[Intel-gfx] [PATCH 5/7] drm/i915: Expose RPCS (SSEU) configuration to userspace (Gen11 only)

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-12-31 15:21:15)
> 
> On 14/12/2018 13:33, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2018-12-14 12:34:47)
> >> +static int get_sseu(struct i915_gem_context *ctx,
> >> +                   struct drm_i915_gem_context_param *args)
> >> +{
> >> +       struct drm_i915_gem_context_param_sseu user_sseu;
> >> +       struct intel_engine_cs *engine;
> >> +       struct intel_context *ce;
> >> +       int ret;
> >> +
> >> +       if (args->size == 0)
> >> +               goto out;
> >> +       else if (args->size < sizeof(user_sseu))
> >> +               return -EINVAL;
> >> +
> >> +       if (copy_from_user(&user_sseu, u64_to_user_ptr(args->value),
> >> +                          sizeof(user_sseu)))
> >> +               return -EFAULT;
> >> +
> >> +       if (user_sseu.rsvd1 || user_sseu.rsvd2)
> >> +               return -EINVAL;
> > 
> > I'd vote for s/rsvd2/flags/ straight away as already I can suggest we
> > allow for USE_CTX_ENGINE to swap class/instance for engine-id so that we
> > can set rpcs for, and not least, a virtual engine.
> 
> Hm.. would it be useful? It would just be a way of indirection.
> 
> engines = [vcs:0, vcs:1]
> ctx.set_map(engines)
> 
> And then a):
> 
> foreach engine in engines:
>         ctx.set_sseu(engine, flags=0)
> 
> vs b):
> 
> for i = 0; i < len(engines); i++:
>         ctx.set_sseu(i, flags=USE_CTX_ENGINE)
> 
> So I don't see any benefit. But maybe I missed your idea.

The virtual engine doesn't have a valid class:instance, only its index
in the per-context engines[]. And we want to control its context image,
not the context images on each of the real engine.
-Chris