Re: [Intel-gfx] [RFC PATCH 74/97] drm/i915/guc: Capture error state on context reset

[Matthew Brost <matthew.brost@intel.com>]

On Tue, May 11, 2021 at 06:28:25PM +0200, Daniel Vetter wrote:
> On Thu, May 06, 2021 at 12:14:28PM -0700, Matthew Brost wrote:
> > We receive notification of an engine reset from GuC at its
> > completion. Meaning GuC has potentially cleared any HW state
> > we may have been interested in capturing. GuC resumes scheduling
> > on the engine post-reset, as the resets are meant to be transparent,
> > further muddling our error state.
> > 
> > There is ongoing work to define an API for a GuC debug state dump. The
> > suggestion for now is to manually disable FW initiated resets in cases
> > where debug state is needed.
> > 
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> 
> This looks a bit backwards to me:
> 

Definitely a bit hacky but this patch does the best to capture the error as it
can,

> - I figured we should capture error state when we get the G2H, in which
>   case I hope we do know which the offending context was that got shot.
>

We know which context was shot based on the G2H. See 'hung_ce' in this patch.

> - For now we're missing the hw state, but we should still be able to
>   capture the buffers userspace wants us to capture. So that could be
>   wired up already?

Which buffers exactly? We dump all buffers associated with the context. 

> 
> But yeah register state capturing needs support from GuC fw.
>
> I think this is a big enough miss in GuC features that we should list it
> on the rfc as a thing to fix.

Agree this needs to be fixed.

Matt

> -Daniel
> 
> > ---
> >  drivers/gpu/drm/i915/gt/intel_context.c       | 20 +++++++++++
> >  drivers/gpu/drm/i915/gt/intel_context.h       |  3 ++
> >  drivers/gpu/drm/i915/gt/intel_engine.h        | 21 ++++++++++-
> >  drivers/gpu/drm/i915/gt/intel_engine_cs.c     | 11 ++++--
> >  drivers/gpu/drm/i915/gt/intel_engine_types.h  |  2 ++
> >  .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 35 +++++++++----------
> >  drivers/gpu/drm/i915/i915_gpu_error.c         | 25 ++++++++++---
> >  7 files changed, 91 insertions(+), 26 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
> > index 2f01437056a8..3fe7794b2bfd 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_context.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_context.c
> > @@ -514,6 +514,26 @@ struct i915_request *intel_context_create_request(struct intel_context *ce)
> >  	return rq;
> >  }
> >  
> > +struct i915_request *intel_context_find_active_request(struct intel_context *ce)
> > +{
> > +	struct i915_request *rq, *active = NULL;
> > +	unsigned long flags;
> > +
> > +	GEM_BUG_ON(!intel_engine_uses_guc(ce->engine));
> > +
> > +	spin_lock_irqsave(&ce->guc_active.lock, flags);
> > +	list_for_each_entry_reverse(rq, &ce->guc_active.requests,
> > +				    sched.link) {
> > +		if (i915_request_completed(rq))
> > +			break;
> > +
> > +		active = rq;
> > +	}
> > +	spin_unlock_irqrestore(&ce->guc_active.lock, flags);
> > +
> > +	return active;
> > +}
> > +
> >  #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
> >  #include "selftest_context.c"
> >  #endif
> > diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
> > index 9b211ca5ecc7..d2b499ed8a05 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_context.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_context.h
> > @@ -195,6 +195,9 @@ int intel_context_prepare_remote_request(struct intel_context *ce,
> >  
> >  struct i915_request *intel_context_create_request(struct intel_context *ce);
> >  
> > +struct i915_request *
> > +intel_context_find_active_request(struct intel_context *ce);
> > +
> >  static inline struct intel_ring *__intel_context_ring_size(u64 sz)
> >  {
> >  	return u64_to_ptr(struct intel_ring, sz);
> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h
> > index 3321d0917a99..bb94963a9fa2 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine.h
> > @@ -242,7 +242,7 @@ ktime_t intel_engine_get_busy_time(struct intel_engine_cs *engine,
> >  				   ktime_t *now);
> >  
> >  struct i915_request *
> > -intel_engine_find_active_request(struct intel_engine_cs *engine);
> > +intel_engine_execlist_find_hung_request(struct intel_engine_cs *engine);
> >  
> >  u32 intel_engine_context_size(struct intel_gt *gt, u8 class);
> >  
> > @@ -316,4 +316,23 @@ intel_engine_get_sibling(struct intel_engine_cs *engine, unsigned int sibling)
> >  	return engine->cops->get_sibling(engine, sibling);
> >  }
> >  
> > +static inline void
> > +intel_engine_set_hung_context(struct intel_engine_cs *engine,
> > +			      struct intel_context *ce)
> > +{
> > +	engine->hung_ce = ce;
> > +}
> > +
> > +static inline void
> > +intel_engine_clear_hung_context(struct intel_engine_cs *engine)
> > +{
> > +	intel_engine_set_hung_context(engine, NULL);
> > +}
> > +
> > +static inline struct intel_context *
> > +intel_engine_get_hung_context(struct intel_engine_cs *engine)
> > +{
> > +	return engine->hung_ce;
> > +}
> > +
> >  #endif /* _INTEL_RINGBUFFER_H_ */
> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> > index 10300db1c9a6..ad3987289f09 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> > @@ -1727,7 +1727,7 @@ void intel_engine_dump(struct intel_engine_cs *engine,
> >  	drm_printf(m, "\tRequests:\n");
> >  
> >  	spin_lock_irqsave(&engine->sched_engine->lock, flags);
> > -	rq = intel_engine_find_active_request(engine);
> > +	rq = intel_engine_execlist_find_hung_request(engine);
> >  	if (rq) {
> >  		struct intel_timeline *tl = get_timeline(rq);
> >  
> > @@ -1838,10 +1838,17 @@ static bool match_ring(struct i915_request *rq)
> >  }
> >  
> >  struct i915_request *
> > -intel_engine_find_active_request(struct intel_engine_cs *engine)
> > +intel_engine_execlist_find_hung_request(struct intel_engine_cs *engine)
> >  {
> >  	struct i915_request *request, *active = NULL;
> >  
> > +	/*
> > +	 * This search does not work in GuC submission mode. However, the GuC
> > +	 * will report the hanging context directly to the driver itself. So
> > +	 * the driver should never get here when in GuC mode.
> > +	 */
> > +	GEM_BUG_ON(intel_uc_uses_guc_submission(&engine->gt->uc));
> > +
> >  	/*
> >  	 * We are called by the error capture, reset and to dump engine
> >  	 * state at random points in time. In particular, note that neither is
> > diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> > index b84562b2708b..bba53e3b39b9 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> > @@ -304,6 +304,8 @@ struct intel_engine_cs {
> >  	/* keep a request in reserve for a [pm] barrier under oom */
> >  	struct i915_request *request_pool;
> >  
> > +	struct intel_context *hung_ce;
> > +
> >  	struct llist_head barrier_tasks;
> >  
> >  	struct intel_context *kernel_context; /* pinned */
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > index 22f17a055b21..6b3b74e50b31 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > @@ -726,24 +726,6 @@ __unwind_incomplete_requests(struct intel_context *ce)
> >  	spin_unlock_irqrestore(&sched_engine->lock, flags);
> >  }
> >  
> > -static struct i915_request *context_find_active_request(struct intel_context *ce)
> > -{
> > -	struct i915_request *rq, *active = NULL;
> > -	unsigned long flags;
> > -
> > -	spin_lock_irqsave(&ce->guc_active.lock, flags);
> > -	list_for_each_entry_reverse(rq, &ce->guc_active.requests,
> > -				    sched.link) {
> > -		if (i915_request_completed(rq))
> > -			break;
> > -
> > -		active = rq;
> > -	}
> > -	spin_unlock_irqrestore(&ce->guc_active.lock, flags);
> > -
> > -	return active;
> > -}
> > -
> >  static void __guc_reset_context(struct intel_context *ce, bool stalled)
> >  {
> >  	struct i915_request *rq;
> > @@ -757,7 +739,7 @@ static void __guc_reset_context(struct intel_context *ce, bool stalled)
> >  	 */
> >  	clr_context_enabled(ce);
> >  
> > -	rq = context_find_active_request(ce);
> > +	rq = intel_context_find_active_request(ce);
> >  	if (!rq) {
> >  		head = ce->ring->tail;
> >  		stalled = false;
> > @@ -2192,6 +2174,20 @@ int intel_guc_sched_done_process_msg(struct intel_guc *guc,
> >  	return 0;
> >  }
> >  
> > +static void capture_error_state(struct intel_guc *guc,
> > +				struct intel_context *ce)
> > +{
> > +	struct intel_gt *gt = guc_to_gt(guc);
> > +	struct drm_i915_private *i915 = gt->i915;
> > +	struct intel_engine_cs *engine = __context_to_physical_engine(ce);
> > +	intel_wakeref_t wakeref;
> > +
> > +	intel_engine_set_hung_context(engine, ce);
> > +	with_intel_runtime_pm(&i915->runtime_pm, wakeref)
> > +		i915_capture_error_state(gt, engine->mask);
> > +	atomic_inc(&i915->gpu_error.reset_engine_count[engine->uabi_class]);
> > +}
> > +
> >  static void guc_context_replay(struct intel_context *ce)
> >  {
> >  	struct i915_sched_engine *sched_engine = ce->engine->sched_engine;
> > @@ -2204,6 +2200,7 @@ static void guc_handle_context_reset(struct intel_guc *guc,
> >  				     struct intel_context *ce)
> >  {
> >  	trace_intel_context_reset(ce);
> > +	capture_error_state(guc, ce);
> >  	guc_context_replay(ce);
> >  }
> >  
> > diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> > index 3352f56bcf63..825bdfe44225 100644
> > --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> > +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> > @@ -1435,20 +1435,37 @@ capture_engine(struct intel_engine_cs *engine,
> >  {
> >  	struct intel_engine_capture_vma *capture = NULL;
> >  	struct intel_engine_coredump *ee;
> > -	struct i915_request *rq;
> > +	struct intel_context *ce;
> > +	struct i915_request *rq = NULL;
> >  	unsigned long flags;
> >  
> >  	ee = intel_engine_coredump_alloc(engine, GFP_KERNEL);
> >  	if (!ee)
> >  		return NULL;
> >  
> > -	spin_lock_irqsave(&engine->sched_engine->lock, flags);
> > -	rq = intel_engine_find_active_request(engine);
> > +	ce = intel_engine_get_hung_context(engine);
> > +	if (ce) {
> > +		intel_engine_clear_hung_context(engine);
> > +		rq = intel_context_find_active_request(ce);
> > +		if (!rq || !i915_request_started(rq))
> > +			goto no_request_capture;
> > +	} else {
> > +		/*
> > +		 * Getting here with GuC enabled means it is a forced error capture
> > +		 * with no actual hang. So, no need to attempt the execlist search.
> > +		 */
> > +		if (!intel_uc_uses_guc_submission(&engine->gt->uc)) {
> > +			spin_lock_irqsave(&engine->sched_engine->lock, flags);
> > +			rq = intel_engine_execlist_find_hung_request(engine);
> > +			spin_unlock_irqrestore(&engine->sched_engine->lock,
> > +					       flags);
> > +		}
> > +	}
> >  	if (rq)
> >  		capture = intel_engine_coredump_add_request(ee, rq,
> >  							    ATOMIC_MAYFAIL);
> > -	spin_unlock_irqrestore(&engine->sched_engine->lock, flags);
> >  	if (!capture) {
> > +no_request_capture:
> >  		kfree(ee);
> >  		return NULL;
> >  	}
> > -- 
> > 2.28.0
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch