On 03/04/2020 10:13, Chris Wilson wrote:
Let userspace know if they can trust timeslicing by including it as part
of the I915_PARAM_HAS_SCHEDULER::I915_SCHEDULER_CAP_TIMESLICING

v2: Only declare timeslicing if we can safely preempt userspace.

Fixes: 8ee36e048c98 ("drm/i915/execlists: Minimalistic timeslicing")
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Kenneth Graunke <kenn...@whitecape.org>
---
  drivers/gpu/drm/i915/gt/intel_engine.h      | 3 ++-
  drivers/gpu/drm/i915/gt/intel_engine_user.c | 5 +++++
  include/uapi/drm/i915_drm.h                 | 1 +
  3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h 
b/drivers/gpu/drm/i915/gt/intel_engine.h
index b469de0dd9b6..424672ee7874 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine.h
@@ -339,7 +339,8 @@ intel_engine_has_timeslices(const struct intel_engine_cs 
*engine)
        if (!IS_ACTIVE(CONFIG_DRM_I915_TIMESLICE_DURATION))
                return false;
- return intel_engine_has_semaphores(engine);
+       return (intel_engine_has_semaphores(engine) &&
+               intel_engine_has_preemption(engine));

This is turning off timeslicing on Gen8? Well it wouldn't have worked anyway, outside the batch boundaries.. so it does sound technically correct.

  }
#endif /* _INTEL_RINGBUFFER_H_ */
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_user.c 
b/drivers/gpu/drm/i915/gt/intel_engine_user.c
index 848decee9066..b84fdd722781 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_user.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_user.c
@@ -121,6 +121,11 @@ static void set_scheduler_caps(struct drm_i915_private 
*i915)
                        else
                                disabled |= BIT(map[i].sched);
                }
+
+               if (intel_engine_has_timeslices(engine))
+                       enabled |= I915_SCHEDULER_CAP_TIMESLICING;
+               else
+                       disabled |= I915_SCHEDULER_CAP_TIMESLICING;
        }
i915->caps.scheduler = enabled & ~disabled;
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 704dd0e3bc1d..1ee227b5131a 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -523,6 +523,7 @@ typedef struct drm_i915_irq_wait {
  #define   I915_SCHEDULER_CAP_PREEMPTION       (1ul << 2)
  #define   I915_SCHEDULER_CAP_SEMAPHORES       (1ul << 3)
  #define   I915_SCHEDULER_CAP_ENGINE_BUSY_STATS        (1ul << 4)
+#define   I915_SCHEDULER_CAP_TIMESLICING       (1ul << 5)

Split uapi from Gen8 fix?

Regards,

Tvrtko

#define I915_PARAM_HUC_STATUS 42
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