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Subject: Re: [Qemu-devel] [PATCH] Change virtio-console to
	PCI_CLASS_SERIAL_OTHER
From: Mark McLoughlin <markmc@redhat.com>
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Date: Wed, 27 May 2009 18:42:33 +0100
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To: Anthony Liguori <aliguori@us.ibm.com>
Cc: Dor Laor <dlaor@redhat.com>, ajax@redhat.com, qemu-devel <qemu-devel@nongnu.org>

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

How about running qemu on the dest machine with -model-version=0.10 ?

At least that way it's something the management system can easily figure
out (i.e. source is running in qemu 0.10, rather than source qemu is
using class=XXX).

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?

Cheers,
Mark.