kernel/linux.git/include/linux/dma-buf.h, branch v6.19.11

dma-buf: provide phys_vec to scatter-gather mapping routine

2025-11-20T19:02:19+00:00

Add dma_buf_phys_vec_to_sgt() and dma_buf_free_sgt() helpers to convert an array of MMIO physical address ranges into scatter-gather tables with proper DMA mapping. These common functions are a starting point and support any PCI drivers creating mappings from their BAR's MMIO addresses. VFIO is one case, as shortly will be RDMA. We can review existing DRM drivers to refactor them separately. We hope this will evolve into routines to help common DRM that include mixed CPU and MMIO mappings. Compared to the dma_map_resource() abuse this implementation handles the complicated PCI P2P scenarios properly, especially when an IOMMU is enabled: - Direct bus address mapping without IOVA allocation for PCI_P2PDMA_MAP_BUS_ADDR, using pci_p2pdma_bus_addr_map(). This happens if the IOMMU is enabled but the PCIe switch ACS flags allow transactions to avoid the host bridge. Further, this handles the slightly obscure, case of MMIO with a phys_addr_t that is different from the physical BAR programming (bus offset). The phys_addr_t is converted to a dma_addr_t and accommodates this effect. This enables certain real systems to work, especially on ARM platforms. - Mapping through host bridge with IOVA allocation and DMA_ATTR_MMIO attribute for MMIO memory regions (PCI_P2PDMA_MAP_THRU_HOST_BRIDGE). This happens when the IOMMU is enabled and the ACS flags are forcing all traffic to the IOMMU - ie for virtualization systems. - Cases where P2P is not supported through the host bridge/CPU. The P2P subsystem is the proper place to detect this and block it. Helper functions fill_sg_entry() and calc_sg_nents() handle the scatter-gather table construction, splitting large regions into UINT_MAX-sized chunks to fit within sg->length field limits. Since the physical address based DMA API forbids use of the CPU list of the scatterlist this will produce a mangled scatterlist that has a fully zero-length and NULL'd CPU list. The list is 0 length, all the struct page pointers are NULL and zero sized. This is stronger and more robust than the existing mangle_sg_table() technique. It is a future project to migrate DMABUF as a subsystem away from using scatterlist for this data structure. Reviewed-by: Kevin Tian Reviewed-by: Nicolin Chen Reviewed-by: Jason Gunthorpe Tested-by: Alex Mastro Tested-by: Nicolin Chen Signed-off-by: Leon Romanovsky Acked-by: Christian König Acked-by: Ankit Agrawal Link: https://lore.kernel.org/r/20251120-dmabuf-vfio-v9-6-d7f71607f371@nvidia.com Signed-off-by: Alex Williamson

Merge tag 'bpf-next-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2025-05-28T22:52:42+00:00

Pull bpf updates from Alexei Starovoitov: - Fix and improve BTF deduplication of identical BTF types (Alan Maguire and Andrii Nakryiko) - Support up to 12 arguments in BPF trampoline on arm64 (Xu Kuohai and Alexis Lothoré) - Support load-acquire and store-release instructions in BPF JIT on riscv64 (Andrea Parri) - Fix uninitialized values in BPF_{CORE,PROBE}_READ macros (Anton Protopopov) - Streamline allowed helpers across program types (Feng Yang) - Support atomic update for hashtab of BPF maps (Hou Tao) - Implement json output for BPF helpers (Ihor Solodrai) - Several s390 JIT fixes (Ilya Leoshkevich) - Various sockmap fixes (Jiayuan Chen) - Support mmap of vmlinux BTF data (Lorenz Bauer) - Support BPF rbtree traversal and list peeking (Martin KaFai Lau) - Tests for sockmap/sockhash redirection (Michal Luczaj) - Introduce kfuncs for memory reads into dynptrs (Mykyta Yatsenko) - Add support for dma-buf iterators in BPF (T.J. Mercier) - The verifier support for __bpf_trap() (Yonghong Song) * tag 'bpf-next-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (135 commits) bpf, arm64: Remove unused-but-set function and variable. selftests/bpf: Add tests with stack ptr register in conditional jmp bpf: Do not include stack ptr register in precision backtracking bookkeeping selftests/bpf: enable many-args tests for arm64 bpf, arm64: Support up to 12 function arguments bpf: Check rcu_read_lock_trace_held() in bpf_map_lookup_percpu_elem() bpf: Avoid __bpf_prog_ret0_warn when jit fails bpftool: Add support for custom BTF path in prog load/loadall selftests/bpf: Add unit tests with __bpf_trap() kfunc bpf: Warn with __bpf_trap() kfunc maybe due to uninitialized variable bpf: Remove special_kfunc_set from verifier selftests/bpf: Add test for open coded dmabuf_iter selftests/bpf: Add test for dmabuf_iter bpf: Add open coded dmabuf iterator bpf: Add dmabuf iterator dma-buf: Rename debugfs symbols bpf: Fix error return value in bpf_copy_from_user_dynptr libbpf: Use mmap to parse vmlinux BTF from sysfs selftests: bpf: Add a test for mmapable vmlinux BTF btf: Allow mmap of vmlinux btf ...

bpf: Add dmabuf iterator

2025-05-27T16:51:25+00:00

The dmabuf iterator traverses the list of all DMA buffers. DMA buffers are refcounted through their associated struct file. A reference is taken on each buffer as the list is iterated to ensure each buffer persists for the duration of the bpf program execution without holding the list mutex. Signed-off-by: T.J. Mercier Reviewed-by: Christian König Acked-by: Song Liu Link: https://lore.kernel.org/r/20250522230429.941193-3-tjmercier@google.com Signed-off-by: Alexei Starovoitov

dma-buf: Rename debugfs symbols

2025-05-27T16:51:25+00:00

Rename the debugfs list and mutex so it's clear they are now usable without the need for CONFIG_DEBUG_FS. The list will always be populated to support the creation of a BPF iterator for dmabufs. Signed-off-by: T.J. Mercier Reviewed-by: Christian König Acked-by: Song Liu Link: https://lore.kernel.org/r/20250522230429.941193-2-tjmercier@google.com Signed-off-by: Alexei Starovoitov

dma-buf: drop caching of sg_tables

2025-03-06T14:21:36+00:00

That was purely for the transition from static to dynamic dma-buf handling and can be removed again now. Signed-off-by: Christian König Reviewed-by: Simona Vetter Reviewed-by: Dmitry Osipenko Link: https://patchwork.freedesktop.org/patch/msgid/20250211163109.12200-5-christian.koenig@amd.com

dma-buf: dma-buf: stop mapping sg_tables on attach v2

2025-03-06T14:21:29+00:00

As a workaround to smoothly transit from static to dynamic DMA-buf handling we cached the sg_table on attach if dynamic handling mismatched between exporter and importer. Since Dmitry and Thomas cleaned that up and also documented the lock handling we can drop this workaround now. V2: implement Sima's comments Signed-off-by: Christian König Reviewed-by: Simona Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20250211163109.12200-4-christian.koenig@amd.com

dma-buf: Do not build debugfs related code when !CONFIG_DEBUG_FS

2024-04-15T16:56:32+00:00

There is no point in compiling in the list and mutex operations which are only used from the dma-buf debugfs code, if debugfs is not compiled in. Put the code in questions behind some kconfig guards and so save some text and maybe even a pointer per object at runtime when not enabled. Signed-off-by: Tvrtko Ursulin Cc: Sumit Semwal Cc: Christian König Cc: linux-media@vger.kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linaro-mm-sig@lists.linaro.org Cc: linux-kernel@vger.kernel.org Cc: kernel-dev@igalia.com Reviewed-by: T.J. Mercier Reviewed-by: Christian König Signed-off-by: Maíra Canal Link: https://patchwork.freedesktop.org/patch/msgid/20240328145323.68872-1-tursulin@igalia.com

dma-buf: Correct the documentation of name and exp_name symbols

2023-11-30T13:24:54+00:00

Fix the documentation of struct dma_buf members name and exp_name as to how these members are to be used and accessed. Signed-off-by: Ramesh Errabolu Reviewed-by: Christian König Link: https://patchwork.freedesktop.org/patch/msgid/20231122160556.24948-1-Ramesh.Errabolu@amd.com Signed-off-by: Christian König

dma-buf: A collection of typo and documentation fixes

2022-11-24T09:39:08+00:00

I've been collecting these typo fixes for a while and it feels like time to send them in. Signed-off-by: T.J. Mercier Reviewed-by: Randy Dunlap Acked-by: Christian König Reviewed-by: Tommaso Merciai Link: https://patchwork.freedesktop.org/patch/msgid/20221123193519.3948105-1-tjmercier@google.com Signed-off-by: Christian König

dma-buf: Remove obsoleted internal lock

2022-10-17T22:21:55+00:00

The internal dma-buf lock isn't needed anymore because the updated locking specification claims that dma-buf reservation must be locked by importers, and thus, the internal data is already protected by the reservation lock. Remove the obsoleted internal lock. Acked-by: Sumit Semwal Acked-by: Christian König Reviewed-by: Christian König Signed-off-by: Dmitry Osipenko Link: https://patchwork.freedesktop.org/patch/msgid/20221017172229.42269-22-dmitry.osipenko@collabora.com