Re: [PATCH v6 5/5] drm/i915: Tidy up execbuffer command parsing code

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On 12/11/2014 05:49 AM, Bloomfield, Jon wrote:


-----Original Message-----
From: Nguyen, Michael H
Sent: Monday, December 08, 2014 10:34 PM
To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: Bloomfield, Jon; Brad Volkin
Subject: [PATCH v6 5/5] drm/i915: Tidy up execbuffer command parsing code

From: Brad Volkin <bradley.d.volkin@xxxxxxxxx>

Move it to a separate function since the main do_execbuffer function
already has so much going on.

v2:
- Move pin/unpin calls inside i915_parse_cmds() (Chris W, v4 7/7
   feedback)

Issue: VIZ-4719
Signed-off-by: Brad Volkin <bradley.d.volkin@xxxxxxxxx>

Conflicts:
	drivers/gpu/drm/i915/i915_gem_execbuffer.c
---
  drivers/gpu/drm/i915/i915_cmd_parser.c     |   8 ++
  drivers/gpu/drm/i915/i915_gem_execbuffer.c | 126 ++++++++++++++++---
----------
  2 files changed, 77 insertions(+), 57 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c
b/drivers/gpu/drm/i915/i915_cmd_parser.c
index 118079d..80b1b28 100644
--- a/drivers/gpu/drm/i915/i915_cmd_parser.c
+++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
@@ -1042,10 +1042,17 @@ int i915_parse_cmds(struct intel_engine_cs
*ring,
  	struct drm_i915_cmd_descriptor default_desc = { 0 };
  	bool oacontrol_set = false; /* OACONTROL tracking. See
check_cmd() */

+	ret = i915_gem_obj_ggtt_pin(shadow_batch_obj, 4096, 0);
+	if (ret) {
+		DRM_DEBUG_DRIVER("CMD: Failed to pin shadow batch\n");
+		return -1;
+	}
+
  	batch_base = copy_batch(shadow_batch_obj, batch_obj,
  				batch_start_offset, batch_len);
  	if (IS_ERR(batch_base)) {
  		DRM_DEBUG_DRIVER("CMD: Failed to copy batch\n");
+		i915_gem_object_ggtt_unpin(shadow_batch_obj);
  		return PTR_ERR(batch_base);
  	}

@@ -1116,6 +1123,7 @@ int i915_parse_cmds(struct intel_engine_cs *ring,
  	}

  	vunmap(batch_base);
+	i915_gem_object_ggtt_unpin(shadow_batch_obj);

  	return ret;
  }
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 2071938..3d36465 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1069,6 +1069,65 @@ i915_emit_box(struct intel_engine_cs *ring,
  	return 0;
  }

+static struct drm_i915_gem_object*
+i915_gem_execbuffer_parse(struct intel_engine_cs *ring,
+			  struct drm_i915_gem_exec_object2
*shadow_exec_entry,
+			  struct eb_vmas *eb,
+			  struct drm_i915_gem_object *batch_obj,
+			  u32 batch_start_offset,
+			  u32 batch_len,
+			  bool is_master,
+			  u32 *flags)
+{
+	struct drm_i915_private *dev_priv = to_i915(batch_obj->base.dev);
+	struct drm_i915_gem_object *shadow_batch_obj;
+	int ret;
+
+	shadow_batch_obj = i915_gem_batch_pool_get(&dev_priv-
mm.batch_pool,
+						   batch_obj->base.size);
+	if (IS_ERR(shadow_batch_obj))
+		return shadow_batch_obj;
+
+	ret = i915_parse_cmds(ring,
+			      batch_obj,
+			      shadow_batch_obj,
+			      batch_start_offset,
+			      batch_len,
+			      is_master);
+	if (ret) {
+		if (ret == -EACCES)
+			return batch_obj;

Shouldn't this be returning an error code ?
Good question. -EACCESS tells the caller of i915_parse_cmds() of a special case. There are some comments in its fnc header and implementation.

-EACCESS indicates that batch_obj contains a chained batch in which case we dispatch batch_obj as non-secure. We return batch_obj here b/c the logic below doesn't apply. I believe the reason we safely dispatch chained batches as non-secure is b/c Brad and others probably determined that there weren't any valid use cases where chained batches needed to be dispatched as secure. Leaving them non-secure, HW will NOP bad cmds and its not necessary for i915 to do parsing.

Thanks,
Mike



+	} else {
+		struct i915_vma *vma;
+
+		memset(shadow_exec_entry, 0,
sizeof(*shadow_exec_entry));
+
+		vma = i915_gem_obj_to_ggtt(shadow_batch_obj);
+		vma->exec_entry = shadow_exec_entry;
+		vma->exec_entry->flags = __EXEC_OBJECT_PURGEABLE;
+		drm_gem_object_reference(&shadow_batch_obj->base);
+		list_add_tail(&vma->exec_list, &eb->vmas);
+
+		shadow_batch_obj->base.pending_read_domains =
+			batch_obj->base.pending_read_domains;
+
+		/*
+		 * Set the DISPATCH_SECURE bit to remove the
NON_SECURE
+		 * bit from MI_BATCH_BUFFER_START commands issued in
the
+		 * dispatch_execbuffer implementations. We specifically
+		 * don't want that set when the command parser is
+		 * enabled.
+		 *
+		 * FIXME: with aliasing ppgtt, buffers that should only
+		 * be in ggtt still end up in the aliasing ppgtt. remove
+		 * this check when that is fixed.
+		 */
+		if (USES_FULL_PPGTT(dev))
+			*flags |= I915_DISPATCH_SECURE;
+	}
+
+	return ret ? ERR_PTR(ret) : shadow_batch_obj; }

  int
  i915_gem_ringbuffer_submission(struct drm_device *dev, struct drm_file
*file, @@ -1286,7 +1345,6 @@ i915_gem_do_execbuffer(struct drm_device
*dev, void *data,
  	struct drm_i915_private *dev_priv = dev->dev_private;
  	struct eb_vmas *eb;
  	struct drm_i915_gem_object *batch_obj;
-	struct drm_i915_gem_object *shadow_batch_obj = NULL;
  	struct drm_i915_gem_exec_object2 shadow_exec_entry;
  	struct intel_engine_cs *ring;
  	struct intel_context *ctx;
@@ -1406,63 +1464,17 @@ i915_gem_do_execbuffer(struct drm_device
*dev, void *data,
  	}

  	if (i915_needs_cmd_parser(ring)) {
-		shadow_batch_obj =
-			i915_gem_batch_pool_get(&dev_priv-
mm.batch_pool,
-						batch_obj->base.size);
-		if (IS_ERR(shadow_batch_obj)) {
-			ret = PTR_ERR(shadow_batch_obj);
-			/* Don't try to clean up the obj in the error path */
-			shadow_batch_obj = NULL;
-			goto err;
-		}
-
-		shadow_batch_obj->madv = I915_MADV_WILLNEED;
-
-		ret = i915_gem_obj_ggtt_pin(shadow_batch_obj, 4096, 0);
-		if (ret)
+		batch_obj = i915_gem_execbuffer_parse(ring,
+						      &shadow_exec_entry,
+						      eb,
+						      batch_obj,
+						      args->batch_start_offset,
+						      args->batch_len,
+						      file->is_master,
+						      &flags);
+		if (IS_ERR(batch_obj)) {
+			ret = PTR_ERR(batch_obj);
  			goto err;
-
-		ret = i915_parse_cmds(ring,
-				      batch_obj,
-				      shadow_batch_obj,
-				      args->batch_start_offset,
-				      args->batch_len,
-				      file->is_master);
-		i915_gem_object_ggtt_unpin(shadow_batch_obj);
-
-		if (ret) {
-			if (ret != -EACCES)
-				goto err;
-		} else {
-			struct i915_vma *vma;
-
-			memset(&shadow_exec_entry, 0,
-			       sizeof(shadow_exec_entry));
-
-			vma = i915_gem_obj_to_ggtt(shadow_batch_obj);
-			vma->exec_entry = &shadow_exec_entry;
-			vma->exec_entry->flags =
__EXEC_OBJECT_PURGEABLE;
-			drm_gem_object_reference(&shadow_batch_obj-
base);
-			list_add_tail(&vma->exec_list, &eb->vmas);
-
-			shadow_batch_obj->base.pending_read_domains =
-				batch_obj->base.pending_read_domains;
-
-			batch_obj = shadow_batch_obj;
-
-			/*
-			 * Set the DISPATCH_SECURE bit to remove the
NON_SECURE
-			 * bit from MI_BATCH_BUFFER_START commands
issued in the
-			 * dispatch_execbuffer implementations. We
specifically
-			 * don't want that set when the command parser is
-			 * enabled.
-			 *
-			 * FIXME: with aliasing ppgtt, buffers that should only
-			 * be in ggtt still end up in the aliasing ppgtt. remove
-			 * this check when that is fixed.
-			 */
-			if (USES_FULL_PPGTT(dev))
-				flags |= I915_DISPATCH_SECURE;
  		}
  	}

--
1.9.1

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