gpu_buddy APIs are expected to be called with the driver-provided lock
held, but there is no runtime enforcement of this contract. Add lockdep
annotations to catch locking violations early.
Introduce gpu_buddy_driver_set_lock() for the driver to register the
lock that protects the buddy manager. Add gpu_buddy_driver_lock_held()
assertions to all exported gpu_buddy and drm_buddy APIs that
access/modify the manager state. The lock_dep_map field is only compiled
in when CONFIG_LOCKDEP is enabled, adding zero overhead to production
builds.
Wire up xe_ttm_vram_mgr to register its mutex with the buddy manager
after initialization.
Assisted-by: Copilot:claude-opus-4.6
Suggested-by: Matthew Brost <[email protected]>
Signed-off-by: Tejas Upadhyay <[email protected]>
Reviewed-by: Matthew Auld <[email protected]>
---
drivers/gpu/buddy.c | 11 ++++++++
drivers/gpu/drm/drm_buddy.c | 1 +
drivers/gpu/drm/xe/xe_ttm_vram_mgr.c | 1 +
include/linux/gpu_buddy.h | 41 ++++++++++++++++++++++++++++
4 files changed, 54 insertions(+)
diff --git a/drivers/gpu/buddy.c b/drivers/gpu/buddy.c
index 52686672e99f..eb1457376307 100644
--- a/drivers/gpu/buddy.c
+++ b/drivers/gpu/buddy.c
@@ -437,6 +437,9 @@ int gpu_buddy_init(struct gpu_buddy *mm, u64 size, u64
chunk_size)
root_count++;
} while (size);
+#ifdef CONFIG_LOCKDEP
+ mm->lock_dep_map = NULL;
+#endif
return 0;
out_free_roots:
@@ -538,6 +541,7 @@ void gpu_buddy_reset_clear(struct gpu_buddy *mm, bool
is_clear)
unsigned int order;
int i;
+ gpu_buddy_driver_lock_held(mm);
size = mm->size;
for (i = 0; i < mm->n_roots; ++i) {
order = ilog2(size) - ilog2(mm->chunk_size);
@@ -580,6 +584,7 @@ EXPORT_SYMBOL(gpu_buddy_reset_clear);
void gpu_buddy_free_block(struct gpu_buddy *mm,
struct gpu_buddy_block *block)
{
+ gpu_buddy_driver_lock_held(mm);
BUG_ON(!gpu_buddy_block_is_allocated(block));
mm->avail += gpu_buddy_block_size(mm, block);
if (gpu_buddy_block_is_clear(block))
@@ -633,6 +638,7 @@ void gpu_buddy_free_list(struct gpu_buddy *mm,
{
bool mark_clear = flags & GPU_BUDDY_CLEARED;
+ gpu_buddy_driver_lock_held(mm);
__gpu_buddy_free_list(mm, objects, mark_clear, !mark_clear);
}
EXPORT_SYMBOL(gpu_buddy_free_list);
@@ -1172,6 +1178,8 @@ int gpu_buddy_block_trim(struct gpu_buddy *mm,
u64 new_start;
int err;
+ gpu_buddy_driver_lock_held(mm);
+
if (!list_is_singular(blocks))
return -EINVAL;
@@ -1287,6 +1295,8 @@ int gpu_buddy_alloc_blocks(struct gpu_buddy *mm,
unsigned long pages;
int err;
+ gpu_buddy_driver_lock_held(mm);
+
if (size < mm->chunk_size)
return -EINVAL;
@@ -1475,6 +1485,7 @@ void gpu_buddy_print(struct gpu_buddy *mm)
{
int order;
+ gpu_buddy_driver_lock_held(mm);
pr_info("chunk_size: %lluKiB, total: %lluMiB, free: %lluMiB, clear_free:
%lluMiB\n",
mm->chunk_size >> 10, mm->size >> 20, mm->avail >> 20,
mm->clear_avail >> 20);
diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 841f3de5f307..faa025498de4 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -42,6 +42,7 @@ void drm_buddy_print(struct gpu_buddy *mm, struct drm_printer
*p)
{
int order;
+ gpu_buddy_driver_lock_held(mm);
drm_printf(p, "chunk_size: %lluKiB, total: %lluMiB, free: %lluMiB,
clear_free: %lluMiB\n",
mm->chunk_size >> 10, mm->size >> 20, mm->avail >> 20,
mm->clear_avail >> 20);
diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
index 6ba47996bc7c..9f67df646955 100644
--- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
+++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
@@ -322,6 +322,7 @@ int __xe_ttm_vram_mgr_init(struct xe_device *xe, struct
xe_ttm_vram_mgr *mgr,
if (err)
return err;
+ gpu_buddy_driver_set_lock(&mgr->mm, &mgr->lock);
ttm_set_driver_manager(&xe->ttm, mem_type, &mgr->manager);
ttm_resource_manager_set_used(&mgr->manager, true);
diff --git a/include/linux/gpu_buddy.h b/include/linux/gpu_buddy.h
index 5fa917ba5450..71941a039648 100644
--- a/include/linux/gpu_buddy.h
+++ b/include/linux/gpu_buddy.h
@@ -154,6 +154,7 @@ struct gpu_buddy_block {
* @avail: Total free space currently available for allocation in bytes.
* @clear_avail: Free space available in the clear tree (zeroed memory) in
bytes.
* This is a subset of @avail.
+ * @lock_dep_map: Annotates gpu_buddy API with a driver provided lock.
*/
struct gpu_buddy {
/* private: */
@@ -179,8 +180,48 @@ struct gpu_buddy {
u64 size;
u64 avail;
u64 clear_avail;
+#ifdef CONFIG_LOCKDEP
+ struct lockdep_map *lock_dep_map;
+#endif
};
+#ifdef CONFIG_LOCKDEP
+/**
+ * gpu_buddy_driver_set_lock() - Set the lock protecting accesses to GPU BUDDY
+ * @mm: Pointer to GPU buddy structure.
+ * @lock: the lock used to protect the gpu buddy. The locking primitive
+ * must contain a dep_map field.
+ *
+ * Call this to annotate gpu_buddy APIs which access/modify gpu_buddy manager
+ */
+#define gpu_buddy_driver_set_lock(mm, lock) \
+ do { \
+ struct gpu_buddy *__mm = (mm); \
+ if (!WARN(__mm->lock_dep_map, "GPU BUDDY MM lock should be set only
once.")) \
+ __mm->lock_dep_map = &(lock)->dep_map; \
+ } while (0)
+#else
+#define gpu_buddy_driver_set_lock(mm, lock) do { (void)(mm); (void)(lock); }
while (0)
+#endif
+
+#ifdef CONFIG_LOCKDEP
+/**
+ * gpu_buddy_driver_lock_held() - Assert GPU BUDDY manager lock is held
+ * @mm: Pointer to the GPU BUDDY structure.
+ *
+ * Ensure driver lock is held.
+ */
+static inline void gpu_buddy_driver_lock_held(struct gpu_buddy *mm)
+{
+ if (mm->lock_dep_map)
+ lockdep_assert(lock_is_held_type(mm->lock_dep_map, 0));
+}
+#else
+static inline void gpu_buddy_driver_lock_held(struct gpu_buddy *mm)
+{
+}
+#endif
+
static inline u64
gpu_buddy_block_offset(const struct gpu_buddy_block *block)
{
