drm/i915: Pad GTT views of exec objects up to user specified size

Our GPUs impose certain requirements upon buffers that depend upon how
exactly they are used. Typically this is expressed as that they require
a larger surface than would be naively computed by pitch * height.
Normally such requirements are hidden away in the userspace driver, but
when we accept pointers from strangers and later impose extra conditions
on them, the original client allocator has no idea about the
monstrosities in the GPU and we require the userspace driver to inform
the kernel how many padding pages are required beyond the client
allocation.

v2: Long time, no see
v3: Try an anonymous union for uapi struct compatibility

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470324762-2545-7-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.h

@@ -3032,11 +3032,13 @@ void i915_gem_free_object(struct drm_gem_object *obj);
 int __must_check
 i915_gem_object_pin(struct drm_i915_gem_object *obj,
 		    struct i915_address_space *vm,
+		    u64 size,
 		    u64 alignment,
 		    u64 flags);
 int __must_check
 i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
 			 const struct i915_ggtt_view *view,
+			 u64 size,
 			 u64 alignment,
 			 u64 flags);
 
@@ -3313,8 +3315,8 @@ i915_gem_obj_ggtt_pin(struct drm_i915_gem_object *obj,
 	struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
 	struct i915_ggtt *ggtt = &dev_priv->ggtt;
 
-	return i915_gem_object_pin(obj, &ggtt->base,
+	return i915_gem_object_pin(obj, &ggtt->base, 0, alignment,
-				   alignment, flags | PIN_GLOBAL);
+				   flags | PIN_GLOBAL);
 }
 
 void i915_gem_object_ggtt_unpin_view(struct drm_i915_gem_object *obj,

drivers/gpu/drm/i915/i915_gem.c

@@ -1692,7 +1692,7 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 	}
 
 	/* Now pin it into the GTT if needed */
-	ret = i915_gem_object_ggtt_pin(obj, &view, 0, PIN_MAPPABLE);
+	ret = i915_gem_object_ggtt_pin(obj, &view, 0, 0, PIN_MAPPABLE);
 	if (ret)
 		goto unlock;
 
@@ -2956,6 +2956,7 @@ static bool i915_gem_valid_gtt_space(struct i915_vma *vma,
  * @obj: object to bind
  * @vm: address space to bind into
  * @ggtt_view: global gtt view if applicable
+ * @size: requested size in bytes (can be larger than the VMA)
  * @alignment: requested alignment
  * @flags: mask of PIN_* flags to use
  */
@@ -2963,21 +2964,20 @@ static struct i915_vma *
 i915_gem_object_bind_to_vm(struct drm_i915_gem_object *obj,
 			   struct i915_address_space *vm,
 			   const struct i915_ggtt_view *ggtt_view,
+			   u64 size,
 			   u64 alignment,
 			   u64 flags)
 {
 	struct drm_device *dev = obj->base.dev;
 	struct drm_i915_private *dev_priv = to_i915(dev);
-	struct i915_ggtt *ggtt = &dev_priv->ggtt;
-	u32 fence_alignment, unfenced_alignment;
-	u32 search_flag, alloc_flag;
 	u64 start, end;
-	u64 size, fence_size;
+	u32 search_flag, alloc_flag;
 	struct i915_vma *vma;
 	int ret;
 
 	if (i915_is_ggtt(vm)) {
-		u32 view_size;
+		u32 fence_size, fence_alignment, unfenced_alignment;
+		u64 view_size;
 
 		if (WARN_ON(!ggtt_view))
 			return ERR_PTR(-EINVAL);
@@ -2995,29 +2995,9 @@ i915_gem_object_bind_to_vm(struct drm_i915_gem_object *obj,
 								view_size,
 								obj->tiling_mode,
 								false);
-		size = flags & PIN_MAPPABLE ? fence_size : view_size;
+		size = max(size, view_size);
-	} else {
-		fence_size = i915_gem_get_gtt_size(dev,
-						   obj->base.size,
-						   obj->tiling_mode);
-		fence_alignment = i915_gem_get_gtt_alignment(dev,
-							     obj->base.size,
-							     obj->tiling_mode,
-							     true);
-		unfenced_alignment =
-			i915_gem_get_gtt_alignment(dev,
-						   obj->base.size,
-						   obj->tiling_mode,
-						   false);
-		size = flags & PIN_MAPPABLE ? fence_size : obj->base.size;
-	}
-
-	start = flags & PIN_OFFSET_BIAS ? flags & PIN_OFFSET_MASK : 0;
-	end = vm->total;
 		if (flags & PIN_MAPPABLE)
-		end = min_t(u64, end, ggtt->mappable_end);
+			size = max_t(u64, size, fence_size);
-	if (flags & PIN_ZONE_4G)
-		end = min_t(u64, end, (1ULL << 32) - PAGE_SIZE);
 
 		if (alignment == 0)
 			alignment = flags & PIN_MAPPABLE ? fence_alignment :
@@ -3028,15 +3008,26 @@ i915_gem_object_bind_to_vm(struct drm_i915_gem_object *obj,
 				  alignment);
 			return ERR_PTR(-EINVAL);
 		}
+	} else {
+		size = max_t(u64, size, obj->base.size);
+		alignment = 4096;
+	}
+
+	start = flags & PIN_OFFSET_BIAS ? flags & PIN_OFFSET_MASK : 0;
+	end = vm->total;
+	if (flags & PIN_MAPPABLE)
+		end = min_t(u64, end, dev_priv->ggtt.mappable_end);
+	if (flags & PIN_ZONE_4G)
+		end = min_t(u64, end, (1ULL << 32) - PAGE_SIZE);
 
 	/* If binding the object/GGTT view requires more space than the entire
 	 * aperture has, reject it early before evicting everything in a vain
 	 * attempt to find space.
 	 */
 	if (size > end) {
-		DRM_DEBUG("Attempting to bind an object (view type=%u) larger than the aperture: size=%llu > %s aperture=%llu\n",
+		DRM_DEBUG("Attempting to bind an object (view type=%u) larger than the aperture: request=%llu [object=%zd] > %s aperture=%llu\n",
 			  ggtt_view ? ggtt_view->type : 0,
-			  size,
+			  size, obj->base.size,
 			  flags & PIN_MAPPABLE ? "mappable" : "total",
 			  end);
 		return ERR_PTR(-E2BIG);
@@ -3530,7 +3521,7 @@ i915_gem_object_pin_to_display_plane(struct drm_i915_gem_object *obj,
 	 * (e.g. libkms for the bootup splash), we have to ensure that we
 	 * always use map_and_fenceable for all scanout buffers.
 	 */
-	ret = i915_gem_object_ggtt_pin(obj, view, alignment,
+	ret = i915_gem_object_ggtt_pin(obj, view, 0, alignment,
 				       view->type == I915_GGTT_VIEW_NORMAL ?
 				       PIN_MAPPABLE : 0);
 	if (ret)
@@ -3678,12 +3669,14 @@ i915_gem_ring_throttle(struct drm_device *dev, struct drm_file *file)
 }
 
 static bool
-i915_vma_misplaced(struct i915_vma *vma, u64 alignment, u64 flags)
+i915_vma_misplaced(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 {
 	struct drm_i915_gem_object *obj = vma->obj;
 
-	if (alignment &&
+	if (vma->node.size < size)
-	    vma->node.start & (alignment - 1))
+		return true;
+
+	if (alignment && vma->node.start & (alignment - 1))
 		return true;
 
 	if (flags & PIN_MAPPABLE && !obj->map_and_fenceable)
@@ -3727,6 +3720,7 @@ static int
 i915_gem_object_do_pin(struct drm_i915_gem_object *obj,
 		       struct i915_address_space *vm,
 		       const struct i915_ggtt_view *ggtt_view,
+		       u64 size,
 		       u64 alignment,
 		       u64 flags)
 {
@@ -3754,7 +3748,7 @@ i915_gem_object_do_pin(struct drm_i915_gem_object *obj,
 		if (WARN_ON(vma->pin_count == DRM_I915_GEM_OBJECT_MAX_PIN_COUNT))
 			return -EBUSY;
 
-		if (i915_vma_misplaced(vma, alignment, flags)) {
+		if (i915_vma_misplaced(vma, size, alignment, flags)) {
 			WARN(vma->pin_count,
 			     "bo is already pinned in %s with incorrect alignment:"
 			     " offset=%08x %08x, req.alignment=%llx, req.map_and_fenceable=%d,"
@@ -3775,8 +3769,8 @@ i915_gem_object_do_pin(struct drm_i915_gem_object *obj,
 
 	bound = vma ? vma->bound : 0;
 	if (vma == NULL || !drm_mm_node_allocated(&vma->node)) {
-		vma = i915_gem_object_bind_to_vm(obj, vm, ggtt_view, alignment,
+		vma = i915_gem_object_bind_to_vm(obj, vm, ggtt_view,
-						 flags);
+						 size, alignment, flags);
 		if (IS_ERR(vma))
 			return PTR_ERR(vma);
 	} else {
@@ -3798,17 +3792,19 @@ i915_gem_object_do_pin(struct drm_i915_gem_object *obj,
 int
 i915_gem_object_pin(struct drm_i915_gem_object *obj,
 		    struct i915_address_space *vm,
+		    u64 size,
 		    u64 alignment,
 		    u64 flags)
 {
 	return i915_gem_object_do_pin(obj, vm,
 				      i915_is_ggtt(vm) ? &i915_ggtt_view_normal : NULL,
-				      alignment, flags);
+				      size, alignment, flags);
 }
 
 int
 i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
 			 const struct i915_ggtt_view *view,
+			 u64 size,
 			 u64 alignment,
 			 u64 flags)
 {
@@ -3819,7 +3815,7 @@ i915_gem_object_ggtt_pin(struct drm_i915_gem_object *obj,
 	BUG_ON(!view);
 
 	return i915_gem_object_do_pin(obj, &ggtt->base, view,
-				      alignment, flags | PIN_GLOBAL);
+				      size, alignment, flags | PIN_GLOBAL);
 }
 
 void

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -682,10 +682,14 @@ i915_gem_execbuffer_reserve_vma(struct i915_vma *vma,
 			flags |= PIN_HIGH;
 	}
 
-	ret = i915_gem_object_pin(obj, vma->vm, entry->alignment, flags);
+	ret = i915_gem_object_pin(obj, vma->vm,
+				  entry->pad_to_size,
+				  entry->alignment,
+				  flags);
 	if ((ret == -ENOSPC  || ret == -E2BIG) &&
 	    only_mappable_for_reloc(entry->flags))
 		ret = i915_gem_object_pin(obj, vma->vm,
+					  entry->pad_to_size,
 					  entry->alignment,
 					  flags & ~PIN_MAPPABLE);
 	if (ret)
@@ -748,6 +752,9 @@ eb_vma_misplaced(struct i915_vma *vma)
 	    vma->node.start & (entry->alignment - 1))
 		return true;
 
+	if (vma->node.size < entry->pad_to_size)
+		return true;
+
 	if (entry->flags & EXEC_OBJECT_PINNED &&
 	    vma->node.start != entry->offset)
 		return true;
@@ -1091,6 +1098,14 @@ validate_exec_list(struct drm_device *dev,
 		if (exec[i].alignment && !is_power_of_2(exec[i].alignment))
 			return -EINVAL;
 
+		/* pad_to_size was once a reserved field, so sanitize it */
+		if (exec[i].flags & EXEC_OBJECT_PAD_TO_SIZE) {
+			if (offset_in_page(exec[i].pad_to_size))
+				return -EINVAL;
+		} else {
+			exec[i].pad_to_size = 0;
+		}
+
 		/* First check for malicious input causing overflow in
 		 * the worst case where we need to allocate the entire
 		 * relocation tree as a single array.

include/uapi/drm/i915_drm.h

@@ -727,11 +727,15 @@ struct drm_i915_gem_exec_object2 {
 #define EXEC_OBJECT_WRITE		 (1<<2)
 #define EXEC_OBJECT_SUPPORTS_48B_ADDRESS (1<<3)
 #define EXEC_OBJECT_PINNED		 (1<<4)
+#define EXEC_OBJECT_PAD_TO_SIZE		 (1<<5)
 /* All remaining bits are MBZ and RESERVED FOR FUTURE USE */
-#define __EXEC_OBJECT_UNKNOWN_FLAGS	(-(EXEC_OBJECT_PINNED<<1))
+#define __EXEC_OBJECT_UNKNOWN_FLAGS -(EXEC_OBJECT_PAD_TO_SIZE<<1)
 	__u64 flags;
 
+	union {
 		__u64 rsvd1;
+		__u64 pad_to_size;
+	};
 	__u64 rsvd2;
 };