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iommu/dma: Document min_align_mask assumption

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iommu-dma does not explicitly reference min_align_mask since we already
assume that will be less than or equal to any typical IOVA granule.
We wouldn't realistically expect to see the case where it is larger, and
that would be non-trivial to support, however for the sake of reasoning
(particularly around the interaction with SWIOTLB), let's clearly
enforce the assumption.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/dbb4d2d8e5d1691ac9a6c67e9758904e6c447ba5.1709553942.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
This commit is contained in:
Robin Murphy 2024-03-04 12:05:42 +00:00 committed by Joerg Roedel
parent b5a1f7513a
commit e2addba493
1 changed files with 5 additions and 0 deletions
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5
drivers/iommu/dma-iommu.c
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@ -859,6 +859,11 @@ static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys,
iommu_deferred_attach(dev, domain))
return DMA_MAPPING_ERROR;
/* If anyone ever wants this we'd need support in the IOVA allocator */
if (dev_WARN_ONCE(dev, dma_get_min_align_mask(dev) > iova_mask(iovad),
"Unsupported alignment constraint\n"))
return DMA_MAPPING_ERROR;
size = iova_align(iovad, size + iova_off);
iova = iommu_dma_alloc_iova(domain, size, dma_mask, dev);