linux/kernel/dma, branch v6.17

dma-debug: don't enforce dma mapping check on noncoherent allocations

2025-09-02T08:18:16Z

As discussed in [1], there is no need to enforce dma mapping check on noncoherent allocations, a simple test on the returned CPU address is good enough. Add a new pair of debug helpers and use them for noncoherent alloc/free to fix this issue. Fixes: efa70f2fdc84 ("dma-mapping: add a new dma_alloc_pages API") Link: https://lore.kernel.org/all/ff6c1fe6-820f-4e58-8395-df06aa91706c@oss.qualcomm.com # 1 Signed-off-by: Baochen Qiang Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20250828-dma-debug-fix-noncoherent-dma-check-v1-1-76e9be0dd7fc@oss.qualcomm.com

dma/pool: Ensure DMA_DIRECT_REMAP allocations are decrypted

2025-08-13T09:02:10Z

When CONFIG_DMA_DIRECT_REMAP is enabled, atomic pool pages are remapped via dma_common_contiguous_remap() using the supplied pgprot. Currently, the mapping uses pgprot_dmacoherent(PAGE_KERNEL), which leaves the memory encrypted on systems with memory encryption enabled (e.g., ARM CCA Realms). This can cause the DMA layer to fail or crash when accessing the memory, as the underlying physical pages are not configured as expected. Fix this by requesting a decrypted mapping in the vmap() call: pgprot_decrypted(pgprot_dmacoherent(PAGE_KERNEL)) This ensures that atomic pool memory is consistently mapped unencrypted. Cc: stable@vger.kernel.org Signed-off-by: Shanker Donthineni Reviewed-by: Catalin Marinas Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20250811181759.998805-1-sdonthineni@nvidia.com

of: reserved_mem: Restructure call site for dma_contiguous_early_fixup()

2025-08-11T11:05:38Z

Restructure the call site for dma_contiguous_early_fixup() to where the reserved_mem nodes are being parsed from the DT so that dma_mmu_remap[] is populated before dma_contiguous_remap() is called. Fixes: 8a6e02d0c00e ("of: reserved_mem: Restructure how the reserved memory regions are processed") Signed-off-by: Oreoluwa Babatunde Tested-by: William Zhang Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20250806172421.2748302-1-oreoluwa.babatunde@oss.qualcomm.com

dma-contiguous: hornor the cma address limit setup by user

2025-06-12T06:38:40Z

When porting a cma related usage from x86_64 server to arm64 server, the "cma=4G@4G" setup failed on arm64. The reason is arm64 and some other architectures have specific physical address limit for reserved cma area, like 4GB due to the device's need for 32 bit dma. Actually lots of platforms of those architectures don't have this device dma limit, but still have to obey it, and are not able to reserve a huge cma pool. This situation could be improved by honoring the user input cma physical address than the arch limit. As when users specify it, they already knows what the default is which probably can't suit them. Suggested-by: Robin Murphy Signed-off-by: Feng Tang Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20250612021417.44929-1-feng.tang@linux.alibaba.com

Merge tag 'dma-mapping-6.16-2025-05-26' of git://git.kernel.org/pub/scm/linux/kernel/git/mszyprowski/linux

2025-05-28T03:09:06Z

Pull dma-mapping updates from Marek Szyprowski: "New two step DMA mapping API, which is is a first step to a long path to provide alternatives to scatterlist and to remove hacks, abuses and design mistakes related to scatterlists. This new approach optimizes some calls to DMA-IOMMU layer and cache maintenance by batching them, reduces memory usage as it is no need to store mapped DMA addresses to unmap them, and reduces some function call overhead. It is a combination effort of many people, lead and developed by Christoph Hellwig and Leon Romanovsky" * tag 'dma-mapping-6.16-2025-05-26' of git://git.kernel.org/pub/scm/linux/kernel/git/mszyprowski/linux: docs: core-api: document the IOVA-based API dma-mapping: add a dma_need_unmap helper dma-mapping: Implement link/unlink ranges API iommu/dma: Factor out a iommu_dma_map_swiotlb helper dma-mapping: Provide an interface to allow allocate IOVA iommu: add kernel-doc for iommu_unmap_fast iommu: generalize the batched sync after map interface dma-mapping: move the PCI P2PDMA mapping helpers to pci-p2pdma.h PCI/P2PDMA: Refactor the p2pdma mapping helpers

dma-mapping: add a dma_need_unmap helper

2025-05-06T06:36:53Z

Add helper that allows a driver to skip calling dma_unmap_* if the DMA layer can guarantee that they are no-nops. Signed-off-by: Christoph Hellwig Tested-by: Jens Axboe Reviewed-by: Luis Chamberlain Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski

dma-mapping: move the PCI P2PDMA mapping helpers to pci-p2pdma.h

2025-05-06T06:36:53Z

To support the upcoming non-scatterlist mapping helpers, we need to go back to have them called outside of the DMA API. Thus move them out of dma-map-ops.h, which is only for DMA API implementations to pci-p2pdma.h, which is for driver use. Note that the core helper is still not exported as the mapping is expected to be done only by very highlevel subsystem code at least for now. Signed-off-by: Christoph Hellwig Reviewed-by: Logan Gunthorpe Acked-by: Bjorn Helgaas Tested-by: Jens Axboe Reviewed-by: Luis Chamberlain Reviewed-by: Lu Baolu Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski

PCI/P2PDMA: Refactor the p2pdma mapping helpers

2025-05-06T06:36:53Z

The current scheme with a single helper to determine the P2P status and map a scatterlist segment force users to always use the map_sg helper to DMA map, which we're trying to get away from because they are very cache inefficient. Refactor the code so that there is a single helper that checks the P2P state for a page, including the result that it is not a P2P page to simplify the callers, and a second one to perform the address translation for a bus mapped P2P transfer that does not depend on the scatterlist structure. Signed-off-by: Christoph Hellwig Reviewed-by: Logan Gunthorpe Acked-by: Bjorn Helgaas Tested-by: Jens Axboe Reviewed-by: Luis Chamberlain Reviewed-by: Lu Baolu Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski

dma-coherent: Warn if OF reserved memory is beyond current coherent DMA mask

2025-04-22T15:44:09Z

When a reserved memory region described in the device tree is attached to a device, it is expected that the device's limitations are correctly included in that description. However, if the device driver failed to implement DMA address masking or addressing beyond the default 32 bits (on arm64), then bad things could happen because the DMA address was truncated, such as playing back audio with no actual audio coming out, or DMA overwriting random blocks of kernel memory. Check against the coherent DMA mask when the memory regions are attached to the device. Give a warning when the memory region can not be covered by the mask. A warning instead of a hard error was chosen, because it is possible that existing drivers could be working fine even if they forgot to extend the coherent DMA mask. Signed-off-by: Chen-Yu Tsai Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20250421083930.374173-1-wenst@chromium.org

dma-mapping: Fix warning reported for missing prototype

2025-04-22T13:06:33Z

lkp reported a warning about missing prototype for a recent patch. The kernel-doc style comments are out of sync, move them to the right function. Cc: Marek Szyprowski Cc: Christoph Hellwig Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202504190615.g9fANxHw-lkp@intel.com/ Signed-off-by: Balbir Singh [mszyprow: reformatted subject] Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20250422114034.3535515-1-balbirs@nvidia.com