[PATCH v8 5/6] drm/xe: Wire up dmem cgroup reclaim for VRAM manager

Register the VRAM manager with the dmem cgroup reclaim infrastructure
so that lowering dmem.max below current VRAM usage triggers TTM
eviction rather than failing with -EBUSY.

v4:
- Rebased on drm-tip; dropped the XE_PL_STOLEN guard as stolen memory
  uses a separate TTM manager and never calls __xe_ttm_vram_mgr_init().

v5:
- Rebased on the introduction of struct dmem_cgroup_init.
- Register the fini drmm action before drmm_cgroup_register_region() so
  that devres LIFO teardown runs unregister_region() first (draining any
  in-flight reclaim callbacks via the rwsem) and xe_ttm_vram_mgr_fini()
  second, ensuring the manager is never accessed by a reclaim callback
  after teardown. (Sashiko-bot)
- Wrap the reclaim callback in xe_ttm_vram_mgr_dmem_reclaim() using
  drm_dev_enter()/drm_dev_exit() to prevent TTM reclaim from running
  after driver unbind.

Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <[email protected]>
Reviewed-by: Maarten Lankhorst <[email protected]>
---
 drivers/gpu/drm/xe/xe_ttm_vram_mgr.c | 54 +++++++++++++++++++++++-----
 1 file changed, 45 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
index 308fda4248eb..b2500344cd57 100644
--- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
+++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
@@ -276,6 +276,28 @@ static const struct ttm_resource_manager_func xe_ttm_vram_mgr_func = {
 	.debug	= xe_ttm_vram_mgr_debug
 };
 
+static const struct dmem_cgroup_ops xe_ttm_vram_mgr_dmem_ops;
+
+static int xe_ttm_vram_mgr_dmem_reclaim(struct dmem_cgroup_pool_state *pool,
+					 u64 target_bytes, void *priv)
+{
+	struct ttm_resource_manager *man = priv;
+	struct xe_device *xe = ttm_to_xe_device(man->bdev);
+	int ret, idx;
+
+	if (!drm_dev_enter(&xe->drm, &idx))
+		return -ENODEV;
+
+	ret = ttm_resource_manager_dmem_reclaim(pool, target_bytes, priv);
+
+	drm_dev_exit(idx);
+	return ret;
+}
+
+static const struct dmem_cgroup_ops xe_ttm_vram_mgr_dmem_ops = {
+	.reclaim = xe_ttm_vram_mgr_dmem_reclaim,
+};
+
 static void xe_ttm_vram_mgr_fini(struct drm_device *dev, void *arg)
 {
 	struct xe_device *xe = to_xe_device(dev);
@@ -301,17 +323,10 @@ int __xe_ttm_vram_mgr_init(struct xe_device *xe, struct xe_ttm_vram_mgr *mgr,
 			   u64 default_page_size)
 {
 	struct ttm_resource_manager *man = &mgr->manager;
+	struct dmem_cgroup_region *cg;
 	const char *name;
 	int err;
 
-	name = mem_type == XE_PL_VRAM0 ? "vram0" : "vram1";
-	man->cg = drmm_cgroup_register_region(&xe->drm, name,
-					      &(struct dmem_cgroup_init){
-						.size = size,
-					      });
-	if (IS_ERR(man->cg))
-		return PTR_ERR(man->cg);
-
 	man->func = &xe_ttm_vram_mgr_func;
 	mgr->mem_type = mem_type;
 	err = drmm_mutex_init(&xe->drm, &mgr->lock);
@@ -330,7 +345,28 @@ int __xe_ttm_vram_mgr_init(struct xe_device *xe, struct xe_ttm_vram_mgr *mgr,
 	ttm_set_driver_manager(&xe->ttm, mem_type, &mgr->manager);
 	ttm_resource_manager_set_used(&mgr->manager, true);
 
-	return drmm_add_action_or_reset(&xe->drm, xe_ttm_vram_mgr_fini, mgr);
+	/*
+	 * Register the fini action before the cgroup region so that devres
+	 * LIFO teardown runs unregister_region first (draining any in-flight
+	 * reclaim callbacks) and the manager fini second.
+	 */
+	err = drmm_add_action_or_reset(&xe->drm, xe_ttm_vram_mgr_fini, mgr);
+	if (err)
+		return err;
+
+	name = mem_type == XE_PL_VRAM0 ? "vram0" : "vram1";
+	cg = drmm_cgroup_register_region(&xe->drm, name,
+					 &(struct dmem_cgroup_init){
+						.size = size,
+						.ops = &xe_ttm_vram_mgr_dmem_ops,
+						.reclaim_priv = man,
+					 });
+	if (IS_ERR(cg))
+		return PTR_ERR(cg);
+
+	ttm_resource_manager_set_dmem_region(man, cg);
+
+	return 0;
 }
 
 /**
-- 
2.55.0