drm/ttm: Move swapped objects off the manager's LRU list

Resources of swapped objects remains on the TTM_PL_SYSTEM manager's
LRU list, which is bad for the LRU walk efficiency.

Rename the device-wide "pinned" list to "unevictable" and move
also resources of swapped-out objects to that list.

An alternative would be to create an "UNEVICTABLE" priority to
be able to keep the pinned- and swapped objects on their
respective manager's LRU without affecting the LRU walk efficiency.

v2:
- Remove a bogus WARN_ON (Christian König)
- Update ttm_resource_[add|del] bulk move (Christian König)
- Fix TTM KUNIT tests (Intel CI)
v3:
- Check for non-NULL bo->resource in ttm_bo_populate().
v4:
- Don't move to LRU tail during swapout until the resource
  is properly swapped or there was a swapout failure.
  (Intel Ci)
- Add a newline after checkpatch check.
v5:
- Introduce ttm_resource_is_swapped() to avoid a corner-case where
  a newly created resource was considered swapped. (Intel CI)
v6:
- Move an assert.

Cc: Christian König <christian.koenig@amd.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: <dri-devel@lists.freedesktop.org>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240911121859.85387-2-thomas.hellstrom@linux.intel.com

drivers/gpu/drm/i915/gem/i915_gem_ttm.c

@@ -808,7 +808,7 @@ static int __i915_ttm_get_pages(struct drm_i915_gem_object *obj,
 	}
 
 	if (bo->ttm && !ttm_tt_is_populated(bo->ttm)) {
-		ret = ttm_tt_populate(bo->bdev, bo->ttm, &ctx);
+		ret = ttm_bo_populate(bo, &ctx);
 		if (ret)
 			return ret;
 

drivers/gpu/drm/i915/gem/i915_gem_ttm_move.c

@@ -624,7 +624,7 @@ int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,
 
 	/* Populate ttm with pages if needed. Typically system memory. */
 	if (ttm && (dst_man->use_tt || (ttm->page_flags & TTM_TT_FLAG_SWAPPED))) {
-		ret = ttm_tt_populate(bo->bdev, ttm, ctx);
+		ret = ttm_bo_populate(bo, ctx);
 		if (ret)
 			return ret;
 	}

drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c

@@ -90,7 +90,7 @@ static int i915_ttm_backup(struct i915_gem_apply_to_region *apply,
 		goto out_no_lock;
 
 	backup_bo = i915_gem_to_ttm(backup);
-	err = ttm_tt_populate(backup_bo->bdev, backup_bo->ttm, &ctx);
+	err = ttm_bo_populate(backup_bo, &ctx);
 	if (err)
 		goto out_no_populate;
 
@@ -189,7 +189,7 @@ static int i915_ttm_restore(struct i915_gem_apply_to_region *apply,
 	if (!backup_bo->resource)
 		err = ttm_bo_validate(backup_bo, i915_ttm_sys_placement(), &ctx);
 	if (!err)
-		err = ttm_tt_populate(backup_bo->bdev, backup_bo->ttm, &ctx);
+		err = ttm_bo_populate(backup_bo, &ctx);
 	if (!err) {
 		err = i915_gem_obj_copy_ttm(obj, backup, pm_apply->allow_gpu,
 					    false);

drivers/gpu/drm/ttm/tests/ttm_bo_test.c

@@ -308,11 +308,11 @@ static void ttm_bo_unreserve_pinned(struct kunit *test)
 	err = ttm_resource_alloc(bo, place, &res2);
 	KUNIT_ASSERT_EQ(test, err, 0);
 	KUNIT_ASSERT_EQ(test,
-			list_is_last(&res2->lru.link, &priv->ttm_dev->pinned), 1);
+			list_is_last(&res2->lru.link, &priv->ttm_dev->unevictable), 1);
 
 	ttm_bo_unreserve(bo);
 	KUNIT_ASSERT_EQ(test,
-			list_is_last(&res1->lru.link, &priv->ttm_dev->pinned), 1);
+			list_is_last(&res1->lru.link, &priv->ttm_dev->unevictable), 1);
 
 	ttm_resource_free(bo, &res1);
 	ttm_resource_free(bo, &res2);

drivers/gpu/drm/ttm/tests/ttm_resource_test.c

@@ -164,18 +164,18 @@ static void ttm_resource_init_pinned(struct kunit *test)
 
 	res = kunit_kzalloc(test, sizeof(*res), GFP_KERNEL);
 	KUNIT_ASSERT_NOT_NULL(test, res);
-	KUNIT_ASSERT_TRUE(test, list_empty(&bo->bdev->pinned));
+	KUNIT_ASSERT_TRUE(test, list_empty(&bo->bdev->unevictable));
 
 	dma_resv_lock(bo->base.resv, NULL);
 	ttm_bo_pin(bo);
 	ttm_resource_init(bo, place, res);
-	KUNIT_ASSERT_TRUE(test, list_is_singular(&bo->bdev->pinned));
+	KUNIT_ASSERT_TRUE(test, list_is_singular(&bo->bdev->unevictable));
 
 	ttm_bo_unpin(bo);
 	ttm_resource_fini(man, res);
 	dma_resv_unlock(bo->base.resv);
 
-	KUNIT_ASSERT_TRUE(test, list_empty(&bo->bdev->pinned));
+	KUNIT_ASSERT_TRUE(test, list_empty(&bo->bdev->unevictable));
 }
 
 static void ttm_resource_fini_basic(struct kunit *test)

drivers/gpu/drm/ttm/ttm_bo.c

@@ -139,7 +139,7 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
 			goto out_err;
 
 		if (mem->mem_type != TTM_PL_SYSTEM) {
-			ret = ttm_tt_populate(bo->bdev, bo->ttm, ctx);
+			ret = ttm_bo_populate(bo, ctx);
 			if (ret)
 				goto out_err;
 		}
@@ -1128,9 +1128,20 @@ ttm_bo_swapout_cb(struct ttm_lru_walk *walk, struct ttm_buffer_object *bo)
 	if (bo->bdev->funcs->swap_notify)
 		bo->bdev->funcs->swap_notify(bo);
 
-	if (ttm_tt_is_populated(bo->ttm))
+	if (ttm_tt_is_populated(bo->ttm)) {
+		spin_lock(&bo->bdev->lru_lock);
+		ttm_resource_del_bulk_move(bo->resource, bo);
+		spin_unlock(&bo->bdev->lru_lock);
+
 		ret = ttm_tt_swapout(bo->bdev, bo->ttm, swapout_walk->gfp_flags);
 
+		spin_lock(&bo->bdev->lru_lock);
+		if (ret)
+			ttm_resource_add_bulk_move(bo->resource, bo);
+		ttm_resource_move_to_lru_tail(bo->resource);
+		spin_unlock(&bo->bdev->lru_lock);
+	}
+
 out:
 	/* Consider -ENOMEM and -ENOSPC non-fatal. */
 	if (ret == -ENOMEM || ret == -ENOSPC)
@@ -1180,3 +1191,47 @@ void ttm_bo_tt_destroy(struct ttm_buffer_object *bo)
 	ttm_tt_destroy(bo->bdev, bo->ttm);
 	bo->ttm = NULL;
 }
+
+/**
+ * ttm_bo_populate() - Ensure that a buffer object has backing pages
+ * @bo: The buffer object
+ * @ctx: The ttm_operation_ctx governing the operation.
+ *
+ * For buffer objects in a memory type whose manager uses
+ * struct ttm_tt for backing pages, ensure those backing pages
+ * are present and with valid content. The bo's resource is also
+ * placed on the correct LRU list if it was previously swapped
+ * out.
+ *
+ * Return: 0 if successful, negative error code on failure.
+ * Note: May return -EINTR or -ERESTARTSYS if @ctx::interruptible
+ * is set to true.
+ */
+int ttm_bo_populate(struct ttm_buffer_object *bo,
+		    struct ttm_operation_ctx *ctx)
+{
+	struct ttm_tt *tt = bo->ttm;
+	bool swapped;
+	int ret;
+
+	dma_resv_assert_held(bo->base.resv);
+
+	if (!tt)
+		return 0;
+
+	swapped = ttm_tt_is_swapped(tt);
+	ret = ttm_tt_populate(bo->bdev, tt, ctx);
+	if (ret)
+		return ret;
+
+	if (swapped && !ttm_tt_is_swapped(tt) && !bo->pin_count &&
+	    bo->resource) {
+		spin_lock(&bo->bdev->lru_lock);
+		ttm_resource_add_bulk_move(bo->resource, bo);
+		ttm_resource_move_to_lru_tail(bo->resource);
+		spin_unlock(&bo->bdev->lru_lock);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(ttm_bo_populate);

drivers/gpu/drm/ttm/ttm_bo_util.c

@@ -163,7 +163,7 @@ int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
 	src_man = ttm_manager_type(bdev, src_mem->mem_type);
 	if (ttm && ((ttm->page_flags & TTM_TT_FLAG_SWAPPED) ||
 		    dst_man->use_tt)) {
-		ret = ttm_tt_populate(bdev, ttm, ctx);
+		ret = ttm_bo_populate(bo, ctx);
 		if (ret)
 			return ret;
 	}
@@ -350,7 +350,7 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 
 	BUG_ON(!ttm);
 
-	ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
+	ret = ttm_bo_populate(bo, &ctx);
 	if (ret)
 		return ret;
 
@@ -507,7 +507,7 @@ int ttm_bo_vmap(struct ttm_buffer_object *bo, struct iosys_map *map)
 		pgprot_t prot;
 		void *vaddr;
 
-		ret = ttm_tt_populate(bo->bdev, ttm, &ctx);
+		ret = ttm_bo_populate(bo, &ctx);
 		if (ret)
 			return ret;
 

drivers/gpu/drm/ttm/ttm_bo_vm.c

@@ -224,7 +224,7 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
 		};
 
 		ttm = bo->ttm;
-		err = ttm_tt_populate(bdev, bo->ttm, &ctx);
+		err = ttm_bo_populate(bo, &ctx);
 		if (err) {
 			if (err == -EINTR || err == -ERESTARTSYS ||
 			    err == -EAGAIN)

drivers/gpu/drm/ttm/ttm_device.c

@@ -216,7 +216,7 @@ int ttm_device_init(struct ttm_device *bdev, const struct ttm_device_funcs *func
 
 	bdev->vma_manager = vma_manager;
 	spin_lock_init(&bdev->lru_lock);
-	INIT_LIST_HEAD(&bdev->pinned);
+	INIT_LIST_HEAD(&bdev->unevictable);
 	bdev->dev_mapping = mapping;
 	mutex_lock(&ttm_global_mutex);
 	list_add_tail(&bdev->device_list, &glob->device_list);
@@ -283,7 +283,7 @@ void ttm_device_clear_dma_mappings(struct ttm_device *bdev)
 	struct ttm_resource_manager *man;
 	unsigned int i, j;
 
-	ttm_device_clear_lru_dma_mappings(bdev, &bdev->pinned);
+	ttm_device_clear_lru_dma_mappings(bdev, &bdev->unevictable);
 
 	for (i = TTM_PL_SYSTEM; i < TTM_NUM_MEM_TYPES; ++i) {
 		man = ttm_manager_type(bdev, i);

drivers/gpu/drm/ttm/ttm_resource.c

@@ -30,6 +30,7 @@
 #include <drm/ttm/ttm_bo.h>
 #include <drm/ttm/ttm_placement.h>
 #include <drm/ttm/ttm_resource.h>
+#include <drm/ttm/ttm_tt.h>
 
 #include <drm/drm_util.h>
 
@@ -235,19 +236,34 @@ static void ttm_lru_bulk_move_del(struct ttm_lru_bulk_move *bulk,
 	}
 }
 
+static bool ttm_resource_is_swapped(struct ttm_resource *res, struct ttm_buffer_object *bo)
+{
+	/*
+	 * Take care when creating a new resource for a bo, that it is not considered
+	 * swapped if it's not the current resource for the bo and is thus logically
+	 * associated with the ttm_tt. Think a VRAM resource created to move a
+	 * swapped-out bo to VRAM.
+	 */
+	if (bo->resource != res || !bo->ttm)
+		return false;
+
+	dma_resv_assert_held(bo->base.resv);
+	return ttm_tt_is_swapped(bo->ttm);
+}
+
 /* Add the resource to a bulk move if the BO is configured for it */
 void ttm_resource_add_bulk_move(struct ttm_resource *res,
 				struct ttm_buffer_object *bo)
 {
-	if (bo->bulk_move && !bo->pin_count)
+	if (bo->bulk_move && !bo->pin_count && !ttm_resource_is_swapped(res, bo))
 		ttm_lru_bulk_move_add(bo->bulk_move, res);
 }
 
 /* Remove the resource from a bulk move if the BO is configured for it */
 void ttm_resource_del_bulk_move(struct ttm_resource *res,
 				struct ttm_buffer_object *bo)
 {
-	if (bo->bulk_move && !bo->pin_count)
+	if (bo->bulk_move && !bo->pin_count && !ttm_resource_is_swapped(res, bo))
 		ttm_lru_bulk_move_del(bo->bulk_move, res);
 }
 
@@ -259,8 +275,8 @@ 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.link, &bdev->pinned);
+	if (bo->pin_count || ttm_resource_is_swapped(res, bo)) {
+		list_move_tail(&res->lru.link, &bdev->unevictable);
 
 	} else	if (bo->bulk_move) {
 		struct ttm_lru_bulk_move_pos *pos =
@@ -301,8 +317,8 @@ 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.link, &bo->bdev->pinned);
+	if (bo->pin_count || ttm_resource_is_swapped(res, bo))
+		list_add_tail(&res->lru.link, &bo->bdev->unevictable);
 	else
 		list_add_tail(&res->lru.link, &man->lru[bo->priority]);
 	man->usage += res->size;

drivers/gpu/drm/ttm/ttm_tt.c

@@ -367,7 +367,10 @@ int ttm_tt_populate(struct ttm_device *bdev,
 	}
 	return ret;
 }
+
+#if IS_ENABLED(CONFIG_DRM_TTM_KUNIT_TEST)
 EXPORT_SYMBOL(ttm_tt_populate);
+#endif
 
 void ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
 {

drivers/gpu/drm/xe/xe_bo.c

@@ -901,7 +901,7 @@ int xe_bo_evict_pinned(struct xe_bo *bo)
 		}
 	}
 
-	ret = ttm_tt_populate(bo->ttm.bdev, bo->ttm.ttm, &ctx);
+	ret = ttm_bo_populate(&bo->ttm, &ctx);
 	if (ret)
 		goto err_res_free;
 
@@ -954,7 +954,7 @@ int xe_bo_restore_pinned(struct xe_bo *bo)
 	if (ret)
 		return ret;
 
-	ret = ttm_tt_populate(bo->ttm.bdev, bo->ttm.ttm, &ctx);
+	ret = ttm_bo_populate(&bo->ttm, &ctx);
 	if (ret)
 		goto err_res_free;
 

include/drm/ttm/ttm_bo.h

@@ -462,5 +462,7 @@ int ttm_bo_pipeline_gutting(struct ttm_buffer_object *bo);
 pgprot_t ttm_io_prot(struct ttm_buffer_object *bo, struct ttm_resource *res,
 		     pgprot_t tmp);
 void ttm_bo_tt_destroy(struct ttm_buffer_object *bo);
+int ttm_bo_populate(struct ttm_buffer_object *bo,
+		    struct ttm_operation_ctx *ctx);
 
 #endif

include/drm/ttm/ttm_device.h

@@ -252,9 +252,10 @@ struct ttm_device {
 	spinlock_t lru_lock;
 
 	/**
-	 * @pinned: Buffer objects which are pinned and so not on any LRU list.
+	 * @unevictable Buffer objects which are pinned or swapped and as such
+	 * not on an LRU list.
 	 */
-	struct list_head pinned;
+	struct list_head unevictable;
 
 	/**
 	 * @dev_mapping: A pointer to the struct address_space for invalidating

include/drm/ttm/ttm_tt.h

@@ -129,6 +129,11 @@ static inline bool ttm_tt_is_populated(struct ttm_tt *tt)
 	return tt->page_flags & TTM_TT_FLAG_PRIV_POPULATED;
 }
 
+static inline bool ttm_tt_is_swapped(const struct ttm_tt *tt)
+{
+	return tt->page_flags & TTM_TT_FLAG_SWAPPED;
+}
+
 /**
  * ttm_tt_create
  *