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Date: Fri, 26 Jul 2013 17:30:29 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 14/14] i386: ACPI table generation code
 from seabios
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org

  Hi,

>> That's something I think that it's best for firmware to avoid.
>> Much better to load tables in memory and use standard ACPI
>> methods to find specific tables.
> 
> Problem is this happens relatively late in the firmware boot process.

Completely different idea to tackle the issue: use COMMAND_ADD_POINTER
not only for table pointers, but also register offsets.  So the firmware
doesn't need to parse fadt to figure how it should program pm_base, but
instead can fixup the fadt according to the pm_base it has used.

That is more in line with how firmware works (pm_base and simliar things
tends to be #defines and are not runtime-configurable).  And I think
it's also more robust when extending/changing tables for newer acpi spec
revisions.

cheers,
  Gerd