From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45149) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WYGDV-0001DQ-Mg for qemu-devel@nongnu.org; Thu, 10 Apr 2014 10:44:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WYGDP-0005IM-Dw for qemu-devel@nongnu.org; Thu, 10 Apr 2014 10:44:37 -0400 Received: from mail-pa0-f52.google.com ([209.85.220.52]:62974) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WYGDP-0005Hz-8e for qemu-devel@nongnu.org; Thu, 10 Apr 2014 10:44:31 -0400 Received: by mail-pa0-f52.google.com with SMTP id rd3so4100024pab.11 for ; Thu, 10 Apr 2014 07:44:30 -0700 (PDT) Message-ID: <5346AE49.5040708@ozlabs.ru> Date: Fri, 11 Apr 2014 00:44:25 +1000 From: Alexey Kardashevskiy MIME-Version: 1.0 References: <1395888071-28677-1-git-send-email-aik@ozlabs.ru> <53341B8F.7040904@suse.de> <53341E41.7050101@ozlabs.ru> <533422AB.7080106@ozlabs.ru> <53435036.9020901@ozlabs.ru> <53468A29.50404@suse.de> <5346AC43.2060600@ozlabs.ru> <7CC94F60-7580-4986-9026-7C16262F5778@suse.de> In-Reply-To: <7CC94F60-7580-4986-9026-7C16262F5778@suse.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH] target-ppc: Add @cpu_dt_id into migration stream List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: Peter Maydell , Juan Quintela , "qemu-ppc@nongnu.org" , =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= , QEMU Developers On 04/11/2014 12:41 AM, Alexander Graf wrote: > > On 10.04.2014, at 16:35, Alexey Kardashevskiy wrote: > >> On 04/10/2014 10:10 PM, Alexander Graf wrote: >>> >>> On 08.04.14 03:26, Alexey Kardashevskiy wrote: >>>> On 03/28/2014 12:07 AM, Alexey Kardashevskiy wrote: >>>>> On 03/27/2014 11:57 PM, Peter Maydell wrote: >>>>>> On 27 March 2014 12:49, Alexey Kardashevskiy wrote: >>>>>>> On 03/27/2014 11:37 PM, Andreas Färber wrote: >>>>>>>> Am 27.03.2014 03:41, schrieb Alexey Kardashevskiy: >>>>>>>>> This should prevent the destination guest from misbehaving when >>>>>>>>> the threads number is different in "-smp" command. >>>>>>>> Sorry, I don't understand. When migrating, surely -smp needs to be the >>>>>>>> same on source and destination, so how can they differ? >>>>>>> >>>>>>> The idea is that "-smp" does not migrate and if we run source and >>>>>>> destination guests with different numbers in -smp, we end up with weird >>>>>>> machine >>>>>> Yes, so don't do that. As I understand it: >>>>>> (1) if you don't run QEMU with the exact same command line >>>>>> and config at both ends then migration won't work >>>>>> (2) we don't guarantee to detect and cleanly fail if you >>>>>> don't do (1) >>>>>> >>>>>> It would probably be nice if we did detect config mismatches, >>>>> Yep, we do not send the device tree (as libvirt does). Pure command line >>>>> matching won't work. >>>>> >>>>>> but that seems to me like a problem we should be addressing >>>>>> more globally than just for one particular config item for >>>>>> one particular target... >>>> >>>> Ok. So. Let's assume I want to implement migration of "-smp" parameters. >>>> What would be the correct way of doing this in terms of the current QOM >>>> principles? Thanks. >>> >>> You don't. The migration protocol doesn't migrate configuration. If you >>> want to start to transfer VM configuration (which I'd be all in for), do it >>> properly and transfer _all_ configuration. >> >> >> Then what is the purpose of many, many VMSTATE_.*_EQUAL? > > Probably legacy from old vmstate layouts. So this should not be used from now on? >> And I do not want to send configuration by the proposed patch, I want to >> make sure that the new guest is able to continue. Why exactly is this bad? > > It's not bad, but we should solve this properly, not one field at a time. -- Alexey