From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LruiO-0004Wz-UN for qemu-devel@nongnu.org; Thu, 09 Apr 2009 09:54:49 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LruiK-0004VO-Gy for qemu-devel@nongnu.org; Thu, 09 Apr 2009 09:54:48 -0400 Received: from [199.232.76.173] (port=50132 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LruiK-0004VC-3i for qemu-devel@nongnu.org; Thu, 09 Apr 2009 09:54:44 -0400 Received: from mx2.redhat.com ([66.187.237.31]:43545) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1LruiI-0002wK-Nj for qemu-devel@nongnu.org; Thu, 09 Apr 2009 09:54:43 -0400 Received: from int-mx2.corp.redhat.com (int-mx2.corp.redhat.com [172.16.27.26]) by mx2.redhat.com (8.13.8/8.13.8) with ESMTP id n39DsbNT022055 for ; Thu, 9 Apr 2009 09:54:37 -0400 Received: from ns3.rdu.redhat.com (ns3.rdu.redhat.com [10.11.255.199]) by int-mx2.corp.redhat.com (8.13.1/8.13.1) with ESMTP id n39Dsd27031070 for ; Thu, 9 Apr 2009 09:54:39 -0400 Received: from zweiblum.home.kraxel.org (vpn-10-195.str.redhat.com [10.32.10.195]) by ns3.rdu.redhat.com (8.13.8/8.13.8) with ESMTP id n39DsaXw002892 for ; Thu, 9 Apr 2009 09:54:37 -0400 Message-ID: <49DDFE1A.9040202@redhat.com> Date: Thu, 09 Apr 2009 15:54:34 +0200 From: Gerd Hoffmann MIME-Version: 1.0 Subject: Re: [Qemu-devel] buffer alignment for block backends References: <49DCA80A.1020808@eu.citrix.com> <49DCF2C0.9070704@codemonkey.ws> <49DDC66F.2000404@eu.citrix.com> <49DDF3FF.8050706@codemonkey.ws> <49DDF877.8090805@eu.citrix.com> In-Reply-To: <49DDF877.8090805@eu.citrix.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org 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? The xen block protocol can handle unaligned requests just fine. The granted page is splitted into 512 sectors (8 pieces in case of 4k pages on x86). You can then request only some of the of the sectors being transfered. If you have two sectors with a 1024 byte offset to the page border you'll just ask for sectors 2+3. cheers, Gerd