[PATCH 1/1] drm/amdgpu: fix amdgpu_vm_pt_free warning

[Felix Kuehling]

Am 2022-09-09 um 14:25 schrieb Philip Yang:
> Free page table BO from vm resv unlocked context generate below
> warnings.
>
> Add a free_work in vm_bo base of each page table BO, pass vm resv
> unlock status from page table update caller, and schedule the
> work if calling with vm resv unlocked.
>
>   WARNING: CPU: 12 PID: 3238 at
>   drivers/gpu/drm/ttm/ttm_bo.c:106 ttm_bo_set_bulk_move+0xa1/0xc0
>   Call Trace:
>    amdgpu_vm_pt_free+0x42/0xd0 [amdgpu]
>    amdgpu_vm_pt_free_dfs+0xb3/0xf0 [amdgpu]
>    amdgpu_vm_ptes_update+0x52d/0x850 [amdgpu]
>    amdgpu_vm_update_range+0x2a6/0x640 [amdgpu]
>    svm_range_unmap_from_gpus+0x110/0x300 [amdgpu]
>    svm_range_cpu_invalidate_pagetables+0x535/0x600 [amdgpu]
>   __mmu_notifier_invalidate_range_start+0x1cd/0x230
>    unmap_vmas+0x9d/0x140
>    unmap_region+0xa8/0x110
>
>   WARNING: CPU: 0 PID: 1475 at
>   drivers/dma-buf/dma-resv.c:483 dma_resv_iter_next
>   Call Trace:
>    dma_resv_iter_first+0x43/0xa0
>    amdgpu_vm_sdma_update+0x69/0x2d0 [amdgpu]
>    amdgpu_vm_ptes_update+0x29c/0x870 [amdgpu]
>    amdgpu_vm_update_range+0x2f6/0x6c0 [amdgpu]
>    svm_range_unmap_from_gpus+0x115/0x300 [amdgpu]
>    svm_range_cpu_invalidate_pagetables+0x510/0x5e0 [amdgpu]
>    __mmu_notifier_invalidate_range_start+0x1d3/0x230
>    unmap_vmas+0x140/0x150
>    unmap_region+0xa8/0x110
>
> Signed-off-by: Philip Yang <Philip.Yang at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h    |  3 ++
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c | 40 +++++++++++++++++++----
>   2 files changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> index 9ecb7f663e19..ac7cd2c738e5 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> @@ -150,6 +150,9 @@ struct amdgpu_vm_bo_base {
>   
>   	/* protected by the BO being reserved */
>   	bool				moved;
> +
> +	/* work to free pt bo if vm resv is not hold */
> +	struct work_struct              free_work;
>   };
>   
>   /* provided by hw blocks that can write ptes, e.g., sdma */
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> index 88de9f0d4728..e6f6d7e6368f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c
> @@ -37,6 +37,8 @@ struct amdgpu_vm_pt_cursor {
>   	unsigned int level;
>   };
>   
> +static void amdgpu_vm_pt_free_work(struct work_struct *work);
> +
>   /**
>    * amdgpu_vm_pt_level_shift - return the addr shift for each level
>    *
> @@ -607,6 +609,7 @@ static int amdgpu_vm_pt_alloc(struct amdgpu_device *adev,
>   	pt_bo = &pt->bo;
>   	pt_bo->parent = amdgpu_bo_ref(cursor->parent->bo);
>   	amdgpu_vm_bo_base_init(entry, vm, pt_bo);
> +	INIT_WORK(&entry->free_work, amdgpu_vm_pt_free_work);
>   	r = amdgpu_vm_pt_clear(adev, vm, pt, immediate);
>   	if (r)
>   		goto error_free_pt;
> @@ -624,23 +627,46 @@ static int amdgpu_vm_pt_alloc(struct amdgpu_device *adev,
>    *
>    * @entry: PDE to free
>    */
> -static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry)
> +static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry, bool unlocked)
>   {
>   	struct amdgpu_bo *shadow;
>   
>   	if (!entry->bo)
>   		return;
> +
> +	if (unlocked) {
> +		schedule_work(&entry->free_work);
> +		return;
> +	}
> +
>   	shadow = amdgpu_bo_shadowed(entry->bo);
>   	if (shadow) {
>   		ttm_bo_set_bulk_move(&shadow->tbo, NULL);
>   		amdgpu_bo_unref(&shadow);
>   	}
>   	ttm_bo_set_bulk_move(&entry->bo->tbo, NULL);
> +
>   	entry->bo->vm_bo = NULL;
>   	list_del(&entry->vm_status);
>   	amdgpu_bo_unref(&entry->bo);
>   }
>   
> +static void amdgpu_vm_pt_free_work(struct work_struct *work)
> +{
> +	struct amdgpu_vm_bo_base *entry;
> +	struct amdgpu_bo *root;
> +
> +	entry = container_of(work, struct amdgpu_vm_bo_base, delayed_work);
> +
> +	root = amdgpu_bo_ref(entry->vm->root.bo);
> +	amdgpu_bo_reserve(root, true);
> +
> +	amdgpu_vm_pt_free(entry, true);

Doesn't this just cause the work to be scheduled again, rather than 
actually freeing the BO?

Regards,
   Felix


> +
> +	amdgpu_bo_unreserve(root);
> +	amdgpu_bo_unref(&root);
> +}
> +
>   /**
>    * amdgpu_vm_pt_free_dfs - free PD/PT levels
>    *
> @@ -652,16 +678,17 @@ static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry)
>    */
>   static void amdgpu_vm_pt_free_dfs(struct amdgpu_device *adev,
>   				  struct amdgpu_vm *vm,
> -				  struct amdgpu_vm_pt_cursor *start)
> +				  struct amdgpu_vm_pt_cursor *start,
> +				  bool unlocked)
>   {
>   	struct amdgpu_vm_pt_cursor cursor;
>   	struct amdgpu_vm_bo_base *entry;
>   
>   	for_each_amdgpu_vm_pt_dfs_safe(adev, vm, start, cursor, entry)
> -		amdgpu_vm_pt_free(entry);
> +		amdgpu_vm_pt_free(entry, unlocked);
>   
>   	if (start)
> -		amdgpu_vm_pt_free(start->entry);
> +		amdgpu_vm_pt_free(start->entry, unlocked);
>   }
>   
>   /**
> @@ -673,7 +700,7 @@ static void amdgpu_vm_pt_free_dfs(struct amdgpu_device *adev,
>    */
>   void amdgpu_vm_pt_free_root(struct amdgpu_device *adev, struct amdgpu_vm *vm)
>   {
> -	amdgpu_vm_pt_free_dfs(adev, vm, NULL);
> +	amdgpu_vm_pt_free_dfs(adev, vm, NULL, false);
>   }
>   
>   /**
> @@ -966,7 +993,8 @@ int amdgpu_vm_ptes_update(struct amdgpu_vm_update_params *params,
>   				if (cursor.entry->bo) {
>   					params->table_freed = true;
>   					amdgpu_vm_pt_free_dfs(adev, params->vm,
> -							      &cursor);
> +							      &cursor,
> +							      params->unlocked);
>   				}
>   				amdgpu_vm_pt_next(adev, &cursor);
>   			}