[PATCH] drm/xe/vm: don't ignore error when in_kthread

[Matthew Auld]

If GUP fails and we are in_kthread, we can have pinned = 0 and ret = 0.
If that happens we call sg_alloc_append_table_from_pages() with n_pages
= 0, which is not well behaved and can trigger:

kernel BUG at include/linux/scatterlist.h:115!

depending on if the pages array happens to be zeroed or not. Even if we
don't hit that it crashes later when trying to dma_map the returned
table.

Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
Cc: Matthew Brost <matthew.brost at intel.com>
---
 drivers/gpu/drm/xe/xe_vm.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 9c1c68a2fff7..63aeb3aead04 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -114,11 +114,8 @@ int xe_vma_userptr_pin_pages(struct xe_userptr_vma *uvma)
 					  num_pages - pinned,
 					  read_only ? 0 : FOLL_WRITE,
 					  &pages[pinned]);
-		if (ret < 0) {
-			if (in_kthread)
-				ret = 0;
+		if (ret < 0)
 			break;
-		}
 
 		pinned += ret;
 		ret = 0;
-- 
2.43.0