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Date: Mon, 20 Mar 2017 20:20:32 -0300
From: Marcelo Tosatti <mtosatti@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/2] acpi_piix4: fix migration of gpe fields
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To: Philipp Hahn <hahn@univention.de>
Cc: Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org, kvm@vger.kernel.org

On Mon, Mar 20, 2017 at 01:02:10PM +0100, Philipp Hahn wrote:
> Hello Marcelo, cc:qemu,
> 
> Sorry for re-using this old thread, but I have a problem loading some
> saved state from qemu-kvm-1.1.2, which fails for piix4_pm.
> 
> You following patch was committed as
> <http://git.qemu-project.org/?p=qemu.git;a=commitdiff;h=b0b873a07872f7ab7f66f259c73fb9dd42aa66a9>:
> 
> Am 15.11.2012 um 01:11 schrieb Marcelo Tosatti:
> > Migrate 16 bytes for en/sts fields (which is the correct size),
> > increase version to 3, and document how to support incoming
> > migration from qemu-kvm 1.2.
> 
> I my case qemu-kvm-1.1.2/hw/acpi_piix4.c:284
> | VMSTATE_STRUCT(ar.gpe, PIIX4PMState, 2, vmstate_gpe, ACPIGPE),
> only saves 4 bytes, not 16 bytes.

Hi Philipp,

IIRC qemu-1.1.2 saved 16 bytes, which is the correct size, not 4 bytes.

So while merging from qemu-kvm -> qemu, it was decided to maintain
backwards compability with qemu, and not qemu-kvm.

Is there any way to differentiate between the two (qemu vs qemu-kvm, 
perhaps via some other field not in the VMState of ACPI PIIX4), so
your patch can be integrated upstream?