6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Will Deacon <will@xxxxxxxxxx>
commit 14cebf689a78e8a1c041138af221ef6eac6bc7da upstream.
For swiotlb allocations >= PAGE_SIZE, the slab search historically
adjusted the stride to avoid checking unaligned slots. This had the
side-effect of aligning large mapping requests to PAGE_SIZE, but that
was broken by 0eee5ae10256 ("swiotlb: fix slot alignment checks").
Since this alignment could be relied upon drivers, reinstate PAGE_SIZE
alignment for swiotlb mappings >= PAGE_SIZE.
Cc: stable@xxxxxxxxxxxxxxx # v6.6+
Reported-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
Reviewed-by: Petr Tesarik <petr.tesarik1@xxxxxxxxxxxxxxxxxxx>
Tested-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
Tested-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Fabio Estevam <festevam@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/dma/swiotlb.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -993,6 +993,17 @@ static int swiotlb_area_find_slots(struc
BUG_ON(area_index >= pool->nareas);
/*
+ * Historically, swiotlb allocations >= PAGE_SIZE were guaranteed to be
+ * page-aligned in the absence of any other alignment requirements.
+ * 'alloc_align_mask' was later introduced to specify the alignment
+ * explicitly, however this is passed as zero for streaming mappings
+ * and so we preserve the old behaviour there in case any drivers are
+ * relying on it.
+ */
+ if (!alloc_align_mask && !iotlb_align_mask && alloc_size >= PAGE_SIZE)
+ alloc_align_mask = PAGE_SIZE - 1;
+
+ /*
* Ensure that the allocation is at least slot-aligned and update
* 'iotlb_align_mask' to ignore bits that will be preserved when
* offsetting into the allocation.
@@ -1006,13 +1017,6 @@ static int swiotlb_area_find_slots(struc
*/
stride = get_max_slots(max(alloc_align_mask, iotlb_align_mask));
- /*
- * For allocations of PAGE_SIZE or larger only look for page aligned
- * allocations.
- */
- if (alloc_size >= PAGE_SIZE)
- stride = umax(stride, PAGE_SHIFT - IO_TLB_SHIFT + 1);
-
spin_lock_irqsave(&area->lock, flags);
if (unlikely(nslots > pool->area_nslabs - area->used))
goto not_found;
