dma-direct: swiotlb: handle swiotlb alloc/free outside __dma_direct_alloc_pages

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Move swiotlb allocation out of __dma_direct_alloc_pages() and handle it in
dma_direct_alloc() / dma_direct_alloc_pages().

This is needed for follow-up changes that simplify the handling of
memory encryption/decryption based on the DMA attribute flags.

swiotlb backing pages are already mapped decrypted by
swiotlb_update_mem_attributes() and rmem_swiotlb_device_init(), so
dma-direct should not call dma_set_decrypted() on allocation nor
dma_set_encrypted() on free for swiotlb-backed memory.

Update alloc/free paths to detect swiotlb-backed pages and skip
encrypt/decrypt transitions for those paths. Keep the existing highmem
rejection in dma_direct_alloc_pages() for swiotlb allocations.

Only for "restricted-dma-pool", we currently set `for_alloc = true`, while
rmem_swiotlb_device_init() decrypts the whole pool up front. This pool is
typically used together with "shared-dma-pool", where the shared region is
accessed after remap/ioremap and the returned address is suitable for
decrypted memory access. So existing code paths remain valid.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Jiri Pirko <jiri@nvidia.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Link: https://lore.kernel.org/r/20260717180442.110954-8-aneesh.kumar@kernel.org
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

...

This commit is contained in:

Aneesh Kumar K.V (Arm) 2026-07-17 23:34:25 +05:30 • committed by Marek Szyprowski

parent f38ab0d7f5

commit a7139dbbb1

3 changed files with 65 additions and 18 deletions

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6

include/linux/swiotlb.h

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71

kernel/dma/direct.c

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6

kernel/dma/swiotlb.c

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