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Re: [Xen-devel] HVM Migration of domU on Qemu-upstream DM loses ACPI data in xenstore


--On 18 May 2013 12:02:23 +0100 Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:

These keys have nothing to do with that, all they do is cause hvmloader
to expose ACPI tables to the guest or to tweak the content of those
tables. That state is preserved as part of the memory image of the
guest. The qemu state is also pickled as part of the save image.

ACPI is jut a set of tables describing the hardware, there's no
"emulation" to turn off and on. Whatever magic I/O ports the ACPI AML
references are always on, the setting just controls whether the guest
gets to see that via the AML.

Thanks. So it could not be that the guest gets to see that via the AML
pre migration, but not post migration?

In that case I can only conclude that some part of the qemu state
is not migrating correctly, and the fact that it the cluck stock
doesn't happen if ACPI is enabled in xl.conf is only relevant as
it influences how the guest (linux in this case) chooses its clock
source (i.e. its broken in any case, just the guest does not notice
if the relevant ACPI dtables aren't exposed).

Any ideas on how to debug this further? It is odd that the date command
(used to set a date) will unstick the clock.

Alex Bligh

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