drm: improve drm_buddy_alloc function

- Make drm_buddy_alloc a single function to handle
  range allocation and non-range allocation demands

- Implemented a new function alloc_range() which allocates
  the requested power-of-two block comply with range limitations

- Moved order computation and memory alignment logic from
  i915 driver to drm buddy

v2:
  merged below changes to keep the build unbroken
   - drm_buddy_alloc_range() becomes obsolete and may be removed
   - enable ttm range allocation (fpfn / lpfn) support in i915 driver
   - apply enhanced drm_buddy_alloc() function to i915 driver

v3(Matthew Auld):
  - Fix alignment issues and remove unnecessary list_empty check
  - add more validation checks for input arguments
  - make alloc_range() block allocations as bottom-up
  - optimize order computation logic
  - replace uint64_t with u64, which is preferred in the kernel

v4(Matthew Auld):
  - keep drm_buddy_alloc_range() function implementation for generic
    actual range allocations
  - keep alloc_range() implementation for end bias allocations

v5(Matthew Auld):
  - modify drm_buddy_alloc() passing argument place->lpfn to lpfn
    as place->lpfn will currently always be zero for i915

v6(Matthew Auld):
  - fixup potential uaf - If we are unlucky and can't allocate
    enough memory when splitting blocks, where we temporarily
    end up with the given block and its buddy on the respective
    free list, then we need to ensure we delete both blocks,
    and no just the buddy, before potentially freeing them

  - fix warnings reported by kernel test robot <lkp@intel.com>

v7(Matthew Auld):
  - revert fixup potential uaf
  - keep __alloc_range() add node to the list logic same as
    drm_buddy_alloc_blocks() by having a temporary list variable
  - at drm_buddy_alloc_blocks() keep i915 range_overflows macro
    and add a new check for end variable

v8:
  - fix warnings reported by kernel test robot <lkp@intel.com>

v9(Matthew Auld):
  - remove DRM_BUDDY_RANGE_ALLOCATION flag
  - remove unnecessary function description

v10:
   - keep DRM_BUDDY_RANGE_ALLOCATION flag as removing the flag
     and replacing with (end < size) logic fails amdgpu driver load

Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@amd.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220221164552.2434-1-Arunpravin.PaneerSelvam@amd.com

1 files changed, 215 insertions, 77 deletions

diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index d60878bc9c20..1d801c88b286 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -282,23 +282,97 @@ void drm_buddy_free_list(struct drm_buddy *mm, struct list_head *objects)
 }
 EXPORT_SYMBOL(drm_buddy_free_list);
 
-/**
- * drm_buddy_alloc_blocks - allocate power-of-two blocks
- *
- * @mm: DRM buddy manager to allocate from
- * @order: size of the allocation
- *
- * The order value here translates to:
- *
- * 0 = 2^0 * mm->chunk_size
- * 1 = 2^1 * mm->chunk_size
- * 2 = 2^2 * mm->chunk_size
- *
- * Returns:
- * allocated ptr to the &drm_buddy_block on success
- */
-struct drm_buddy_block *
-drm_buddy_alloc_blocks(struct drm_buddy *mm, unsigned int order)
+static inline bool overlaps(u64 s1, u64 e1, u64 s2, u64 e2)
+{
+	return s1 <= e2 && e1 >= s2;
+}
+
+static inline bool contains(u64 s1, u64 e1, u64 s2, u64 e2)
+{
+	return s1 <= s2 && e1 >= e2;
+}
+
+static struct drm_buddy_block *
+alloc_range_bias(struct drm_buddy *mm,
+		 u64 start, u64 end,
+		 unsigned int order)
+{
+	struct drm_buddy_block *block;
+	struct drm_buddy_block *buddy;
+	LIST_HEAD(dfs);
+	int err;
+	int i;
+
+	end = end - 1;
+
+	for (i = 0; i < mm->n_roots; ++i)
+		list_add_tail(&mm->roots[i]->tmp_link, &dfs);
+
+	do {
+		u64 block_start;
+		u64 block_end;
+
+		block = list_first_entry_or_null(&dfs,
+						 struct drm_buddy_block,
+						 tmp_link);
+		if (!block)
+			break;
+
+		list_del(&block->tmp_link);
+
+		if (drm_buddy_block_order(block) < order)
+			continue;
+
+		block_start = drm_buddy_block_offset(block);
+		block_end = block_start + drm_buddy_block_size(mm, block) - 1;
+
+		if (!overlaps(start, end, block_start, block_end))
+			continue;
+
+		if (drm_buddy_block_is_allocated(block))
+			continue;
+
+		if (contains(start, end, block_start, block_end) &&
+		    order == drm_buddy_block_order(block)) {
+			/*
+			 * Find the free block within the range.
+			 */
+			if (drm_buddy_block_is_free(block))
+				return block;
+
+			continue;
+		}
+
+		if (!drm_buddy_block_is_split(block)) {
+			err = split_block(mm, block);
+			if (unlikely(err))
+				goto err_undo;
+		}
+
+		list_add(&block->right->tmp_link, &dfs);
+		list_add(&block->left->tmp_link, &dfs);
+	} while (1);
+
+	return ERR_PTR(-ENOSPC);
+
+err_undo:
+	/*
+	 * We really don't want to leave around a bunch of split blocks, since
+	 * bigger is better, so make sure we merge everything back before we
+	 * free the allocated blocks.
+	 */
+	buddy = get_buddy(block);
+	if (buddy &&
+	    (drm_buddy_block_is_free(block) &&
+	     drm_buddy_block_is_free(buddy)))
+		__drm_buddy_free(mm, block);
+	return ERR_PTR(err);
+}
+
+static struct drm_buddy_block *
+alloc_from_freelist(struct drm_buddy *mm,
+		    unsigned int order,
+		    unsigned long flags)
 {
 	struct drm_buddy_block *block = NULL;
 	unsigned int i;
@@ -320,78 +394,29 @@ drm_buddy_alloc_blocks(struct drm_buddy *mm, unsigned int order)
 	while (i != order) {
 		err = split_block(mm, block);
 		if (unlikely(err))
-			goto out_free;
+			goto err_undo;
 
-		/* Go low */
-		block = block->left;
+		block = block->right;
 		i--;
 	}
-
-	mark_allocated(block);
-	mm->avail -= drm_buddy_block_size(mm, block);
-	kmemleak_update_trace(block);
 	return block;
 
-out_free:
+err_undo:
 	if (i != order)
 		__drm_buddy_free(mm, block);
 	return ERR_PTR(err);
 }
-EXPORT_SYMBOL(drm_buddy_alloc_blocks);
-
-static inline bool overlaps(u64 s1, u64 e1, u64 s2, u64 e2)
-{
-	return s1 <= e2 && e1 >= s2;
-}
-
-static inline bool contains(u64 s1, u64 e1, u64 s2, u64 e2)
-{
-	return s1 <= s2 && e1 >= e2;
-}
 
-/**
- * drm_buddy_alloc_range - allocate range
- *
- * @mm: DRM buddy manager to allocate from
- * @blocks: output list head to add allocated blocks
- * @start: start of the allowed range for this block
- * @size: size of the allocation
- *
- * Intended for pre-allocating portions of the address space, for example to
- * reserve a block for the initial framebuffer or similar, hence the expectation
- * here is that drm_buddy_alloc_blocks() is still the main vehicle for
- * allocations, so if that's not the case then the drm_mm range allocator is
- * probably a much better fit, and so you should probably go use that instead.
- *
- * Note that it's safe to chain together multiple alloc_ranges
- * with the same blocks list
- *
- * Returns:
- * 0 on success, error code on failure.
- */
-int drm_buddy_alloc_range(struct drm_buddy *mm,
-			  struct list_head *blocks,
-			  u64 start, u64 size)
+static int __alloc_range(struct drm_buddy *mm,
+			 struct list_head *dfs,
+			 u64 start, u64 size,
+			 struct list_head *blocks)
 {
 	struct drm_buddy_block *block;
 	struct drm_buddy_block *buddy;
 	LIST_HEAD(allocated);
-	LIST_HEAD(dfs);
 	u64 end;
 	int err;
-	int i;
-
-	if (size < mm->chunk_size)
-		return -EINVAL;
-
-	if (!IS_ALIGNED(size | start, mm->chunk_size))
-		return -EINVAL;
-
-	if (range_overflows(start, size, mm->size))
-		return -EINVAL;
-
-	for (i = 0; i < mm->n_roots; ++i)
-		list_add_tail(&mm->roots[i]->tmp_link, &dfs);
 
 	end = start + size - 1;
 
@@ -399,7 +424,7 @@ int drm_buddy_alloc_range(struct drm_buddy *mm,
 		u64 block_start;
 		u64 block_end;
 
-		block = list_first_entry_or_null(&dfs,
+		block = list_first_entry_or_null(dfs,
 						 struct drm_buddy_block,
 						 tmp_link);
 		if (!block)
@@ -436,8 +461,8 @@ int drm_buddy_alloc_range(struct drm_buddy *mm,
 				goto err_undo;
 		}
 
-		list_add(&block->right->tmp_link, &dfs);
-		list_add(&block->left->tmp_link, &dfs);
+		list_add(&block->right->tmp_link, dfs);
+		list_add(&block->left->tmp_link, dfs);
 	} while (1);
 
 	list_splice_tail(&allocated, blocks);
@@ -459,7 +484,120 @@ err_free:
 	drm_buddy_free_list(mm, &allocated);
 	return err;
 }
-EXPORT_SYMBOL(drm_buddy_alloc_range);
+
+static int __drm_buddy_alloc_range(struct drm_buddy *mm,
+				   u64 start,
+				   u64 size,
+				   struct list_head *blocks)
+{
+	LIST_HEAD(dfs);
+	int i;
+
+	for (i = 0; i < mm->n_roots; ++i)
+		list_add_tail(&mm->roots[i]->tmp_link, &dfs);
+
+	return __alloc_range(mm, &dfs, start, size, blocks);
+}
+
+/**
+ * drm_buddy_alloc_blocks - allocate power-of-two blocks
+ *
+ * @mm: DRM buddy manager to allocate from
+ * @start: start of the allowed range for this block
+ * @end: end of the allowed range for this block
+ * @size: size of the allocation
+ * @min_page_size: alignment of the allocation
+ * @blocks: output list head to add allocated blocks
+ * @flags: DRM_BUDDY_*_ALLOCATION flags
+ *
+ * alloc_range_bias() called on range limitations, which traverses
+ * the tree and returns the desired block.
+ *
+ * alloc_from_freelist() called when *no* range restrictions
+ * are enforced, which picks the block from the freelist.
+ *
+ * Returns:
+ * 0 on success, error code on failure.
+ */
+int drm_buddy_alloc_blocks(struct drm_buddy *mm,
+			   u64 start, u64 end, u64 size,
+			   u64 min_page_size,
+			   struct list_head *blocks,
+			   unsigned long flags)
+{
+	struct drm_buddy_block *block = NULL;
+	unsigned int min_order, order;
+	unsigned long pages;
+	LIST_HEAD(allocated);
+	int err;
+
+	if (size < mm->chunk_size)
+		return -EINVAL;
+
+	if (min_page_size < mm->chunk_size)
+		return -EINVAL;
+
+	if (!is_power_of_2(min_page_size))
+		return -EINVAL;
+
+	if (!IS_ALIGNED(start | end | size, mm->chunk_size))
+		return -EINVAL;
+
+	if (end > mm->size)
+		return -EINVAL;
+
+	if (range_overflows(start, size, mm->size))
+		return -EINVAL;
+
+	/* Actual range allocation */
+	if (start + size == end)
+		return __drm_buddy_alloc_range(mm, start, size, blocks);
+
+	pages = size >> ilog2(mm->chunk_size);
+	order = fls(pages) - 1;
+	min_order = ilog2(min_page_size) - ilog2(mm->chunk_size);
+
+	do {
+		order = min(order, (unsigned int)fls(pages) - 1);
+		BUG_ON(order > mm->max_order);
+		BUG_ON(order < min_order);
+
+		do {
+			if (flags & DRM_BUDDY_RANGE_ALLOCATION)
+				/* Allocate traversing within the range */
+				block = alloc_range_bias(mm, start, end, order);
+			else
+				/* Allocate from freelist */
+				block = alloc_from_freelist(mm, order, flags);
+
+			if (!IS_ERR(block))
+				break;
+
+			if (order-- == min_order) {
+				err = -ENOSPC;
+				goto err_free;
+			}
+		} while (1);
+
+		mark_allocated(block);
+		mm->avail -= drm_buddy_block_size(mm, block);
+		kmemleak_update_trace(block);
+		list_add_tail(&block->link, &allocated);
+
+		pages -= BIT(order);
+
+		if (!pages)
+			break;
+	} while (1);
+
+	list_splice_tail(&allocated, blocks);
+	return 0;
+
+err_free:
+	drm_buddy_free_list(mm, &allocated);
+	return err;
+}
+EXPORT_SYMBOL(drm_buddy_alloc_blocks);
 
 /**
  * drm_buddy_block_print - print block information