[PATCH v2 03/11] mm/gup: migrate PIN_LONGTERM dev coherent pages to system

Alex Sierra
2021-12-06T18:53:20Z

Avoid long term pinning for Coherent device type pages. This could
interfere with their own device memory manager.
If caller tries to get user device coherent pages with PIN_LONGTERM flag
set, those pages will be migrated back to system memory.

Signed-off-by: Alex Sierra <alex.sierra@amd.com>
---
mm/gup.c | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 886d6148d3d0..1572eacf07f4 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1689,17 +1689,37 @@ struct page *get_dump_page(unsigned long addr)
#endif /* CONFIG_ELF_CORE */

#ifdef CONFIG_MIGRATION
+static int migrate_device_page(unsigned long address,
+ struct page *page)
+{
+ struct vm_area_struct *vma = find_vma(current->mm, address);
+ struct vm_fault vmf = {
+ .vma = vma,
+ .address = address & PAGE_MASK,
+ .flags = FAULT_FLAG_USER,
+ .pgoff = linear_page_index(vma, address),
+ .gfp_mask = GFP_KERNEL,
+ .page = page,
+ };
+ if (page->pgmap && page->pgmap->ops->migrate_to_ram)
+ return page->pgmap->ops->migrate_to_ram(&vmf);
+
+ return -EBUSY;
+}
+
/*
* Check whether all pages are pinnable, if so return number of pages. If some
* pages are not pinnable, migrate them, and unpin all pages. Return zero if
* pages were migrated, or if some pages were not successfully isolated.
* Return negative error if migration fails.
*/
-static long check_and_migrate_movable_pages(unsigned long nr_pages,
+static long check_and_migrate_movable_pages(unsigned long start,
+ unsigned long nr_pages,
struct page **pages,
unsigned int gup_flags)
{
unsigned long i;
+ unsigned long page_index;
unsigned long isolation_error_count = 0;
bool drain_allow = true;
LIST_HEAD(movable_page_list);
@@ -1720,6 +1740,10 @@ 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)) {
+ page_index = i;
+ goto unpin_pages;
+ }
if (!is_pinnable_page(head)) {
if (PageHuge(head)) {
if (!isolate_huge_page(head, &movable_page_list))
@@ -1750,12 +1774,16 @@ 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 {
for (i = 0; i < nr_pages; i++)
put_page(pages[i]);
}
+ if (is_device_page(head))
+ return migrate_device_page(start + page_index * PAGE_SIZE, head);
+
if (!list_empty(&movable_page_list)) {
ret = migrate_pages(&movable_page_list, alloc_migration_target,
NULL, (unsigned long)&mtc, MIGRATE_SYNC,
@@ -1798,7 +1826,7 @@ static long __gup_longterm_locked(struct mm_struct *mm,
NULL, gup_flags);
if (rc <= 0)
break;
- rc = check_and_migrate_movable_pages(rc, pages, gup_flags);
+ rc = check_and_migrate_movable_pages(start, rc, pages, gup_flags);
} while (!rc);
memalloc_pin_restore(flags);

--
2.32.0