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

["Huang, Kai" <kai.huang@xxxxxxxxxxxxxxx>]

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
> > > 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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