Re: [PATCH 2/2] drm/i915/gt: Set default CCS mode '1'

[Andi Shyti <andi.shyti@linux.intel.com>]

Hi Tvrtko,

On Mon, Feb 19, 2024 at 12:51:44PM +0000, Tvrtko Ursulin wrote:
> On 19/02/2024 11:16, Tvrtko Ursulin wrote:
> > On 15/02/2024 13:59, Andi Shyti wrote:

...

> > > +/*
> > > + * Exclude unavailable engines.
> > > + *
> > > + * Only the first CCS engine is utilized due to the disabling of
> > > CCS auto load
> > > + * balancing. As a result, all CCS engines operate collectively,
> > > functioning
> > > + * essentially as a single CCS engine, hence the count of active
> > > CCS engines is
> > > + * considered '1'.
> > > + * Currently, this applies to platforms with more than one CCS engine,
> > > + * specifically DG2.
> > > + */
> > > +#define for_each_available_uabi_engine(engine__, i915__) \
> > > +    for_each_uabi_engine(engine__, i915__) \
> > > +        if ((IS_DG2(i915__)) && \
> > > +            ((engine__)->uabi_class == I915_ENGINE_CLASS_COMPUTE) && \
> > > +            ((engine__)->uabi_instance)) { } \
> > > +        else
> > > +
> > 
> > If you don't want userspace to see some engines, just don't add them to
> > the uabi list in intel_engines_driver_register or thereabouts?

It will be dynamic. In next series I am preparing the user will
be able to increase the number of CCS engines he wants to use.

> > Similar as we do for gsc which uses I915_NO_UABI_CLASS, although for ccs
> > you can choose a different approach, whatever is more elegant.
> > 
> > That is also needed for i915->engine_uabi_class_count to be right, so
> > userspace stats which rely on it are correct.

Oh yes. Will update it.

> I later realized it is more than that - everything that uses
> intel_engine_lookup_user to look up class instance passed in from userspace
> relies on the engine not being on the user list otherwise userspace could
> bypass the fact engine query does not list it. Like PMU, Perf/POA, context
> engine map and SSEU context query.

Correct, will look into that, thank you!

Andi