Re: [PATCH 4/5] drm/i915: Expose RPCS (SSEU) configuration to userspace (Gen11 only)

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 30/01/2019 09:45, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2019-01-30 09:34:15)
>> +       rq = i915_request_alloc(engine, i915->kernel_context);
>> +       if (IS_ERR(rq)) {
>> +               ret = PTR_ERR(rq);
>> +               goto out_put;
>> +       }
>> +
>> +       /* Queue this switch after all other activity by this context. */
>> +       prev = i915_gem_active_raw(&ce->ring->timeline->last_request,
>> +                                  &i915->drm.struct_mutex);
>> +       if (prev && !i915_request_completed(prev)) {
>> +               ret = i915_request_await_dma_fence(rq, &prev->fence);
>> +               if (ret < 0)
>> +                       goto out_add;
>> +       }
>> +
>> +       ret = gen8_emit_rpcs_config(rq, ce, sseu);
>> +       if (ret)
>> +               goto out_add;
>> +
>> +       /* Order all following requests to be after. */
>> +       i915_timeline_set_barrier(ce->ring->timeline, rq);
> 
> You are making me regret not adding __must_check everywhere.
> 
> If you set the barrier before the emit_rpcs_config, then as we maintain
> barrier ordering, it will be ok if we have to not emit the config
> change.

Ah rings a bell.. forgot about it..

Regards,

Tvrtko

> 
>> +
>> +       /*
>> +        * Guarantee context image and the timeline remains pinned until the
>> +        * modifying request is retired by setting the ce activity tracker.
>> +        *
>> +        * But we only need to take one pin on the account of it. Or in other
>> +        * words transfer the pinned ce object to tracked active request.
>> +        */
>> +       if (!i915_gem_active_isset(&ce->active_tracker))
>> +               __intel_context_pin(ce);
>> +       i915_gem_active_set(&ce->active_tracker, rq);
> 
> Hello ce->active_tracker, I have great plans for you.
> -Chris
> 
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