Re: [PATCH v6 6/6] drm/amdgpu: Wire up dmem cgroup reclaim for VRAM manager

[Thomas Hellström]

On Thu, 2026-06-11 at 19:33 +0200, Thomas Hellström wrote:
> 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,
> +};

Probably might want to block reclaim after device unbind, just like xe.
I'll look at that for v7.

> +
>  /**
>   * 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 {