[PATCH] drm/i915: Change context lifecycle

[Nick Hoath <nicholas.hoath@intel.com>]

Use the first retired request on a new context to unpin
the old context. This ensures that the hw context remains
bound until it has been saved.
Now that the context is pinned until later in the request/context
lifecycle, it no longer needs to be pinned from context_queue to
retire_requests.
This is to solve a hang with GuC submission, and a theoretical
issue with execlist submission.

v2: Moved the new pin to cover GuC submission (Alex Dai)
    Moved the new unpin to request_retire to fix coverage leak
v3: Added switch to default context if freeing a still pinned
    context just in case the hw was actually still using it
v4: Unwrapped context unpin to allow calling without a request

Signed-off-by: Nick Hoath <nicholas.hoath@intel.com>
Issue: VIZ-4277
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Gordon <david.s.gordon@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Alex Dai <yu.dai@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h  |  1 +
 drivers/gpu/drm/i915/i915_gem.c  |  9 ++++-
 drivers/gpu/drm/i915/intel_lrc.c | 73 ++++++++++++++++++++++++++++++----------
 drivers/gpu/drm/i915/intel_lrc.h |  1 +
 4 files changed, 65 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index d5cf30b..4d2f44c 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -889,6 +889,7 @@ struct intel_context {
 	struct {
 		struct drm_i915_gem_object *state;
 		struct intel_ringbuffer *ringbuf;
+		bool unsaved;
 		int pin_count;
 	} engine[I915_NUM_RINGS];
 
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e955499..6fee473 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1354,6 +1354,14 @@ static void i915_gem_request_retire(struct drm_i915_gem_request *request)
 {
 	trace_i915_gem_request_retire(request);
 
+	if (i915.enable_execlists) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&request->ring->execlist_lock, flags);
+		intel_lr_context_complete_check(request);
+		spin_unlock_irqrestore(&request->ring->execlist_lock, flags);
+	}
+
 	/* We know the GPU must have read the request to have
 	 * sent us the seqno + interrupt, so use the position
 	 * of tail of the request to update the last known position
@@ -1384,7 +1392,6 @@ __i915_gem_request_retire__upto(struct drm_i915_gem_request *req)
 	do {
 		tmp = list_first_entry(&engine->request_list,
 				       typeof(*tmp), list);
-
 		i915_gem_request_retire(tmp);
 	} while (tmp != req);
 
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 06180dc..a527c21 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -566,9 +566,6 @@ static int execlists_context_queue(struct drm_i915_gem_request *request)
 	struct drm_i915_gem_request *cursor;
 	int num_elements = 0;
 
-	if (request->ctx != ring->default_context)
-		intel_lr_context_pin(request);
-
 	i915_gem_request_reference(request);
 
 	spin_lock_irq(&ring->execlist_lock);
@@ -728,10 +725,16 @@ intel_logical_ring_advance_and_submit(struct drm_i915_gem_request *request)
 	intel_logical_ring_advance(request->ringbuf);
 
 	request->tail = request->ringbuf->tail;
-
 	if (intel_ring_stopped(ring))
 		return;
 
+	if (request->ctx != ring->default_context) {
+		if (!request->ctx->engine[ring->id].unsaved) {
+			intel_lr_context_pin(request);
+			request->ctx->engine[ring->id].unsaved = true;
+		}
+	}
+
 	if (dev_priv->guc.execbuf_client)
 		i915_guc_submit(dev_priv->guc.execbuf_client, request);
 	else
@@ -958,12 +961,6 @@ void intel_execlists_retire_requests(struct intel_engine_cs *ring)
 	spin_unlock_irq(&ring->execlist_lock);
 
 	list_for_each_entry_safe(req, tmp, &retired_list, execlist_link) {
-		struct intel_context *ctx = req->ctx;
-		struct drm_i915_gem_object *ctx_obj =
-				ctx->engine[ring->id].state;
-
-		if (ctx_obj && (ctx != ring->default_context))
-			intel_lr_context_unpin(req);
 		list_del(&req->execlist_link);
 		i915_gem_request_unreference(req);
 	}
@@ -1058,21 +1055,41 @@ reset_pin_count:
 	return ret;
 }
 
-void intel_lr_context_unpin(struct drm_i915_gem_request *rq)
+static void intel_lr_context_unpin_no_req(struct intel_engine_cs *ring,
+		struct intel_context *ctx)
 {
-	struct intel_engine_cs *ring = rq->ring;
-	struct drm_i915_gem_object *ctx_obj = rq->ctx->engine[ring->id].state;
-	struct intel_ringbuffer *ringbuf = rq->ringbuf;
-
+	struct drm_i915_gem_object *ctx_obj = ctx->engine[ring->id].state;
+	struct intel_ringbuffer *ringbuf = ctx->engine[ring->id].ringbuf;
 	if (ctx_obj) {
 		WARN_ON(!mutex_is_locked(&ring->dev->struct_mutex));
-		if (--rq->ctx->engine[ring->id].pin_count == 0) {
+		if (--ctx->engine[ring->id].pin_count == 0) {
 			intel_unpin_ringbuffer_obj(ringbuf);
 			i915_gem_object_ggtt_unpin(ctx_obj);
 		}
 	}
 }
 
+void intel_lr_context_unpin(struct drm_i915_gem_request *rq)
+{
+	intel_lr_context_unpin_no_req(rq->ring, rq->ctx);
+}
+
+void intel_lr_context_complete_check(struct drm_i915_gem_request *req)
+{
+	struct intel_engine_cs *ring = req->ring;
+
+	assert_spin_locked(&ring->execlist_lock);
+
+	if (ring->last_context && ring->last_context != req->ctx &&
+			ring->last_context->engine[ring->id].unsaved) {
+		intel_lr_context_unpin_no_req(
+				ring,
+				ring->last_context);
+		ring->last_context->engine[ring->id].unsaved = false;
+	}
+	ring->last_context = req->ctx;
+}
+
 static int intel_logical_ring_workarounds_emit(struct drm_i915_gem_request *req)
 {
 	int ret, i;
@@ -2378,7 +2395,7 @@ void intel_lr_context_free(struct intel_context *ctx)
 {
 	int i;
 
-	for (i = 0; i < I915_NUM_RINGS; i++) {
+	for (i = 0; i < I915_NUM_RINGS; ++i) {
 		struct drm_i915_gem_object *ctx_obj = ctx->engine[i].state;
 
 		if (ctx_obj) {
@@ -2390,7 +2407,20 @@ void intel_lr_context_free(struct intel_context *ctx)
 				intel_unpin_ringbuffer_obj(ringbuf);
 				i915_gem_object_ggtt_unpin(ctx_obj);
 			}
-			WARN_ON(ctx->engine[ring->id].pin_count);
+
+			if (ctx->engine[ring->id].unsaved) {
+				int ret;
+				struct drm_i915_gem_request *req;
+
+				ret = i915_gem_request_alloc(ring,
+					ring->default_context, &req);
+				if (!ret) {
+					i915_add_request(req);
+					i915_wait_request(req);
+				}
+			}
+
+			WARN_ON(ctx->engine[i].pin_count);
 			intel_ringbuffer_free(ringbuf);
 			drm_gem_object_unreference(&ctx_obj->base);
 		}
@@ -2554,5 +2584,12 @@ void intel_lr_context_reset(struct drm_device *dev,
 
 		ringbuf->head = 0;
 		ringbuf->tail = 0;
+
+		if (ctx->engine[ring->id].unsaved) {
+			intel_lr_context_unpin_no_req(
+					ring,
+					ctx);
+			ctx->engine[ring->id].unsaved = false;
+		}
 	}
 }
diff --git a/drivers/gpu/drm/i915/intel_lrc.h b/drivers/gpu/drm/i915/intel_lrc.h
index 4e60d54..cbc42b8 100644
--- a/drivers/gpu/drm/i915/intel_lrc.h
+++ b/drivers/gpu/drm/i915/intel_lrc.h
@@ -86,6 +86,7 @@ void intel_lr_context_reset(struct drm_device *dev,
 			struct intel_context *ctx);
 uint64_t intel_lr_context_descriptor(struct intel_context *ctx,
 				     struct intel_engine_cs *ring);
+void intel_lr_context_complete_check(struct drm_i915_gem_request *req);
 
 /* Execlists */
 int intel_sanitize_enable_execlists(struct drm_device *dev, int enable_execlists);
-- 
1.9.1

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