kernel/linux.git/drivers/dma-buf/Makefile, 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

dma-buf: cleanup dma_fence_unwrap implementation

2022-05-30T12:16:32+00:00

Move the code from the inline functions into exported functions. Signed-off-by: Christian König Acked-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20220518135844.3338-3-christian.koenig@amd.com

dma-buf: add dma_fence_unwrap v2

2022-03-25T13:18:28+00:00

Add a general purpose helper to deep dive into dma_fence_chain/dma_fence_array structures and iterate over all the fences in them. This is useful when we need to flatten out all fences in those structures. v2: some selftests cleanup, improved function naming and documentation Signed-off-by: Christian König Reviewed-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20220311110244.1245-1-christian.koenig@amd.com

dma-buf: add dma_resv selftest v4

2021-10-22T12:19:51+00:00

Just exercising a very minor subset of the functionality, but already proven useful. v2: add missing locking v3: some more cleanup and consolidation, add unlocked test as well v4: add a dma_resv_get_fences selftest Signed-off-by: Christian König Reviewed-by: Tvrtko Ursulin (v3) Reviewed-by: Daniel Vetter (v3) Link: https://patchwork.freedesktop.org/patch/msgid/20211005113742.1101-4-christian.koenig@amd.com

dma-buf: nuke seqno-fence

2021-08-16T12:07:17+00:00

Entirely unused. Signed-off-by: Christian König Acked-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210729070330.41443-1-christian.koenig@amd.com

dmabuf: Add the capability to expose DMA-BUF stats in sysfs

2021-06-15T09:50:24+00:00

Overview ======== The patch adds DMA-BUF statistics to /sys/kernel/dmabuf/buffers. It allows statistics to be enabled for each DMA-BUF in sysfs by enabling the config CONFIG_DMABUF_SYSFS_STATS. The following stats will be exposed by the interface: /sys/kernel/dmabuf/buffers//exporter_name /sys/kernel/dmabuf/buffers//size /sys/kernel/dmabuf/buffers//attachments//device /sys/kernel/dmabuf/buffers//attachments//map_counter The inode_number is unique for each DMA-BUF and was added earlier [1] in order to allow userspace to track DMA-BUF usage across different processes. Use Cases ========= The interface provides a way to gather DMA-BUF per-buffer statistics from production devices. These statistics will be used to derive DMA-BUF per-exporter stats and per-device usage stats for Android Bug reports. The corresponding userspace changes can be found at [2]. Telemetry tools will also capture this information(along with other memory metrics) periodically as well as on important events like a foreground app kill (which might have been triggered by Low Memory Killer). It will also contribute to provide a snapshot of the system memory usage on other events such as OOM kills and Application Not Responding events. Background ========== Currently, there are two existing interfaces that provide information about DMA-BUFs. 1) /sys/kernel/debug/dma_buf/bufinfo debugfs is however unsuitable to be mounted in production systems and cannot be considered as an alternative to the sysfs interface being proposed. 2) proc//fdinfo/ The proc//fdinfo/ files expose information about DMA-BUF fds. However, the existing procfs interfaces can only provide information about the buffers for which processes hold fds or have the buffers mmapped into their address space. Since the procfs interfaces alone cannot provide a full picture of all DMA-BUFs in the system, there is the need for an alternate interface to provide this information on production systems. The patch contains the following major improvements over v1: 1) Each attachment is represented by its own directory to allow creating a symlink to the importing device and to also provide room for future expansion. 2) The number of distinct mappings of each attachment is exposed in a separate file. 3) The per-buffer statistics are now in /sys/kernel/dmabuf/buffers inorder to make the interface expandable in future. All of the improvements above are based on suggestions/feedback from Daniel Vetter and Christian König. A shell script that can be run on a classic Linux environment to read out the DMA-BUF statistics can be found at [3](suggested by John Stultz). [1]: https://lore.kernel.org/patchwork/patch/1088791/ [2]: https://android-review.googlesource.com/q/topic:%22dmabuf-sysfs%22+(status:open%20OR%20status:merged) [3]: https://android-review.googlesource.com/c/platform/system/memory/libmeminfo/+/1549734 Reviewed-by: Greg Kroah-Hartman Signed-off-by: Hridya Valsaraju Reported-by: kernel test robot Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20210603214758.2955251-1-hridya@google.com

dma-buf: Exercise dma-fence-chain under selftests

2020-04-09T18:58:55+00:00

A few very simple testcases to exercise the dma-fence-chain API. Signed-off-by: Chris Wilson Reviewed-by: Venkata Sandeep Dhanalakota Link: https://patchwork.freedesktop.org/patch/msgid/20200409110101.18400-3-chris@chris-wilson.co.uk

dma-buf: heaps: Add heap helpers

2019-12-11T05:43:35+00:00

Add generic helper dmabuf ops for dma heaps, so we can reduce the amount of duplicative code for the exported dmabufs. This code is an evolution of the Android ION implementation, so thanks to its original authors and maintainters: Rebecca Schultz Zavin, Colin Cross, Laura Abbott, and others! Cc: Laura Abbott Cc: Benjamin Gaignard Cc: Sumit Semwal Cc: Liam Mark Cc: Pratik Patel Cc: Brian Starkey Cc: Vincent Donnefort Cc: Sudipto Paul Cc: Andrew F. Davis Cc: Christoph Hellwig Cc: Chenbo Feng Cc: Alistair Strachan Cc: Hridya Valsaraju Cc: Sandeep Patil Cc: Hillf Danton Cc: Dave Airlie Cc: dri-devel@lists.freedesktop.org Reviewed-by: Benjamin Gaignard Reviewed-by: Brian Starkey Acked-by: Sandeep Patil Acked-by: Laura Abbott Tested-by: Ayan Kumar Halder Signed-off-by: John Stultz Signed-off-by: Sumit Semwal Link: https://patchwork.freedesktop.org/patch/msgid/20191203172641.66642-3-john.stultz@linaro.org

dma-buf: Add dma-buf heaps framework

2019-12-11T05:43:33+00:00

This framework allows a unified userspace interface for dma-buf exporters, allowing userland to allocate specific types of memory for use in dma-buf sharing. Each heap is given its own device node, which a user can allocate a dma-buf fd from using the DMA_HEAP_IOC_ALLOC. This code is an evoluiton of the Android ION implementation, and a big thanks is due to its authors/maintainers over time for their effort: Rebecca Schultz Zavin, Colin Cross, Benjamin Gaignard, Laura Abbott, and many other contributors! Cc: Laura Abbott Cc: Benjamin Gaignard Cc: Sumit Semwal Cc: Liam Mark Cc: Pratik Patel Cc: Brian Starkey Cc: Vincent Donnefort Cc: Sudipto Paul Cc: Andrew F. Davis Cc: Christoph Hellwig Cc: Chenbo Feng Cc: Alistair Strachan Cc: Hridya Valsaraju Cc: Sandeep Patil Cc: Hillf Danton Cc: Dave Airlie Cc: dri-devel@lists.freedesktop.org Reviewed-by: Brian Starkey Acked-by: Sandeep Patil Signed-off-by: Andrew F. Davis Signed-off-by: John Stultz Signed-off-by: Sumit Semwal Link: https://patchwork.freedesktop.org/patch/msgid/20191203172641.66642-2-john.stultz@linaro.org

Revert "dma-buf: Add dma-buf heaps framework"

2019-10-30T20:41:49+00:00

This reverts commit a69b0e855d3fd278ff6f09a23e1edf929538e304. This patchset doesn't meet the UAPI requirements set out in [1] for the DRM subsystem. Once the userspace component is reviewed and ready for merge we can try again. [1]- https://01.org/linuxgraphics/gfx-docs/drm/gpu/drm-uapi.html#open-source-userspace-requirements Fixes: a69b0e855d3f ("dma-buf: Add dma-buf heaps framework") Cc: Laura Abbott Cc: Benjamin Gaignard Cc: Sumit Semwal Cc: Liam Mark Cc: Pratik Patel Cc: Brian Starkey Cc: Vincent Donnefort Cc: Sudipto Paul Cc: Andrew F. Davis Cc: Christoph Hellwig Cc: Chenbo Feng Cc: Alistair Strachan Cc: Hridya Valsaraju Cc: Hillf Danton Cc: dri-devel@lists.freedesktop.org Cc: Brian Starkey Cc: John Stultz Cc: Mauro Carvalho Chehab Cc: "David S. Miller" Cc: Greg Kroah-Hartman Cc: Rob Herring Cc: Jonathan Cameron Cc: "Paul E. McKenney" Cc: Sean Paul Cc: "Andrew F. Davis" Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Acked-by: David Airlie Signed-off-by: Sean Paul Link: https://patchwork.freedesktop.org/patch/msgid/20191030203003.101156-6-sean@poorly.run