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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH] Change virtio-console to
	PCI_CLASS_SERIAL_OTHER
Date: Thu, 28 May 2009 13:53:49 +0100
References: <1243012478.29542.18.camel@blaa> <4A1D4C57.6010109@us.ibm.com>
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To: qemu-devel@nongnu.org, Mark McLoughlin <markmc@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, Dor Laor <dlaor@redhat.com>, ajax@redhat.com

On Wednesday 27 May 2009, 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

IMHO think the only sane response is "don't do that". Trying to support 
migration between different qemu versions just isn't worth the pain.

Paul