From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:46222) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S7LP2-00067X-Df for qemu-devel@nongnu.org; Tue, 13 Mar 2012 02:40:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S7LP0-00049Y-LG for qemu-devel@nongnu.org; Tue, 13 Mar 2012 02:40:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:21920) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S7LP0-00049M-DB for qemu-devel@nongnu.org; Tue, 13 Mar 2012 02:40:10 -0400 Message-ID: <4F5EEBC4.7030704@redhat.com> Date: Tue, 13 Mar 2012 07:40:04 +0100 From: Gerd Hoffmann MIME-Version: 1.0 References: <4F5CA590.1000605@redhat.com> <4F5CB429.4000907@codemonkey.ws> <20120311152528.GD7273@garlic.redhat.com> <4F5CC692.7050002@codemonkey.ws> <4F5DAC69.6010002@redhat.com> <4F5DB906.2030508@redhat.com> <4F5DC604.9010702@redhat.com> <4F5DF074.2030305@redhat.com> <4F5DFF3B.3040007@redhat.com> <4F5E445A.7000201@redhat.com> In-Reply-To: <4F5E445A.7000201@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [Spice-devel] seamless migration with spice List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Yonit Halperin Cc: Anthony Liguori , Hans de Goede , Alon Levy , qemu-devel , "spice-devel@freedesktop.org" On 03/12/12 19:45, Yonit Halperin wrote: > Hi, > On 03/12/2012 03:50 PM, Gerd Hoffmann wrote: >> Hi, >> >>> Can you explain/exemplify, why sending data as a blob (either by (a) or >>> (b)), that is verified only by the two ends that actually use it, is a >>> problem? >> >> It tends to be not very robust. Especially when the creating/parsing is >> done ad-hoc and the format changes now and then due to more info needing >> to be stored later on. The qemu migration format which has almost no >> structure breaks now and then because of that. Thus I'd prefer to not >> go down this route when creating something new. >> >> cheers, >> Gerd > > Exposing spice server internals to the client/qemu seems to me more > vulnerable then sending it as a blob. That also depends on what and how much we need to transfer. > Nonetheless, it introduces more > complexity to backward compatibility support and it will need to involve > not only the capabilities/versions of the server but also those of the > qemu/client Backward compatibility isn't that easy both ways. >.Which reminds me, that we also need capabilities > negotiation for the migration protocol between the src and the destination. If this is a hard requirement then using the vmstate channel isn't going to work. The vmstate is a one-way channel, no way to negotiate anything between source and target. cheers, Gerd