Re: [RFC v5 1/1] drm/xe/pf: Restrict device query responses in admin-only PF mode

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Fri, 06 Mar 2026 06:00:02 -0800, Rodrigo Vivi wrote:
>
> On Tue, Mar 03, 2026 at 08:39:56PM +0000, Souza, Jose wrote:
> > On Fri, 2026-02-27 at 12:07 +0000, Satyanarayana K V P wrote:
> > > When a PF is configured in admin-only mode, it is intended for
> > > management
> > > only and must not expose workload-facing capabilities to userspace.
> > >
> > > Limit the exposed ioctl set in admin-only PF mode to XE_DEVICE_QUERY,
> > > and
> > > suppress capability-bearing query payloads so userspace cannot
> > > discover
> > > execution-related device details in this mode.
> >
> > Mesa MR:
> > https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40206
>
> Looking to this patch I got myself wondering if query.size == 0 is
> long-term proof...   I mean, if we need to get some OA/RAS/telemetry
> kind of API that end up needing some kind of query information....
>
> Michals, thoughts on this?
>
> I know, I know, this solution is indeed much better than my
> proposal of no ioctl exposed. But I mean, since we are taking
> this path and allowing some ioctl. Shouldn't we prepare at least
> the query for that and then only limiting the number of engines
> and memory regions to zero?

I think UMD's should handle both these cases, either:

1. The returned query size is 0, so there is no further information, which
   can only mean nothing is supported (engine, memory region counts are
   all 0)
2. Or, returned query size is non-zero but engine or memory region counts
   returned are 0.

And then KMD can implement either (or switch between the two later) as
needed?

Also, there were some questions about supporting OA in the
admin-only-pf. Here are some high level points about this:

* OA/EUSTALL is not supported in VF's in current products, this might
  change in the future
* OA/EUSTALL in admin-only-pf can be used to profile global counts across
  VF's
* OA/EUSTALL themselves don't allow workload submission etc. They only
  allow reading profiling data from HW
* OA/EUSTALL in admin-only-pf will need the observation ioctl to be
  supported. Also, some other query ioctls such as hw configuration,
  topology, frequency will be needed to make sense of OA/EUSTALL data.

Thanks.
--
Ashutosh