drm/i915/gem: Refactor placement setup for i915_gem_object_create* (v2)

Since we don't allow changing the set of regions after creation, we can
make ext_set_placements() build up the region set directly in the
create_ext and assign it to the object later.  This is similar to what
we did for contexts with the proto-context only simpler because there's
no funny object shuffling.  This will be used in the next patch to allow
us to de-duplicate a bunch of code.  Also, since we know the maximum
number of regions up-front, we can use a fixed-size temporary array for
the regions.  This simplifies memory management a bit for this new
delayed approach.

v2 (Matthew Auld):
 - Get rid of MAX_N_PLACEMENTS
 - Drop kfree(placements) from set_placements()
v3 (Matthew Auld):
 - Properly set ext_data->n_placements
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210723172142.3273510-3-jason@jlekstrand.net

drivers/gpu/drm/i915/gem/i915_gem_create.c

@@ -27,10 +27,13 @@ static u32 object_max_page_size(struct drm_i915_gem_object *obj)
 	return max_page_size;
 }
 
-static void object_set_placements(struct drm_i915_gem_object *obj,
-				  struct intel_memory_region **placements,
-				  unsigned int n_placements)
+static int object_set_placements(struct drm_i915_gem_object *obj,
+				 struct intel_memory_region **placements,
+				 unsigned int n_placements)
 {
+	struct intel_memory_region **arr;
+	unsigned int i;
+
 	GEM_BUG_ON(!n_placements);
 
 	/*
@@ -44,9 +47,20 @@ static void object_set_placements(struct drm_i915_gem_object *obj,
 		obj->mm.placements = &i915->mm.regions[mr->id];
 		obj->mm.n_placements = 1;
 	} else {
-		obj->mm.placements = placements;
+		arr = kmalloc_array(n_placements,
+				    sizeof(struct intel_memory_region *),
+				    GFP_KERNEL);
+		if (!arr)
+			return -ENOMEM;
+
+		for (i = 0; i < n_placements; i++)
+			arr[i] = placements[i];
+
+		obj->mm.placements = arr;
 		obj->mm.n_placements = n_placements;
 	}
+
+	return 0;
 }
 
 static int i915_gem_publish(struct drm_i915_gem_object *obj,
@@ -148,7 +162,9 @@ i915_gem_dumb_create(struct drm_file *file,
 		return -ENOMEM;
 
 	mr = intel_memory_region_by_type(to_i915(dev), mem_type);
-	object_set_placements(obj, &mr, 1);
+	ret = object_set_placements(obj, &mr, 1);
+	if (ret)
+		goto object_free;
 
 	ret = i915_gem_setup(obj, args->size);
 	if (ret)
@@ -184,7 +200,9 @@ i915_gem_create_ioctl(struct drm_device *dev, void *data,
 		return -ENOMEM;
 
 	mr = intel_memory_region_by_type(i915, INTEL_MEMORY_SYSTEM);
-	object_set_placements(obj, &mr, 1);
+	ret = object_set_placements(obj, &mr, 1);
+	if (ret)
+		goto object_free;
 
 	ret = i915_gem_setup(obj, args->size);
 	if (ret)
@@ -199,7 +217,8 @@ i915_gem_create_ioctl(struct drm_device *dev, void *data,
 
 struct create_ext {
 	struct drm_i915_private *i915;
-	struct drm_i915_gem_object *vanilla_object;
+	struct intel_memory_region *placements[INTEL_REGION_UNKNOWN];
+	unsigned int n_placements;
 };
 
 static void repr_placements(char *buf, size_t size,
@@ -230,8 +249,7 @@ static int set_placements(struct drm_i915_gem_create_ext_memory_regions *args,
 	struct drm_i915_private *i915 = ext_data->i915;
 	struct drm_i915_gem_memory_class_instance __user *uregions =
 		u64_to_user_ptr(args->regions);
-	struct drm_i915_gem_object *obj = ext_data->vanilla_object;
-	struct intel_memory_region **placements;
+	struct intel_memory_region *placements[INTEL_REGION_UNKNOWN];
 	u32 mask;
 	int i, ret = 0;
 
@@ -245,6 +263,8 @@ static int set_placements(struct drm_i915_gem_create_ext_memory_regions *args,
 		ret = -EINVAL;
 	}
 
+	BUILD_BUG_ON(ARRAY_SIZE(i915->mm.regions) != ARRAY_SIZE(placements));
+	BUILD_BUG_ON(ARRAY_SIZE(ext_data->placements) != ARRAY_SIZE(placements));
 	if (args->num_regions > ARRAY_SIZE(i915->mm.regions)) {
 		drm_dbg(&i915->drm, "num_regions is too large\n");
 		ret = -EINVAL;
@@ -253,21 +273,13 @@ static int set_placements(struct drm_i915_gem_create_ext_memory_regions *args,
 	if (ret)
 		return ret;
 
-	placements = kmalloc_array(args->num_regions,
-				   sizeof(struct intel_memory_region *),
-				   GFP_KERNEL);
-	if (!placements)
-		return -ENOMEM;
-
 	mask = 0;
 	for (i = 0; i < args->num_regions; i++) {
 		struct drm_i915_gem_memory_class_instance region;
 		struct intel_memory_region *mr;
 
-		if (copy_from_user(&region, uregions, sizeof(region))) {
-			ret = -EFAULT;
-			goto out_free;
-		}
+		if (copy_from_user(&region, uregions, sizeof(region)))
+			return -EFAULT;
 
 		mr = intel_memory_region_lookup(i915,
 						region.memory_class,
@@ -293,14 +305,14 @@ static int set_placements(struct drm_i915_gem_create_ext_memory_regions *args,
 		++uregions;
 	}
 
-	if (obj->mm.placements) {
+	if (ext_data->n_placements) {
 		ret = -EINVAL;
 		goto out_dump;
 	}
 
-	object_set_placements(obj, placements, args->num_regions);
-	if (args->num_regions == 1)
-		kfree(placements);
+	ext_data->n_placements = args->num_regions;
+	for (i = 0; i < args->num_regions; i++)
+		ext_data->placements[i] = placements[i];
 
 	return 0;
 
@@ -308,11 +320,11 @@ static int set_placements(struct drm_i915_gem_create_ext_memory_regions *args,
 	if (1) {
 		char buf[256];
 
-		if (obj->mm.placements) {
+		if (ext_data->n_placements) {
 			repr_placements(buf,
 					sizeof(buf),
-					obj->mm.placements,
-					obj->mm.n_placements);
+					ext_data->placements,
+					ext_data->n_placements);
 			drm_dbg(&i915->drm,
 				"Placements were already set in previous EXT. Existing placements: %s\n",
 				buf);
@@ -322,8 +334,6 @@ static int set_placements(struct drm_i915_gem_create_ext_memory_regions *args,
 		drm_dbg(&i915->drm, "New placements(so far validated): %s\n", buf);
 	}
 
-out_free:
-	kfree(placements);
 	return ret;
 }
 
@@ -358,7 +368,6 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data,
 	struct drm_i915_private *i915 = to_i915(dev);
 	struct drm_i915_gem_create_ext *args = data;
 	struct create_ext ext_data = { .i915 = i915 };
-	struct intel_memory_region **placements_ext;
 	struct drm_i915_gem_object *obj;
 	int ret;
 
@@ -371,21 +380,22 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data,
 	if (!obj)
 		return -ENOMEM;
 
-	ext_data.vanilla_object = obj;
 	ret = i915_user_extensions(u64_to_user_ptr(args->extensions),
 				   create_extensions,
 				   ARRAY_SIZE(create_extensions),
 				   &ext_data);
-	placements_ext = obj->mm.placements;
 	if (ret)
 		goto object_free;
 
-	if (!placements_ext) {
-		struct intel_memory_region *mr =
+	if (!ext_data.n_placements) {
+		ext_data.placements[0] =
 			intel_memory_region_by_type(i915, INTEL_MEMORY_SYSTEM);
-
-		object_set_placements(obj, &mr, 1);
+		ext_data.n_placements = 1;
 	}
+	ret = object_set_placements(obj, ext_data.placements,
+				    ext_data.n_placements);
+	if (ret)
+		goto object_free;
 
 	ret = i915_gem_setup(obj, args->size);
 	if (ret)
@@ -395,7 +405,7 @@ i915_gem_create_ext_ioctl(struct drm_device *dev, void *data,
 
 object_free:
 	if (obj->mm.n_placements > 1)
-		kfree(placements_ext);
+		kfree(obj->mm.placements);
 	i915_gem_object_free(obj);
 	return ret;
 }