From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:32941) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QjDT6-0007xU-T7 for qemu-devel@nongnu.org; Tue, 19 Jul 2011 12:48:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QjDT2-0003Gq-Cu for qemu-devel@nongnu.org; Tue, 19 Jul 2011 12:48:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:8818) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QjDT1-0003Ge-UJ for qemu-devel@nongnu.org; Tue, 19 Jul 2011 12:48:20 -0400 Date: Tue, 19 Jul 2011 17:47:55 +0100 From: "Daniel P. Berrange" Message-ID: <20110719164755.GF12026@redhat.com> References: <4E2055AE.8090107@redhat.com> <4E253136.4080509@redhat.com> <4E258635.2040108@redhat.com> <4E258D70.6000205@redhat.com> <4E25902D.2000403@redhat.com> <4E2593B0.1030508@redhat.com> <4E2594FB.4050203@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4E2594FB.4050203@redhat.com> Subject: Re: [Qemu-devel] live snapshot wiki updated Reply-To: "Daniel P. Berrange" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jes Sorensen Cc: "libvir-list@redhat.com" , Stefan Hajnoczi , Eric Blake , QEMU Developers , Stefan Hajnoczi On Tue, Jul 19, 2011 at 04:30:19PM +0200, Jes Sorensen wrote: > On 07/19/11 16:24, Eric Blake wrote: > > [adding the libvir-list] > > On 07/19/2011 08:09 AM, Jes Sorensen wrote: > >> Urgh, libvirt parsing image files is really unfortunate, it really > >> doesn't give me warm fuzzy feelings :( libvirt really should not know > >> about internals of image formats. > > > > But even if you add new features to qemu to avoid needing this in the > > future, it doesn't change the past - libvirt will always have to know > > how to parse image files understood by older qemu, and so as long as > > libvirt already knows how to do that parsing, we might as well take > > advantage of it. > > What has been done here in the past is plain wrong. Continuing to do it > isn't the right thing to do here. > > > Besides, I feel that having a well-documented file format, so that > > independent applications can both parse the same file with the same > > semantics by obeying the file format specification, is a good design goal. > > We all know that documentation is rarely uptodate, new features may not > get added and libvirt will never be able to keep up. The driver for a > file format belongs in QEMU and nowhere else. This would be possible if QEMU to provide a libblockformat.so library which allowed apps to extract metadata from file formats using a stable API. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|