From: Alex Williamson <alex.williamson@redhat.com>
Date: Wed, 10 Aug 2022 10:53:59 -0600
Subject: mm: re-allow pinning of zero pfns (again)
Git-commit: fcab34b433e2c13e333b2f53c4a8409eadc432c7
Patch-mainline: v6.0-rc3
References: jsc#PED-1294
The below referenced commit makes the same error as 1c563432588d ("mm: fix
is_pinnable_page against a cma page"), re-interpreting the logic to
exclude pinning of the zero page, which breaks device assignment with
vfio.
To avoid further subtle mistakes, split the logic into discrete tests.
[akpm@linux-foundation.org: simplify comment, per John]
Link: https://lkml.kernel.org/r/166015037385.760108.16881097713975517242.stgit@omen
Link: https://lore.kernel.org/all/165490039431.944052.12458624139225785964.stgit@omen
Fixes: f25cbb7a95a2 ("mm: add zone device coherent type memory support")
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Suggested-by: Felix Kuehling <felix.kuehling@amd.com>
Tested-by: Slawomir Laba <slawomirx.laba@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Alex Sierra <alex.sierra@amd.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Alistair Popple <apopple@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
include/linux/mm.h | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1466,9 +1466,16 @@ static inline bool is_longterm_pinnable_
if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE)
return false;
#endif
- return !(is_device_coherent_page(page) ||
- is_zone_movable_page(page) ||
- is_zero_pfn(page_to_pfn(page)));
+ /* The zero page may always be pinned */
+ if (is_zero_pfn(page_to_pfn(page)))
+ return true;
+
+ /* Coherent device memory must always allow eviction. */
+ if (is_device_coherent_page(page))
+ return false;
+
+ /* Otherwise, non-movable zone pages can be pinned. */
+ return !is_zone_movable_page(page);
}
#else
static inline bool is_longterm_pinnable_page(struct page *page)