drm/xe/userptr: restore invalidation list on error

On error restore anything still on the pin_list back to the invalidation
list on error. For the actual pin, so long as the vma is tracked on
either list it should get picked up on the next pin, however it looks
possible for the vma to get nuked but still be present on this per vm
pin_list leading to corruption. An alternative might be then to instead
just remove the link when destroying the vma.

v2:
 - Also add some asserts.
 - Keep the overzealous locking so that we are consistent with the docs;
   updating the docs and related bits will be done as a follow up.

Fixes: ed2bdf3 ("drm/xe/vm: Subclass userptr vmas")
Suggested-by: Matthew Brost <[email protected]>
Signed-off-by: Matthew Auld <[email protected]>
Cc: Thomas Hellström <[email protected]>
Cc: <[email protected]> # v6.8+
Reviewed-by: Matthew Brost <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Signed-off-by: Lucas De Marchi <[email protected]>
(cherry picked from commit 4e37e92)
Signed-off-by: Rodrigo Vivi <[email protected]>

Author: matt-auld

drivers/gpu/drm/xe/xe_vm.c

@@ -666,15 +666,16 @@ int xe_vm_userptr_pin(struct xe_vm *vm)
 
 	/* Collect invalidated userptrs */
 	spin_lock(&vm->userptr.invalidated_lock);
+	xe_assert(vm->xe, list_empty(&vm->userptr.repin_list));
 	list_for_each_entry_safe(uvma, next, &vm->userptr.invalidated,
 				 userptr.invalidate_link) {
 		list_del_init(&uvma->userptr.invalidate_link);
-		list_move_tail(&uvma->userptr.repin_link,
-			       &vm->userptr.repin_list);
+		list_add_tail(&uvma->userptr.repin_link,
+			      &vm->userptr.repin_list);
 	}
 	spin_unlock(&vm->userptr.invalidated_lock);
 
-	/* Pin and move to temporary list */
+	/* Pin and move to bind list */
 	list_for_each_entry_safe(uvma, next, &vm->userptr.repin_list,
 				 userptr.repin_link) {
 		err = xe_vma_userptr_pin_pages(uvma);
@@ -690,18 +691,30 @@ int xe_vm_userptr_pin(struct xe_vm *vm)
 			err = xe_vm_invalidate_vma(&uvma->vma);
 			xe_vm_unlock(vm);
 			if (err)
-				return err;
+				break;
 		} else {
-			if (err < 0)
-				return err;
+			if (err)
+				break;
 
 			list_del_init(&uvma->userptr.repin_link);
 			list_move_tail(&uvma->vma.combined_links.rebind,
 				       &vm->rebind_list);
 		}
 	}
 
-	return 0;
+	if (err) {
+		down_write(&vm->userptr.notifier_lock);
+		spin_lock(&vm->userptr.invalidated_lock);
+		list_for_each_entry_safe(uvma, next, &vm->userptr.repin_list,
+					 userptr.repin_link) {
+			list_del_init(&uvma->userptr.repin_link);
+			list_move_tail(&uvma->userptr.invalidate_link,
+				       &vm->userptr.invalidated);
+		}
+		spin_unlock(&vm->userptr.invalidated_lock);
+		up_write(&vm->userptr.notifier_lock);
+	}
+	return err;
 }
 
 /**
@@ -1066,6 +1079,7 @@ static void xe_vma_destroy(struct xe_vma *vma, struct dma_fence *fence)
 		xe_assert(vm->xe, vma->gpuva.flags & XE_VMA_DESTROYED);
 
 		spin_lock(&vm->userptr.invalidated_lock);
+		xe_assert(vm->xe, list_empty(&to_userptr_vma(vma)->userptr.repin_link));
 		list_del(&to_userptr_vma(vma)->userptr.invalidate_link);
 		spin_unlock(&vm->userptr.invalidated_lock);
 	} else if (!xe_vma_is_null(vma)) {