[PATCH 27/34] drm/i915: Allow contexts to share a single timeline across all engines

Chris Wilson chris at chris-wilson.co.uk
Wed Oct 10 13:46:05 UTC 2018


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 at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 26 ++++++++++++++++-
 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 +++-
 include/uapi/drm/i915_drm.h             |  3 +-
 8 files changed, 91 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 308941a866e5..5c3cb85a3d36 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -223,6 +223,9 @@ 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);
 
@@ -402,6 +405,7 @@ static void __destroy_hw_context(struct i915_gem_context *ctx,
 }
 
 #define CREATE_VM BIT(0)
+#define CREATE_TIMELINE BIT(1)
 
 static struct i915_gem_context *
 i915_gem_create_context(struct drm_i915_private *dev_priv,
@@ -412,6 +416,9 @@ i915_gem_create_context(struct drm_i915_private *dev_priv,
 
 	lockdep_assert_held(&dev_priv->drm.struct_mutex);
 
+	if (flags & CREATE_TIMELINE && !HAS_EXECLISTS(dev_priv))
+		return ERR_PTR(-EINVAL);
+
 	/* Reap the most stale context */
 	contexts_free_first(dev_priv);
 
@@ -434,6 +441,18 @@ i915_gem_create_context(struct drm_i915_private *dev_priv,
 		ctx->desc_template = default_desc_template(dev_priv, ppgtt);
 	}
 
+	if (flags & CREATE_TIMELINE) {
+		struct i915_timeline *timeline;
+
+		timeline = i915_timeline_create(dev_priv, ctx->name);
+		if (IS_ERR(timeline)) {
+			__destroy_hw_context(ctx, file_priv);
+			return ERR_CAST(timeline);
+		}
+
+		ctx->timeline = timeline;
+	}
+
 	trace_i915_context_create(ctx);
 
 	return ctx;
@@ -796,7 +815,9 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
 	if (args->pad != 0)
 		return -EINVAL;
 
-	if (args->flags & ~I915_GEM_CONTEXT_SHARE_GTT)
+	if (args->flags &
+	    ~(I915_GEM_CONTEXT_SHARE_GTT |
+	      I915_GEM_CONTEXT_SINGLE_TIMELINE))
 		return -EINVAL;
 
 	if (client_is_banned(file_priv)) {
@@ -820,6 +841,9 @@ int i915_gem_context_create_ioctl(struct drm_device *dev, void *data,
 		flags &= ~CREATE_VM;
 	}
 
+	if (args->flags & I915_GEM_CONTEXT_SINGLE_TIMELINE)
+		flags |= CREATE_TIMELINE;
+
 	err = i915_mutex_lock_interruptible(dev);
 	if (err)
 		goto out;
diff --git a/drivers/gpu/drm/i915/i915_gem_context.h b/drivers/gpu/drm/i915/i915_gem_context.h
index f6d870b1f73e..c5323269cad9 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.h
+++ b/drivers/gpu/drm/i915/i915_gem_context.h
@@ -41,6 +41,7 @@ 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;
 
@@ -66,6 +67,8 @@ 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 fe422547f2ca..677fabb5db16 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -998,8 +998,14 @@ void i915_request_add(struct i915_request *request)
 	prev = i915_gem_active_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 (prev->engine == engine)
+			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 90e9d170a0cd..68d36eeb5edb 100644
--- a/drivers/gpu/drm/i915/i915_request.h
+++ b/drivers/gpu/drm/i915/i915_request.h
@@ -116,7 +116,10 @@ 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;
+	};
 	wait_queue_head_t execute;
 
 	/*
diff --git a/drivers/gpu/drm/i915/i915_sw_fence.c b/drivers/gpu/drm/i915/i915_sw_fence.c
index 6dbeed079ae5..b68883fe73c5 100644
--- a/drivers/gpu/drm/i915/i915_sw_fence.c
+++ b/drivers/gpu/drm/i915/i915_sw_fence.c
@@ -362,11 +362,6 @@ 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;
@@ -483,6 +478,40 @@ 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 fe2ef4dadfc6..914a734d49bc 100644
--- a/drivers/gpu/drm/i915/i915_sw_fence.h
+++ b/drivers/gpu/drm/i915/i915_sw_fence.h
@@ -10,14 +10,13 @@
 #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 {
@@ -69,10 +68,20 @@ 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 ff0e2b36cb8b..1ef8074d9854 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2652,7 +2652,10 @@ static int execlists_context_deferred_alloc(struct i915_gem_context *ctx,
 		goto error_deref_obj;
 	}
 
-	timeline = i915_timeline_create(ctx->i915, ctx->name);
+	if (ctx->timeline)
+		timeline = i915_timeline_get(ctx->timeline);
+	else
+		timeline = i915_timeline_create(ctx->i915, ctx->name);
 	if (IS_ERR(timeline)) {
 		ret = PTR_ERR(timeline);
 		goto error_deref_obj;
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 9779b12ecad2..906acfc898fa 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -1442,7 +1442,8 @@ struct drm_i915_gem_context_create_v2 {
 	/*  output: id of new context*/
 	__u32 ctx_id;
 	__u32 flags;
-#define I915_GEM_CONTEXT_SHARE_GTT 0x1
+#define I915_GEM_CONTEXT_SHARE_GTT		0x1
+#define I915_GEM_CONTEXT_SINGLE_TIMELINE	0x2
 	__u32 share_ctx;
 	__u32 pad;
 };
-- 
2.19.1



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