Re: [RFC XEN PATCH 1/6] x86/pvh: report ACPI VFCT table to dom0 if present

[Huang Rui <ray.huang@amd.com>]

On Mon, Mar 13, 2023 at 08:27:02PM +0800, Andrew Cooper wrote:
> On 13/03/2023 12:21 pm, Roger Pau Monné wrote:
> > On Mon, Mar 13, 2023 at 11:55:56AM +0000, Andrew Cooper wrote:
> >> On 12/03/2023 7:54 am, Huang Rui wrote:
> >>> From: Roger Pau Monne <roger.pau@citrix.com>
> >>>
> >>> The VFCT ACPI table is used by AMD GPUs to expose the vbios ROM image
> >>> from the firmware instead of doing it on the PCI ROM on the physical
> >>> device.
> >>>
> >>> As such, this needs to be available for PVH dom0 to access, or else
> >>> the GPU won't work.
> >>>
> >>> Reported-by: Huang Rui <ray.huang@amd.com>
> >>> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> >>> Acked-and-Tested-by: Huang Rui <ray.huang@amd.com>
> >>> Release-acked-by: Henry Wang <Henry.Wang@arm.com>
> >>> Signed-off-by: Huang Rui <ray.huang@amd.com>
> >> Huh...  Despite the release ack, this didn't get committed for 4.17.
> > There was a pending query from Jan as to where was this table
> > signature documented or at least registered, as it's not in the ACPI
> > spec or any related files.
> >
> > I don't oppose to the change, as it's already used by Linux, so I
> > think it's impossible for the table signature to be reused, even if
> > not properly documented (it would cause havoc).
> >
> > It's however not ideal to set this kind of precedents.
> 
> It's not great, but this exists in real systems, for several generations
> it seems.
> 
> Making things work for users trumps any idealistic beliefs about
> firmware actually conforming to spec.
> 

Thanks Andrew for understanding! These tables have been there for more than
10+ years on all AMD GPU platforms.

Thanks,
Ray