From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NCZnI-0007DB-Rw for qemu-devel@nongnu.org; Mon, 23 Nov 2009 09:21:32 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NCZnE-0007CL-BZ for qemu-devel@nongnu.org; Mon, 23 Nov 2009 09:21:32 -0500 Received: from [199.232.76.173] (port=43055 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NCZnE-0007CI-6k for qemu-devel@nongnu.org; Mon, 23 Nov 2009 09:21:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:8229) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NCZnD-0008C9-S0 for qemu-devel@nongnu.org; Mon, 23 Nov 2009 09:21:28 -0500 Message-ID: <4B0A9A64.2090109@redhat.com> Date: Mon, 23 Nov 2009 15:21:24 +0100 From: Paolo Bonzini MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: Live migration protocol, device features, ABIs and other beasts References: <4B0952C9.9010803@redhat.com> <4B095D86.700@codemonkey.ws> <4B09F0CA.3060705@codemonkey.ws> <1258983457-sup-5031@blackpad.lan.raisama.net> In-Reply-To: <1258983457-sup-5031@blackpad.lan.raisama.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: qemu-devel On 11/23/2009 02:51 PM, Eduardo Habkost wrote: > Right, but I wouldn't be surprised if a user complains that "I know that > my guest don't use that VM feature, so I want to be able to migrate to > an older version anyway". That's a bit more tricky. What if the older version doesn't support sound (just making up an example) and you know that you're not using a client that plays sound, but still the sound card is part of the machine? I think there is no doubt that the migration (or save/restore) should be aborted in that case. I would not generalize very much, the problem that Dor posed is very specific and probably quite rare. However, it's real. Paolo