drm/amdgpu: fix another potential cause of VM faults

The root PD can be evicted directly after allocating it, just validate
it on first use.

Signed-off-by: Christian König <[e-mail]>
Acked-by: Felix Kuehling <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

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

···
 {
 	const unsigned align = min(AMDGPU_VM_PTB_ALIGN_SIZE,
 		AMDGPU_VM_PTE_COUNT(adev) * 8);
+	uint64_t init_pde_value = 0, flags;
 	unsigned ring_instance;
 	struct amdgpu_ring *ring;
 	struct drm_sched_rq *rq;
+	unsigned long size;
 	int r, i;
-	u64 flags;
-	uint64_t init_pde_value = 0;
 
 	vm->va = RB_ROOT_CACHED;
 	for (i = 0; i < AMDGPU_MAX_VMHUBS; i++)
···
 		flags |= (AMDGPU_GEM_CREATE_NO_CPU_ACCESS |
 				AMDGPU_GEM_CREATE_SHADOW);
 
-	r = amdgpu_bo_create(adev,
-			     amdgpu_vm_bo_size(adev, adev->vm_manager.root_level),
-			     align, true,
-			     AMDGPU_GEM_DOMAIN_VRAM,
-			     flags,
-			     NULL, NULL, init_pde_value, &vm->root.base.bo);
+	size = amdgpu_vm_bo_size(adev, adev->vm_manager.root_level);
+	r = amdgpu_bo_create(adev, size, align, true, AMDGPU_GEM_DOMAIN_VRAM,
+			     flags, NULL, NULL, init_pde_value,
+			     &vm->root.base.bo);
 	if (r)
 		goto error_free_sched_entity;
 
+	r = amdgpu_bo_reserve(vm->root.base.bo, true);
+	if (r)
+		goto error_free_root;
+
 	vm->root.base.vm = vm;
 	list_add_tail(&vm->root.base.bo_list, &vm->root.base.bo->va);
-	INIT_LIST_HEAD(&vm->root.base.vm_status);
-
-	if (vm->use_cpu_for_update) {
-		r = amdgpu_bo_reserve(vm->root.base.bo, false);
-		if (r)
-			goto error_free_root;
-
-		r = amdgpu_bo_kmap(vm->root.base.bo, NULL);
-		amdgpu_bo_unreserve(vm->root.base.bo);
-		if (r)
-			goto error_free_root;
-	}
+	list_add_tail(&vm->root.base.vm_status, &vm->evicted);
+	amdgpu_bo_unreserve(vm->root.base.bo);
 
 	if (pasid) {
 		unsigned long flags;