From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=59143 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OZNfX-0005IC-7I for qemu-devel@nongnu.org; Thu, 15 Jul 2010 08:36:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OZNfS-0001De-1A for qemu-devel@nongnu.org; Thu, 15 Jul 2010 08:36:02 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:54149) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OZNfR-0001DM-RD for qemu-devel@nongnu.org; Thu, 15 Jul 2010 08:35:57 -0400 Received: from d01relay01.pok.ibm.com (d01relay01.pok.ibm.com [9.56.227.233]) by e7.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id o6FCNOqx032664 for ; Thu, 15 Jul 2010 08:23:24 -0400 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d01relay01.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o6FCZs7M093420 for ; Thu, 15 Jul 2010 08:35:54 -0400 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id o6FCZhk3012445 for ; Thu, 15 Jul 2010 06:35:43 -0600 Message-ID: <4C3F00A5.2080201@linux.vnet.ibm.com> Date: Thu, 15 Jul 2010 07:35:49 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] Make default invocation of block drivers safer References: <1279123952-1576-1-git-send-email-aliguori@us.ibm.com> <20100714184311.GA9383@lst.de> <4C3E06DA.8080302@codemonkey.ws> <20100715092056.GA14564@redhat.com> In-Reply-To: <20100715092056.GA14564@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: Kevin Wolf , Anthony Liguori , Stefan Hajnoczi , qemu-devel@nongnu.org, Christoph Hellwig On 07/15/2010 04:20 AM, Daniel P. Berrange wrote: > On Wed, Jul 14, 2010 at 01:50:02PM -0500, Anthony Liguori wrote: > >> On 07/14/2010 01:43 PM, Christoph Hellwig wrote: >> >>> Err, strong NACK. Please don't start messing with the contents of the >>> data plane, we're getting into real trouble there. It's perfectly >>> valid for a guest to create an image inside an image, and with hardware >>> support for nested virtualization I guess this use case will become >>> rather common, just as it already is on S/390 with VM. >>> >>> >> Then we have to remove block format probing. >> >> The two things are fundamentally incompatible. >> > FWIW, the latest libvirt code will now always set a fmt=XXX arg even > for raw, so probing will never be performed. We also always set a backing > store format when creating qcow2 files. > I assume libvirt probes once, then updates the guest's XML? This is definitely the most user friendly option of all except for the fact that we don't have a writeable config file in QEMU today. Regards, Anthony Liguori > The main remaining unsolved issues are backing stores with non-qcow2 > files for which QEMU will always probe, and pre-existing qcow2 files > which have been created without backing store formats. It would be > nice to have an explicit arg to disable all backing store probing, > forcing backing format to either be raw, or match the parent image > format. > > Regards, > Daniel >