From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:48877) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QjXtS-0000KZ-7D for qemu-devel@nongnu.org; Wed, 20 Jul 2011 10:37:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QjXtN-0004If-Uw for qemu-devel@nongnu.org; Wed, 20 Jul 2011 10:36:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60525) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QjX7F-0002YS-KP for qemu-devel@nongnu.org; Wed, 20 Jul 2011 09:47:10 -0400 Message-ID: <4E26DC52.2010206@redhat.com> Date: Wed, 20 Jul 2011 07:46:58 -0600 From: Eric Blake MIME-Version: 1.0 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> <4E25AD51.4000802@codemonkey.ws> <4E269101.8030904@redhat.com> <4E26A767.8090101@redhat.com> <4E26D735.7050507@redhat.com> In-Reply-To: <4E26D735.7050507@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] live snapshot wiki updated List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jes Sorensen Cc: Kevin Wolf , Stefan Hajnoczi , "libvir-list@redhat.com" , Stefan Hajnoczi , QEMU Developers On 07/20/2011 07:25 AM, Jes Sorensen wrote: >> I think if libvirt wants qemu to use an fd instead of a file name, it >> shouldn't pass a file name but an fd in the first place. Which means >> that the two that we need are support for an fd: protocol (patches on >> the list, need review), and a way for libvirt to override the backing >> file of an image. > > The problem is that QEMU will find backing file file names inside the > images which it will be unable to open. How do you suggest we get around > that? We've already told you - qemu must have a way to be passed fds which are associated with names, and when a file refers to another backing file by name, then qemu falls back on its fd/name mapping to use the already-passed fd instead. Which implies that someone else, either libvirt or a qemu-maintained libblockformat.so, needs to have a stable interface for parsing the backing file name out of an arbitrary qcow2 file, and that this interface must work no matter how many other extensions are added to qcow2. -- Eric Blake eblake@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org