Messages in this thread | | | Date | Thu, 29 Feb 2024 16:47:56 +0100 | From | Christoph Hellwig <> | Subject | Re: [PATCH v5 6/6] swiotlb: Remove pointless stride adjustment for allocations >= PAGE_SIZE |
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On Thu, Feb 29, 2024 at 03:44:11PM +0000, Michael Kelley wrote: > Any thoughts on how that historical behavior should apply if > the DMA min_align_mask is non-zero, or the alloc_align_mask > parameter to swiotbl_tbl_map_single() is non-zero? As currently > used, alloc_align_mask is page aligned if the IOMMU granule is > >= PAGE_SIZE. But a non-zero min_align_mask could mandate > returning a buffer that is not page aligned. Perhaps do the > historical behavior only if alloc_align_mask and min_align_mask > are both zero?
I think the driver setting min_align_mask is a clear indicator that the driver requested a specific alignment and the defaults don't apply. For swiotbl_tbl_map_single as used by dma-iommu I'd have to tak a closer look at how it is used.
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