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Re: [Xen-devel] [PATCH 15/15] xen: tools: expose EPC in ACPI table

On 7/18/2017 10:21 PM, Roger Pau Monné wrote:
On Tue, Jul 18, 2017 at 08:36:15PM +1200, Huang, Kai wrote:

On 7/17/2017 10:54 PM, Roger Pau Monné wrote:
On Sun, Jul 09, 2017 at 08:16:05PM +1200, Kai Huang wrote:
On physical machine EPC is exposed in ACPI table via "INT0E0C". Although EPC
can be discovered by CPUID but Windows driver requires EPC to be exposed in
ACPI table as well. This patch exposes EPC in ACPI table.

Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
   tools/firmware/hvmloader/util.c  | 23 +++++++++++++++++++
   tools/firmware/hvmloader/util.h  |  3 +++

Is there any reason this needs to be done in hvmloader instead of
libacpi? I'm mostly asking this because PVH guests can also get ACPI
tables, so it would be good to be able to expose EPC to them using

Hi Roger,

Thanks for comments. I didn't deliberately choose to do in hvmloader instead
of libacpi. It seems libxl only builds ACPI table when guest is HVM, and it
doesn't use any device model, and I think I have covered this part (see
changes to init_acpi_config). Is there anything that I missed?

dsdt.asl is only used for HVM guests, PVH guests basically get an
empty dsdt + dsdt_acpi_info + processor objects populated by make_dsdt
(see Makefile in libacpi), so they end up without the EPC Device

It would be good if a new empty dsdt is created, that contains the
Device EPC block, or a ssdt is used, and it's added to both HVM/PVH

Alternatively you could also code the EPC Device block in mk_dsdt, but
that's going to be cumbersome IMHO.

Hi Roger,

I got your point. I think it's definitely better to cover PVH if we can. Let me see whether it is possible to do.


Thanks, Roger.

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