[PATCH v5 0/6] [PATCH v5 0/6] Add reclaim to the dmem cgroup controller

[PATCH v5 0/6] [PATCH v5 0/6] Add reclaim to the dmem cgroup controller

[Thomas Hellström]

When writing a "max" limit lower than the current usage, the
existing code silently failed. This series aims to improve
on that by returning -EBUSY on failure and also attempt
to synchronously reclaim device memory to push the usage
under the new max limit to avoid the error.

Patch 1 fixes a pre-existing amdgpu_vram_mgr_init() error path
Patch 2 introduces struct dmem_cgroup_init for extensible region
      registration.
Patch 3 implements and documents a reclaim callback interface
      for the dmem controller.
Patch 4 implements a TTM reclaim callback.
Patches 5-6 hook up the reclaim callback to the dmem cgroup-aware
      drivers xe and amdgpu.

v2:
- Remove the error propagation that was in a previous series (Maarten)
- A number of updates in patch 1. See its commit message for
  details (Maarten)

v3:
- Add patch 1 fixing a pre-existing amdgpu_vram_mgr_init() error path
  bug where drmm_cgroup_register_region() was called before
  INIT_LIST_HEAD() and gpu_buddy_init(), causing a kernel panic on
  failure. (Sashiko-bot)
- Use an rwsem to protect reclaim callback registration and region
  unregister against concurrent reclaim invocations. (Sashiko-bot)
- Fix ttm_resource_manager_set_dmem_region() storing an error pointer
  in man->cg unconditionally. (Sashiko-bot)
- Fix kernel-doc function name format for ttm_bo_evict_cgroup() and
  ttm_resource_manager_set_dmem_region().

v4:
- Rebased on drm-tip; dropped the XE_PL_STOLEN guard in the xe patch
  as stolen memory uses a separate TTM manager.

v5:
- Add patch 2 introducing struct dmem_cgroup_init to make the
  dmem_cgroup_register_region() API extensible without adding positional
  arguments in the future.
- Use nonblock=true in reset_all_resource_limits() to avoid sleeping
  inside rcu_read_lock() in dmemcs_offline(). (Sashiko-bot)
- Compare usage against the truncated limit stored in cnt.max, not the
  original u64. (Sashiko-bot)
- Use DMEM_MAX_RECLAIM_RETRIES (16) retry budget instead of 5, matching
  the memcg controller; only -ENOSPC (no progress) counts against the
  budget, other errors abort immediately.
- Handle NULL region in ttm_resource_manager_set_dmem_region() to clear
  the reclaim callback, preventing use-after-free when the manager is
  torn down while the dmem region outlives it. (Sashiko-bot)
- Return 0 on any eviction progress; reserve -ENOSPC for zero progress.
- Register xe fini devres action before drmm_cgroup_register_region()
  so LIFO teardown runs unregister first, draining callbacks before the
  manager is destroyed. (Sashiko-bot)
- Switch amdgpu to explicit dmem_cgroup_unregister_region() at the top
  of amdgpu_vram_mgr_fini() before any manager teardown, since amdgpu's
  fini is called explicitly during driver unbind before drmm cleanup.
  (Sashiko-bot)
- Wrap the xe reclaim callback with drm_dev_enter()/drm_dev_exit() to
  prevent TTM reclaim from running after driver unbind.

User-space tests are at
https://patchwork.freedesktop.org/series/163935/

Test-with: 20260428065411.4222-1-thomas.hellstrom@linux.intel.com

Thomas Hellström (6):
  drm/amdgpu: Fix init ordering in amdgpu_vram_mgr_init()
  cgroup/dmem: Introduce struct dmem_cgroup_init for region initialization
  cgroup/dmem: Add reclaim callback for lowering max below current usage
  drm/ttm: Hook up a cgroup-aware reclaim callback for the dmem
    controller
  drm/xe: Wire up dmem cgroup reclaim for VRAM manager
  drm/amdgpu: Wire up dmem cgroup reclaim for VRAM manager

 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c      |   2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c |  10 +-
 drivers/gpu/drm/ttm/ttm_bo.c                 |  95 ++++++++++++++++-
 drivers/gpu/drm/ttm/ttm_bo_util.c            |   3 +-
 drivers/gpu/drm/ttm/ttm_resource.c           |  37 +++++++
 drivers/gpu/drm/xe/xe_ttm_vram_mgr.c         |  19 ++--
 include/drm/ttm/ttm_bo.h                     |  10 ++
 include/drm/ttm/ttm_resource.h               |   4 +
 include/linux/cgroup_dmem.h                  |  24 +++++
 kernel/cgroup/dmem.c                         | 106 +++++++++++++++++--
 10 files changed, 286 insertions(+), 24 deletions(-)

-- 
2.54.0

Thomas Hellström (6):
  drm/amdgpu: Fix init ordering in amdgpu_vram_mgr_init()
  cgroup/dmem: Introduce struct dmem_cgroup_init for region
    initialization
  cgroup/dmem: Add reclaim callback for lowering max below current usage
  drm/ttm: Hook up a cgroup-aware reclaim callback for the dmem
    controller
  drm/xe: Wire up dmem cgroup reclaim for VRAM manager
  drm/amdgpu: Wire up dmem cgroup reclaim for VRAM manager

 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c      |   2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c |  28 +++-
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.h |   2 +
 drivers/gpu/drm/drm_drv.c                    |   8 +-
 drivers/gpu/drm/ttm/ttm_bo.c                 |  95 +++++++++++++-
 drivers/gpu/drm/ttm/ttm_bo_util.c            |   3 +-
 drivers/gpu/drm/ttm/ttm_resource.c           |  50 +++++++
 drivers/gpu/drm/xe/xe_ttm_vram_mgr.c         |  53 +++++++-
 include/drm/drm_drv.h                        |   4 +-
 include/drm/ttm/ttm_bo.h                     |  10 ++
 include/drm/ttm/ttm_resource.h               |   7 +
 include/linux/cgroup_dmem.h                  |  37 +++++-
 kernel/cgroup/dmem.c                         | 129 +++++++++++++++++--
 13 files changed, 393 insertions(+), 35 deletions(-)

-- 
2.54.0

[PATCH v5 1/6] drm/amdgpu: Fix init ordering in amdgpu_vram_mgr_init()

[Thomas Hellström]

drmm_cgroup_register_region() is called before INIT_LIST_HEAD() and
gpu_buddy_init() in amdgpu_vram_mgr_init(). If it fails, the function
returns early and bypasses those initializations.

Since adev->mman.initialized is set to true before amdgpu_vram_mgr_init()
is called, a failure triggers amdgpu_ttm_fini(), which calls
amdgpu_vram_mgr_fini(), which then:

 - Calls list_for_each_entry_safe() on reservations_pending and
   reserved_pages, whose list_head::next pointers are zero-initialized
   (NULL). The loop does not recognize them as empty and dereferences NULL.

 - Calls gpu_buddy_fini(), which iterates free_trees[] unconditionally
   via for_each_free_tree(). Since mm->free_trees is NULL
   (never allocated), this dereferences NULL.

Both result in a kernel panic on the module load error path.

Fix by moving drmm_cgroup_register_region() to after the list and buddy
allocator are fully initialized, so the teardown path is safe to run.

Reported-by: Sashiko-bot <sashiko-bot@kernel.org>
Closes: https://sashiko.dev/#/patchset/20260428073116.15687-1-thomas.hellstrom@linux.intel.com?part=4
Fixes: 2b624a2c1865 ("drm/ttm: Handle cgroup based eviction in TTM")
Cc: Friedrich Vock <friedrich.vock@gmx.de>
Cc: Maarten Lankhorst <dev@lankhorst.se>
Cc: Tejun Heo <tj@kernel.org>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v6.14+
Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index 2a241a5b12c4..ac3f71d77140 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -918,9 +918,6 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
 	struct ttm_resource_manager *man = &mgr->manager;
 	int err;
 
-	man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram", adev->gmc.real_vram_size);
-	if (IS_ERR(man->cg))
-		return PTR_ERR(man->cg);
 	ttm_resource_manager_init(man, &adev->mman.bdev,
 				  adev->gmc.real_vram_size);
 
@@ -935,6 +932,10 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
 	if (err)
 		return err;
 
+	man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram", adev->gmc.real_vram_size);
+	if (IS_ERR(man->cg))
+		return PTR_ERR(man->cg);
+
 	ttm_set_driver_manager(&adev->mman.bdev, TTM_PL_VRAM, &mgr->manager);
 	ttm_resource_manager_set_used(man, true);
 	return 0;
-- 
2.54.0

[PATCH v5 2/6] cgroup/dmem: Introduce struct dmem_cgroup_init for region initialization

[Thomas Hellström]

Replace the bare u64 size argument to dmem_cgroup_register_region() and
drmm_cgroup_register_region() with a const struct dmem_cgroup_init *
pointer. The struct currently carries only the size field, but using a
struct makes the API extensible: future callers can supply additional
initialization parameters without adding more positional arguments.

Update all in-tree callers (amdgpu, xe) to use a compound-literal
initializer.

v5:
- Commit introduced.

Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c |  6 +++++-
 drivers/gpu/drm/drm_drv.c                    |  8 +++++---
 drivers/gpu/drm/xe/xe_ttm_vram_mgr.c         |  7 ++++++-
 include/drm/drm_drv.h                        |  4 +++-
 include/linux/cgroup_dmem.h                  | 16 +++++++++++++---
 kernel/cgroup/dmem.c                         | 10 ++++++----
 6 files changed, 38 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index ac3f71d77140..08f05c3aed1d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -23,6 +23,7 @@
  */
 
 #include <linux/dma-mapping.h>
+#include <linux/cgroup_dmem.h>
 #include <drm/ttm/ttm_range_manager.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_buddy.h>
@@ -932,7 +933,10 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
 	if (err)
 		return err;
 
-	man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram", adev->gmc.real_vram_size);
+	man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram",
+					      &(struct dmem_cgroup_init){
+						.size = adev->gmc.real_vram_size,
+					      });
 	if (IS_ERR(man->cg))
 		return PTR_ERR(man->cg);
 
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 1ff0bf7cba6a..3c570f9393b9 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -960,17 +960,19 @@ static void drmm_cg_unregister_region(struct drm_device *dev, void *arg)
  * drmm_cgroup_register_region - Register a region of a DRM device to cgroups
  * @dev: device for region
  * @region_name: Region name for registering
- * @size: Size of region in bytes
+ * @init: Initialization parameters for the region.
  *
  * This decreases the ref-count of @dev by one. The device is destroyed if the
  * ref-count drops to zero.
  */
-struct dmem_cgroup_region *drmm_cgroup_register_region(struct drm_device *dev, const char *region_name, u64 size)
+struct dmem_cgroup_region *
+drmm_cgroup_register_region(struct drm_device *dev, const char *region_name,
+			    const struct dmem_cgroup_init *init)
 {
 	struct dmem_cgroup_region *region;
 	int ret;
 
-	region = dmem_cgroup_register_region(size, "drm/%s/%s", dev->unique, region_name);
+	region = dmem_cgroup_register_region(init, "drm/%s/%s", dev->unique, region_name);
 	if (IS_ERR_OR_NULL(region))
 		return region;
 
diff --git a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
index b518f7dec680..308fda4248eb 100644
--- a/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
+++ b/drivers/gpu/drm/xe/xe_ttm_vram_mgr.c
@@ -4,6 +4,8 @@
  * Copyright (C) 2021-2022 Red Hat
  */
 
+#include <linux/cgroup_dmem.h>
+
 #include <drm/drm_managed.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_buddy.h>
@@ -303,7 +305,10 @@ int __xe_ttm_vram_mgr_init(struct xe_device *xe, struct xe_ttm_vram_mgr *mgr,
 	int err;
 
 	name = mem_type == XE_PL_VRAM0 ? "vram0" : "vram1";
-	man->cg = drmm_cgroup_register_region(&xe->drm, name, size);
+	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);
 
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index e09559495c5b..b23830494ed4 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -34,6 +34,7 @@
 
 #include <drm/drm_device.h>
 
+struct dmem_cgroup_init;
 struct dmem_cgroup_region;
 struct drm_fb_helper;
 struct drm_fb_helper_surface_size;
@@ -433,7 +434,8 @@ void *__devm_drm_dev_alloc(struct device *parent,
 
 struct dmem_cgroup_region *
 drmm_cgroup_register_region(struct drm_device *dev,
-			    const char *region_name, u64 size);
+			    const char *region_name,
+			    const struct dmem_cgroup_init *init);
 
 /**
  * devm_drm_dev_alloc - Resource managed allocation of a &drm_device instance
diff --git a/include/linux/cgroup_dmem.h b/include/linux/cgroup_dmem.h
index dd4869f1d736..d9eab8a2c1ee 100644
--- a/include/linux/cgroup_dmem.h
+++ b/include/linux/cgroup_dmem.h
@@ -14,8 +14,18 @@ struct dmem_cgroup_pool_state;
 /* Opaque definition of a cgroup region, used internally */
 struct dmem_cgroup_region;
 
+/**
+ * struct dmem_cgroup_init - Initialization parameters for a dmem cgroup region.
+ * @size: Size of the region in bytes.
+ */
+struct dmem_cgroup_init {
+	u64 size;
+};
+
 #if IS_ENABLED(CONFIG_CGROUP_DMEM)
-struct dmem_cgroup_region *dmem_cgroup_register_region(u64 size, const char *name_fmt, ...) __printf(2,3);
+struct dmem_cgroup_region *
+dmem_cgroup_register_region(const struct dmem_cgroup_init *init,
+			    const char *name_fmt, ...) __printf(2, 3);
 void dmem_cgroup_unregister_region(struct dmem_cgroup_region *region);
 int dmem_cgroup_try_charge(struct dmem_cgroup_region *region, u64 size,
 			   struct dmem_cgroup_pool_state **ret_pool,
@@ -27,8 +37,8 @@ bool dmem_cgroup_state_evict_valuable(struct dmem_cgroup_pool_state *limit_pool,
 
 void dmem_cgroup_pool_state_put(struct dmem_cgroup_pool_state *pool);
 #else
-static inline __printf(2,3) struct dmem_cgroup_region *
-dmem_cgroup_register_region(u64 size, const char *name_fmt, ...)
+static inline __printf(2, 3) struct dmem_cgroup_region *
+dmem_cgroup_register_region(const struct dmem_cgroup_init *init, const char *name_fmt, ...)
 {
 	return NULL;
 }
diff --git a/kernel/cgroup/dmem.c b/kernel/cgroup/dmem.c
index 6430c7ce1e03..d12c8543f3fe 100644
--- a/kernel/cgroup/dmem.c
+++ b/kernel/cgroup/dmem.c
@@ -502,7 +502,7 @@ EXPORT_SYMBOL_GPL(dmem_cgroup_unregister_region);
 
 /**
  * dmem_cgroup_register_region() - Register a regions for dev cgroup.
- * @size: Size of region to register, in bytes.
+ * @init: Initialization parameters for the region.
  * @fmt: Region parameters to register
  *
  * This function registers a node in the dmem cgroup with the
@@ -511,13 +511,15 @@ EXPORT_SYMBOL_GPL(dmem_cgroup_unregister_region);
  *
  * Return: NULL or a struct on success, PTR_ERR on failure.
  */
-struct dmem_cgroup_region *dmem_cgroup_register_region(u64 size, const char *fmt, ...)
+struct dmem_cgroup_region *
+dmem_cgroup_register_region(const struct dmem_cgroup_init *init,
+			    const char *fmt, ...)
 {
 	struct dmem_cgroup_region *ret;
 	char *region_name;
 	va_list ap;
 
-	if (!size)
+	if (!init || !init->size)
 		return NULL;
 
 	va_start(ap, fmt);
@@ -534,7 +536,7 @@ struct dmem_cgroup_region *dmem_cgroup_register_region(u64 size, const char *fmt
 
 	INIT_LIST_HEAD(&ret->pools);
 	ret->name = region_name;
-	ret->size = size;
+	ret->size = init->size;
 	kref_init(&ret->ref);
 
 	spin_lock(&dmemcg_lock);
-- 
2.54.0

[PATCH v5 3/6] cgroup/dmem: Add reclaim callback for lowering max below current usage

[Thomas Hellström]

Add an optional reclaim callback to struct dmem_cgroup_region. When
dmem.max is set below the current usage of a cgroup pool, the new limit
is applied immediately (so that concurrent allocations are throttled
while reclaim is in progress) and then the driver is asked to evict
memory to bring usage back below the limit.

Reclaim is attempted up to a bounded number of times. No error is
returned to userspace if usage remains above the limit after reclaim,
and a pending signal will abort the reclaim loop early. This matches
the behavior of memory.max in the memory cgroup controller.

Also honor O_NONBLOCK so that if that flag is set during the
max value write, no reclaim is initiated. The idea is to avoid
charging the reclaim cost to the writer of the max value.

v2:
- Write max before reclaim is attempted (Maarten)
- Let signals abort the reclaim without error (Maarten)
- If a new max value is written with the O_NONBLOCK flag,
  reclaim is not attempted (Maarten)
- Extract region from the pool parameter rather than
  passing it explicitly to set_resource_xxx().

v3:
- Use an rwsem to protect reclaim callback registration and
  region unregister against concurrent reclaim invocations,
  ensuring reclaim_priv is visible when the callback is
  invoked. (Sashiko-bot)

v5:
- Rebased on the introduction of struct dmem_cgroup_init.
- Use nonblock=true in reset_all_resource_limits() to avoid sleeping
  inside rcu_read_lock() in dmemcs_offline(). (Sashiko-bot)
- Compare usage against the truncated limit value stored in cnt.max,
  not the original u64. (Sashiko-bot)
- Use a DMEM_MAX_RECLAIM_RETRIES (16) retry budget instead of 5, matching
  the memcg controller's MAX_RECLAIM_RETRIES. Only -ENOSPC (no progress)
  counts against the retry budget; other errors terminate the loop
  immediately.
Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 include/linux/cgroup_dmem.h |  21 +++++++
 kernel/cgroup/dmem.c        | 119 +++++++++++++++++++++++++++++++++---
 2 files changed, 130 insertions(+), 10 deletions(-)

diff --git a/include/linux/cgroup_dmem.h b/include/linux/cgroup_dmem.h
index d9eab8a2c1ee..d705e94d8784 100644
--- a/include/linux/cgroup_dmem.h
+++ b/include/linux/cgroup_dmem.h
@@ -14,12 +14,33 @@ struct dmem_cgroup_pool_state;
 /* Opaque definition of a cgroup region, used internally */
 struct dmem_cgroup_region;
 
+/**
+ * struct dmem_cgroup_ops - Operations for a dmem cgroup region.
+ * @reclaim: Optional callback invoked when dmem.max is set below the current
+ *           usage of a pool. The driver should attempt to free at least
+ *           @target_bytes from @pool. May be called multiple times if usage
+ *           remains above the limit after returning.
+ *
+ *           Return: 0 if some progress was made (even if less than
+ *           @target_bytes was freed), -ENOSPC if no progress could be made,
+ *           or another negative error code if a fatal error occurred.
+ *           Any non-zero return stops further reclaim attempts.
+ */
+struct dmem_cgroup_ops {
+	int (*reclaim)(struct dmem_cgroup_pool_state *pool,
+		       u64 target_bytes, void *priv);
+};
+
 /**
  * struct dmem_cgroup_init - Initialization parameters for a dmem cgroup region.
  * @size: Size of the region in bytes.
+ * @ops: Optional operations for this region. May be NULL.
+ * @reclaim_priv: Opaque pointer passed to @ops->reclaim. May be NULL.
  */
 struct dmem_cgroup_init {
 	u64 size;
+	const struct dmem_cgroup_ops *ops;
+	void *reclaim_priv;
 };
 
 #if IS_ENABLED(CONFIG_CGROUP_DMEM)
diff --git a/kernel/cgroup/dmem.c b/kernel/cgroup/dmem.c
index d12c8543f3fe..da99d133182c 100644
--- a/kernel/cgroup/dmem.c
+++ b/kernel/cgroup/dmem.c
@@ -18,6 +18,13 @@
 #include <linux/rculist.h>
 #include <linux/slab.h>
 
+/*
+ * Number of reclaim attempts before giving up when lowering dmem.max
+ * below current usage. Mirrors memcg's MAX_RECLAIM_RETRIES; unify the
+ * two in a follow-up instead of duplicating the constant.
+ */
+#define DMEM_MAX_RECLAIM_RETRIES 16
+
 struct dmem_cgroup_region {
 	/**
 	 * @ref: References keeping the region alive.
@@ -51,6 +58,24 @@ struct dmem_cgroup_region {
 	 * No new pools should be added to the region afterwards.
 	 */
 	bool unregistered;
+
+	/**
+	 * @ops: Optional operations, set from dmem_cgroup_init at registration.
+	 */
+	const struct dmem_cgroup_ops *ops;
+
+	/** @reclaim_priv: Private data passed to @ops->reclaim. */
+	void *reclaim_priv;
+
+	/**
+	 * @unregister_sem: Serialises reclaim callbacks against unregistration.
+	 *
+	 * Readers (reclaim) hold the read side for the duration of a callback
+	 * invocation.  dmem_cgroup_unregister_region() takes the write side to
+	 * drain any in-flight callbacks before returning, so callers may safely
+	 * free @reclaim_priv once unregister returns.
+	 */
+	struct rw_semaphore unregister_sem;
 };
 
 struct dmemcg_state {
@@ -145,21 +170,71 @@ static void free_cg_pool(struct dmem_cgroup_pool_state *pool)
 }
 
 static void
-set_resource_min(struct dmem_cgroup_pool_state *pool, u64 val)
+set_resource_min(struct dmem_cgroup_pool_state *pool, u64 val, bool nonblock)
 {
 	page_counter_set_min(&pool->cnt, val);
 }
 
 static void
-set_resource_low(struct dmem_cgroup_pool_state *pool, u64 val)
+set_resource_low(struct dmem_cgroup_pool_state *pool, u64 val, bool nonblock)
 {
 	page_counter_set_low(&pool->cnt, val);
 }
 
 static void
-set_resource_max(struct dmem_cgroup_pool_state *pool, u64 val)
+set_resource_max(struct dmem_cgroup_pool_state *pool, u64 val, bool nonblock)
 {
-	page_counter_set_max(&pool->cnt, val);
+	struct dmem_cgroup_region *region = pool->region;
+	unsigned long limit = (unsigned long)val;
+
+	/*
+	 * Always update the limit, even if usage currently exceeds it.
+	 * Concurrent allocations will be throttled against the new limit
+	 * while reclaim is in progress.
+	 */
+	xchg(&pool->cnt.max, limit);
+
+	if (nonblock)
+		return;
+
+	/*
+	 * Hold the read side for the duration of the reclaim loop so that
+	 * dmem_cgroup_unregister_region() cannot return (and the caller
+	 * cannot free reclaim_priv) while a callback is in progress.
+	 *
+	 * The ops check must happen inside the lock.  A caller may have
+	 * observed ops != NULL before dmem_cgroup_unregister_region()
+	 * acquired the write side; rechecking under down_read() is safe
+	 * because region->unregistered is set while the write side is
+	 * held, so any down_read() that succeeds after up_write() will
+	 * see unregistered = true and skip the loop.
+	 */
+	down_read(&region->unregister_sem);
+	if (!region->unregistered && region->ops && region->ops->reclaim) {
+		for (int retries = DMEM_MAX_RECLAIM_RETRIES; ; ) {
+			u64 usage = page_counter_read(&pool->cnt);
+			int ret;
+
+			if (usage <= limit)
+				break;
+
+			if (signal_pending(current))
+				break;
+
+			ret = region->ops->reclaim(pool, usage - limit, region->reclaim_priv);
+
+			/*
+			 * Mirror memcg's retry strategy: only count -ENOSPC (no
+			 * progress) against the retry budget; any other error is
+			 * fatal and terminates the loop immediately.
+			 */
+			if (ret && (ret != -ENOSPC || !retries--))
+				break;
+
+			cond_resched();
+		}
+	}
+	up_read(&region->unregister_sem);
 }
 
 static u64 get_resource_low(struct dmem_cgroup_pool_state *pool)
@@ -189,9 +264,14 @@ static u64 get_resource_peak(struct dmem_cgroup_pool_state *pool)
 
 static void reset_all_resource_limits(struct dmem_cgroup_pool_state *rpool)
 {
-	set_resource_min(rpool, 0);
-	set_resource_low(rpool, 0);
-	set_resource_max(rpool, PAGE_COUNTER_MAX);
+	set_resource_min(rpool, 0, false);
+	set_resource_low(rpool, 0, false);
+	/*
+	 * Use nonblock=true: we are raising the limit to PAGE_COUNTER_MAX so
+	 * reclaim is pointless, and dmemcs_offline() holds rcu_read_lock()
+	 * which forbids sleeping.
+	 */
+	set_resource_max(rpool, PAGE_COUNTER_MAX, true);
 }
 
 static void dmemcs_offline(struct cgroup_subsys_state *css)
@@ -468,7 +548,10 @@ static void dmemcg_free_region(struct kref *ref)
  * dmem_cgroup_unregister_region() - Unregister a previously registered region.
  * @region: The region to unregister.
  *
- * This function undoes dmem_cgroup_register_region.
+ * This function undoes dmem_cgroup_register_region.  It drains any
+ * in-flight reclaim callbacks before returning, so the caller may safely
+ * free the resources pointed to by @init.reclaim_priv once this function
+ * returns.
  */
 void dmem_cgroup_unregister_region(struct dmem_cgroup_region *region)
 {
@@ -477,6 +560,15 @@ void dmem_cgroup_unregister_region(struct dmem_cgroup_region *region)
 	if (!region)
 		return;
 
+	/*
+	 * Acquire the write side to drain any in-flight reclaim callbacks.
+	 * After up_write() below, set_resource_max() will observe
+	 * region->unregistered = true under its own down_read() and skip
+	 * the reclaim loop, so reclaim_priv is safe to free once this
+	 * function returns.
+	 */
+	down_write(&region->unregister_sem);
+
 	spin_lock(&dmemcg_lock);
 
 	/* Remove from global region list */
@@ -496,6 +588,8 @@ void dmem_cgroup_unregister_region(struct dmem_cgroup_region *region)
 	region->unregistered = true;
 	spin_unlock(&dmemcg_lock);
 
+	up_write(&region->unregister_sem);
+
 	kref_put(&region->ref, dmemcg_free_region);
 }
 EXPORT_SYMBOL_GPL(dmem_cgroup_unregister_region);
@@ -537,7 +631,10 @@ dmem_cgroup_register_region(const struct dmem_cgroup_init *init,
 	INIT_LIST_HEAD(&ret->pools);
 	ret->name = region_name;
 	ret->size = init->size;
+	ret->ops = init->ops;
+	ret->reclaim_priv = init->reclaim_priv;
 	kref_init(&ret->ref);
+	init_rwsem(&ret->unregister_sem);
 
 	spin_lock(&dmemcg_lock);
 	list_add_tail_rcu(&ret->region_node, &dmem_cgroup_regions);
@@ -733,9 +830,10 @@ static int dmemcg_parse_limit(char *options, u64 *new_limit)
 
 static ssize_t dmemcg_limit_write(struct kernfs_open_file *of,
 				 char *buf, size_t nbytes, loff_t off,
-				 void (*apply)(struct dmem_cgroup_pool_state *, u64))
+				 void (*apply)(struct dmem_cgroup_pool_state *, u64, bool))
 {
 	struct dmemcg_state *dmemcs = css_to_dmemcs(of_css(of));
+	bool nonblock = of->file->f_flags & O_NONBLOCK;
 	int err = 0;
 
 	while (buf && !err) {
@@ -780,7 +878,8 @@ static ssize_t dmemcg_limit_write(struct kernfs_open_file *of,
 		}
 
 		/* And commit */
-		apply(pool, new_limit);
+		apply(pool, new_limit, nonblock);
+
 		dmemcg_pool_put(pool);
 
 out_put:
-- 
2.54.0

[PATCH v5 4/6] drm/ttm: Hook up a cgroup-aware reclaim callback for the dmem controller

[Thomas Hellström]

Add ttm_bo_evict_cgroup() to evict buffer objects charged to a specific
dmem cgroup pool from a resource manager's LRU until a byte target is
met.  Add ttm_resource_manager_set_dmem_region() to associate a dmem
cgroup region with a resource manager; drivers supply their own
dmem_cgroup_ops with ttm_resource_manager_dmem_reclaim as the reclaim
function and the manager pointer as reclaim_priv in the dmem_cgroup_init
to wire up TTM eviction as the reclaim callback.

The eviction context is interruptible; signals abort the operation and
propagate back through the write() syscall.

Introduce a new mode for the bo LRU walker so that sleeping locks
can be taken. This can be used when the caller doesn't hold any
previous dma_resv locks, and where it intends to hold at most
one lock at a time.

Like the rest of the TTM eviction this should sooner than later
be converted to full WW transactions.

v3:
- Fix ttm_resource_manager_set_dmem_region() storing an error pointer
  in man->cg unconditionally. (Sashiko-bot)
- Fix kernel-doc function name format for ttm_bo_evict_cgroup() and
  ttm_resource_manager_set_dmem_region().

v5:
- Rebased on the introduction of struct dmem_cgroup_init.
- Handle NULL region in ttm_resource_manager_set_dmem_region() to clear
  the reclaim callback, preventing use-after-free when the manager is
  torn down while the dmem region outlives it. (Sashiko-bot)
- Return 0 on any progress (even partial eviction), -ENOSPC only when
  nothing was freed; fixes callers that expected 0 on partial success.
- Document that the reclaim callback should return 0 if some progress
  was made, -ENOSPC if no progress at all, or another error for fatal
  failures.

Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c       | 95 +++++++++++++++++++++++++++++-
 drivers/gpu/drm/ttm/ttm_bo_util.c  |  3 +-
 drivers/gpu/drm/ttm/ttm_resource.c | 50 ++++++++++++++++
 include/drm/ttm/ttm_bo.h           | 10 ++++
 include/drm/ttm/ttm_resource.h     |  7 +++
 5 files changed, 161 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index bcd76f6bb7f0..db0e38bd8a43 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -515,12 +515,20 @@ static s64 ttm_bo_evict_cb(struct ttm_lru_walk *walk, struct ttm_buffer_object *
 {
 	struct ttm_bo_evict_walk *evict_walk =
 		container_of(walk, typeof(*evict_walk), walk);
+	/* Capture size before eviction in case res is cleared. */
+	s64 bo_size = bo->base.size;
 	s64 lret;
 
 	if (!dmem_cgroup_state_evict_valuable(evict_walk->limit_pool, bo->resource->css,
 					      evict_walk->try_low, &evict_walk->hit_low))
 		return 0;
 
+	/*
+	 * evict_walk->place is NULL in cgroup drain mode.  Drivers'
+	 * eviction_valuable() callbacks must handle a NULL place, treating it
+	 * as "any placement": the TTM base implementation already does so via
+	 * ttm_resource_intersects().
+	 */
 	if (bo->pin_count || !bo->bdev->funcs->eviction_valuable(bo, evict_walk->place))
 		return 0;
 
@@ -536,11 +544,15 @@ static s64 ttm_bo_evict_cb(struct ttm_lru_walk *walk, struct ttm_buffer_object *
 		goto out;
 
 	evict_walk->evicted++;
-	if (evict_walk->res)
+	if (evict_walk->res) {
 		lret = ttm_resource_alloc(evict_walk->evictor, evict_walk->place,
 					  evict_walk->res, NULL);
-	if (lret == 0)
-		return 1;
+		if (lret == 0)
+			return 1;
+	} else {
+		/* Cgroup drain: return bytes freed for byte-denominated progress. */
+		return bo_size;
+	}
 out:
 	/* Errors that should terminate the walk. */
 	if (lret == -ENOSPC)
@@ -614,6 +626,83 @@ static int ttm_bo_evict_alloc(struct ttm_device *bdev,
 	return 0;
 }
 
+/**
+ * ttm_bo_evict_cgroup() - Evict buffer objects charged to a specific cgroup.
+ * @bdev: The TTM device.
+ * @man: The resource manager whose LRU to walk.
+ * @limit_pool: The cgroup pool state whose members should be evicted.
+ * @target_bytes: Number of bytes to free.
+ * @ctx: The TTM operation context.
+ *
+ * Walk the LRU of @man and evict buffer objects that are charged to the
+ * cgroup identified by @limit_pool, until at least @target_bytes have been
+ * freed.  Mirrors the two-pass (trylock -> sleeping-lock, low-watermark)
+ * strategy used by ttm_bo_evict_alloc().
+ *
+ * Return: >= @target_bytes on full success, 0..target_bytes-1 if partial,
+ *         negative error code on fatal error.
+ */
+s64 ttm_bo_evict_cgroup(struct ttm_device *bdev,
+			struct ttm_resource_manager *man,
+			struct dmem_cgroup_pool_state *limit_pool,
+			s64 target_bytes,
+			struct ttm_operation_ctx *ctx)
+{
+	struct ttm_bo_evict_walk evict_walk = {
+		.walk = {
+			.ops = &ttm_evict_walk_ops,
+			.arg = { .ctx = ctx },
+		},
+		.limit_pool = limit_pool,
+		/* place, evictor, res left NULL: selects cgroup drain mode */
+	};
+	s64 lret, pass;
+
+	evict_walk.walk.arg.trylock_only = true;
+	lret = ttm_lru_walk_for_evict(&evict_walk.walk, bdev, man, target_bytes);
+	if (lret < 0 || lret >= target_bytes)
+		return lret;
+
+	/* Second pass: also evict BOs at the low watermark. */
+	if (evict_walk.hit_low) {
+		evict_walk.try_low = true;
+		pass = ttm_lru_walk_for_evict(&evict_walk.walk, bdev, man,
+					      target_bytes - lret);
+		if (pass < 0)
+			return pass;
+		lret += pass;
+		if (lret >= target_bytes)
+			return lret;
+	}
+
+	/* Full sleeping-lock pass for remaining target. */
+	evict_walk.try_low = evict_walk.hit_low = false;
+	evict_walk.walk.arg.trylock_only = false;
+
+retry:
+	evict_walk.walk.arg.sleeping_lock = true;
+	do {
+		evict_walk.evicted = 0;
+		pass = ttm_lru_walk_for_evict(&evict_walk.walk, bdev, man,
+					      target_bytes - lret);
+		if (pass < 0) {
+			lret = pass;
+			goto out;
+		}
+		lret += pass;
+	} while (lret < target_bytes && evict_walk.evicted);
+
+	/* One more attempt if we hit the low limit during sleeping-lock pass. */
+	if (lret < target_bytes && evict_walk.hit_low && !evict_walk.try_low) {
+		evict_walk.try_low = true;
+		goto retry;
+	}
+
+out:
+	return lret;
+}
+EXPORT_SYMBOL(ttm_bo_evict_cgroup);
+
 /**
  * ttm_bo_pin - Pin the buffer object.
  * @bo: The buffer object to pin
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 3e3c201a0222..bd0b23ac2cc4 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -999,7 +999,8 @@ __ttm_bo_lru_cursor_next(struct ttm_bo_lru_cursor *curs)
 		bo = res->bo;
 		if (ttm_lru_walk_trylock(curs, bo))
 			bo_locked = true;
-		else if (!arg->ticket || arg->ctx->no_wait_gpu || arg->trylock_only)
+		else if ((!arg->ticket && !arg->sleeping_lock) || arg->ctx->no_wait_gpu ||
+			 arg->trylock_only)
 			continue;
 
 		if (!ttm_bo_get_unless_zero(bo)) {
diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
index 154d6739256f..ad00723e99ef 100644
--- a/drivers/gpu/drm/ttm/ttm_resource.c
+++ b/drivers/gpu/drm/ttm/ttm_resource.c
@@ -953,3 +953,53 @@ void ttm_resource_manager_create_debugfs(struct ttm_resource_manager *man,
 #endif
 }
 EXPORT_SYMBOL(ttm_resource_manager_create_debugfs);
+
+/**
+ * ttm_resource_manager_dmem_reclaim() - dmem cgroup reclaim callback for TTM
+ *                                       resource managers.
+ * @pool: The dmem cgroup pool state for the cgroup being reclaimed.
+ * @target_bytes: Number of bytes to try to free.
+ * @priv: The &ttm_resource_manager pointer, passed as @init.reclaim_priv to
+ *        dmem_cgroup_register_region().
+ *
+ * Drivers should use this as the @reclaim member of their own
+ * &struct dmem_cgroup_ops, with the &ttm_resource_manager pointer as
+ * @init.reclaim_priv.
+ *
+ * Return: 0 if some memory was freed, -ENOSPC if nothing was freed, or
+ *         another negative error code on fatal failure.
+ */
+int ttm_resource_manager_dmem_reclaim(struct dmem_cgroup_pool_state *pool,
+				      u64 target_bytes, void *priv)
+{
+	struct ttm_resource_manager *man = priv;
+	struct ttm_operation_ctx ctx = { .interruptible = true };
+	s64 freed;
+
+	freed = ttm_bo_evict_cgroup(man->bdev, man, pool, target_bytes, &ctx);
+	if (freed < 0)
+		return freed;
+
+	return freed > 0 ? 0 : -ENOSPC;
+}
+EXPORT_SYMBOL(ttm_resource_manager_dmem_reclaim);
+
+/**
+ * ttm_resource_manager_set_dmem_region() - Associate a dmem cgroup region with a
+ *                                        resource manager.
+ * @man: The resource manager.
+ * @region: The dmem cgroup region to associate, may be NULL or IS_ERR().
+ *
+ * When @region is valid, stores it in @man->cg so that TTM can look up the
+ * associated pool during charging and eviction-target selection.
+ * The reclaim callback must be wired up using ttm_resource_manager_dmem_reclaim()
+ * in the driver's own &struct dmem_cgroup_ops, with the manager pointer as
+ * @init.reclaim_priv.
+ */
+void ttm_resource_manager_set_dmem_region(struct ttm_resource_manager *man,
+					  struct dmem_cgroup_region *region)
+{
+	if (!IS_ERR_OR_NULL(region))
+		man->cg = region;
+}
+EXPORT_SYMBOL(ttm_resource_manager_set_dmem_region);
diff --git a/include/drm/ttm/ttm_bo.h b/include/drm/ttm/ttm_bo.h
index 8310bc3d55f9..32791c4db2a9 100644
--- a/include/drm/ttm/ttm_bo.h
+++ b/include/drm/ttm/ttm_bo.h
@@ -226,6 +226,11 @@ struct ttm_lru_walk_arg {
 	struct ww_acquire_ctx *ticket;
 	/** @trylock_only: Only use trylock for locking. */
 	bool trylock_only;
+	/**
+	 * @sleeping_lock: Use sleeping locks even with %NULL @ticket.
+	 * @trylock_only has precedence over this field.
+	 */
+	bool sleeping_lock;
 };
 
 /**
@@ -431,6 +436,11 @@ void ttm_bo_unpin(struct ttm_buffer_object *bo);
 int ttm_bo_evict_first(struct ttm_device *bdev,
 		       struct ttm_resource_manager *man,
 		       struct ttm_operation_ctx *ctx);
+s64 ttm_bo_evict_cgroup(struct ttm_device *bdev,
+			struct ttm_resource_manager *man,
+			struct dmem_cgroup_pool_state *limit_pool,
+			s64 target_bytes,
+			struct ttm_operation_ctx *ctx);
 int ttm_bo_access(struct ttm_buffer_object *bo, unsigned long offset,
 		  void *buf, int len, int write);
 vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
index a5d386583fb6..32e485fdce9a 100644
--- a/include/drm/ttm/ttm_resource.h
+++ b/include/drm/ttm/ttm_resource.h
@@ -39,6 +39,7 @@
 
 struct dentry;
 struct dmem_cgroup_device;
+struct dmem_cgroup_region;
 struct drm_printer;
 struct ttm_device;
 struct ttm_resource_manager;
@@ -477,6 +478,12 @@ void ttm_resource_manager_init(struct ttm_resource_manager *man,
 			       struct ttm_device *bdev,
 			       uint64_t size);
 
+void ttm_resource_manager_set_dmem_region(struct ttm_resource_manager *man,
+					  struct dmem_cgroup_region *region);
+
+int ttm_resource_manager_dmem_reclaim(struct dmem_cgroup_pool_state *pool,
+				      u64 target_bytes, void *priv);
+
 int ttm_resource_manager_evict_all(struct ttm_device *bdev,
 				   struct ttm_resource_manager *man);
 
-- 
2.54.0

[PATCH v5 5/6] drm/xe: Wire up dmem cgroup reclaim for VRAM manager

[Thomas Hellström]

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 <thomas.hellstrom@linux.intel.com>
---
 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;
 }
 
 /**
-- 
2.54.0

[PATCH v5 6/6] drm/amdgpu: Wire up dmem cgroup reclaim for VRAM manager

[Thomas Hellström]

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.

Guard place->flags in amdgpu_ttm_bo_eviction_valuable() against NULL,
as the TTM reclaim path passes a NULL place in cgroup drain mode.

v3:
- Rebased on fix for uninitialized list and buddy allocator on the
  drmm_cgroup_register_region() error path.

v5:
- Rebased on the introduction of struct dmem_cgroup_init.
- Clear the reclaim callback in amdgpu_vram_mgr_fini() to prevent
  use-after-free if cgroup reclaim is triggered after driver unbind
  while userspace holds an open DRM file descriptor. (Sashiko-bot)
- Switch from drmm_cgroup_register_region() to the raw
  dmem_cgroup_register_region() and store the region in
  amdgpu_vram_mgr.cg_region. Explicitly call
  dmem_cgroup_unregister_region() at the top of amdgpu_vram_mgr_fini()
  before any manager teardown, draining in-flight reclaim callbacks via
  the rwsem before the manager is destroyed. This is required because
  amdgpu's vram manager fini is called explicitly during driver unbind,
  which may precede the DRM device release and thus precede any
  drmm-based cleanup. (Sashiko-bot)

Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c      |  2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 29 ++++++++++++++++----
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.h |  2 ++
 3 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 2740de94e93c..8cbcd33f51a5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1488,7 +1488,7 @@ static bool amdgpu_ttm_bo_eviction_valuable(struct ttm_buffer_object *bo,
 	dma_resv_for_each_fence(&resv_cursor, bo->base.resv,
 				DMA_RESV_USAGE_BOOKKEEP, f) {
 		if (amdkfd_fence_check_mm(f, current->mm) &&
-		    !(place->flags & TTM_PL_FLAG_CONTIGUOUS))
+		    !(place && (place->flags & TTM_PL_FLAG_CONTIGUOUS)))
 			return false;
 	}
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
index 08f05c3aed1d..ee98b963e84a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
@@ -906,6 +906,10 @@ static const struct ttm_resource_manager_func amdgpu_vram_mgr_func = {
 	.debug	= amdgpu_vram_mgr_debug
 };
 
+static const struct dmem_cgroup_ops amdgpu_vram_mgr_dmem_ops = {
+	.reclaim = ttm_resource_manager_dmem_reclaim,
+};
+
 /**
  * amdgpu_vram_mgr_init - init VRAM manager and DRM MM
  *
@@ -917,6 +921,7 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
 {
 	struct amdgpu_vram_mgr *mgr = &adev->mman.vram_mgr;
 	struct ttm_resource_manager *man = &mgr->manager;
+	struct dmem_cgroup_region *cg;
 	int err;
 
 	ttm_resource_manager_init(man, &adev->mman.bdev,
@@ -933,12 +938,15 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
 	if (err)
 		return err;
 
-	man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram",
-					      &(struct dmem_cgroup_init){
-						.size = adev->gmc.real_vram_size,
-					      });
-	if (IS_ERR(man->cg))
-		return PTR_ERR(man->cg);
+	cg = dmem_cgroup_register_region(&(struct dmem_cgroup_init){
+					     .size = adev->gmc.real_vram_size,
+					     .ops = &amdgpu_vram_mgr_dmem_ops,
+					     .reclaim_priv = man,
+					 }, "vram");
+	if (IS_ERR(cg))
+		return PTR_ERR(cg);
+
+	ttm_resource_manager_set_dmem_region(man, cg);
 
 	ttm_set_driver_manager(&adev->mman.bdev, TTM_PL_VRAM, &mgr->manager);
 	ttm_resource_manager_set_used(man, true);
@@ -960,6 +968,15 @@ void amdgpu_vram_mgr_fini(struct amdgpu_device *adev)
 	int ret;
 	struct amdgpu_vram_reservation *rsv, *temp;
 
+	/*
+	 * Drain any in-flight dmem cgroup reclaim callbacks and remove the
+	 * region from the global list before tearing down the manager.
+	 * This must happen first so no reclaim callback can access the
+	 * manager after this point.
+	 */
+	dmem_cgroup_unregister_region(mgr->cg_region);
+	mgr->cg_region = NULL;
+
 	ttm_resource_manager_set_used(man, false);
 
 	ret = ttm_resource_manager_evict_all(&adev->mman.bdev, man);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.h
index 429a21a2e9b2..07103cddb335 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.h
@@ -36,6 +36,8 @@ struct amdgpu_vram_mgr {
 	atomic64_t vis_usage;
 	u64 default_page_size;
 	struct list_head allocated_vres_list;
+	/** @cg_region: dmem cgroup region for VRAM; unregistered in fini. */
+	struct dmem_cgroup_region *cg_region;
 };
 
 struct amdgpu_vres_task {
-- 
2.54.0