Re: [Intel-gfx] [PATCH 5/6] drm/i915/gt: Discard stale context state from across idling

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Before we idle, on parking, we switch to the kernel context such that we
> have a scratch context loaded while the GPU idle, protecting any
> precious user state. Be paranoid and assume that the idle state may have
> been trashed, and reset the kernel_context image after idling.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_engine_pm.c | 6 ++++++
>  drivers/gpu/drm/i915/gt/intel_gt_pm.c     | 8 --------
>  drivers/gpu/drm/i915/gt/mock_engine.c     | 5 +++++
>  3 files changed, 11 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> index cd82f0baef49..1b9f73948f22 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
> @@ -20,6 +20,7 @@ static int __engine_unpark(struct intel_wakeref *wf)
>  {
>  	struct intel_engine_cs *engine =
>  		container_of(wf, typeof(*engine), wakeref);
> +	struct intel_context *ce;
>  	void *map;
>  
>  	ENGINE_TRACE(engine, "\n");
> @@ -34,6 +35,11 @@ static int __engine_unpark(struct intel_wakeref *wf)
>  	if (!IS_ERR_OR_NULL(map))
>  		engine->pinned_default_state = map;
>  
> +	/* Discard stale context state from across idling */
> +	ce = engine->kernel_context;
> +	if (ce)
> +		ce->ops->reset(ce);
> +

Expect the worst, sure.
Checksum would get us datapoints tho.

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>


>  	if (engine->unpark)
>  		engine->unpark(engine);
>  
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> index 9b220c930ebc..d1c2f034296a 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
> @@ -213,16 +213,8 @@ int intel_gt_resume(struct intel_gt *gt)
>  	intel_llc_enable(&gt->llc);
>  
>  	for_each_engine(engine, gt, id) {
> -		struct intel_context *ce;
> -
>  		intel_engine_pm_get(engine);
>  
> -		ce = engine->kernel_context;
> -		if (ce) {
> -			GEM_BUG_ON(!intel_context_is_pinned(ce));
> -			ce->ops->reset(ce);
> -		}
> -
>  		engine->serial++; /* kernel context lost */
>  		err = engine->resume(engine);
>  
> diff --git a/drivers/gpu/drm/i915/gt/mock_engine.c b/drivers/gpu/drm/i915/gt/mock_engine.c
> index 4e1eafa94be9..d0e68ce9aa51 100644
> --- a/drivers/gpu/drm/i915/gt/mock_engine.c
> +++ b/drivers/gpu/drm/i915/gt/mock_engine.c
> @@ -152,6 +152,10 @@ static int mock_context_pin(struct intel_context *ce)
>  	return intel_context_active_acquire(ce);
>  }
>  
> +static void mock_context_reset(struct intel_context *ce)
> +{
> +}
> +
>  static const struct intel_context_ops mock_context_ops = {
>  	.alloc = mock_context_alloc,
>  
> @@ -161,6 +165,7 @@ static const struct intel_context_ops mock_context_ops = {
>  	.enter = intel_context_enter_engine,
>  	.exit = intel_context_exit_engine,
>  
> +	.reset = mock_context_reset,
>  	.destroy = mock_context_destroy,
>  };
>  
> -- 
> 2.25.0.rc0
>
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