[PATCH v3 03/10] mm/gup: fail get_user_pages for LONGTERM dev coherent type

Alex Sierra
2022-01-10T22:32:30Z

Avoid long term pinning for Coherent device type pages. This could
interfere with their own device memory manager. For now, we are just
returning error for PIN_LONGTERM Coherent device type pages. Eventually,
these type of pages will get migrated to system memory, once the device
migration pages support is added.

Signed-off-by: Alex Sierra <alex.sierra@amd.com>
---
mm/gup.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/mm/gup.c b/mm/gup.c
index 886d6148d3d0..9c8a075d862d 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1720,6 +1720,12 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
* If we get a movable page, since we are going to be pinning
* these entries, try to move them out if possible.
*/
+ if (is_device_page(head)) {
+ WARN_ON_ONCE(is_device_private_page(head));
+ ret = -EFAULT;
+ goto unpin_pages;
+ }
+
if (!is_pinnable_page(head)) {
if (PageHuge(head)) {
if (!isolate_huge_page(head, &movable_page_list))
@@ -1750,6 +1756,7 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
if (list_empty(&movable_page_list) && !isolation_error_count)
return nr_pages;

+unpin_pages:
if (gup_flags & FOLL_PIN) {
unpin_user_pages(pages, nr_pages);
} else {
--
2.32.0