From 14cebf689a78e8a1c041138af221ef6eac6bc7da Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 8 Mar 2024 15:28:29 +0000 Subject: swiotlb: Reinstate page-alignment for mappings >= PAGE_SIZE 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 Signed-off-by: Will Deacon Reviewed-by: Robin Murphy Reviewed-by: Petr Tesarik Tested-by: Nicolin Chen Tested-by: Michael Kelley Signed-off-by: Christoph Hellwig --- kernel/dma/swiotlb.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) (limited to 'kernel') diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index f212943e51ca..86fe172b5958 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -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; -- cgit v1.2.3