[PATCH for v4.9 LTS 76/86] swiotlb: ensure that page-sized mappings are page-aligned

[Levin, Alexander (Sasha Levin)]

From: Nikita Yushchenko <nikita.yoush@xxxxxxxxxxxxxxxxxx>

[ Upstream commit 602d9858f07c72eab64f5f00e2fae55f9902cfbe ]

Some drivers do depend on page mappings to be page aligned.

Swiotlb already enforces such alignment for mappings greater than page,
extend that to page-sized mappings as well.

Without this fix, nvme hits BUG() in nvme_setup_prps(), because that routine
assumes page-aligned mappings.

Signed-off-by: Nikita Yushchenko <nikita.yoush@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 lib/swiotlb.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index ad1d2962d129..b7812df04437 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -456,11 +456,11 @@ phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
 		    : 1UL << (BITS_PER_LONG - IO_TLB_SHIFT);
 
 	/*
-	 * For mappings greater than a page, we limit the stride (and
-	 * hence alignment) to a page size.
+	 * For mappings greater than or equal to a page, we limit the stride
+	 * (and hence alignment) to a page size.
 	 */
 	nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
-	if (size > PAGE_SIZE)
+	if (size >= PAGE_SIZE)
 		stride = (1 << (PAGE_SHIFT - IO_TLB_SHIFT));
 	else
 		stride = 1;
-- 
2.11.0