020808@eu.citrix.com> <49DCF2C0.9070704@codemonkey.ws>
	<49DDC66F.2000404@eu.citrix.com> <49DDF3FF.8050706@codemonkey.ws>
	<49DDF877.8090805@eu.citrix.com> <49DDFE1A.9040202@redhat.com>
	<20090409152107.GE5457@const.bordeaux.inria.fr>
	<20090409155550.GA14196@shareable.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <20090409155550.GA14196@shareable.org>
Reply-To: qemu-devel@nongnu.org
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: qemu-devel@nongnu.org

Jamie Lokier, le Thu 09 Apr 2009 16:55:50 +0100, a écrit :
> Samuel Thibault wrote:
> > Gerd Hoffmann, le Thu 09 Apr 2009 15:54:34 +0200, a écrit :
> > > On 04/09/09 15:30, Stefano Stabellini wrote:
> > > >The userspace\kernelspace distinction does not make much sense in
> > > >minios, but yes it provides an interface to communicate with blkback in
> > > >dom0. This interface is used by block-vbd in qemu instead of
> > > >block-raw-posix when run in minios.
> > > 
> > > Sit back, look again.  Do you really need it being page-aligned?
> > 
> > Page aligned is an optimization which comes for free when you can
> > already choose the alignment.
> > 
> > > The xen block protocol can handle unaligned requests just fine.
> > 
> > Not completely arbitrarily aligned requests. They need to be
> > sector-aligned.
> 
> Thought about 4k sectors, to be found in new disks sometime soon?

Same wording: they will have to be sector-aligned (the blkback announces
the size of its sector).

Samuel