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RE: [Xen-devel] [PATCH 00/02] firmware changes as part of QEMU/Xen merge

To: Keir Fraser <keir@xxxxxxx>, Anthony Perard <anthony.perard@xxxxxxxxxx>, Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH 00/02] firmware changes as part of QEMU/Xen merge.
From: Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>
Date: Mon, 18 Oct 2010 15:52:30 +0100
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Thread-topic: [Xen-devel] [PATCH 00/02] firmware changes as part of QEMU/Xen merge.
> We cannot make changes to qemu-dm that are not backwards compatible with
> saved guests. Not only does this affect qemu in this case, but the
> register
> blocks you move around also affect Xen's emulation of ACPI pmtimer. Both
> will/would need to be configurable based on whether this is an old or new
> guest.
> Hence this has to be strongly NACKed in its current form.

It's getting to the point where we might have to consider having two qemu 
binaries, one for compatibility, one that new VMs are transitioned on to.

Things are now so different that I'm worried that installed guests might 
complain even when just fresh booted on the new qemu. This is something that 
we'd need to test and devise workarounds. Trying to retain saved image 
compatibility with a single binary looks ugly.


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