From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=44685 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OZKd3-0008PF-7O for qemu-devel@nongnu.org; Thu, 15 Jul 2010 05:21:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OZKd1-0000NO-Rl for qemu-devel@nongnu.org; Thu, 15 Jul 2010 05:21:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:64829) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OZKd1-0000N5-L9 for qemu-devel@nongnu.org; Thu, 15 Jul 2010 05:21:15 -0400 Date: Thu, 15 Jul 2010 10:20:56 +0100 From: "Daniel P. Berrange" Subject: Re: [Qemu-devel] [PATCH] Make default invocation of block drivers safer Message-ID: <20100715092056.GA14564@redhat.com> References: <1279123952-1576-1-git-send-email-aliguori@us.ibm.com> <20100714184311.GA9383@lst.de> <4C3E06DA.8080302@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C3E06DA.8080302@codemonkey.ws> Reply-To: "Daniel P. Berrange" List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Kevin Wolf , Anthony Liguori , Christoph Hellwig , Stefan Hajnoczi , qemu-devel@nongnu.org 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. 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 -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|