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a18eb86401
From Yishai, Overview -------- This patch series aims to enable multi-path DMA support, allowing an mlx5 RDMA device to issue DMA commands through multiple paths. This feature is critical for improving performance and reaching line rate in certain environments where issuing PCI transactions over one path may be significantly faster than over another. These differences can arise from various PCI generations in the system or the specific system topology. To achieve this functionality, we introduced a data direct DMA device that can serve the RDMA device by issuing DMA transactions on its behalf. The main key features and changes are described below. Multi-Path Discovery -------------------- API Implementation: * Introduced an API to discover multiple paths for a given mlx5 RDMA device. IOCTL Command: * Added a new IOCTL command, MLX5_IB_METHOD_GET_DATA_DIRECT_SYSFS_PATH, to the DEVICE object. When an affiliated Data-Direct/DMA device is present, its sysfs path is returned. Feature Activation by mlx5 RDMA Application ------------------------------------------- UVERBS Extension: * Extended UVERBS_METHOD_REG_DMABUF_MR over UVERBS_OBJECT_MR to include mlx5 extended flags. Access Flag: * Introduced the MLX5_IB_UAPI_REG_DMABUF_ACCESS_DATA_DIRECT flag, allowing applications to request the use of the affiliated DMA device for DMABUF registration. Data-Direct/DMA Device ---------------------- New Driver: * Introduced a new driver to manage the new DMA PF device ID (0x2100). Its registration/un-registration is handled as part of the mlx5_ib init/exit flows, with mlx5 IB devices as its clients. Functionality: * The driver does not interface directly with the firmware (no command interface, no caps, etc.) but works over PCI to activate its DMA functionality. It serves as the DMA device for efficiently accessing other PCI devices (e.g., GPU PF) and reads its VUID over PCI to handle NICs registrations with the same VUID. mlx5 IB RDMA Device --------------------------- VUID Query: * Reads its affiliated DMA PF VUID via the QUERY_VUID command with the data_direct bit set. Driver Registration: * Registers with the DMA PF driver to be notified upon bind/unbind. Application Request Handling: * Uses the DMA PF device upon application request as described above. DMABUF over Umem ---------------- Introduced an option to obtain a DMABUF UMEM using a different DMA device instead of the IB device, allowing the device to register over IOMMU with the expected DMA device for a given buffer registration. Further details are provided in the commit logs of the patches in this series. Thanks Link: https://lore.kernel.org/all/cover.1722512548.git.leon@kernel.org Signed-off-by: Leon Romanovsky <leon@kernel.org> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.