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From: Peter Maydell <peter.maydell@linaro.org>
Date: Mon, 3 Mar 2014 21:39:43 +0000
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Subject: Re: [Qemu-devel] [RFC 4/4] Relevant changes to enable KVM to TCG
	migration
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To: alvise rigo <a.rigo@virtualopensystems.com>
Cc: "tech@virtualopensystems.com" <tech@virtualopensystems.com>, QEMU Developers <qemu-devel@nongnu.org>

On 26 February 2014 10:02, alvise rigo <a.rigo@virtualopensystems.com> wrote:
> I agree that this is a sort of workaround, but it seems to me that a
> proper solution is not possible without changing the ideas contemplated
> now in the migration code.
> Are we willing to accept some major changes in the code to embrace
> this type of migration?

Incidentally it occurred to me recently that the design we've gone for
for AArch64 support (canonical copy of system register info is the AArch64
view, AArch32 register encoding is a non-migratable view onto the same
underlying data) clashes rather with the idea of being able to migrate
AArch32 TCG<->KVM. (Migrating AArch32 TCG to/from a KVM which
is configured to run the VM in AArch32 on an AArch64 host doesn't run
into the same problems, because in that case what KVM exposes to
userspace will also be the AArch64 views of registers.)
That was accidental, not an intentional tradeoff, but I'm not entirely
sure how to reconcile things...

thanks
-- PMM