[PATCH v6 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. Call dmem_cgroup_unregister_region()
  in amdgpu_vram_mgr_fini() after ttm_resource_manager_evict_all()
  to drain in-flight reclaim callbacks, and clear man->cg afterwards.
  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)

v6:
- Fix mgr->cg_region never being assigned, so
  dmem_cgroup_unregister_region() in fini silently no-ops on NULL
  and leaks the region. (Sashiko-bot)
- Reorder 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)

Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c      |  2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c | 31 ++++++++++++++++----
 drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.h |  2 ++
 3 files changed, 28 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..2250bab0970d 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 +938,16 @@ 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);
+
+	mgr->cg_region = 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);
@@ -966,6 +975,16 @@ void amdgpu_vram_mgr_fini(struct amdgpu_device *adev)
 	if (ret)
 		return;
 
+	/*
+	 * Drain any in-flight dmem cgroup reclaim callbacks and remove the
+	 * region from the global list.  This must happen after evict_all()
+	 * so that ttm_resource_free() can still uncharge via man->cg while
+	 * BOs are being evicted.
+	 */
+	dmem_cgroup_unregister_region(mgr->cg_region);
+	mgr->cg_region = NULL;
+	man->cg = NULL;
+
 	mutex_lock(&mgr->lock);
 	list_for_each_entry_safe(rsv, temp, &mgr->reservations_pending, blocks)
 		kfree(rsv);
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