[PATCH 13/43] drm/i915: Allow contexts to share a single timeline across all engines

[Chris Wilson <chris@chris-wilson.co.uk>]

Previously, our view has been always to run the engines independently
within a context. (Multiple engines happened before we had contexts and
timelines, so they always operated independently and that behaviour
persisted into contexts.) However, at the user level the context often
represents a single timeline (e.g. GL contexts) and userspace must
ensure that the individual engines are serialised to present that
ordering to the client (or forgot about this detail entirely and hope no
one notices - a fair ploy if the client can only directly control one
engine themselves ;)

In the next patch, we will want to construct a set of engines that
operate as one, that have a single timeline interwoven between them, to
present a single virtual engine to the user. (They submit to the virtual
engine, then we decide which engine to execute on based.)

To that end, we want to be able to create contexts which have a single
timeline (fence context) shared between all engines, rather than multiple
timelines.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_context.c       | 32 ++++++++++++---
 drivers/gpu/drm/i915/i915_gem_context.h       |  3 ++
 drivers/gpu/drm/i915/i915_request.c           | 10 ++++-
 drivers/gpu/drm/i915/i915_request.h           |  5 ++-
 drivers/gpu/drm/i915/i915_sw_fence.c          | 39 ++++++++++++++++---
 drivers/gpu/drm/i915/i915_sw_fence.h          | 13 ++++++-
 drivers/gpu/drm/i915/intel_lrc.c              |  5 ++-
 .../gpu/drm/i915/selftests/i915_gem_context.c | 18 +++++----
 drivers/gpu/drm/i915/selftests/mock_context.c |  2 +-
 include/uapi/drm/i915_drm.h                   |  3 +-
 10 files changed, 103 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index bc042b0e0082..9927f1296fd6 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -241,6 +241,9 @@ static void i915_gem_context_free(struct i915_gem_context *ctx)
 			ce->ops->destroy(ce);
 	}
 
+	if (ctx->timeline)
+		i915_timeline_put(ctx->timeline);
+
 	kfree(ctx->name);
 	put_pid(ctx->pid);
 
@@ -480,12 +483,17 @@ static void __assign_ppgtt(struct i915_gem_context *ctx,
 
 static struct i915_gem_context *
 i915_gem_create_context(struct drm_i915_private *dev_priv,
-			struct drm_i915_file_private *file_priv)
+			struct drm_i915_file_private *file_priv,
+			unsigned int flags)
 {
 	struct i915_gem_context *ctx;
 
 	lockdep_assert_held(&dev_priv->drm.struct_mutex);
 
+	if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE &&
+	    !HAS_EXECLISTS(dev_priv))
+		return ERR_PTR(-EINVAL);
+
 	/* Reap the most stale context */
 	contexts_free_first(dev_priv);
 
@@ -508,6 +516,18 @@ i915_gem_create_context(struct drm_i915_private *dev_priv,
 		i915_ppgtt_put(ppgtt);
 	}
 
+	if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE) {
+		struct i915_timeline *timeline;
+
+		timeline = i915_timeline_create(dev_priv, ctx->name, NULL);
+		if (IS_ERR(timeline)) {
+			__destroy_hw_context(ctx, file_priv);
+			return ERR_CAST(timeline);
+		}
+
+		ctx->timeline = timeline;
+	}
+
 	trace_i915_context_create(ctx);
 
 	return ctx;
@@ -536,7 +556,7 @@ i915_gem_context_create_gvt(struct drm_device *dev)
 	if (ret)
 		return ERR_PTR(ret);
 
-	ctx = i915_gem_create_context(to_i915(dev), NULL);
+	ctx = i915_gem_create_context(to_i915(dev), NULL, 0);
 	if (IS_ERR(ctx))
 		goto out;
 
@@ -572,7 +592,7 @@ i915_gem_context_create_kernel(struct drm_i915_private *i915, int prio)
 	struct i915_gem_context *ctx;
 	int err;
 
-	ctx = i915_gem_create_context(i915, NULL);
+	ctx = i915_gem_create_context(i915, NULL, 0);
 	if (IS_ERR(ctx))
 		return ctx;
 
@@ -704,7 +724,7 @@ int i915_gem_context_open(struct drm_i915_private *i915,
 	idr_init_base(&file_priv->vm_idr, 1);
 
 	mutex_lock(&i915->drm.struct_mutex);
-	ctx = i915_gem_create_context(i915, file_priv);
+	ctx = i915_gem_create_context(i915, file_priv, 0);
 	mutex_unlock(&i915->drm.struct_mutex);
 	if (IS_ERR(ctx)) {
 		idr_destroy(&file_priv->context_idr);
@@ -820,7 +840,7 @@ last_request_on_engine(struct i915_timeline *timeline,
 
 	rq = i915_active_request_raw(&timeline->last_request,
 				     &engine->i915->drm.struct_mutex);
-	if (rq && rq->engine == engine) {
+	if (rq && rq->engine->mask & engine->mask) {
 		GEM_TRACE("last request for %s on engine %s: %llx:%llu\n",
 			  timeline->name, engine->name,
 			  rq->fence.context, rq->fence.seqno);
@@ -1478,7 +1498,7 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
 	if (ret)
 		return ret;
 
-	ctx = i915_gem_create_context(i915, file_priv);
+	ctx = i915_gem_create_context(i915, file_priv, args->flags);
 	mutex_unlock(&dev->struct_mutex);
 	if (IS_ERR(ctx))
 		return PTR_ERR(ctx);
diff --git a/drivers/gpu/drm/i915/i915_gem_context.h b/drivers/gpu/drm/i915/i915_gem_context.h
index 92c2eecae12e..755b2d97c32c 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.h
+++ b/drivers/gpu/drm/i915/i915_gem_context.h
@@ -43,6 +43,7 @@ struct drm_i915_private;
 struct drm_i915_file_private;
 struct i915_hw_ppgtt;
 struct i915_request;
+struct i915_timeline;
 struct i915_vma;
 struct intel_ring;
 
@@ -78,6 +79,8 @@ struct i915_gem_context {
 	/** file_priv: owning file descriptor */
 	struct drm_i915_file_private *file_priv;
 
+	struct i915_timeline *timeline;
+
 	/**
 	 * @ppgtt: unique address space (GTT)
 	 *
diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 9533a85cb0b3..18f49132a526 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -1047,8 +1047,14 @@ void i915_request_add(struct i915_request *request)
 	prev = i915_active_request_raw(&timeline->last_request,
 				       &request->i915->drm.struct_mutex);
 	if (prev && !i915_request_completed(prev)) {
-		i915_sw_fence_await_sw_fence(&request->submit, &prev->submit,
-					     &request->submitq);
+		if (is_power_of_2(prev->engine->mask | engine->mask))
+			i915_sw_fence_await_sw_fence(&request->submit,
+						     &prev->submit,
+						     &request->submitq);
+		else
+			__i915_sw_fence_await_dma_fence(&request->submit,
+							&prev->fence,
+							&request->dmaq);
 		if (engine->schedule)
 			__i915_sched_node_add_dependency(&request->sched,
 							 &prev->sched,
diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h
index 8c8fa5010644..cd6c130964cd 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -128,7 +128,10 @@ struct i915_request {
 	 * It is used by the driver to then queue the request for execution.
 	 */
 	struct i915_sw_fence submit;
-	wait_queue_entry_t submitq;
+	union {
+		wait_queue_entry_t submitq;
+		struct i915_sw_dma_fence_cb dmaq;
+	};
 	struct list_head execute_cb;
 
 	/*
diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c b/drivers/gpu/drm/i915/i915_sw_fence.c
index 8d1400d378d7..5387aafd3424 100644
--- a/drivers/gpu/drm/i915/i915_sw_fence.c
+++ b/drivers/gpu/drm/i915/i915_sw_fence.c
@@ -359,11 +359,6 @@ int i915_sw_fence_await_sw_fence_gfp(struct i915_sw_fence *fence,
 	return __i915_sw_fence_await_sw_fence(fence, signaler, NULL, gfp);
 }
 
-struct i915_sw_dma_fence_cb {
-	struct dma_fence_cb base;
-	struct i915_sw_fence *fence;
-};
-
 struct i915_sw_dma_fence_cb_timer {
 	struct i915_sw_dma_fence_cb base;
 	struct dma_fence *dma;
@@ -480,6 +475,40 @@ int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
 	return ret;
 }
 
+static void __dma_i915_sw_fence_wake(struct dma_fence *dma,
+				     struct dma_fence_cb *data)
+{
+	struct i915_sw_dma_fence_cb *cb = container_of(data, typeof(*cb), base);
+
+	i915_sw_fence_complete(cb->fence);
+}
+
+int __i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
+				    struct dma_fence *dma,
+				    struct i915_sw_dma_fence_cb *cb)
+{
+	int ret;
+
+	debug_fence_assert(fence);
+
+	if (dma_fence_is_signaled(dma))
+		return 0;
+
+	cb->fence = fence;
+	i915_sw_fence_await(fence);
+
+	ret = dma_fence_add_callback(dma, &cb->base, __dma_i915_sw_fence_wake);
+	if (ret == 0) {
+		ret = 1;
+	} else {
+		i915_sw_fence_complete(fence);
+		if (ret == -ENOENT) /* fence already signaled */
+			ret = 0;
+	}
+
+	return ret;
+}
+
 int i915_sw_fence_await_reservation(struct i915_sw_fence *fence,
 				    struct reservation_object *resv,
 				    const struct dma_fence_ops *exclude,
diff --git a/drivers/gpu/drm/i915/i915_sw_fence.h b/drivers/gpu/drm/i915/i915_sw_fence.h
index 6dec9e1d1102..9cb5c3b307a6 100644
--- a/drivers/gpu/drm/i915/i915_sw_fence.h
+++ b/drivers/gpu/drm/i915/i915_sw_fence.h
@@ -9,14 +9,13 @@
 #ifndef _I915_SW_FENCE_H_
 #define _I915_SW_FENCE_H_
 
+#include <linux/dma-fence.h>
 #include <linux/gfp.h>
 #include <linux/kref.h>
 #include <linux/notifier.h> /* for NOTIFY_DONE */
 #include <linux/wait.h>
 
 struct completion;
-struct dma_fence;
-struct dma_fence_ops;
 struct reservation_object;
 
 struct i915_sw_fence {
@@ -68,10 +67,20 @@ int i915_sw_fence_await_sw_fence(struct i915_sw_fence *fence,
 int i915_sw_fence_await_sw_fence_gfp(struct i915_sw_fence *fence,
 				     struct i915_sw_fence *after,
 				     gfp_t gfp);
+
+struct i915_sw_dma_fence_cb {
+	struct dma_fence_cb base;
+	struct i915_sw_fence *fence;
+};
+
+int __i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
+				    struct dma_fence *dma,
+				    struct i915_sw_dma_fence_cb *cb);
 int i915_sw_fence_await_dma_fence(struct i915_sw_fence *fence,
 				  struct dma_fence *dma,
 				  unsigned long timeout,
 				  gfp_t gfp);
+
 int i915_sw_fence_await_reservation(struct i915_sw_fence *fence,
 				    struct reservation_object *resv,
 				    const struct dma_fence_ops *exclude,
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index a9a47dbeac88..0bd837b64ade 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2860,7 +2860,10 @@ static int execlists_context_deferred_alloc(struct i915_gem_context *ctx,
 		goto error_deref_obj;
 	}
 
-	timeline = i915_timeline_create(ctx->i915, ctx->name, NULL);
+	if (ctx->timeline)
+		timeline = i915_timeline_get(ctx->timeline);
+	else
+		timeline = i915_timeline_create(ctx->i915, ctx->name, NULL);
 	if (IS_ERR(timeline)) {
 		ret = PTR_ERR(timeline);
 		goto error_deref_obj;
diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/selftests/i915_gem_context.c
index 1c6ce9e0195a..df1380498612 100644
--- a/drivers/gpu/drm/i915/selftests/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_context.c
@@ -76,7 +76,7 @@ static int live_nop_switch(void *arg)
 	}
 
 	for (n = 0; n < nctx; n++) {
-		ctx[n] = i915_gem_create_context(i915, file->driver_priv);
+		ctx[n] = i915_gem_create_context(i915, file->driver_priv, 0);
 		if (IS_ERR(ctx[n])) {
 			err = PTR_ERR(ctx[n]);
 			goto out_unlock;
@@ -526,7 +526,8 @@ static int igt_ctx_exec(void *arg)
 			struct i915_gem_context *ctx;
 			intel_wakeref_t wakeref;
 
-			ctx = i915_gem_create_context(i915, file->driver_priv);
+			ctx = i915_gem_create_context(i915,
+						      file->driver_priv, 0);
 			if (IS_ERR(ctx)) {
 				err = PTR_ERR(ctx);
 				goto out_unlock;
@@ -611,7 +612,7 @@ static int igt_shared_ctx_exec(void *arg)
 
 	mutex_lock(&i915->drm.struct_mutex);
 
-	parent = i915_gem_create_context(i915, file->driver_priv);
+	parent = i915_gem_create_context(i915, file->driver_priv, 0);
 	if (IS_ERR(parent)) {
 		err = PTR_ERR(parent);
 		goto out_unlock;
@@ -645,7 +646,8 @@ static int igt_shared_ctx_exec(void *arg)
 			if (ctx)
 				__destroy_hw_context(ctx, file->driver_priv);
 
-			ctx = i915_gem_create_context(i915, file->driver_priv);
+			ctx = i915_gem_create_context(i915,
+						      file->driver_priv, 0);
 			if (IS_ERR(ctx)) {
 				err = PTR_ERR(ctx);
 				goto out_unlock;
@@ -1087,7 +1089,7 @@ __igt_ctx_sseu(struct drm_i915_private *i915,
 
 	mutex_lock(&i915->drm.struct_mutex);
 
-	ctx = i915_gem_create_context(i915, file->driver_priv);
+	ctx = i915_gem_create_context(i915, file->driver_priv, 0);
 	if (IS_ERR(ctx)) {
 		ret = PTR_ERR(ctx);
 		goto out_unlock;
@@ -1197,7 +1199,7 @@ static int igt_ctx_readonly(void *arg)
 	if (err)
 		goto out_unlock;
 
-	ctx = i915_gem_create_context(i915, file->driver_priv);
+	ctx = i915_gem_create_context(i915, file->driver_priv, 0);
 	if (IS_ERR(ctx)) {
 		err = PTR_ERR(ctx);
 		goto out_unlock;
@@ -1525,13 +1527,13 @@ static int igt_vm_isolation(void *arg)
 	if (err)
 		goto out_unlock;
 
-	ctx_a = i915_gem_create_context(i915, file->driver_priv);
+	ctx_a = i915_gem_create_context(i915, file->driver_priv, 0);
 	if (IS_ERR(ctx_a)) {
 		err = PTR_ERR(ctx_a);
 		goto out_unlock;
 	}
 
-	ctx_b = i915_gem_create_context(i915, file->driver_priv);
+	ctx_b = i915_gem_create_context(i915, file->driver_priv, 0);
 	if (IS_ERR(ctx_b)) {
 		err = PTR_ERR(ctx_b);
 		goto out_unlock;
diff --git a/drivers/gpu/drm/i915/selftests/mock_context.c b/drivers/gpu/drm/i915/selftests/mock_context.c
index 5eddf9fcfe8a..5d0ff2293abc 100644
--- a/drivers/gpu/drm/i915/selftests/mock_context.c
+++ b/drivers/gpu/drm/i915/selftests/mock_context.c
@@ -95,7 +95,7 @@ live_context(struct drm_i915_private *i915, struct drm_file *file)
 {
 	lockdep_assert_held(&i915->drm.struct_mutex);
 
-	return i915_gem_create_context(i915, file->driver_priv);
+	return i915_gem_create_context(i915, file->driver_priv, 0);
 }
 
 struct i915_gem_context *
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 0db92a4153c8..007d77ff7295 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -1454,8 +1454,9 @@ struct drm_i915_gem_context_create_ext {
 	__u32 ctx_id; /* output: id of new context*/
 	__u32 flags;
 #define I915_CONTEXT_CREATE_FLAGS_USE_EXTENSIONS	(1u << 0)
+#define I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE	(1u << 1)
 #define I915_CONTEXT_CREATE_FLAGS_UNKNOWN \
-	(-(I915_CONTEXT_CREATE_FLAGS_USE_EXTENSIONS << 1))
+	(-(I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE << 1))
 	__u64 extensions;
 };
 
-- 
2.20.1

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