From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1M9Rl5-0004lL-Qq for qemu-devel@nongnu.org; Wed, 27 May 2009 18:38:03 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1M9Rl0-0004i2-Un for qemu-devel@nongnu.org; Wed, 27 May 2009 18:38:03 -0400 Received: from [199.232.76.173] (port=38594 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1M9Rl0-0004hv-Nd for qemu-devel@nongnu.org; Wed, 27 May 2009 18:37:58 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:60779) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1M9Rl0-0007xx-99 for qemu-devel@nongnu.org; Wed, 27 May 2009 18:37:58 -0400 Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by e2.ny.us.ibm.com (8.13.1/8.13.1) with ESMTP id n4RMXhPD016332 for ; Wed, 27 May 2009 18:33:43 -0400 Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay02.pok.ibm.com (8.13.8/8.13.8/NCO v9.2) with ESMTP id n4RMbuFS222248 for ; Wed, 27 May 2009 18:37:56 -0400 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n4RMbuYB010094 for ; Wed, 27 May 2009 18:37:56 -0400 Message-ID: <4A1DC0C0.2060200@us.ibm.com> Date: Wed, 27 May 2009 17:37:52 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH] Change virtio-console to PCI_CLASS_SERIAL_OTHER References: <1243012478.29542.18.camel@blaa> <4A1D4C57.6010109@us.ibm.com> <1243446153.4852.9.camel@blaa> In-Reply-To: <1243446153.4852.9.camel@blaa> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Mark McLoughlin Cc: Dor Laor , ajax@redhat.com, qemu-devel Mark McLoughlin wrote: > On Wed, 2009-05-27 at 09:21 -0500, Anthony Liguori wrote: > > >> We need a mechanism to toggle this for both this and virtio-blk. The >> reason a toggle is needed is so that 0.11 can create the same device >> model as 0.10. >> > > Okay, so the scenario is: > > - 0.10 guest running on source machine > > - migrate to dest machine running 0.11 > > - the device model cannot change or the guest OS will get confused > Correct, but in this case, the problem is when you shutdown and start up the VM again. In the process, it may trigger something like a driver reinstallation or worse, reactivation. It's necessary to be able to prevent this by creating exactly the same device model that was previously created. This is can't really be a hard rule yet without the machine config, but we should do our best when we can. > How about running qemu on the dest machine with -model-version=0.10 ? > Linear versioning is a bit too fickle esp due to distro backporting. > Nasty thing about it is that the distributions couldn't cherry-pick > changes like this because they'd deviate from the device model contract > for a given upstream version. > > Could we not put this stuff in savevm and change the device model > post-init? > It's shutdown/restart that's the problem. Windows uses a lot of different information to calculate whether activation is required again and even small changes can end up pushing things over the edge. Regards, Anthony Liguori > Cheers, > Mark. > >