kernel/linux.git/include/linux/dma-mapping.h, branch v7.0-rc7

dma-mapping: add missing `inline` for `dma_free_attrs`

2026-03-25T07:01:21+00:00

Under an UML build for an upcoming series [1], I got `-Wstatic-in-inline` for `dma_free_attrs`: BINDGEN rust/bindings/bindings_generated.rs - due to target missing In file included from rust/helpers/helpers.c:59: rust/helpers/dma.c:17:2: warning: static function 'dma_free_attrs' is used in an inline function with external linkage [-Wstatic-in-inline] 17 | dma_free_attrs(dev, size, cpu_addr, dma_handle, attrs); | ^ rust/helpers/dma.c:12:1: note: use 'static' to give inline function 'rust_helper_dma_free_attrs' internal linkage 12 | __rust_helper void rust_helper_dma_free_attrs(struct device *dev, size_t size, | ^ | static The issue is that `dma_free_attrs` was not marked `inline` when it was introduced alongside the rest of the stubs. Thus mark it. Fixes: ed6ccf10f24b ("dma-mapping: properly stub out the DMA API for !CONFIG_HAS_DMA") Closes: https://lore.kernel.org/rust-for-linux/20260322194616.89847-1-ojeda@kernel.org/ [1] Signed-off-by: Miguel Ojeda Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20260325015548.70912-1-ojeda@kernel.org

dma-mapping: Introduce DMA require coherency attribute

2026-03-20T11:05:36+00:00

The mapping buffers which carry this attribute require DMA coherent system. This means that they can't take SWIOTLB path, can perform CPU cache overlap and doesn't perform cache flushing. Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20260316-dma-debug-overlap-v3-4-1dde90a7f08b@nvidia.com

dma-mapping: Clarify valid conditions for CPU cache line overlap

2026-03-20T10:33:24+00:00

Rename the DMA_ATTR_CPU_CACHE_CLEAN attribute to better reflect that it is debugging aid to inform DMA core code that CPU cache line overlaps are allowed, and refine the documentation describing its use. Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20260316-dma-debug-overlap-v3-3-1dde90a7f08b@nvidia.com

dma-mapping: add DMA_ATTR_CPU_CACHE_CLEAN

2026-01-01T00:30:02+00:00

When multiple small DMA_FROM_DEVICE or DMA_BIDIRECTIONAL buffers share a cacheline, and DMA_API_DEBUG is enabled, we get this warning: cacheline tracking EEXIST, overlapping mappings aren't supported. This is because when one of the mappings is removed, while another one is active, CPU might write into the buffer. Add an attribute for the driver to promise not to do this, making the overlapping safe, and suppressing the warning. Message-ID: <2d5d091f9d84b68ea96abd545b365dd1d00bbf48.1767601130.git.mst@redhat.com> Reviewed-by: Petr Tesarik Acked-by: Marek Szyprowski Signed-off-by: Michael S. Tsirkin

dma-mapping: add __dma_from_device_group_begin()/end()

2026-01-01T00:27:45+00:00

When a structure contains a buffer that DMA writes to alongside fields that the CPU writes to, cache line sharing between the DMA buffer and CPU-written fields can cause data corruption on non-cache-coherent platforms. Add __dma_from_device_group_begin()/end() annotations to ensure proper alignment to prevent this: struct my_device { spinlock_t lock1; __dma_from_device_group_begin(); char dma_buffer1[16]; char dma_buffer2[16]; __dma_from_device_group_end(); spinlock_t lock2; }; Message-ID: <19163086d5e4704c316f18f6da06bc1c72968904.1767601130.git.mst@redhat.com> Acked-by: Marek Szyprowski Reviewed-by: Petr Tesarik Signed-off-by: Michael S. Tsirkin

dma-mapping: Fix DMA_BIT_MASK() macro being broken

2025-12-08T08:40:57+00:00

After commit a50f7456f853 ("dma-mapping: Allow use of DMA_BIT_MASK(64) in global scope"), the DMA_BIT_MASK() macro is broken when passed non trivial statements for the value of 'n'. This is caused by the new version missing parenthesis around 'n' when evaluating 'n'. One example of this breakage is the IPU6 driver now crashing due to it getting DMA-addresses with address bit 32 set even though it has tried to set a 32 bit DMA mask. The IPU6 CSI2 engine has a DMA mask of either 31 or 32 bits depending on if it is in secure mode or not and it sets this masks like this: mmu_info->aperture_end = (dma_addr_t)DMA_BIT_MASK(isp->secure_mode ? IPU6_MMU_ADDR_BITS : IPU6_MMU_ADDR_BITS_NON_SECURE); So the 'n' argument here is "isp->secure_mode ? IPU6_MMU_ADDR_BITS : IPU6_MMU_ADDR_BITS_NON_SECURE" which gets expanded into: isp->secure_mode ? IPU6_MMU_ADDR_BITS : IPU6_MMU_ADDR_BITS_NON_SECURE - 1 With the -1 only being applied in the non secure case, causing the secure mode mask to be one 1 bit too large. Fixes: a50f7456f853 ("dma-mapping: Allow use of DMA_BIT_MASK(64) in global scope") Cc: Sakari Ailus Cc: James Clark Cc: Nathan Chancellor Cc: stable@vger.kernel.org Signed-off-by: Hans de Goede Reviewed-by: Nathan Chancellor Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20251207184756.97904-1-johannes.goede@oss.qualcomm.com

dma-mapping: Allow use of DMA_BIT_MASK(64) in global scope

2025-11-05T12:43:41+00:00

Clang doesn't like that (1ULL<<(64)) overflows when initializing a global scope variable, even if that part of the ternary isn't used when n = 64. The same initialization can be done without warnings in function scopes, and GCC doesn't mind either way. The build failure that highlighted this was already fixed in a different way [1], which also has detailed links to the Clang issues. However it's not going to be long before the same thing happens again, so it's better to fix the root cause. Fix it by using GENMASK_ULL() which does exactly the same thing, is much more readable anyway, and doesn't have a shift that overflows. [1]: https://lore.kernel.org/all/20250918-mmp-pdma-simplify-dma-addressing-v1-1-5c2be2b85696@riscstar.com/ Signed-off-by: James Clark Reviewed-by: Nathan Chancellor Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20251030-james-fix-dma_bit_mask-v1-1-ad1ce7cfab6e@linaro.org

dma-mapping: export new dma_*map_phys() interface

2025-09-11T22:18:21+00:00

Introduce new DMA mapping functions dma_map_phys() and dma_unmap_phys() that operate directly on physical addresses instead of page+offset parameters. This provides a more efficient interface for drivers that already have physical addresses available. The new functions are implemented as the primary mapping layer, with the existing dma_map_page_attrs()/dma_map_resource() and dma_unmap_page_attrs()/dma_unmap_resource() functions converted to simple wrappers around the phys-based implementations. In case dma_map_page_attrs(), the struct page is converted to physical address with help of page_to_phys() function and dma_map_resource() provides physical address as is together with addition of DMA_ATTR_MMIO attribute. The old page-based API is preserved in mapping.c to ensure that existing code won't be affected by changing EXPORT_SYMBOL to EXPORT_SYMBOL_GPL variant for dma_*map_phys(). Reviewed-by: Jason Gunthorpe Reviewed-by: Keith Busch Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/54cc52af91777906bbe4a386113437ba0bcfba9c.1757423202.git.leonro@nvidia.com

dma-mapping: introduce new DMA attribute to indicate MMIO memory

2025-09-11T22:08:07+00:00

This patch introduces the DMA_ATTR_MMIO attribute to mark DMA buffers that reside in memory-mapped I/O (MMIO) regions, such as device BARs exposed through the host bridge, which are accessible for peer-to-peer (P2P) DMA. This attribute is especially useful for exporting device memory to other devices for DMA without CPU involvement, and avoids unnecessary or potentially detrimental CPU cache maintenance calls. DMA_ATTR_MMIO is supposed to provide dma_map_resource() functionality without need to call to special function and perform branching when processing generic containers like bio_vec by the callers. Reviewed-by: Jason Gunthorpe Signed-off-by: Leon Romanovsky Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/6f058ec395c5348014860dbc2eed348c17975843.1757423202.git.leonro@nvidia.com

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

2025-05-28T03:09:06+00:00

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