drm/i915/guc: Support request cancellation

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@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210727002348.97202-26-matthew.brost@intel.com

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);
 }

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

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__ */

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,

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,

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) {

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