Re: [Intel-gfx] [PATCH 01/20] drm: improve drm_buddy_alloc function

Jani Nikula
2022-01-26T18:03:19Z

On Wed, 26 Jan 2022, Matthew Auld <matthew.auld@intel.com> wrote:
> From: Arunpravin <Arunpravin.PaneerSelvam@amd.com>
>
> - 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>
>
> Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@amd.com>
> ---
> drivers/gpu/drm/drm_buddy.c | 326 +++++++++++++-----
> drivers/gpu/drm/i915/i915_ttm_buddy_manager.c | 67 ++--
> drivers/gpu/drm/i915/i915_ttm_buddy_manager.h | 2 +
> include/drm/drm_buddy.h | 22 +-
> 4 files changed, 293 insertions(+), 124 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
> index d60878bc9c20..954e31962c74 100644
> --- a/drivers/gpu/drm/drm_buddy.c
> +++ b/drivers/gpu/drm/drm_buddy.c
> @@ -282,23 +282,99 @@ 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))) {
> + list_del(&block->link);
> + __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 +396,30 @@ 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:
> - if (i != order)
> +err_undo:
> + if (i != order) {
> + list_del(&block->link);
> __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 +427,7 @@ 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)
> @@ -426,7 +454,7 @@ int drm_buddy_alloc_range(struct drm_buddy *mm,
>
> mark_allocated(block);
> mm->avail -= drm_buddy_block_size(mm, block);
> - list_add_tail(&block->link, &allocated);
> + list_add_tail(&block->link, blocks);
> continue;
> }
>
> @@ -436,11 +464,10 @@ 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);
> return 0;
>
> err_undo:
> @@ -452,14 +479,149 @@ int drm_buddy_alloc_range(struct drm_buddy *mm,
> buddy = get_buddy(block);
> if (buddy &&
> (drm_buddy_block_is_free(block) &&
> - drm_buddy_block_is_free(buddy)))
> + drm_buddy_block_is_free(buddy))) {
> + list_del(&block->link);
> __drm_buddy_free(mm, block);
> + }
> +
> +err_free:
> + drm_buddy_free_list(mm, blocks);
> + return err;
> +}
> +
> +/**
> + * __drm_buddy_alloc_range - actual range allocation
> + *
> + * @mm: DRM buddy manager to allocate from
> + * @start: start of the allowed range for this block
> + * @size: size of the allocation
> + * @blocks: output list head to add allocated blocks
> + *
> + * Intended for pre-allocating portions of the address space, for example to
> + * reserve a block for the initial framebuffer or similar
> + *
> + * Note that it's safe to chain together multiple alloc_ranges
> + * with the same blocks list
> + *
> + * Returns:
> + * 0 on success, error code on failure.
> + */
> +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.
> + *
> + * blocks are allocated in order, 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:
> + * 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 (check_range_overflow(start, end, 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_range);
> +EXPORT_SYMBOL(drm_buddy_alloc_blocks);
>
> /**
> * drm_buddy_block_print - print block information
> diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> index 6ba314f9836a..1411f4cf1f21 100644
> --- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> +++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> @@ -36,13 +36,14 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
> struct i915_ttm_buddy_manager *bman = to_buddy_manager(man);
> struct i915_ttm_buddy_resource *bman_res;
> struct drm_buddy *mm = &bman->mm;
> - unsigned long n_pages;
> - unsigned int min_order;
> + unsigned long n_pages, lpfn;
> u64 min_page_size;
> u64 size;
> int err;
>
> - GEM_BUG_ON(place->fpfn || place->lpfn);
> + lpfn = place->lpfn;
> + if (!lpfn)
> + lpfn = man->size;
>
> bman_res = kzalloc(sizeof(*bman_res), GFP_KERNEL);
> if (!bman_res)
> @@ -52,6 +53,9 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
> INIT_LIST_HEAD(&bman_res->blocks);
> bman_res->mm = mm;
>
> + if (place->fpfn || lpfn != man->size)
> + bman_res->flags |= DRM_BUDDY_RANGE_ALLOCATION;
> +
> GEM_BUG_ON(!bman_res->base.num_pages);
> size = bman_res->base.num_pages << PAGE_SHIFT;
>
> @@ -60,10 +64,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
> min_page_size = bo->page_alignment << PAGE_SHIFT;
>
> GEM_BUG_ON(min_page_size < mm->chunk_size);
> - min_order = ilog2(min_page_size) - ilog2(mm->chunk_size);
> +
> if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
> + unsigned long pages;
> +
> size = roundup_pow_of_two(size);
> - min_order = ilog2(size) - ilog2(mm->chunk_size);
> + min_page_size = size;
> +
> + pages = size >> ilog2(mm->chunk_size);
> + if (pages > lpfn)
> + lpfn = pages;
> }
>
> if (size > mm->size) {
> @@ -73,34 +83,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
>
> n_pages = size >> ilog2(mm->chunk_size);
>
> - do {
> - struct drm_buddy_block *block;
> - unsigned int order;
> -
> - order = fls(n_pages) - 1;
> - GEM_BUG_ON(order > mm->max_order);
> - GEM_BUG_ON(order < min_order);
> -
> - do {
> - mutex_lock(&bman->lock);
> - block = drm_buddy_alloc_blocks(mm, order);
> - mutex_unlock(&bman->lock);
> - if (!IS_ERR(block))
> - break;
> -
> - if (order-- == min_order) {
> - err = -ENOSPC;
> - goto err_free_blocks;
> - }
> - } while (1);
> -
> - n_pages -= BIT(order);
> -
> - list_add_tail(&block->link, &bman_res->blocks);
> -
> - if (!n_pages)
> - break;
> - } while (1);
> + mutex_lock(&bman->lock);
> + err = drm_buddy_alloc_blocks(mm, (u64)place->fpfn << PAGE_SHIFT,
> + (u64)lpfn << PAGE_SHIFT,
> + (u64)n_pages << PAGE_SHIFT,
> + min_page_size,
> + &bman_res->blocks,
> + bman_res->flags);
> + mutex_unlock(&bman->lock);
> + if (unlikely(err))
> + goto err_free_blocks;
>
> *res = &bman_res->base;
> return 0;
> @@ -266,10 +258,17 @@ int i915_ttm_buddy_man_reserve(struct ttm_resource_manager *man,
> {
> struct i915_ttm_buddy_manager *bman = to_buddy_manager(man);
> struct drm_buddy *mm = &bman->mm;
> + unsigned long flags = 0;
> int ret;
>
> + flags |= DRM_BUDDY_RANGE_ALLOCATION;
> +
> mutex_lock(&bman->lock);
> - ret = drm_buddy_alloc_range(mm, &bman->reserved, start, size);
> + ret = drm_buddy_alloc_blocks(mm, start,
> + start + size,
> + size, mm->chunk_size,
> + &bman->reserved,
> + flags);
> mutex_unlock(&bman->lock);
>
> return ret;
> diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
> index 312077941411..72c90b432e87 100644
> --- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
> +++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
> @@ -20,6 +20,7 @@ struct drm_buddy;
> *
> * @base: struct ttm_resource base class we extend
> * @blocks: the list of struct i915_buddy_block for this resource/allocation
> + * @flags: DRM_BUDDY_*_ALLOCATION flags
> * @mm: the struct i915_buddy_mm for this resource
> *
> * Extends the struct ttm_resource to manage an address space allocation with
> @@ -28,6 +29,7 @@ struct drm_buddy;
> struct i915_ttm_buddy_resource {
> struct ttm_resource base;
> struct list_head blocks;
> + unsigned long flags;
> struct drm_buddy *mm;
> };
>
> diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
> index f524db152413..865664b90a8a 100644
> --- a/include/drm/drm_buddy.h
> +++ b/include/drm/drm_buddy.h
> @@ -13,15 +13,22 @@
>
> #include <drm/drm_print.h>
>
> -#define range_overflows(start, size, max) ({ \
> +#define check_range_overflow(start, end, size, max) ({ \

Random drive-by comment, why the rename? The old one is understandable,
it's a bool, while "check", to me, implies it might *do* something in
case of overflow.

> typeof(start) start__ = (start); \
> + typeof(end) end__ = (end);\
> typeof(size) size__ = (size); \
> typeof(max) max__ = (max); \
> (void)(&start__ == &size__); \
> (void)(&start__ == &max__); \
> - start__ >= max__ || size__ > max__ - start__; \
> + (void)(&start__ == &end__); \
> + (void)(&end__ == &size__); \
> + (void)(&end__ == &max__); \
> + start__ >= max__ || end__ > max__ || \
> + size__ > end__ - start__; \
> })
>
> +#define DRM_BUDDY_RANGE_ALLOCATION (1 << 0)
> +
> struct drm_buddy_block {
> #define DRM_BUDDY_HEADER_OFFSET GENMASK_ULL(63, 12)
> #define DRM_BUDDY_HEADER_STATE GENMASK_ULL(11, 10)
> @@ -131,12 +138,11 @@ int drm_buddy_init(struct drm_buddy *mm, u64 size, u64 chunk_size);
>
> void drm_buddy_fini(struct drm_buddy *mm);
>
> -struct drm_buddy_block *
> -drm_buddy_alloc_blocks(struct drm_buddy *mm, unsigned int order);
> -
> -int drm_buddy_alloc_range(struct drm_buddy *mm,
> - struct list_head *blocks,
> - u64 start, u64 size);
> +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);
>
> void drm_buddy_free_block(struct drm_buddy *mm, struct drm_buddy_block *block);

--
Jani Nikula, Intel Open Source Graphics Center