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swiotlb: Reinstate page-alignment for mappings >= PAGE_SIZE

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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.

Reported-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Petr Tesarik <petr.tesarik1@huawei-partners.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Will Deacon 2024-03-08 15:28:29 +00:00 committed by Christoph Hellwig
parent afc5aa46ed
commit 14cebf689a
1 changed files with 11 additions and 7 deletions
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18
kernel/dma/swiotlb.c
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@ -1014,6 +1014,17 @@ static int swiotlb_search_pool_area(struct device *dev, struct io_tlb_pool *pool
BUG_ON(!nslots);
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
@ -1028,13 +1039,6 @@ static int swiotlb_search_pool_area(struct device *dev, struct io_tlb_pool *pool
*/
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;