[PATCH v6 0/6] [PATCH v6 0/6] Add reclaim to the dmem cgroup controller

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

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.
- Clear the reclaim callback in xe and amdgpu fini paths to prevent
  use-after-free after driver unbind with open DRM file descriptors.
  (Sashiko-bot)
- 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.

v6:
- Move the ops check inside down_read() in set_resource_max(), guarded
  by region->unregistered, to close a UAF race against
  dmem_cgroup_unregister_region(). (Sashiko-bot)
- Fix dmem_cgroup_ops->reclaim docstring: -ENOSPC is retried up to
  DMEM_MAX_RECLAIM_RETRIES times, not an immediate stop. (Sashiko-bot)
- Fix mgr->cg_region never being assigned in amdgpu_vram_mgr_init(),
  causing dmem_cgroup_unregister_region() in fini to silently no-op.
  (Sashiko-bot)
- Reorder amdgpu_vram_mgr_fini() to call set_used(false) and
  evict_all() before dmem_cgroup_unregister_region(), so
  ttm_resource_free() can uncharge via man->cg during eviction; clear
  man->cg after unregister. (Sashiko-bot)

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 |  30 ++++++-
 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                  |  38 +++++++-
 kernel/cgroup/dmem.c                         | 129 ++++++++++++++++++++++++---
 13 files changed, 396 insertions(+), 35 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 |  30 ++++-
 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                  |  38 +++++-
 kernel/cgroup/dmem.c                         | 129 +++++++++++++++++--
 13 files changed, 396 insertions(+), 35 deletions(-)

-- 
2.54.0