Re: [PATCH 6/6] drm/i915/gt: Lift set-wedged engine dumping out of user paths

[Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>]

Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:

> The user (e.g. gem_eio) can manipulate the driver into wedging itself,
> allowing the user to trigger voluminous logging of inconsequential
> details. If we lift the dump to direct calls to intel_gt_set_wedged(),
> out of the intel_reset failure handling, we keep the detail logging for
> what we expect are true HW or test failures without being tricked.
>
> Reported-by: Tomi Sarvela <tomi.p.sarvela@xxxxxxxxx>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> Cc: Tomi Sarvela <tomi.p.sarvela@xxxxxxxxx>
> ---
>  drivers/gpu/drm/i915/gt/intel_reset.c | 30 +++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
> index beee0cf89bce..423a02506b2d 100644
> --- a/drivers/gpu/drm/i915/gt/intel_reset.c
> +++ b/drivers/gpu/drm/i915/gt/intel_reset.c
> @@ -800,13 +800,6 @@ static void __intel_gt_set_wedged(struct intel_gt *gt)
>  	if (test_bit(I915_WEDGED, &gt->reset.flags))
>  		return;
>  
> -	if (GEM_SHOW_DEBUG() && !intel_engines_are_idle(gt)) {
> -		struct drm_printer p = drm_debug_printer(__func__);
> -
> -		for_each_engine(engine, gt, id)
> -			intel_engine_dump(engine, &p, "%s\n", engine->name);
> -	}
> -
>  	GT_TRACE(gt, "start\n");
>  
>  	/*
> @@ -845,10 +838,29 @@ void intel_gt_set_wedged(struct intel_gt *gt)
>  {
>  	intel_wakeref_t wakeref;
>  
> +	if (test_bit(I915_WEDGED, &gt->reset.flags))
> +		return;
> +
> +	wakeref = intel_runtime_pm_get(gt->uncore->rpm);
>  	mutex_lock(&gt->reset.mutex);
> -	with_intel_runtime_pm(gt->uncore->rpm, wakeref)
> -		__intel_gt_set_wedged(gt);
> +
> +	if (GEM_SHOW_DEBUG() && !intel_engines_are_idle(gt)) {

As you inspect each engine separately the precursory idle check
seems superfluous.

-Mika

> +		struct drm_printer p = drm_debug_printer(__func__);
> +		struct intel_engine_cs *engine;
> +		enum intel_engine_id id;
> +
> +		for_each_engine(engine, gt, id) {
> +			if (intel_engine_is_idle(engine))
> +				continue;
> +
> +			intel_engine_dump(engine, &p, "%s\n", engine->name);
> +		}
> +	}
> +
> +	__intel_gt_set_wedged(gt);
> +
>  	mutex_unlock(&gt->reset.mutex);
> +	intel_runtime_pm_put(gt->uncore->rpm, wakeref);
>  }
>  
>  static bool __intel_gt_unset_wedged(struct intel_gt *gt)
> -- 
> 2.25.0
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