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

["Huang, Kai" <kai.huang@linux.intel.com>]

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@linux.intel.com>
>>>> ---
>>>>    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
>>> ACPI.
>>
>> 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
> block.
> 
> 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
> guests.
> 
> 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,
-Kai
> 
> Thanks, Roger.
> 

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