drm/amdgpu: Fix amdgpu_vm_pt_free warning

Free page table BO from vm resv unlocked context generate below
warnings.

Add a pt_free_work in vm to free page table BO from vm->pt_freed list.
pass vm resv unlock status from page table update caller, and add vm_bo
entry to vm->pt_freed list and schedule the pt_free_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

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

@@ -2055,6 +2055,8 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm)
 	spin_lock_init(&vm->status_lock);
 	INIT_LIST_HEAD(&vm->freed);
 	INIT_LIST_HEAD(&vm->done);
+	INIT_LIST_HEAD(&vm->pt_freed);
+	INIT_WORK(&vm->pt_free_work, amdgpu_vm_pt_free_work);
 
 	/* create scheduler entities for page table updates */
 	r = drm_sched_entity_init(&vm->immediate, DRM_SCHED_PRIORITY_NORMAL,
@@ -2256,6 +2258,8 @@ void amdgpu_vm_fini(struct amdgpu_device *adev, struct amdgpu_vm *vm)
 
 	amdgpu_amdkfd_gpuvm_destroy_cb(adev, vm);
 
+	flush_work(&vm->pt_free_work);
+
 	root = amdgpu_bo_ref(vm->root.bo);
 	amdgpu_bo_reserve(root, true);
 	amdgpu_vm_set_pasid(adev, vm, 0);

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h

@@ -278,6 +278,10 @@ struct amdgpu_vm {
 	/* BOs which are invalidated, has been updated in the PTs */
 	struct list_head        done;
 
+	/* PT BOs scheduled to free and fill with zero if vm_resv is not hold */
+	struct list_head	pt_freed;
+	struct work_struct	pt_free_work;
+
 	/* contains the page directory */
 	struct amdgpu_vm_bo_base     root;
 	struct dma_fence	*last_update;
@@ -473,6 +477,7 @@ int amdgpu_vm_pde_update(struct amdgpu_vm_update_params *params,
 int amdgpu_vm_ptes_update(struct amdgpu_vm_update_params *params,
 			  uint64_t start, uint64_t end,
 			  uint64_t dst, uint64_t flags);
+void amdgpu_vm_pt_free_work(struct work_struct *work);
 
 #if defined(CONFIG_DEBUG_FS)
 void amdgpu_debugfs_vm_bo_info(struct amdgpu_vm *vm, struct seq_file *m);

drivers/gpu/drm/amd/amdgpu/amdgpu_vm_pt.c

@@ -644,6 +644,27 @@ static void amdgpu_vm_pt_free(struct amdgpu_vm_bo_base *entry)
 	amdgpu_bo_unref(&entry->bo);
 }
 
+void amdgpu_vm_pt_free_work(struct work_struct *work)
+{
+	struct amdgpu_vm_bo_base *entry, *next;
+	struct amdgpu_vm *vm;
+	LIST_HEAD(pt_freed);
+
+	vm = container_of(work, struct amdgpu_vm, pt_free_work);
+
+	spin_lock(&vm->status_lock);
+	list_splice_init(&vm->pt_freed, &pt_freed);
+	spin_unlock(&vm->status_lock);
+
+	/* flush_work in amdgpu_vm_fini ensure vm->root.bo is valid. */
+	amdgpu_bo_reserve(vm->root.bo, true);
+
+	list_for_each_entry_safe(entry, next, &pt_freed, vm_status)
+		amdgpu_vm_pt_free(entry);
+
+	amdgpu_bo_unreserve(vm->root.bo);
+}
+
 /**
  * amdgpu_vm_pt_free_dfs - free PD/PT levels
  *
@@ -655,11 +676,24 @@ 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;
 
+	if (unlocked) {
+		spin_lock(&vm->status_lock);
+		for_each_amdgpu_vm_pt_dfs_safe(adev, vm, start, cursor, entry)
+			list_move(&entry->vm_status, &vm->pt_freed);
+
+		if (start)
+			list_move(&start->entry->vm_status, &vm->pt_freed);
+		spin_unlock(&vm->status_lock);
+		schedule_work(&vm->pt_free_work);
+		return;
+	}
+
 	for_each_amdgpu_vm_pt_dfs_safe(adev, vm, start, cursor, entry)
 		amdgpu_vm_pt_free(entry);
 
@@ -676,7 +710,7 @@ 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);
 }
 
 /**
@@ -969,7 +1003,8 @@ 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);
 			}