Re: [PATCH 25/33] drm/i915/guc: Support request cancellation

[Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>]

On 7/26/2021 5:23 PM, Matthew Brost wrote:
> This adds GuC backend support for i915_request_cancel(), which in turn
> makes CONFIG_DRM_I915_REQUEST_TIMEOUT work.
>
> This implementation makes use of fence while there are likely simplier
> options. A fence was chosen because of another feature coming soon
> which requires a user to block on a context until scheduling is
> disabled. In that case we return the fence to the user and the user can
> wait on that fence.
>
> v2:
>   (Daniele)
>    - A comment about locking the blocked incr / decr
>    - A comments about the use of the fence
>    - Update commit message explaining why fence
>    - Delete redundant check blocked count in unblock function
>    - Ring buffer implementation
>    - Comment about blocked in submission path
>    - Shorter rpm path
> v3:
>   (Checkpatch)
>    - Fix typos in commit message
>   (Daniel)
>    - Rework to simplier locking structure in guc_context_block / unblock
>
> Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@xxxxxxxxx>

Daniele

> ---
>   drivers/gpu/drm/i915/gt/intel_context.c       |  13 ++
>   drivers/gpu/drm/i915/gt/intel_context.h       |   7 +
>   drivers/gpu/drm/i915/gt/intel_context_types.h |   9 +-
>   .../drm/i915/gt/intel_execlists_submission.c  |  18 ++
>   .../gpu/drm/i915/gt/intel_ring_submission.c   |  16 ++
>   .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 188 ++++++++++++++++++
>   drivers/gpu/drm/i915/i915_request.c           |  14 +-
>   7 files changed, 251 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
> index 237b70e98744..477c42d7d693 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.c
> +++ b/drivers/gpu/drm/i915/gt/intel_context.c
> @@ -366,6 +366,12 @@ static int __intel_context_active(struct i915_active *active)
>   	return 0;
>   }
>   
> +static int sw_fence_dummy_notify(struct i915_sw_fence *sf,
> +				 enum i915_sw_fence_notify state)
> +{
> +	return NOTIFY_DONE;
> +}
> +
>   void
>   intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine)
>   {
> @@ -399,6 +405,13 @@ intel_context_init(struct intel_context *ce, struct intel_engine_cs *engine)
>   	ce->guc_id = GUC_INVALID_LRC_ID;
>   	INIT_LIST_HEAD(&ce->guc_id_link);
>   
> +	/*
> +	 * Initialize fence to be complete as this is expected to be complete
> +	 * unless there is a pending schedule disable outstanding.
> +	 */
> +	i915_sw_fence_init(&ce->guc_blocked, sw_fence_dummy_notify);
> +	i915_sw_fence_commit(&ce->guc_blocked);
> +
>   	i915_active_init(&ce->active,
>   			 __intel_context_active, __intel_context_retire, 0);
>   }
> diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
> index 814d9277096a..876bdb08303c 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context.h
> @@ -70,6 +70,13 @@ intel_context_is_pinned(struct intel_context *ce)
>   	return atomic_read(&ce->pin_count);
>   }
>   
> +static inline void intel_context_cancel_request(struct intel_context *ce,
> +						struct i915_request *rq)
> +{
> +	GEM_BUG_ON(!ce->ops->cancel_request);
> +	return ce->ops->cancel_request(ce, rq);
> +}
> +
>   /**
>    * intel_context_unlock_pinned - Releases the earlier locking of 'pinned' status
>    * @ce - the context
> diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
> index 57c19ee3e313..a5bc876face7 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> @@ -13,6 +13,7 @@
>   #include <linux/types.h>
>   
>   #include "i915_active_types.h"
> +#include "i915_sw_fence.h"
>   #include "i915_utils.h"
>   #include "intel_engine_types.h"
>   #include "intel_sseu.h"
> @@ -42,6 +43,9 @@ struct intel_context_ops {
>   	void (*unpin)(struct intel_context *ce);
>   	void (*post_unpin)(struct intel_context *ce);
>   
> +	void (*cancel_request)(struct intel_context *ce,
> +			       struct i915_request *rq);
> +
>   	void (*enter)(struct intel_context *ce);
>   	void (*exit)(struct intel_context *ce);
>   
> @@ -156,7 +160,7 @@ struct intel_context {
>   		 * sched_state: scheduling state of this context using GuC
>   		 * submission
>   		 */
> -		u8 sched_state;
> +		u16 sched_state;
>   		/*
>   		 * fences: maintains of list of requests that have a submit
>   		 * fence related to GuC submission
> @@ -184,6 +188,9 @@ struct intel_context {
>   	 * GuC ID link - in list when unpinned but guc_id still valid in GuC
>   	 */
>   	struct list_head guc_id_link;
> +
> +	/* GuC context blocked fence */
> +	struct i915_sw_fence guc_blocked;
>   };
>   
>   #endif /* __INTEL_CONTEXT_TYPES__ */
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> index b4a876736074..de5f9c86b9a4 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -114,6 +114,7 @@
>   #include "gen8_engine_cs.h"
>   #include "intel_breadcrumbs.h"
>   #include "intel_context.h"
> +#include "intel_engine_heartbeat.h"
>   #include "intel_engine_pm.h"
>   #include "intel_engine_stats.h"
>   #include "intel_execlists_submission.h"
> @@ -2587,11 +2588,26 @@ static int execlists_context_alloc(struct intel_context *ce)
>   	return lrc_alloc(ce, ce->engine);
>   }
>   
> +static void execlists_context_cancel_request(struct intel_context *ce,
> +					     struct i915_request *rq)
> +{
> +	struct intel_engine_cs *engine = NULL;
> +
> +	i915_request_active_engine(rq, &engine);
> +
> +	if (engine && intel_engine_pulse(engine))
> +		intel_gt_handle_error(engine->gt, engine->mask, 0,
> +				      "request cancellation by %s",
> +				      current->comm);
> +}
> +
>   static const struct intel_context_ops execlists_context_ops = {
>   	.flags = COPS_HAS_INFLIGHT,
>   
>   	.alloc = execlists_context_alloc,
>   
> +	.cancel_request = execlists_context_cancel_request,
> +
>   	.pre_pin = execlists_context_pre_pin,
>   	.pin = execlists_context_pin,
>   	.unpin = lrc_unpin,
> @@ -3608,6 +3624,8 @@ static const struct intel_context_ops virtual_context_ops = {
>   
>   	.alloc = virtual_context_alloc,
>   
> +	.cancel_request = execlists_context_cancel_request,
> +
>   	.pre_pin = virtual_context_pre_pin,
>   	.pin = virtual_context_pin,
>   	.unpin = lrc_unpin,
> diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> index 05bb9f449df1..2958e2fae380 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> @@ -16,6 +16,7 @@
>   #include "intel_reset.h"
>   #include "intel_ring.h"
>   #include "shmem_utils.h"
> +#include "intel_engine_heartbeat.h"
>   
>   /* Rough estimate of the typical request size, performing a flush,
>    * set-context and then emitting the batch.
> @@ -604,9 +605,24 @@ static void ring_context_ban(struct intel_context *ce,
>   		}
>   }
>   
> +static void ring_context_cancel_request(struct intel_context *ce,
> +					struct i915_request *rq)
> +{
> +	struct intel_engine_cs *engine = NULL;
> +
> +	i915_request_active_engine(rq, &engine);
> +
> +	if (engine && intel_engine_pulse(engine))
> +		intel_gt_handle_error(engine->gt, engine->mask, 0,
> +				      "request cancellation by %s",
> +				      current->comm);
> +}
> +
>   static const struct intel_context_ops ring_context_ops = {
>   	.alloc = ring_context_alloc,
>   
> +	.cancel_request = ring_context_cancel_request,
> +
>   	.ban = ring_context_ban,
>   
>   	.pre_pin = ring_context_pre_pin,
> 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 ad9a38a861df..ee4f1f996efa 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -126,6 +126,9 @@ static inline void clr_context_pending_enable(struct intel_context *ce)
>   #define SCHED_STATE_DESTROYED				BIT(1)
>   #define SCHED_STATE_PENDING_DISABLE			BIT(2)
>   #define SCHED_STATE_BANNED				BIT(3)
> +#define SCHED_STATE_BLOCKED_SHIFT			4
> +#define SCHED_STATE_BLOCKED		BIT(SCHED_STATE_BLOCKED_SHIFT)
> +#define SCHED_STATE_BLOCKED_MASK	(0xfff << SCHED_STATE_BLOCKED_SHIFT)
>   static inline void init_sched_state(struct intel_context *ce)
>   {
>   	/* Only should be called from guc_lrc_desc_pin() */
> @@ -203,6 +206,32 @@ static inline void clr_context_banned(struct intel_context *ce)
>   	ce->guc_state.sched_state &= ~SCHED_STATE_BANNED;
>   }
>   
> +static inline u32 context_blocked(struct intel_context *ce)
> +{
> +	return (ce->guc_state.sched_state & SCHED_STATE_BLOCKED_MASK) >>
> +		SCHED_STATE_BLOCKED_SHIFT;
> +}
> +
> +static inline void incr_context_blocked(struct intel_context *ce)
> +{
> +	lockdep_assert_held(&ce->engine->sched_engine->lock);
> +	lockdep_assert_held(&ce->guc_state.lock);
> +
> +	ce->guc_state.sched_state += SCHED_STATE_BLOCKED;
> +
> +	GEM_BUG_ON(!context_blocked(ce));	/* Overflow check */
> +}
> +
> +static inline void decr_context_blocked(struct intel_context *ce)
> +{
> +	lockdep_assert_held(&ce->engine->sched_engine->lock);
> +	lockdep_assert_held(&ce->guc_state.lock);
> +
> +	GEM_BUG_ON(!context_blocked(ce));	/* Underflow check */
> +
> +	ce->guc_state.sched_state -= SCHED_STATE_BLOCKED;
> +}
> +
>   static inline bool context_guc_id_invalid(struct intel_context *ce)
>   {
>   	return ce->guc_id == GUC_INVALID_LRC_ID;
> @@ -404,6 +433,14 @@ static int guc_add_request(struct intel_guc *guc, struct i915_request *rq)
>   		if (unlikely(err))
>   			goto out;
>   	}
> +
> +	/*
> +	 * The request / context will be run on the hardware when scheduling
> +	 * gets enabled in the unblock.
> +	 */
> +	if (unlikely(context_blocked(ce)))
> +		goto out;
> +
>   	enabled = context_enabled(ce);
>   
>   	if (!enabled) {
> @@ -532,6 +569,7 @@ static void __guc_context_destroy(struct intel_context *ce);
>   static void release_guc_id(struct intel_guc *guc, struct intel_context *ce);
>   static void guc_signal_context_fence(struct intel_context *ce);
>   static void guc_cancel_context_requests(struct intel_context *ce);
> +static void guc_blocked_fence_complete(struct intel_context *ce);
>   
>   static void scrub_guc_desc_for_outstanding_g2h(struct intel_guc *guc)
>   {
> @@ -579,6 +617,10 @@ static void scrub_guc_desc_for_outstanding_g2h(struct intel_guc *guc)
>   			}
>   			intel_context_sched_disable_unpin(ce);
>   			atomic_dec(&guc->outstanding_submission_g2h);
> +			spin_lock_irqsave(&ce->guc_state.lock, flags);
> +			guc_blocked_fence_complete(ce);
> +			spin_unlock_irqrestore(&ce->guc_state.lock, flags);
> +
>   			intel_context_put(ce);
>   		}
>   	}
> @@ -1354,6 +1396,21 @@ static void guc_context_post_unpin(struct intel_context *ce)
>   	lrc_post_unpin(ce);
>   }
>   
> +static void __guc_context_sched_enable(struct intel_guc *guc,
> +				       struct intel_context *ce)
> +{
> +	u32 action[] = {
> +		INTEL_GUC_ACTION_SCHED_CONTEXT_MODE_SET,
> +		ce->guc_id,
> +		GUC_CONTEXT_ENABLE
> +	};
> +
> +	trace_intel_context_sched_enable(ce);
> +
> +	guc_submission_send_busy_loop(guc, action, ARRAY_SIZE(action),
> +				      G2H_LEN_DW_SCHED_CONTEXT_MODE_SET, true);
> +}
> +
>   static void __guc_context_sched_disable(struct intel_guc *guc,
>   					struct intel_context *ce,
>   					u16 guc_id)
> @@ -1372,17 +1429,143 @@ static void __guc_context_sched_disable(struct intel_guc *guc,
>   				      G2H_LEN_DW_SCHED_CONTEXT_MODE_SET, true);
>   }
>   
> +static void guc_blocked_fence_complete(struct intel_context *ce)
> +{
> +	lockdep_assert_held(&ce->guc_state.lock);
> +
> +	if (!i915_sw_fence_done(&ce->guc_blocked))
> +		i915_sw_fence_complete(&ce->guc_blocked);
> +}
> +
> +static void guc_blocked_fence_reinit(struct intel_context *ce)
> +{
> +	lockdep_assert_held(&ce->guc_state.lock);
> +	GEM_BUG_ON(!i915_sw_fence_done(&ce->guc_blocked));
> +
> +	/*
> +	 * This fence is always complete unless a pending schedule disable is
> +	 * outstanding. We arm the fence here and complete it when we receive
> +	 * the pending schedule disable complete message.
> +	 */
> +	i915_sw_fence_fini(&ce->guc_blocked);
> +	i915_sw_fence_reinit(&ce->guc_blocked);
> +	i915_sw_fence_await(&ce->guc_blocked);
> +	i915_sw_fence_commit(&ce->guc_blocked);
> +}
> +
>   static u16 prep_context_pending_disable(struct intel_context *ce)
>   {
>   	lockdep_assert_held(&ce->guc_state.lock);
>   
>   	set_context_pending_disable(ce);
>   	clr_context_enabled(ce);
> +	guc_blocked_fence_reinit(ce);
>   	intel_context_get(ce);
>   
>   	return ce->guc_id;
>   }
>   
> +static struct i915_sw_fence *guc_context_block(struct intel_context *ce)
> +{
> +	struct intel_guc *guc = ce_to_guc(ce);
> +	struct i915_sched_engine *sched_engine = ce->engine->sched_engine;
> +	unsigned long flags;
> +	struct intel_runtime_pm *runtime_pm = ce->engine->uncore->rpm;
> +	intel_wakeref_t wakeref;
> +	u16 guc_id;
> +	bool enabled;
> +
> +	spin_lock_irqsave(&ce->guc_state.lock, flags);
> +
> +	/*
> +	 * Sync with submission path, increment before below changes to context
> +	 * state.
> +	 */
> +	spin_lock(&sched_engine->lock);
> +	incr_context_blocked(ce);
> +	spin_unlock(&sched_engine->lock);
> +
> +	enabled = context_enabled(ce);
> +	if (unlikely(!enabled || submission_disabled(guc))) {
> +		if (enabled)
> +			clr_context_enabled(ce);
> +		spin_unlock_irqrestore(&ce->guc_state.lock, flags);
> +		return &ce->guc_blocked;
> +	}
> +
> +	/*
> +	 * We add +2 here as the schedule disable complete CTB handler calls
> +	 * intel_context_sched_disable_unpin (-2 to pin_count).
> +	 */
> +	atomic_add(2, &ce->pin_count);
> +
> +	guc_id = prep_context_pending_disable(ce);
> +
> +	spin_unlock_irqrestore(&ce->guc_state.lock, flags);
> +
> +	with_intel_runtime_pm(runtime_pm, wakeref)
> +		__guc_context_sched_disable(guc, ce, guc_id);
> +
> +	return &ce->guc_blocked;
> +}
> +
> +static void guc_context_unblock(struct intel_context *ce)
> +{
> +	struct intel_guc *guc = ce_to_guc(ce);
> +	struct i915_sched_engine *sched_engine = ce->engine->sched_engine;
> +	unsigned long flags;
> +	struct intel_runtime_pm *runtime_pm = ce->engine->uncore->rpm;
> +	intel_wakeref_t wakeref;
> +	bool enable;
> +
> +	GEM_BUG_ON(context_enabled(ce));
> +
> +	spin_lock_irqsave(&ce->guc_state.lock, flags);
> +
> +	if (unlikely(submission_disabled(guc) ||
> +		     !intel_context_is_pinned(ce) ||
> +		     context_pending_disable(ce) ||
> +		     context_blocked(ce) > 1)) {
> +		enable = false;
> +	} else {
> +		enable = true;
> +		set_context_pending_enable(ce);
> +		set_context_enabled(ce);
> +		intel_context_get(ce);
> +	}
> +
> +	/*
> +	 * Sync with submission path, decrement after above changes to context
> +	 * state.
> +	 */
> +	spin_lock(&sched_engine->lock);
> +	decr_context_blocked(ce);
> +	spin_unlock(&sched_engine->lock);
> +
> +	spin_unlock_irqrestore(&ce->guc_state.lock, flags);
> +
> +	if (enable) {
> +		with_intel_runtime_pm(runtime_pm, wakeref)
> +			__guc_context_sched_enable(guc, ce);
> +	}
> +}
> +
> +static void guc_context_cancel_request(struct intel_context *ce,
> +				       struct i915_request *rq)
> +{
> +	if (i915_sw_fence_signaled(&rq->submit)) {
> +		struct i915_sw_fence *fence = guc_context_block(ce);
> +
> +		i915_sw_fence_wait(fence);
> +		if (!i915_request_completed(rq)) {
> +			__i915_request_skip(rq);
> +			guc_reset_state(ce, intel_ring_wrap(ce->ring, rq->head),
> +					true);
> +		}
> +		guc_context_unblock(ce);
> +	}
> +}
> +
>   static void __guc_context_set_preemption_timeout(struct intel_guc *guc,
>   						 u16 guc_id,
>   						 u32 preemption_timeout)
> @@ -1642,6 +1825,8 @@ static const struct intel_context_ops guc_context_ops = {
>   
>   	.ban = guc_context_ban,
>   
> +	.cancel_request = guc_context_cancel_request,
> +
>   	.enter = intel_context_enter_engine,
>   	.exit = intel_context_exit_engine,
>   
> @@ -1837,6 +2022,8 @@ static const struct intel_context_ops virtual_guc_context_ops = {
>   
>   	.ban = guc_context_ban,
>   
> +	.cancel_request = guc_context_cancel_request,
> +
>   	.enter = guc_virtual_context_enter,
>   	.exit = guc_virtual_context_exit,
>   
> @@ -2295,6 +2482,7 @@ int intel_guc_sched_done_process_msg(struct intel_guc *guc,
>   		clr_context_banned(ce);
>   		clr_context_pending_disable(ce);
>   		__guc_signal_context_fence(ce);
> +		guc_blocked_fence_complete(ce);
>   		spin_unlock_irqrestore(&ce->guc_state.lock, flags);
>   
>   		if (banned) {
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index 28f38b02a5d2..541a20371502 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -710,18 +710,6 @@ void i915_request_unsubmit(struct i915_request *request)
>   	spin_unlock_irqrestore(&engine->sched_engine->lock, flags);
>   }
>   
> -static void __cancel_request(struct i915_request *rq)
> -{
> -	struct intel_engine_cs *engine = NULL;
> -
> -	i915_request_active_engine(rq, &engine);
> -
> -	if (engine && intel_engine_pulse(engine))
> -		intel_gt_handle_error(engine->gt, engine->mask, 0,
> -				      "request cancellation by %s",
> -				      current->comm);
> -}
> -
>   void i915_request_cancel(struct i915_request *rq, int error)
>   {
>   	if (!i915_request_set_error_once(rq, error))
> @@ -729,7 +717,7 @@ void i915_request_cancel(struct i915_request *rq, int error)
>   
>   	set_bit(I915_FENCE_FLAG_SENTINEL, &rq->fence.flags);
>   
> -	__cancel_request(rq);
> +	intel_context_cancel_request(rq->context, rq);
>   }
>   
>   static int __i915_sw_fence_call

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