[PATCH v3 0/4] TTM unlockable restartable LRU list iteration

[PATCH v3 0/4] TTM unlockable restartable LRU list iteration

[Thomas Hellström]

This patch-set is a prerequisite for a standalone TTM shrinker
and for exhaustive TTM eviction using sleeping dma_resv locks,
which is the motivation for it.

Currently when unlocking the TTM lru list lock, iteration needs
to be restarted from the beginning, rather from the next LRU list
node. This can potentially be a big problem, because if eviction
or shrinking fails for whatever reason after unlock, restarting
is likely to cause the same failure over and over again.

There are various schemes to be able to continue the list
iteration from where we left off. One such scheme used by the
GEM LRU list traversal is to pull items already considered off
the LRU list and reinsert them when iteration is done.
This has the drawback that concurrent list iteration doesn't see
the complete list (which is bad for exhaustive eviction) and also
doesn't lend itself well to bulk-move sublists since these will
be split in the process where items from those lists are
temporarily pulled from the list and moved to the list tail.

The approach taken here is that list iterators insert themselves
into the list next position using a special list node. Iteration
is then using that list node as starting point when restarting.
Concurrent iterators just skip over the special list nodes.

This is implemented in patch 1 and 2.

For bulk move sublist the approach is the same, but when a bulk
move sublist is moved to the tail, the iterator is also moved,
causing us to skip parts of the list. That is undesirable.
Patch 3 deals with that, and when iterator detects it is
traversing a sublist, it registers with the ttm_lru_bulk_move
struct using a linked list, and when that bulk move sublist
is moved to the tail, any iterator registered with it will
first be moved to the tail of the sublist.
This is implemented in patch 3.

The restartable property is used in patch 4 to restart swapout if
needed, but the main purpose is this paves the way for
shrinker- and exhaustive eviction.

v2:
- Rework patch 3 completely.
v3:
- Fix a NULL pointer dereference found by Xe CI.

Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: <dri-devel@lists.freedesktop.org>

Thomas Hellström (4):
  drm/ttm: Allow TTM LRU list nodes of different types
  drm/ttm: Use LRU hitches
  drm/ttm, drm/amdgpu, drm/xe: Consider hitch moves within bulk sublist
    moves
  drm/ttm: Allow continued swapout after -ENOSPC falure

 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c |   4 +
 drivers/gpu/drm/ttm/ttm_bo.c           |   1 +
 drivers/gpu/drm/ttm/ttm_device.c       |  33 +++-
 drivers/gpu/drm/ttm/ttm_resource.c     | 228 ++++++++++++++++++++-----
 drivers/gpu/drm/xe/xe_vm.c             |   4 +
 include/drm/ttm/ttm_device.h           |   5 +
 include/drm/ttm/ttm_resource.h         |  96 +++++++++--
 7 files changed, 311 insertions(+), 60 deletions(-)

-- 
2.44.0

[PATCH v3 1/4] drm/ttm: Allow TTM LRU list nodes of different types

[Thomas Hellström]

To be able to handle list unlocking while traversing the LRU
list, we want the iterators not only to point to the next
position of the list traversal, but to insert themselves as
list nodes at that point to work around the fact that the
next node might otherwise disappear from the list while
the iterator is pointing to it.

These list nodes need to be easily distinguishable from other
list nodes so that others traversing the list can skip
over them.

So declare a struct ttm_lru_item, with a struct list_head member
and a type enum. This will slightly increase the size of a
struct ttm_resource.

v2:
- Update enum ttm_lru_item_type documentation.

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_device.c   | 13 ++++--
 drivers/gpu/drm/ttm/ttm_resource.c | 70 ++++++++++++++++++++++--------
 include/drm/ttm/ttm_resource.h     | 51 +++++++++++++++++++++-
 3 files changed, 110 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index 76027960054f..f27406e851e5 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -270,17 +270,22 @@ EXPORT_SYMBOL(ttm_device_fini);
 static void ttm_device_clear_lru_dma_mappings(struct ttm_device *bdev,
 					      struct list_head *list)
 {
-	struct ttm_resource *res;
+	struct ttm_lru_item *lru;
 
 	spin_lock(&bdev->lru_lock);
-	while ((res = list_first_entry_or_null(list, typeof(*res), lru))) {
-		struct ttm_buffer_object *bo = res->bo;
+	while ((lru = list_first_entry_or_null(list, typeof(*lru), link))) {
+		struct ttm_buffer_object *bo;
+
+		if (!ttm_lru_item_is_res(lru))
+			continue;
+
+		bo = ttm_lru_item_to_res(lru)->bo;
 
 		/* Take ref against racing releases once lru_lock is unlocked */
 		if (!ttm_bo_get_unless_zero(bo))
 			continue;
 
-		list_del_init(&res->lru);
+		list_del_init(&bo->resource->lru.link);
 		spin_unlock(&bdev->lru_lock);
 
 		if (bo->ttm)
diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index 65155f2013ca..ee1865f82cb4 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -69,8 +69,8 @@ void ttm_lru_bulk_move_tail(struct ttm_lru_bulk_move *bulk)
 			dma_resv_assert_held(pos->last->bo->base.resv);
 
 			man = ttm_manager_type(pos->first->bo->bdev, i);
-			list_bulk_move_tail(&man->lru[j], &pos->first->lru,
-					    &pos->last->lru);
+			list_bulk_move_tail(&man->lru[j], &pos->first->lru.link,
+					    &pos->last->lru.link);
 		}
 	}
 }
@@ -83,14 +83,38 @@ ttm_lru_bulk_move_pos(struct ttm_lru_bulk_move *bulk, struct ttm_resource *res)
 	return &bulk->pos[res->mem_type][res->bo->priority];
 }
 
+/* Return the previous resource on the list (skip over non-resource list items) */
+static struct ttm_resource *ttm_lru_prev_res(struct ttm_resource *cur)
+{
+	struct ttm_lru_item *lru = &cur->lru;
+
+	do {
+		lru = list_prev_entry(lru, link);
+	} while (!ttm_lru_item_is_res(lru));
+
+	return ttm_lru_item_to_res(lru);
+}
+
+/* Return the next resource on the list (skip over non-resource list items) */
+static struct ttm_resource *ttm_lru_next_res(struct ttm_resource *cur)
+{
+	struct ttm_lru_item *lru = &cur->lru;
+
+	do {
+		lru = list_next_entry(lru, link);
+	} while (!ttm_lru_item_is_res(lru));
+
+	return ttm_lru_item_to_res(lru);
+}
+
 /* Move the resource to the tail of the bulk move range */
 static void ttm_lru_bulk_move_pos_tail(struct ttm_lru_bulk_move_pos *pos,
 				       struct ttm_resource *res)
 {
 	if (pos->last != res) {
 		if (pos->first == res)
-			pos->first = list_next_entry(res, lru);
-		list_move(&res->lru, &pos->last->lru);
+			pos->first = ttm_lru_next_res(res);
+		list_move(&res->lru.link, &pos->last->lru.link);
 		pos->last = res;
 	}
 }
@@ -120,11 +144,11 @@ static void ttm_lru_bulk_move_del(struct ttm_lru_bulk_move *bulk,
 		pos->first = NULL;
 		pos->last = NULL;
 	} else if (pos->first == res) {
-		pos->first = list_next_entry(res, lru);
+		pos->first = ttm_lru_next_res(res);
 	} else if (pos->last == res) {
-		pos->last = list_prev_entry(res, lru);
+		pos->last = ttm_lru_prev_res(res);
 	} else {
-		list_move(&res->lru, &pos->last->lru);
+		list_move(&res->lru.link, &pos->last->lru.link);
 	}
 }
 
@@ -153,7 +177,7 @@ void ttm_resource_move_to_lru_tail(struct ttm_resource *res)
 	lockdep_assert_held(&bo->bdev->lru_lock);
 
 	if (bo->pin_count) {
-		list_move_tail(&res->lru, &bdev->pinned);
+		list_move_tail(&res->lru.link, &bdev->pinned);
 
 	} else	if (bo->bulk_move) {
 		struct ttm_lru_bulk_move_pos *pos =
@@ -164,7 +188,7 @@ void ttm_resource_move_to_lru_tail(struct ttm_resource *res)
 		struct ttm_resource_manager *man;
 
 		man = ttm_manager_type(bdev, res->mem_type);
-		list_move_tail(&res->lru, &man->lru[bo->priority]);
+		list_move_tail(&res->lru.link, &man->lru[bo->priority]);
 	}
 }
 
@@ -195,9 +219,9 @@ void ttm_resource_init(struct ttm_buffer_object *bo,
 	man = ttm_manager_type(bo->bdev, place->mem_type);
 	spin_lock(&bo->bdev->lru_lock);
 	if (bo->pin_count)
-		list_add_tail(&res->lru, &bo->bdev->pinned);
+		list_add_tail(&res->lru.link, &bo->bdev->pinned);
 	else
-		list_add_tail(&res->lru, &man->lru[bo->priority]);
+		list_add_tail(&res->lru.link, &man->lru[bo->priority]);
 	man->usage += res->size;
 	spin_unlock(&bo->bdev->lru_lock);
 }
@@ -219,7 +243,7 @@ void ttm_resource_fini(struct ttm_resource_manager *man,
 	struct ttm_device *bdev = man->bdev;
 
 	spin_lock(&bdev->lru_lock);
-	list_del_init(&res->lru);
+	list_del_init(&res->lru.link);
 	man->usage -= res->size;
 	spin_unlock(&bdev->lru_lock);
 }
@@ -470,14 +494,16 @@ struct ttm_resource *
 ttm_resource_manager_first(struct ttm_resource_manager *man,
 			   struct ttm_resource_cursor *cursor)
 {
-	struct ttm_resource *res;
+	struct ttm_lru_item *lru;
 
 	lockdep_assert_held(&man->bdev->lru_lock);
 
 	for (cursor->priority = 0; cursor->priority < TTM_MAX_BO_PRIORITY;
 	     ++cursor->priority)
-		list_for_each_entry(res, &man->lru[cursor->priority], lru)
-			return res;
+		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
+			if (ttm_lru_item_is_res(lru))
+				return ttm_lru_item_to_res(lru);
+		}
 
 	return NULL;
 }
@@ -496,15 +522,21 @@ ttm_resource_manager_next(struct ttm_resource_manager *man,
 			  struct ttm_resource_cursor *cursor,
 			  struct ttm_resource *res)
 {
+	struct ttm_lru_item *lru = &res->lru;
+
 	lockdep_assert_held(&man->bdev->lru_lock);
 
-	list_for_each_entry_continue(res, &man->lru[cursor->priority], lru)
-		return res;
+	list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
+		if (ttm_lru_item_is_res(lru))
+			return ttm_lru_item_to_res(lru);
+	}
 
 	for (++cursor->priority; cursor->priority < TTM_MAX_BO_PRIORITY;
 	     ++cursor->priority)
-		list_for_each_entry(res, &man->lru[cursor->priority], lru)
-			return res;
+		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
+			if (ttm_lru_item_is_res(lru))
+				ttm_lru_item_to_res(lru);
+		}
 
 	return NULL;
 }
diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
index 7561023db43d..cad8c5476198 100644
--- a/include/drm/ttm/ttm_resource.h
+++ b/include/drm/ttm/ttm_resource.h
@@ -49,6 +49,43 @@ struct io_mapping;
 struct sg_table;
 struct scatterlist;
 
+/**
+ * enum ttm_lru_item_type - enumerate ttm_lru_item subclasses
+ */
+enum ttm_lru_item_type {
+	/** @TTM_LRU_RESOURCE: The resource subclass */
+	TTM_LRU_RESOURCE,
+	/** @TTM_LRU_HITCH: The iterator hitch subclass */
+	TTM_LRU_HITCH
+};
+
+/**
+ * struct ttm_lru_item - The TTM lru list node base class
+ * @link: The list link
+ * @type: The subclass type
+ */
+struct ttm_lru_item {
+	struct list_head link;
+	enum ttm_lru_item_type type;
+};
+
+/**
+ * ttm_lru_item_init() - initialize a struct ttm_lru_item
+ * @item: The item to initialize
+ * @type: The subclass type
+ */
+static inline void ttm_lru_item_init(struct ttm_lru_item *item,
+				     enum ttm_lru_item_type type)
+{
+	item->type = type;
+	INIT_LIST_HEAD(&item->link);
+}
+
+static inline bool ttm_lru_item_is_res(const struct ttm_lru_item *item)
+{
+	return item->type == TTM_LRU_RESOURCE;
+}
+
 struct ttm_resource_manager_func {
 	/**
 	 * struct ttm_resource_manager_func member alloc
@@ -217,9 +254,21 @@ struct ttm_resource {
 	/**
 	 * @lru: Least recently used list, see &ttm_resource_manager.lru
 	 */
-	struct list_head lru;
+	struct ttm_lru_item lru;
 };
 
+/**
+ * ttm_lru_item_to_res() - Downcast a struct ttm_lru_item to a struct ttm_resource
+ * @item: The struct ttm_lru_item to downcast
+ *
+ * Return: Pointer to the embedding struct ttm_resource
+ */
+static inline struct ttm_resource *
+ttm_lru_item_to_res(struct ttm_lru_item *item)
+{
+	return container_of(item, struct ttm_resource, lru);
+}
+
 /**
  * struct ttm_resource_cursor
  *
-- 
2.44.0

[PATCH v3 2/4] drm/ttm: Use LRU hitches

[Thomas Hellström]

Have iterators insert themselves into the list they are iterating
over using hitch list nodes. Since only the iterator owner
can remove these list nodes from the list, it's safe to unlock
the list and when continuing, use them as a starting point. Due to
the way LRU bumping works in TTM, newly added items will not be
missed, and bumped items will be iterated over a second time before
reaching the end of the list.

The exception is list with bulk move sublists. When bumping a
sublist, a hitch that is part of that sublist will also be moved
and we might miss items if restarting from it. This will be
addressed in a later patch.

v2:
- Updated ttm_resource_cursor_fini() documentation.

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c       |  1 +
 drivers/gpu/drm/ttm/ttm_device.c   |  9 ++-
 drivers/gpu/drm/ttm/ttm_resource.c | 94 ++++++++++++++++++++----------
 include/drm/ttm/ttm_resource.h     | 16 +++--
 4 files changed, 82 insertions(+), 38 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index e059b1e1b13b..b6f75a0ff2e5 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -622,6 +622,7 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
 		if (locked)
 			dma_resv_unlock(res->bo->base.resv);
 	}
+	ttm_resource_cursor_fini_locked(&cursor);
 
 	if (!bo) {
 		if (busy_bo && !ttm_bo_get_unless_zero(busy_bo))
diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index f27406e851e5..e8a6a1dab669 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -169,12 +169,17 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
 			num_pages = PFN_UP(bo->base.size);
 			ret = ttm_bo_swapout(bo, ctx, gfp_flags);
 			/* ttm_bo_swapout has dropped the lru_lock */
-			if (!ret)
+			if (!ret) {
+				ttm_resource_cursor_fini(&cursor);
 				return num_pages;
-			if (ret != -EBUSY)
+			}
+			if (ret != -EBUSY) {
+				ttm_resource_cursor_fini(&cursor);
 				return ret;
+			}
 		}
 	}
+	ttm_resource_cursor_fini_locked(&cursor);
 	spin_unlock(&bdev->lru_lock);
 	return 0;
 }
diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index ee1865f82cb4..971014fca10a 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -32,6 +32,37 @@
 
 #include <drm/drm_util.h>
 
+/**
+ * ttm_resource_cursor_fini_locked() - Finalize the LRU list cursor usage
+ * @cursor: The struct ttm_resource_cursor to finalize.
+ *
+ * The function pulls the LRU list cursor off any lists it was previusly
+ * attached to. Needs to be called with the LRU lock held. The function
+ * can be called multiple times after eachother.
+ */
+void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor)
+{
+	lockdep_assert_held(&cursor->man->bdev->lru_lock);
+	list_del_init(&cursor->hitch.link);
+}
+
+/**
+ * ttm_resource_cursor_fini() - Finalize the LRU list cursor usage
+ * @cursor: The struct ttm_resource_cursor to finalize.
+ *
+ * The function pulls the LRU list cursor off any lists it was previusly
+ * attached to. Needs to be called without the LRU list lock held. The
+ * function can be called multiple times after eachother.
+ */
+void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor)
+{
+	spinlock_t *lru_lock = &cursor->man->bdev->lru_lock;
+
+	spin_lock(lru_lock);
+	ttm_resource_cursor_fini_locked(cursor);
+	spin_unlock(lru_lock);
+}
+
 /**
  * ttm_lru_bulk_move_init - initialize a bulk move structure
  * @bulk: the structure to init
@@ -483,62 +514,63 @@ void ttm_resource_manager_debug(struct ttm_resource_manager *man,
 EXPORT_SYMBOL(ttm_resource_manager_debug);
 
 /**
- * ttm_resource_manager_first
- *
- * @man: resource manager to iterate over
+ * ttm_resource_manager_next() - Continue iterating over the resource manager
+ * resources
  * @cursor: cursor to record the position
  *
- * Returns the first resource from the resource manager.
+ * Return: The next resource from the resource manager.
  */
 struct ttm_resource *
-ttm_resource_manager_first(struct ttm_resource_manager *man,
-			   struct ttm_resource_cursor *cursor)
+ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
 {
+	struct ttm_resource_manager *man = cursor->man;
 	struct ttm_lru_item *lru;
 
 	lockdep_assert_held(&man->bdev->lru_lock);
 
-	for (cursor->priority = 0; cursor->priority < TTM_MAX_BO_PRIORITY;
-	     ++cursor->priority)
-		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
-			if (ttm_lru_item_is_res(lru))
+	do {
+		lru = &cursor->hitch;
+		list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
+			if (ttm_lru_item_is_res(lru)) {
+				list_move(&cursor->hitch.link, &lru->link);
 				return ttm_lru_item_to_res(lru);
+			}
 		}
 
+		if (++cursor->priority >= TTM_MAX_BO_PRIORITY)
+			break;
+
+		list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
+	} while (true);
+
+	list_del_init(&cursor->hitch.link);
+
 	return NULL;
 }
 
 /**
- * ttm_resource_manager_next
- *
+ * ttm_resource_manager_first() - Start iterating over the resources
+ * of a resource manager
  * @man: resource manager to iterate over
  * @cursor: cursor to record the position
- * @res: the current resource pointer
  *
- * Returns the next resource from the resource manager.
+ * Initializes the cursor and starts iterating. When done iterating,
+ * the caller must explicitly call ttm_resource_cursor_fini().
+ *
+ * Return: The first resource from the resource manager.
  */
 struct ttm_resource *
-ttm_resource_manager_next(struct ttm_resource_manager *man,
-			  struct ttm_resource_cursor *cursor,
-			  struct ttm_resource *res)
+ttm_resource_manager_first(struct ttm_resource_manager *man,
+			   struct ttm_resource_cursor *cursor)
 {
-	struct ttm_lru_item *lru = &res->lru;
-
 	lockdep_assert_held(&man->bdev->lru_lock);
 
-	list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
-		if (ttm_lru_item_is_res(lru))
-			return ttm_lru_item_to_res(lru);
-	}
+	cursor->priority = 0;
+	cursor->man = man;
+	ttm_lru_item_init(&cursor->hitch, TTM_LRU_HITCH);
+	list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
 
-	for (++cursor->priority; cursor->priority < TTM_MAX_BO_PRIORITY;
-	     ++cursor->priority)
-		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
-			if (ttm_lru_item_is_res(lru))
-				ttm_lru_item_to_res(lru);
-		}
-
-	return NULL;
+	return ttm_resource_manager_next(cursor);
 }
 
 static void ttm_kmap_iter_iomap_map_local(struct ttm_kmap_iter *iter,
diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
index cad8c5476198..b9043c183205 100644
--- a/include/drm/ttm/ttm_resource.h
+++ b/include/drm/ttm/ttm_resource.h
@@ -271,15 +271,23 @@ ttm_lru_item_to_res(struct ttm_lru_item *item)
 
 /**
  * struct ttm_resource_cursor
- *
+ * @man: The resource manager currently being iterated over
+ * @hitch: A hitch list node inserted before the next resource
+ * to iterate over.
  * @priority: the current priority
  *
  * Cursor to iterate over the resources in a manager.
  */
 struct ttm_resource_cursor {
+	struct ttm_resource_manager *man;
+	struct ttm_lru_item hitch;
 	unsigned int priority;
 };
 
+void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor);
+
+void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
+
 /**
  * struct ttm_lru_bulk_move_pos
  *
@@ -435,9 +443,7 @@ struct ttm_resource *
 ttm_resource_manager_first(struct ttm_resource_manager *man,
 			   struct ttm_resource_cursor *cursor);
 struct ttm_resource *
-ttm_resource_manager_next(struct ttm_resource_manager *man,
-			  struct ttm_resource_cursor *cursor,
-			  struct ttm_resource *res);
+ttm_resource_manager_next(struct ttm_resource_cursor *cursor);
 
 /**
  * ttm_resource_manager_for_each_res - iterate over all resources
@@ -449,7 +455,7 @@ ttm_resource_manager_next(struct ttm_resource_manager *man,
  */
 #define ttm_resource_manager_for_each_res(man, cursor, res)		\
 	for (res = ttm_resource_manager_first(man, cursor); res;	\
-	     res = ttm_resource_manager_next(man, cursor, res))
+	     res = ttm_resource_manager_next(cursor))
 
 struct ttm_kmap_iter *
 ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,
-- 
2.44.0

[PATCH v3 3/4] drm/ttm, drm/amdgpu, drm/xe: Consider hitch moves within bulk sublist moves

[Thomas Hellström]

To address the problem with hitches moving when bulk move
sublists are lru-bumped, register the list cursors with the
ttm_lru_bulk_move structure when traversing its list, and
when lru-bumping the list, move the cursor hitch to the tail.
This also means it's mandatory for drivers to call
ttm_lru_bulk_move_init() and ttm_lru_bulk_move_fini() when
initializing and finalizing the bulk move structure, so add
those calls to the amdgpu- and xe driver.

Compared to v1 this is slightly more code but less fragile
and hopefully easier to understand.

v2:
- Completely rework the functionality
v3:
- Avoid a NULL pointer dereference assigning manager->mem_type

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c |  4 ++
 drivers/gpu/drm/ttm/ttm_resource.c     | 90 +++++++++++++++++++++++++-
 drivers/gpu/drm/xe/xe_vm.c             |  4 ++
 include/drm/ttm/ttm_device.h           |  5 ++
 include/drm/ttm/ttm_resource.h         | 55 ++++++++++------
 5 files changed, 137 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index ed4a8c5d26d7..7c2ee5d12bc1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -2264,6 +2264,8 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
 	if (r)
 		return r;
 
+	ttm_lru_bulk_move_init(&vm->lru_bulk_move);
+
 	vm->pte_support_ats = false;
 	vm->is_compute_context = false;
 
@@ -2324,6 +2326,7 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
 error_free_delayed:
 	dma_fence_put(vm->last_tlb_flush);
 	dma_fence_put(vm->last_unlocked);
+	ttm_lru_bulk_move_fini(&adev->mman.bdev, &vm->lru_bulk_move);
 	amdgpu_vm_fini_entities(vm);
 
 	return r;
@@ -2497,6 +2500,7 @@ void amdgpu_vm_fini(struct amdgpu_device *adev, struct amdgpu_vm *vm)
 		}
 	}
 
+	ttm_lru_bulk_move_fini(&adev->mman.bdev, &vm->lru_bulk_move);
 }
 
 /**
diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index 971014fca10a..0acd4bf764b2 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -32,6 +32,49 @@
 
 #include <drm/drm_util.h>
 
+/* Detach the cursor from the bulk move list*/
+static void
+ttm_resource_cursor_clear_bulk(struct ttm_resource_cursor *cursor)
+{
+	cursor->bulk = NULL;
+	list_del_init(&cursor->bulk_link);
+}
+
+/* Move the cursor to the end of the bulk move list it's in */
+static void ttm_resource_cursor_move_bulk_tail(struct ttm_lru_bulk_move *bulk,
+					       struct ttm_resource_cursor *cursor)
+{
+	struct ttm_lru_bulk_move_pos *pos;
+
+	if (WARN_ON_ONCE(bulk != cursor->bulk)) {
+		list_del_init(&cursor->bulk_link);
+		return;
+	}
+
+	pos = &bulk->pos[cursor->man->mem_type][cursor->priority];
+	if (pos)
+		list_move(&cursor->hitch.link, &pos->last->lru.link);
+	ttm_resource_cursor_clear_bulk(cursor);
+}
+
+/* Move all cursors attached to a bulk move to its end */
+static void ttm_bulk_move_adjust_cursors(struct ttm_lru_bulk_move *bulk)
+{
+	struct ttm_resource_cursor *cursor, *next;
+
+	list_for_each_entry_safe(cursor, next, &bulk->cursor_list, bulk_link)
+		ttm_resource_cursor_move_bulk_tail(bulk, cursor);
+}
+
+/* Remove a cursor from an empty bulk move list */
+static void ttm_bulk_move_drop_cursors(struct ttm_lru_bulk_move *bulk)
+{
+	struct ttm_resource_cursor *cursor, *next;
+
+	list_for_each_entry_safe(cursor, next, &bulk->cursor_list, bulk_link)
+		ttm_resource_cursor_clear_bulk(cursor);
+}
+
 /**
  * ttm_resource_cursor_fini_locked() - Finalize the LRU list cursor usage
  * @cursor: The struct ttm_resource_cursor to finalize.
@@ -44,6 +87,7 @@ void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor)
 {
 	lockdep_assert_held(&cursor->man->bdev->lru_lock);
 	list_del_init(&cursor->hitch.link);
+	ttm_resource_cursor_clear_bulk(cursor);
 }
 
 /**
@@ -72,9 +116,27 @@ void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor)
 void ttm_lru_bulk_move_init(struct ttm_lru_bulk_move *bulk)
 {
 	memset(bulk, 0, sizeof(*bulk));
+	INIT_LIST_HEAD(&bulk->cursor_list);
 }
 EXPORT_SYMBOL(ttm_lru_bulk_move_init);
 
+/**
+ * ttm_lru_bulk_move_fini - finalize a bulk move structure
+ * @bdev: The struct ttm_device
+ * @bulk: the structure to finalize
+ *
+ * Sanity checks that bulk moves don't have any
+ * resources left and hence no cursors attached.
+ */
+void ttm_lru_bulk_move_fini(struct ttm_device *bdev,
+			    struct ttm_lru_bulk_move *bulk)
+{
+	spin_lock(&bdev->lru_lock);
+	ttm_bulk_move_drop_cursors(bulk);
+	spin_unlock(&bdev->lru_lock);
+}
+EXPORT_SYMBOL(ttm_lru_bulk_move_fini);
+
 /**
  * ttm_lru_bulk_move_tail - bulk move range of resources to the LRU tail.
  *
@@ -87,6 +149,7 @@ void ttm_lru_bulk_move_tail(struct ttm_lru_bulk_move *bulk)
 {
 	unsigned i, j;
 
+	ttm_bulk_move_adjust_cursors(bulk);
 	for (i = 0; i < TTM_NUM_MEM_TYPES; ++i) {
 		for (j = 0; j < TTM_MAX_BO_PRIORITY; ++j) {
 			struct ttm_lru_bulk_move_pos *pos = &bulk->pos[i][j];
@@ -417,6 +480,7 @@ void ttm_resource_manager_init(struct ttm_resource_manager *man,
 	man->bdev = bdev;
 	man->size = size;
 	man->usage = 0;
+	man->mem_type = TTM_NUM_MEM_TYPES;
 
 	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i)
 		INIT_LIST_HEAD(&man->lru[i]);
@@ -513,6 +577,27 @@ void ttm_resource_manager_debug(struct ttm_resource_manager *man,
 }
 EXPORT_SYMBOL(ttm_resource_manager_debug);
 
+static void
+ttm_resource_cursor_check_bulk(struct ttm_resource_cursor *cursor,
+			       struct ttm_lru_item *next_lru)
+{
+	struct ttm_resource *next = ttm_lru_item_to_res(next_lru);
+	struct ttm_lru_bulk_move *bulk = NULL;
+	struct ttm_buffer_object *bo = next->bo;
+
+	lockdep_assert_held(&cursor->man->bdev->lru_lock);
+	if (bo && bo->resource == next)
+		bulk = bo->bulk_move;
+
+	if (cursor->bulk != bulk) {
+		if (bulk)
+			list_move_tail(&cursor->bulk_link, &bulk->cursor_list);
+		else
+			list_del_init(&cursor->bulk_link);
+		cursor->bulk = bulk;
+	}
+}
+
 /**
  * ttm_resource_manager_next() - Continue iterating over the resource manager
  * resources
@@ -532,6 +617,7 @@ ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
 		lru = &cursor->hitch;
 		list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
 			if (ttm_lru_item_is_res(lru)) {
+				ttm_resource_cursor_check_bulk(cursor, lru);
 				list_move(&cursor->hitch.link, &lru->link);
 				return ttm_lru_item_to_res(lru);
 			}
@@ -541,9 +627,10 @@ ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
 			break;
 
 		list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
+		ttm_resource_cursor_clear_bulk(cursor);
 	} while (true);
 
-	list_del_init(&cursor->hitch.link);
+	ttm_resource_cursor_fini_locked(cursor);
 
 	return NULL;
 }
@@ -568,6 +655,7 @@ ttm_resource_manager_first(struct ttm_resource_manager *man,
 	cursor->priority = 0;
 	cursor->man = man;
 	ttm_lru_item_init(&cursor->hitch, TTM_LRU_HITCH);
+	INIT_LIST_HEAD(&cursor->bulk_link);
 	list_move(&cursor->hitch.link, &man->lru[cursor->priority]);
 
 	return ttm_resource_manager_next(cursor);
diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 643b3701a738..9fe638f41515 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -1315,6 +1315,8 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32 flags)
 
 	INIT_WORK(&vm->destroy_work, vm_destroy_work_func);
 
+	ttm_lru_bulk_move_init(&vm->lru_bulk_move);
+
 	INIT_LIST_HEAD(&vm->preempt.exec_queues);
 	vm->preempt.min_run_period_ms = 10;	/* FIXME: Wire up to uAPI */
 
@@ -1433,6 +1435,7 @@ struct xe_vm *xe_vm_create(struct xe_device *xe, u32 flags)
 	mutex_destroy(&vm->snap_mutex);
 	for_each_tile(tile, xe, id)
 		xe_range_fence_tree_fini(&vm->rftree[id]);
+	ttm_lru_bulk_move_fini(&xe->ttm, &vm->lru_bulk_move);
 	kfree(vm);
 	if (!(flags & XE_VM_FLAG_MIGRATION))
 		xe_device_mem_access_put(xe);
@@ -1573,6 +1576,7 @@ static void vm_destroy_work_func(struct work_struct *w)
 
 	trace_xe_vm_free(vm);
 	dma_fence_put(vm->rebind_fence);
+	ttm_lru_bulk_move_fini(&xe->ttm, &vm->lru_bulk_move);
 	kfree(vm);
 }
 
diff --git a/include/drm/ttm/ttm_device.h b/include/drm/ttm/ttm_device.h
index c22f30535c84..07722656ffad 100644
--- a/include/drm/ttm/ttm_device.h
+++ b/include/drm/ttm/ttm_device.h
@@ -283,8 +283,13 @@ ttm_manager_type(struct ttm_device *bdev, int mem_type)
 static inline void ttm_set_driver_manager(struct ttm_device *bdev, int type,
 					  struct ttm_resource_manager *manager)
 {
+	struct ttm_resource_manager *old;
+
 	BUILD_BUG_ON(__builtin_constant_p(type) && type >= TTM_NUM_MEM_TYPES);
+	old = bdev->man_drv[type];
 	bdev->man_drv[type] = manager;
+	if (manager)
+		manager->mem_type = type;
 }
 
 int ttm_device_init(struct ttm_device *bdev, const struct ttm_device_funcs *funcs,
diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
index b9043c183205..9084f91a5802 100644
--- a/include/drm/ttm/ttm_resource.h
+++ b/include/drm/ttm/ttm_resource.h
@@ -211,6 +211,9 @@ struct ttm_resource_manager {
 	 * bdev->lru_lock.
 	 */
 	uint64_t usage;
+
+	/** @mem_type: The memory type used for this manager. */
+	unsigned int mem_type;
 };
 
 /**
@@ -269,25 +272,6 @@ ttm_lru_item_to_res(struct ttm_lru_item *item)
 	return container_of(item, struct ttm_resource, lru);
 }
 
-/**
- * struct ttm_resource_cursor
- * @man: The resource manager currently being iterated over
- * @hitch: A hitch list node inserted before the next resource
- * to iterate over.
- * @priority: the current priority
- *
- * Cursor to iterate over the resources in a manager.
- */
-struct ttm_resource_cursor {
-	struct ttm_resource_manager *man;
-	struct ttm_lru_item hitch;
-	unsigned int priority;
-};
-
-void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor);
-
-void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
-
 /**
  * struct ttm_lru_bulk_move_pos
  *
@@ -303,16 +287,45 @@ struct ttm_lru_bulk_move_pos {
 
 /**
  * struct ttm_lru_bulk_move
- *
  * @pos: first/last lru entry for resources in the each domain/priority
+ * @cursor_list: The list of cursors currently traversing any of
+ * the sublists of @pos. Protected by the ttm device's lru_lock.
  *
  * Container for the current bulk move state. Should be used with
  * ttm_lru_bulk_move_init() and ttm_bo_set_bulk_move().
  */
 struct ttm_lru_bulk_move {
 	struct ttm_lru_bulk_move_pos pos[TTM_NUM_MEM_TYPES][TTM_MAX_BO_PRIORITY];
+	struct list_head cursor_list;
+};
+
+/**
+ * struct ttm_resource_cursor
+ * @man: The resource manager currently being iterated over
+ * @hitch: A hitch list node inserted before the next resource
+ * to iterate over.
+ * @bulk_link: A list link for the list of cursors traversing the
+ * bulk sublist of @bulk. Protected by the ttm device's lru_lock.
+ * @bulk: Pointer to struct ttm_lru_bulk_move whose subrange @hitch is
+ * inserted to. NULL if none. Never dereference this pointer since
+ * the struct ttm_lru_bulk_move object pointed to might have been
+ * freed. The pointer is only for comparison.
+ * @priority: the current priority
+ *
+ * Cursor to iterate over the resources in a manager.
+ */
+struct ttm_resource_cursor {
+	struct ttm_resource_manager *man;
+	struct ttm_lru_item hitch;
+	struct list_head bulk_link;
+	struct ttm_lru_bulk_move *bulk;
+	unsigned int priority;
 };
 
+void ttm_resource_cursor_fini_locked(struct ttm_resource_cursor *cursor);
+
+void ttm_resource_cursor_fini(struct ttm_resource_cursor *cursor);
+
 /**
  * struct ttm_kmap_iter_iomap - Specialization for a struct io_mapping +
  * struct sg_table backed struct ttm_resource.
@@ -401,6 +414,8 @@ ttm_resource_manager_cleanup(struct ttm_resource_manager *man)
 
 void ttm_lru_bulk_move_init(struct ttm_lru_bulk_move *bulk);
 void ttm_lru_bulk_move_tail(struct ttm_lru_bulk_move *bulk);
+void ttm_lru_bulk_move_fini(struct ttm_device *bdev,
+			    struct ttm_lru_bulk_move *bulk);
 
 void ttm_resource_add_bulk_move(struct ttm_resource *res,
 				struct ttm_buffer_object *bo);
-- 
2.44.0

[PATCH v3 4/4] drm/ttm: Allow continued swapout after -ENOSPC falure

[Thomas Hellström]

The -ENOSPC failure from ttm_bo_swapout() meant that the lru_lock
was dropped and simply restarting the iteration meant we'd likely
hit the same error again on the same resource. Now that we can
restart the iteration even if the lock was dropped, do that.

Cc: Christian König <christian.koenig@amd.com>
Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_device.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index e8a6a1dab669..4a030b4bc848 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -168,15 +168,20 @@ int ttm_device_swapout(struct ttm_device *bdev, struct ttm_operation_ctx *ctx,
 
 			num_pages = PFN_UP(bo->base.size);
 			ret = ttm_bo_swapout(bo, ctx, gfp_flags);
-			/* ttm_bo_swapout has dropped the lru_lock */
-			if (!ret) {
-				ttm_resource_cursor_fini(&cursor);
-				return num_pages;
-			}
-			if (ret != -EBUSY) {
-				ttm_resource_cursor_fini(&cursor);
-				return ret;
+			/* Couldn't swap out, and retained the lru_lock */
+			if (ret == -EBUSY)
+				continue;
+			/* Couldn't swap out and dropped the lru_lock */
+			if (ret == -ENOSPC) {
+				spin_lock(&bdev->lru_lock);
+				continue;
 			}
+			/*
+			 * Dropped the lock and either succeeded or
+			 * hit an error that forces us to break.
+			 */
+			ttm_resource_cursor_fini(&cursor);
+			return ret ? ret : num_pages;
 		}
 	}
 	ttm_resource_cursor_fini_locked(&cursor);
-- 
2.44.0

Re: [PATCH v3 3/4] drm/ttm, drm/amdgpu, drm/xe: Consider hitch moves within bulk sublist moves

[kernel test robot]

Hi Thomas,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on drm-intel/for-linux-next drm-tip/drm-tip]
[cannot apply to drm-intel/for-linux-next-fixes linus/master v6.8-rc7 next-20240305]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Thomas-Hellstr-m/drm-ttm-Allow-TTM-LRU-list-nodes-of-different-types/20240306-000453
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20240305160202.3555-4-thomas.hellstrom%40linux.intel.com
patch subject: [PATCH v3 3/4] drm/ttm, drm/amdgpu, drm/xe: Consider hitch moves within bulk sublist moves
config: arm-defconfig (https://download.01.org/0day-ci/archive/20240306/202403060640.zCXpVObi-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project.git f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240306/202403060640.zCXpVObi-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202403060640.zCXpVObi-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from drivers/gpu/drm/drm_gem_ttm_helper.c:5:
   In file included from include/drm/drm_gem_ttm_helper.h:10:
   In file included from include/drm/ttm/ttm_bo.h:39:
>> include/drm/ttm/ttm_device.h:286:31: warning: variable 'old' set but not used [-Wunused-but-set-variable]
           struct ttm_resource_manager *old;
                                        ^
   1 warning generated.


vim +/old +286 include/drm/ttm/ttm_device.h

   282	
   283	static inline void ttm_set_driver_manager(struct ttm_device *bdev, int type,
   284						  struct ttm_resource_manager *manager)
   285	{
 > 286		struct ttm_resource_manager *old;
   287	
   288		BUILD_BUG_ON(__builtin_constant_p(type) && type >= TTM_NUM_MEM_TYPES);
   289		old = bdev->man_drv[type];
   290		bdev->man_drv[type] = manager;
   291		if (manager)
   292			manager->mem_type = type;
   293	}
   294	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki