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Wed, 21 Jan 2026 13:42:21 -0800 From: Edward Srouji Subject: [PATCH rdma-next v2 0/3] RDMA: Add support for exporting dma-buf file descriptors Date: Wed, 21 Jan 2026 23:42:10 +0200 Message-ID: <20260121-dmabuf-export-v2-0-6381183bcc3d@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIADJIcWkC/3WNwQ6CMBBEf4Xs2TVbBKye/A/DAdlF9kBLWmwwh H+34e5xMm/ebBAlqES4FxsESRrVuxzKUwH92Lm3oHLOUFLZkCGLPHWvz4Cyzj4sSFzfLNWW2Qj kzRxk0PXwPSFkFp2sC7S5GjUuPnyPp2QO4I80GSRsuLpy1dSW+PJwSVm7c+8naPd9/wFf1kr1t gAAAA== X-Change-ID: 20260108-dmabuf-export-0d598058dd1e To: Jason Gunthorpe , Leon Romanovsky , "Sumit Semwal" , =?utf-8?q?Christian_K=C3=B6nig?= CC: , , , , , Yishai Hadas , "Edward Srouji" X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1769031741; l=3363; i=edwards@nvidia.com; s=20251029; h=from:subject:message-id; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 Jan 2026 21:42:39.9638 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 67556d0d-d9b7-4900-6174-08de59360042 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.118.232];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SA2PEPF00003F65.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB7603 This patch series introduces dma-buf export support for RDMA/InfiniBand devices, enabling userspace applications to export RDMA PCI-backed memory regions (such as device memory or mlx5 UAR pages) as dma-buf file descriptors. This allows PCI device memory to be shared with other kernel subsystems (e.g., graphics or media) or between userspace processes, via the standard dma-buf interface, avoiding unnecessary copies and enabling efficient peer-to-peer (P2P) DMA transfers. See [1] for background on dma-buf. As part of this series, we introduce a new uverbs object of type FD for dma-buf export, along with the corresponding APIs for allocation and teardown. This object encapsulates all attributes required to export a dma-buf. The implementation enforces P2P-only mappings and properly manages resource lifecycle, including: - Cleanup during driver removal or RDMA context destruction. - Revocation via dma_buf_move_notify() when the underlying mmap entries are removed. - Refactors common cleanup logic for reuse across FD uobject types. The infrastructure is generic within uverbs, allowing individual drivers to easily integrate and supply their vendor-specific implementation. The mlx5 driver is the first consumer of this new API, providing: - Initialization of PCI peer-to-peer DMA support. - mlx5-specific implementations of the mmap_get_pfns and pgoff_to_mmap_entry device operations required for dma-buf export. [1] https://docs.kernel.org/driver-api/dma-buf.html Signed-off-by: Yishai Hadas Signed-off-by: Edward Srouji --- Changes in v2: - Split the FD uobject refactoring into a separate patch ("RDMA: Add support for exporting dma-buf file descriptors") - Remove redundant revoked check from attach callback. It is checked during map - Add pin callback that returns -EOPNOTSUPP to explicitly refuse pinned importers - Wait for pending fences after dma_buf_move_notify() using dma_resv_wait_timeout() to ensure hardware has completed all in-flight operations before proceeding - Link to v1: https://lore.kernel.org/r/20260108-dmabuf-export-v1-0-6d47d46580d3@nvidia.com --- Yishai Hadas (3): RDMA/uverbs: Support external FD uobjects RDMA/uverbs: Add DMABUF object type and operations RDMA/mlx5: Implement DMABUF export ops drivers/infiniband/core/Makefile | 1 + drivers/infiniband/core/device.c | 2 + drivers/infiniband/core/ib_core_uverbs.c | 22 +++ drivers/infiniband/core/rdma_core.c | 63 ++++---- drivers/infiniband/core/rdma_core.h | 1 + drivers/infiniband/core/uverbs.h | 10 ++ drivers/infiniband/core/uverbs_std_types_dmabuf.c | 176 ++++++++++++++++++++++ drivers/infiniband/core/uverbs_uapi.c | 1 + drivers/infiniband/hw/mlx5/main.c | 72 +++++++++ include/rdma/ib_verbs.h | 9 ++ include/rdma/uverbs_types.h | 1 + include/uapi/rdma/ib_user_ioctl_cmds.h | 10 ++ 12 files changed, 342 insertions(+), 26 deletions(-) --- base-commit: 325e3b5431ddd27c5f93156b36838a351e3b2f72 change-id: 20260108-dmabuf-export-0d598058dd1e Best regards, -- Edward Srouji