From f8f86b5eecad321f2d0c687133e83ff6d2dcb842 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Fri, 8 Mar 2024 15:28:27 +0000 Subject: [PATCH] swiotlb: Fix alignment checks when both allocation and DMA masks are present [ Upstream commit 51b30ecb73b481d5fac6ccf2ecb4a309c9ee3310 ] Nicolin reports that swiotlb buffer allocations fail for an NVME device behind an IOMMU using 64KiB pages. This is because we end up with a minimum allocation alignment of 64KiB (for the IOMMU to map the buffer safely) but a minimum DMA alignment mask corresponding to a 4KiB NVME page (i.e. preserving the 4KiB page offset from the original allocation). If the original address is not 4KiB-aligned, the allocation will fail because swiotlb_search_pool_area() erroneously compares these unmasked bits with the 64KiB-aligned candidate allocation. Tweak swiotlb_search_pool_area() so that the DMA alignment mask is reduced based on the required alignment of the allocation. Fixes: 82612d66d51d ("iommu: Allow the dma-iommu api to use bounce buffers") Link: https://lore.kernel.org/r/cover.1707851466.git.nicolinc@nvidia.com Reported-by: Nicolin Chen Signed-off-by: Will Deacon Reviewed-by: Michael Kelley Tested-by: Nicolin Chen Tested-by: Michael Kelley Signed-off-by: Christoph Hellwig Signed-off-by: Sasha Levin --- kernel/dma/swiotlb.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index a619e22fecbf..877c4b8fad19 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -981,8 +981,7 @@ static int swiotlb_search_pool_area(struct device *dev, struct io_tlb_pool *pool dma_addr_t tbl_dma_addr = phys_to_dma_unencrypted(dev, pool->start) & boundary_mask; unsigned long max_slots = get_max_slots(boundary_mask); - unsigned int iotlb_align_mask = - dma_get_min_align_mask(dev) & ~(IO_TLB_SIZE - 1); + unsigned int iotlb_align_mask = dma_get_min_align_mask(dev); unsigned int nslots = nr_slots(alloc_size), stride; unsigned int offset = swiotlb_align_offset(dev, orig_addr); unsigned int index, slots_checked, count = 0, i; @@ -993,6 +992,14 @@ static int swiotlb_search_pool_area(struct device *dev, struct io_tlb_pool *pool BUG_ON(!nslots); BUG_ON(area_index >= pool->nareas); + /* + * 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. + */ + alloc_align_mask |= (IO_TLB_SIZE - 1); + iotlb_align_mask &= ~alloc_align_mask; + /* * For mappings with an alignment requirement don't bother looping to * unaligned slots once we found an aligned one.