From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=38167 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PmYJa-0007lc-8z for qemu-devel@nongnu.org; Mon, 07 Feb 2011 16:08:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PmWqo-00026N-J2 for qemu-devel@nongnu.org; Mon, 07 Feb 2011 14:34:19 -0500 Received: from mail-ww0-f53.google.com ([74.125.82.53]:35847) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PmWqo-000262-Ec for qemu-devel@nongnu.org; Mon, 07 Feb 2011 14:34:18 -0500 Received: by wwi18 with SMTP id 18so4839432wwi.10 for ; Mon, 07 Feb 2011 11:34:17 -0800 (PST) Message-ID: <4D504925.3000807@codemonkey.ws> Date: Mon, 07 Feb 2011 13:33:57 -0600 From: Anthony Liguori MIME-Version: 1.0 References: <20110207160751.GC25106@redhat.com> In-Reply-To: <20110207160751.GC25106@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: new->old version migration List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Amit Shah , Alex Williamson , qemu list , Juan Quintela On 02/07/2011 10:07 AM, Michael S. Tsirkin wrote: > New thread stated intentionally, the original patch is Message-ID: > <349e93a4cfc6e1effc1b681cae53f805fdb9624e.1296713825.git.amit.shah@redhat.com> > > On Thu, Feb 03, 2011 at 11:47:08AM +0530, Amit Shah wrote: > >> Add a compat property for older machine types. When this is used (via >> -M pc-0.13, for example), the new flow control mechanisms will not be >> used. This is done to keep migration from a machine started with older >> type on a pc-0.14+ qemu to an older machine working. >> >> The property is named 'flow_control' and defaults to on. >> >> Reported-by: Alex Williamson >> Signed-off-by: Amit Shah >> > So, I think there are two things that need to be agreed on: > > - Can we commit to support migration from new qemu version to an old one? > We haven't in the past but downstreams do want this, > so it makes sense to have the infrastructure upstream. > Only within a stable release series and only when it's possible without sacrificing integrity. I know some downstreams disagree with this but I don't think this is a business we want to get into. Regards, Anthony Liguori > - The infrastructure/command line option for such support. > We have the -M flags to describe the machine that > we are running, but that abstracts away guest-visible machine, > which the migration format is not. > Also, same qemu could migrate to any older version. > So I think we would have to add a flag (call it -V for now) > to savevm/migrate commands to specify the format to be used. > Naturally some machines would be incompatible with > specific -V values, that's nothing new. > > Pls comment. > >