Linaro-mm-sig August 2025

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15 participants
14 discussions

[PATCH v5 0/2] dma-buf: heaps: Support carved-out heaps

by Maxime Ripard

Hi, This series is the follow-up of the discussion that John and I had some time ago here: https://lore.kernel.org/all/CANDhNCquJn6bH3KxKf65BWiTYLVqSd9892-xtFDHHqqyrr… The initial problem we were discussing was that I'm currently working on a platform which has a memory layout with ECC enabled. However, enabling the ECC has a number of drawbacks on that platform: lower performance, increased memory usage, etc. So for things like framebuffers, the trade-off isn't great and thus there's a memory region with ECC disabled to allocate from for such use cases. After a suggestion from John, I chose to first start using heap allocations flags to allow for userspace to ask for a particular ECC setup. This is then backed by a new heap type that runs from reserved memory chunks flagged as such, and the existing DT properties to specify the ECC properties. After further discussion, it was considered that flags were not the right solution, and relying on the names of the heaps would be enough to let userspace know the kind of buffer it deals with. Thus, even though the uAPI part of it has been dropped in this second version, we still need a driver to create heaps out of carved-out memory regions. In addition to the original usecase, a similar driver can be found in BSPs from most vendors, so I believe it would be a useful addition to the kernel. Let me know what you think, Maxime Signed-off-by: Maxime Ripard <mripard(a)kernel.org> --- Changes in v5: - Rebased on 6.16-rc2 - Switch from property to dedicated binding - Link to v4: https://lore.kernel.org/r/20250520-dma-buf-ecc-heap-v4-1-bd2e1f1bb42c@kerne… Changes in v4: - Rebased on 6.15-rc7 - Map buffers only when map is actually called, not at allocation time - Deal with restricted-dma-pool and shared-dma-pool - Reword Kconfig options - Properly report dma_map_sgtable failures - Link to v3: https://lore.kernel.org/r/20250407-dma-buf-ecc-heap-v3-0-97cdd36a5f29@kerne… Changes in v3: - Reworked global variable patch - Link to v2: https://lore.kernel.org/r/20250401-dma-buf-ecc-heap-v2-0-043fd006a1af@kerne… Changes in v2: - Add vmap/vunmap operations - Drop ECC flags uapi - Rebase on top of 6.14 - Link to v1: https://lore.kernel.org/r/20240515-dma-buf-ecc-heap-v1-0-54cbbd049511@kerne… --- Maxime Ripard (2): dt-bindings: reserved-memory: Introduce carved-out memory region binding dma-buf: heaps: Introduce a new heap for reserved memory .../bindings/reserved-memory/carved-out.yaml | 49 +++ drivers/dma-buf/heaps/Kconfig | 8 + drivers/dma-buf/heaps/Makefile | 1 + drivers/dma-buf/heaps/carveout_heap.c | 362 +++++++++++++++++++++ 4 files changed, 420 insertions(+) --- base-commit: d076bed8cb108ba2236d4d49c92303fda4036893 change-id: 20240515-dma-buf-ecc-heap-28a311d2c94e Best regards, -- Maxime Ripard <mripard(a)kernel.org>

6 days, 13 hours

[PATCH v1 00/10] vfio/pci: Allow MMIO regions to be exported through dma-buf

by Leon Romanovsky

Changelog: v1: * Changed commit messages. * Reused DMA_ATTR_MMIO attribute. * Returned support for multiple DMA ranges per-dMABUF. v0: https://lore.kernel.org/all/cover.1753274085.git.leonro@nvidia.com --------------------------------------------------------------------------- Based on "[PATCH v1 00/16] dma-mapping: migrate to physical address-based API" https://lore.kernel.org/all/cover.1754292567.git.leon@kernel.org series. --------------------------------------------------------------------------- This series extends the VFIO PCI subsystem to support exporting MMIO regions from PCI device BARs as dma-buf objects, enabling safe sharing of non-struct page memory with controlled lifetime management. This allows RDMA and other subsystems to import dma-buf FDs and build them into memory regions for PCI P2P operations. The series supports a use case for SPDK where a NVMe device will be owned by SPDK through VFIO but interacting with a RDMA device. The RDMA device may directly access the NVMe CMB or directly manipulate the NVMe device's doorbell using PCI P2P. However, as a general mechanism, it can support many other scenarios with VFIO. This dmabuf approach can be usable by iommufd as well for generic and safe P2P mappings. In addition to the SPDK use-case mentioned above, the capability added in this patch series can also be useful when a buffer (located in device memory such as VRAM) needs to be shared between any two dGPU devices or instances (assuming one of them is bound to VFIO PCI) as long as they are P2P DMA compatible. The implementation provides a revocable attachment mechanism using dma-buf move operations. MMIO regions are normally pinned as BARs don't change physical addresses, but access is revoked when the VFIO device is closed or a PCI reset is issued. This ensures kernel self-defense against potentially hostile userspace. The series includes significant refactoring of the PCI P2PDMA subsystem to separate core P2P functionality from memory allocation features, making it more modular and suitable for VFIO use cases that don't need struct page support. ----------------------------------------------------------------------- The series is based originally on https://lore.kernel.org/all/20250307052248.405803-1-vivek.kasireddy@intel.c… but heavily rewritten to be based on DMA physical API. ----------------------------------------------------------------------- The WIP branch can be found here: https://git.kernel.org/pub/scm/linux/kernel/git/leon/linux-rdma.git/log/?h=… Thanks Leon Romanovsky (8): PCI/P2PDMA: Remove redundant bus_offset from map state PCI/P2PDMA: Separate the mmap() support from the core logic PCI/P2PDMA: Simplify bus address mapping API PCI/P2PDMA: Refactor to separate core P2P functionality from memory allocation PCI/P2PDMA: Export pci_p2pdma_map_type() function types: move phys_vec definition to common header vfio/pci: Enable peer-to-peer DMA transactions by default vfio/pci: Add dma-buf export support for MMIO regions Vivek Kasireddy (2): vfio: Export vfio device get and put registration helpers vfio/pci: Share the core device pointer while invoking feature functions block/blk-mq-dma.c | 7 +- drivers/iommu/dma-iommu.c | 4 +- drivers/pci/p2pdma.c | 154 ++++++++---- drivers/vfio/pci/Kconfig | 20 ++ drivers/vfio/pci/Makefile | 2 + drivers/vfio/pci/vfio_pci_config.c | 22 +- drivers/vfio/pci/vfio_pci_core.c | 59 +++-- drivers/vfio/pci/vfio_pci_dmabuf.c | 390 +++++++++++++++++++++++++++++ drivers/vfio/pci/vfio_pci_priv.h | 23 ++ drivers/vfio/vfio_main.c | 2 + include/linux/dma-buf.h | 1 + include/linux/pci-p2pdma.h | 114 +++++---- include/linux/types.h | 5 + include/linux/vfio.h | 2 + include/linux/vfio_pci_core.h | 4 + include/uapi/linux/vfio.h | 25 ++ kernel/dma/direct.c | 4 +- mm/hmm.c | 2 +- 18 files changed, 715 insertions(+), 125 deletions(-) create mode 100644 drivers/vfio/pci/vfio_pci_dmabuf.c -- 2.50.1

1 week

Re: [PATCH v2 4/4] misc: fastrpc: Skip reference for DMA handles

by kernel test robot

Hi Ling, kernel test robot noticed the following build warnings: [auto build test WARNING on char-misc/char-misc-testing] [also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus linus/master v6.16 next-20250806] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch#_base_tree_information] url: https://github.com/intel-lab-lkp/linux/commits/Ling-Xu/misc-fastrpc-Save-ac… base: char-misc/char-misc-testing patch link: https://lore.kernel.org/r/20250806115114.688814-5-quic_lxu5%40quicinc.com patch subject: [PATCH v2 4/4] misc: fastrpc: Skip reference for DMA handles config: hexagon-randconfig-002-20250807 (https://download.01.org/0day-ci/archive/20250807/202508070731.S30957lV-lkp@…) compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 7b8dea265e72c3037b6b1e54d5ab51b7e14f328b) reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250807/202508070731.S30957lV-lkp@…) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <lkp(a)intel.com> | Closes: https://lore.kernel.org/oe-kbuild-all/202508070731.S30957lV-lkp@intel.com/ All warnings (new ones prefixed by >>): >> drivers/misc/fastrpc.c:368:30: warning: unused variable 'sess' [-Wunused-variable] 368 | struct fastrpc_session_ctx *sess = fl->sctx; | ^~~~ 1 warning generated. vim +/sess +368 drivers/misc/fastrpc.c c68cfb718c8f97 Srinivas Kandagatla 2019-02-08 363 8f6c1d8c4f0cc3 Vamsi Krishna Gattupalli 2022-02-14 364 8f6c1d8c4f0cc3 Vamsi Krishna Gattupalli 2022-02-14 365 static int fastrpc_map_lookup(struct fastrpc_user *fl, int fd, 1922c68c56c660 Ling Xu 2025-08-06 366 struct fastrpc_map **ppmap) c68cfb718c8f97 Srinivas Kandagatla 2019-02-08 367 { 9446fa1683a7e3 Abel Vesa 2022-11-24 @368 struct fastrpc_session_ctx *sess = fl->sctx; c68cfb718c8f97 Srinivas Kandagatla 2019-02-08 369 struct fastrpc_map *map = NULL; d259063578ed76 Ling Xu 2025-08-06 370 struct dma_buf *buf; 9446fa1683a7e3 Abel Vesa 2022-11-24 371 int ret = -ENOENT; c68cfb718c8f97 Srinivas Kandagatla 2019-02-08 372 d259063578ed76 Ling Xu 2025-08-06 373 buf = dma_buf_get(fd); d259063578ed76 Ling Xu 2025-08-06 374 if (IS_ERR(buf)) d259063578ed76 Ling Xu 2025-08-06 375 return PTR_ERR(buf); d259063578ed76 Ling Xu 2025-08-06 376 9446fa1683a7e3 Abel Vesa 2022-11-24 377 spin_lock(&fl->lock); c68cfb718c8f97 Srinivas Kandagatla 2019-02-08 378 list_for_each_entry(map, &fl->maps, node) { d259063578ed76 Ling Xu 2025-08-06 379 if (map->fd != fd || map->buf != buf) 9446fa1683a7e3 Abel Vesa 2022-11-24 380 continue; 9446fa1683a7e3 Abel Vesa 2022-11-24 381 9446fa1683a7e3 Abel Vesa 2022-11-24 382 *ppmap = map; 9446fa1683a7e3 Abel Vesa 2022-11-24 383 ret = 0; 9446fa1683a7e3 Abel Vesa 2022-11-24 384 break; c68cfb718c8f97 Srinivas Kandagatla 2019-02-08 385 } 9446fa1683a7e3 Abel Vesa 2022-11-24 386 spin_unlock(&fl->lock); 8f6c1d8c4f0cc3 Vamsi Krishna Gattupalli 2022-02-14 387 8f6c1d8c4f0cc3 Vamsi Krishna Gattupalli 2022-02-14 388 return ret; 8f6c1d8c4f0cc3 Vamsi Krishna Gattupalli 2022-02-14 389 } 8f6c1d8c4f0cc3 Vamsi Krishna Gattupalli 2022-02-14 390 -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki

1 week, 1 day

Re: [PATCH v1 00/10] vfio/pci: Allow MMIO regions to be exported through dma-buf

by Leon Romanovsky

On Mon, Aug 04, 2025 at 10:10:32AM -0400, Benjamin LaHaise wrote: > FYI: this entire patch series was rejected as spam by large numbers of > linux-mm subscribers using @gmail.com email addresses. Thanks for the heads-up. Are you aware of any issues from my side? I'm sending patches with git-send-email through mail.kernel.org SMTP. Thanks > > -ben (owner-linux-mm)

1 week, 3 days

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