Re: [PATCH 11/47] drm/i915/guc: Implement GuC submission tasklet

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On Tue, Jun 29, 2021 at 03:04:56PM -0700, John Harrison wrote:
> On 6/24/2021 00:04, Matthew Brost wrote:
> > Implement GuC submission tasklet for new interface. The new GuC
> > interface uses H2G to submit contexts to the GuC. Since H2G use a single
> > channel, a single tasklet submits is used for the submission path.
> Re-word? 'a single tasklet submits is used...' doesn't make sense.
> 

Will do.

> > Also the per engine interrupt handler has been updated to disable the
> > rescheduling of the physical engine tasklet, when using GuC scheduling,
> > as the physical engine tasklet is no longer used.
> > 
> > In this patch the field, guc_id, has been added to intel_context and is
> > not assigned. Patches later in the series will assign this value.
> > 
> > Cc: John Harrison<john.c.harrison@xxxxxxxxx>
> > Signed-off-by: Matthew Brost<matthew.brost@xxxxxxxxx>
> > ---
> >   drivers/gpu/drm/i915/gt/intel_context_types.h |   9 +
> >   drivers/gpu/drm/i915/gt/uc/intel_guc.h        |   4 +
> >   .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 231 +++++++++---------
> >   3 files changed, 127 insertions(+), 117 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
> > index ed8c447a7346..bb6fef7eae52 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> > @@ -136,6 +136,15 @@ struct intel_context {
> >   	struct intel_sseu sseu;
> >   	u8 wa_bb_page; /* if set, page num reserved for context workarounds */
> > +
> > +	/* GuC scheduling state that does not require a lock. */
> Maybe 'GuC scheduling state flags that do not require a lock'? Otherwise it
> just looks like a counter or something.
> 

Sure.

> > +	atomic_t guc_sched_state_no_lock;
> > +
> > +	/*
> > +	 * GuC lrc descriptor ID - Not assigned in this patch but future patches
> Not a blocker but s/lrc/LRC/ would keep Michal happy ;). Although presumably
> this comment is at least being amended by later patches in the series.
>

Will fix.

> > +	 * in the series will.
> > +	 */
> > +	u16 guc_id;
> >   };
> >   #endif /* __INTEL_CONTEXT_TYPES__ */
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> > index 2313d9fc087b..9ba8219475b2 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> > @@ -30,6 +30,10 @@ struct intel_guc {
> >   	struct intel_guc_log log;
> >   	struct intel_guc_ct ct;
> > +	/* Global engine used to submit requests to GuC */
> > +	struct i915_sched_engine *sched_engine;
> > +	struct i915_request *stalled_request;
> > +
> >   	/* intel_guc_recv interrupt related state */
> >   	spinlock_t irq_lock;
> >   	unsigned int msg_enabled_mask;
> > 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 23a94a896a0b..ee933efbf0ff 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > @@ -60,6 +60,31 @@
> >   #define GUC_REQUEST_SIZE 64 /* bytes */
> > +/*
> > + * Below is a set of functions which control the GuC scheduling state which do
> > + * not require a lock as all state transitions are mutually exclusive. i.e. It
> > + * is not possible for the context pinning code and submission, for the same
> > + * context, to be executing simultaneously. We still need an atomic as it is
> > + * possible for some of the bits to changing at the same time though.
> > + */
> > +#define SCHED_STATE_NO_LOCK_ENABLED			BIT(0)
> > +static inline bool context_enabled(struct intel_context *ce)
> > +{
> > +	return (atomic_read(&ce->guc_sched_state_no_lock) &
> > +		SCHED_STATE_NO_LOCK_ENABLED);
> > +}
> > +
> > +static inline void set_context_enabled(struct intel_context *ce)
> > +{
> > +	atomic_or(SCHED_STATE_NO_LOCK_ENABLED, &ce->guc_sched_state_no_lock);
> > +}
> > +
> > +static inline void clr_context_enabled(struct intel_context *ce)
> > +{
> > +	atomic_and((u32)~SCHED_STATE_NO_LOCK_ENABLED,
> > +		   &ce->guc_sched_state_no_lock);
> > +}
> > +
> >   static inline struct i915_priolist *to_priolist(struct rb_node *rb)
> >   {
> >   	return rb_entry(rb, struct i915_priolist, node);
> > @@ -122,37 +147,29 @@ static inline void set_lrc_desc_registered(struct intel_guc *guc, u32 id,
> >   	xa_store_irq(&guc->context_lookup, id, ce, GFP_ATOMIC);
> >   }
> > -static void guc_add_request(struct intel_guc *guc, struct i915_request *rq)
> > +static int guc_add_request(struct intel_guc *guc, struct i915_request *rq)
> >   {
> > -	/* Leaving stub as this function will be used in future patches */
> > -}
> > +	int err;
> > +	struct intel_context *ce = rq->context;
> > +	u32 action[3];
> > +	int len = 0;
> > +	bool enabled = context_enabled(ce);
> > -/*
> > - * When we're doing submissions using regular execlists backend, writing to
> > - * ELSP from CPU side is enough to make sure that writes to ringbuffer pages
> > - * pinned in mappable aperture portion of GGTT are visible to command streamer.
> > - * Writes done by GuC on our behalf are not guaranteeing such ordering,
> > - * therefore, to ensure the flush, we're issuing a POSTING READ.
> > - */
> > -static void flush_ggtt_writes(struct i915_vma *vma)
> > -{
> > -	if (i915_vma_is_map_and_fenceable(vma))
> > -		intel_uncore_posting_read_fw(vma->vm->gt->uncore,
> > -					     GUC_STATUS);
> > -}
> > +	if (!enabled) {
> > +		action[len++] = INTEL_GUC_ACTION_SCHED_CONTEXT_MODE_SET;
> > +		action[len++] = ce->guc_id;
> > +		action[len++] = GUC_CONTEXT_ENABLE;
> > +	} else {
> > +		action[len++] = INTEL_GUC_ACTION_SCHED_CONTEXT;
> > +		action[len++] = ce->guc_id;
> > +	}
> > -static void guc_submit(struct intel_engine_cs *engine,
> > -		       struct i915_request **out,
> > -		       struct i915_request **end)
> > -{
> > -	struct intel_guc *guc = &engine->gt->uc.guc;
> > +	err = intel_guc_send_nb(guc, action, len);
> > -	do {
> > -		struct i915_request *rq = *out++;
> > +	if (!enabled && !err)
> > +		set_context_enabled(ce);
> > -		flush_ggtt_writes(rq->ring->vma);
> > -		guc_add_request(guc, rq);
> > -	} while (out != end);
> > +	return err;
> >   }
> >   static inline int rq_prio(const struct i915_request *rq)
> > @@ -160,125 +177,88 @@ static inline int rq_prio(const struct i915_request *rq)
> >   	return rq->sched.attr.priority;
> >   }
> > -static struct i915_request *schedule_in(struct i915_request *rq, int idx)
> > +static int guc_dequeue_one_context(struct intel_guc *guc)
> >   {
> > -	trace_i915_request_in(rq, idx);
> > -
> > -	/*
> > -	 * Currently we are not tracking the rq->context being inflight
> > -	 * (ce->inflight = rq->engine). It is only used by the execlists
> > -	 * backend at the moment, a similar counting strategy would be
> > -	 * required if we generalise the inflight tracking.
> > -	 */
> > -
> > -	__intel_gt_pm_get(rq->engine->gt);
> > -	return i915_request_get(rq);
> > -}
> > -
> > -static void schedule_out(struct i915_request *rq)
> > -{
> > -	trace_i915_request_out(rq);
> > -
> > -	intel_gt_pm_put_async(rq->engine->gt);
> > -	i915_request_put(rq);
> > -}
> > -
> > -static void __guc_dequeue(struct intel_engine_cs *engine)
> > -{
> > -	struct intel_engine_execlists * const execlists = &engine->execlists;
> > -	struct i915_sched_engine * const sched_engine = engine->sched_engine;
> > -	struct i915_request **first = execlists->inflight;
> > -	struct i915_request ** const last_port = first + execlists->port_mask;
> > -	struct i915_request *last = first[0];
> > -	struct i915_request **port;
> > +	struct i915_sched_engine * const sched_engine = guc->sched_engine;
> > +	struct i915_request *last = NULL;
> >   	bool submit = false;
> >   	struct rb_node *rb;
> > +	int ret;
> >   	lockdep_assert_held(&sched_engine->lock);
> > -	if (last) {
> > -		if (*++first)
> > -			return;
> > -
> > -		last = NULL;
> > +	if (guc->stalled_request) {
> > +		submit = true;
> > +		last = guc->stalled_request;
> > +		goto resubmit;
> >   	}
> > -	/*
> > -	 * We write directly into the execlists->inflight queue and don't use
> > -	 * the execlists->pending queue, as we don't have a distinct switch
> > -	 * event.
> > -	 */
> > -	port = first;
> >   	while ((rb = rb_first_cached(&sched_engine->queue))) {
> >   		struct i915_priolist *p = to_priolist(rb);
> >   		struct i915_request *rq, *rn;
> >   		priolist_for_each_request_consume(rq, rn, p) {
> > -			if (last && rq->context != last->context) {
> > -				if (port == last_port)
> > -					goto done;
> > -
> > -				*port = schedule_in(last,
> > -						    port - execlists->inflight);
> > -				port++;
> > -			}
> > +			if (last && rq->context != last->context)
> > +				goto done;
> >   			list_del_init(&rq->sched.link);
> > +
> >   			__i915_request_submit(rq);
> > -			submit = true;
> > +
> > +			trace_i915_request_in(rq, 0);
> >   			last = rq;
> > +			submit = true;
> >   		}
> >   		rb_erase_cached(&p->node, &sched_engine->queue);
> >   		i915_priolist_free(p);
> >   	}
> >   done:
> > -	sched_engine->queue_priority_hint =
> > -		rb ? to_priolist(rb)->priority : INT_MIN;
> >   	if (submit) {
> > -		*port = schedule_in(last, port - execlists->inflight);
> > -		*++port = NULL;
> > -		guc_submit(engine, first, port);
> > +		last->context->lrc_reg_state[CTX_RING_TAIL] =
> > +			intel_ring_set_tail(last->ring, last->tail);
> > +resubmit:
> > +		/*
> > +		 * We only check for -EBUSY here even though it is possible for
> > +		 * -EDEADLK to be returned. If -EDEADLK is returned, the GuC has
> > +		 * died and a full GPU needs to be done. The hangcheck will
> 'full GPU reset'. Although I believe strictly speaking, it is a 'full GT
> reset'. There are other bits of the GPU beyond the GT.

Yep, will fix.

> 
> > +		 * eventually detect that the GuC has died and trigger this
> > +		 * reset so no need to handle -EDEADLK here.
> > +		 */
> > +		ret = guc_add_request(guc, last);
> > +		if (ret == -EBUSY) {
> > +			tasklet_schedule(&sched_engine->tasklet);
> > +			guc->stalled_request = last;
> > +			return false;
> > +		}
> >   	}
> > -	execlists->active = execlists->inflight;
> > +
> > +	guc->stalled_request = NULL;
> > +	return submit;
> >   }
> >   static void guc_submission_tasklet(struct tasklet_struct *t)
> >   {
> >   	struct i915_sched_engine *sched_engine =
> >   		from_tasklet(sched_engine, t, tasklet);
> > -	struct intel_engine_cs * const engine = sched_engine->private_data;
> > -	struct intel_engine_execlists * const execlists = &engine->execlists;
> > -	struct i915_request **port, *rq;
> >   	unsigned long flags;
> > +	bool loop;
> > -	spin_lock_irqsave(&engine->sched_engine->lock, flags);
> > -
> > -	for (port = execlists->inflight; (rq = *port); port++) {
> > -		if (!i915_request_completed(rq))
> > -			break;
> > -
> > -		schedule_out(rq);
> > -	}
> > -	if (port != execlists->inflight) {
> > -		int idx = port - execlists->inflight;
> > -		int rem = ARRAY_SIZE(execlists->inflight) - idx;
> > -		memmove(execlists->inflight, port, rem * sizeof(*port));
> > -	}
> > +	spin_lock_irqsave(&sched_engine->lock, flags);
> > -	__guc_dequeue(engine);
> > +	do {
> > +		loop = guc_dequeue_one_context(sched_engine->private_data);
> > +	} while (loop);
> > -	i915_sched_engine_reset_on_empty(engine->sched_engine);
> > +	i915_sched_engine_reset_on_empty(sched_engine);
> > -	spin_unlock_irqrestore(&engine->sched_engine->lock, flags);
> > +	spin_unlock_irqrestore(&sched_engine->lock, flags);
> >   }
> Not a blocker but it has to be said that it would be much easier to remove
> all of the above if the delete was split into a separate patch. Having two
> completely disparate threads of code interwoven in the diff makes it much
> harder to see what the new version is doing!
> 

Yes, it would be easier to read if this code was deleted in a seperate
patch. I'll keep that in mind going forward. No promises but perhaps
I'll do this in the next rev.

> 
> >   static void cs_irq_handler(struct intel_engine_cs *engine, u16 iir)
> >   {
> > -	if (iir & GT_RENDER_USER_INTERRUPT) {
> > +	if (iir & GT_RENDER_USER_INTERRUPT)
> >   		intel_engine_signal_breadcrumbs(engine);
> > -		tasklet_hi_schedule(&engine->sched_engine->tasklet);
> > -	}
> >   }
> >   static void guc_reset_prepare(struct intel_engine_cs *engine)
> > @@ -349,6 +329,10 @@ static void guc_reset_cancel(struct intel_engine_cs *engine)
> >   	struct rb_node *rb;
> >   	unsigned long flags;
> > +	/* Can be called during boot if GuC fails to load */
> > +	if (!engine->gt)
> > +		return;
> > +
> >   	ENGINE_TRACE(engine, "\n");
> >   	/*
> > @@ -433,8 +417,11 @@ int intel_guc_submission_init(struct intel_guc *guc)
> >   void intel_guc_submission_fini(struct intel_guc *guc)
> >   {
> > -	if (guc->lrc_desc_pool)
> > -		guc_lrc_desc_pool_destroy(guc);
> > +	if (!guc->lrc_desc_pool)
> > +		return;
> > +
> > +	guc_lrc_desc_pool_destroy(guc);
> > +	i915_sched_engine_put(guc->sched_engine);
> >   }
> >   static int guc_context_alloc(struct intel_context *ce)
> > @@ -499,32 +486,32 @@ static int guc_request_alloc(struct i915_request *request)
> >   	return 0;
> >   }
> > -static inline void queue_request(struct intel_engine_cs *engine,
> > +static inline void queue_request(struct i915_sched_engine *sched_engine,
> >   				 struct i915_request *rq,
> >   				 int prio)
> >   {
> >   	GEM_BUG_ON(!list_empty(&rq->sched.link));
> >   	list_add_tail(&rq->sched.link,
> > -		      i915_sched_lookup_priolist(engine->sched_engine, prio));
> > +		      i915_sched_lookup_priolist(sched_engine, prio));
> >   	set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
> >   }
> >   static void guc_submit_request(struct i915_request *rq)
> >   {
> > -	struct intel_engine_cs *engine = rq->engine;
> > +	struct i915_sched_engine *sched_engine = rq->engine->sched_engine;
> >   	unsigned long flags;
> >   	/* Will be called from irq-context when using foreign fences. */
> > -	spin_lock_irqsave(&engine->sched_engine->lock, flags);
> > +	spin_lock_irqsave(&sched_engine->lock, flags);
> > -	queue_request(engine, rq, rq_prio(rq));
> > +	queue_request(sched_engine, rq, rq_prio(rq));
> > -	GEM_BUG_ON(i915_sched_engine_is_empty(engine->sched_engine));
> > +	GEM_BUG_ON(i915_sched_engine_is_empty(sched_engine));
> >   	GEM_BUG_ON(list_empty(&rq->sched.link));
> > -	tasklet_hi_schedule(&engine->sched_engine->tasklet);
> > +	tasklet_hi_schedule(&sched_engine->tasklet);
> > -	spin_unlock_irqrestore(&engine->sched_engine->lock, flags);
> > +	spin_unlock_irqrestore(&sched_engine->lock, flags);
> >   }
> >   static void sanitize_hwsp(struct intel_engine_cs *engine)
> > @@ -602,8 +589,6 @@ static void guc_release(struct intel_engine_cs *engine)
> >   {
> >   	engine->sanitize = NULL; /* no longer in control, nothing to sanitize */
> > -	tasklet_kill(&engine->sched_engine->tasklet);
> > -
> >   	intel_engine_cleanup_common(engine);
> >   	lrc_fini_wa_ctx(engine);
> >   }
> > @@ -674,6 +659,7 @@ static inline void guc_default_irqs(struct intel_engine_cs *engine)
> >   int intel_guc_submission_setup(struct intel_engine_cs *engine)
> >   {
> >   	struct drm_i915_private *i915 = engine->i915;
> > +	struct intel_guc *guc = &engine->gt->uc.guc;
> >   	/*
> >   	 * The setup relies on several assumptions (e.g. irqs always enabled)
> > @@ -681,7 +667,18 @@ int intel_guc_submission_setup(struct intel_engine_cs *engine)
> >   	 */
> >   	GEM_BUG_ON(GRAPHICS_VER(i915) < 11);
> > -	tasklet_setup(&engine->sched_engine->tasklet, guc_submission_tasklet);
> > +	if (!guc->sched_engine) {
> > +		guc->sched_engine = i915_sched_engine_create(ENGINE_VIRTUAL);
> Does the re-work of the sched_engine create/destroy happen later in this
> patch series? Wasn't there issues with the wrong destroy function being
> called in certain situations? Or do those issues (and fixes) only come in
> with the virtual engine support?
> 

We didn't need the destroy until we introduce the guc_submit_engine, but
that is changing after the kasan bug fix I sent out today for the
internal version of this code. I've already reworked my upstream branch
to add a destroy vfunc for sched_engine in seperate patch a bit later in
the series.

Matt

> John.
> 
> > +		if (!guc->sched_engine)
> > +			return -ENOMEM;
> > +
> > +		guc->sched_engine->schedule = i915_schedule;
> > +		guc->sched_engine->private_data = guc;
> > +		tasklet_setup(&guc->sched_engine->tasklet,
> > +			      guc_submission_tasklet);
> > +	}
> > +	i915_sched_engine_put(engine->sched_engine);
> > +	engine->sched_engine = i915_sched_engine_get(guc->sched_engine);
> >   	guc_default_vfuncs(engine);
> >   	guc_default_irqs(engine);
> 



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