[Intel-gfx] [PATCH] drm/i915/guc: Disable preemption if it fails

[Michel Thierry]

On 5/31/2018 1:47 PM, Chris Wilson wrote:
> If we fail to tell the GuC to perform preemption, we get stuck
> attempting to continually retry inject_preempt_context() until we
> eventually timeout and reset the GPU (approximately emitting the same
> warning 1000 times). Bail after the first failure, emit the WARN and
I only see 340 warnings in the 4 seconds before it timed out.

<7>[ ] [drm:intel_guc_send_mmio [i915]] INTEL_GUC_SEND: Action 0x2 
failed; ret=-110 status=0x00000002 response=0x40000000

The status is the same as the action, so something really bad happened 
inside there.

> stop trying to do any further preemption on this engine.
> 
> References: https://intel-gfx-ci.01.org/tree/drm-tip/Trybot_2235/shard-apl4/igt@gem_exec_schedule@preempt-bsd.html
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> Cc: Michel Thierry <michel.thierry at intel.com>
> Cc: Michałt Winiarski <michal.winiarski at intel.com>

Reviewed-by: Michel Thierry <michel.thierry at intel.com>

> ---
>   drivers/gpu/drm/i915/intel_guc_submission.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_guc_submission.c b/drivers/gpu/drm/i915/intel_guc_submission.c
> index 133367a17863..24bdac205c45 100644
> --- a/drivers/gpu/drm/i915/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/intel_guc_submission.c
> @@ -588,6 +588,7 @@ static void inject_preempt_context(struct work_struct *work)
>   	data[6] = intel_guc_ggtt_offset(guc, guc->shared_data);
>   
>   	if (WARN_ON(intel_guc_send(guc, data, ARRAY_SIZE(data)))) {
> +		engine->flags &= ~I915_ENGINE_HAS_PREEMPTION; /* XXX racy! */
>   		execlists_clear_active(&engine->execlists,
>   				       EXECLISTS_ACTIVE_PREEMPT);
>   		tasklet_schedule(&engine->execlists.tasklet);
>