Data Direct Placement (DDP)
Support for Direct Data Placement (DDP) across both the mlx5dv and DevX interfaces enables out-of-order receives and full wire speed on ConnectX-8 adapters. Multiplane mode is enabled conditionally when supported. These patches are included starting in Linux kernel 6.13.
To use the Data Direct interface, a vHCA must create an MKEY with the data_direct bit set. The returned MKEY enables access through the side DMA engine, and the MKEY access mode must be PA.
The following table lists the patches required for bare-metal DDP support.
LKML Discussion | Git Commit | Git Description | Minimum Linux Kernel Release |
https://lore.kernel.org/all/06ac609a5f358c8fb0a090d22c61a2f9329d82e6.1725362773.git.leon@kernel.org/ | 8b36f7c3c661 | RDMA/mlx5: Support OOO RX WQE consumption | 6.13 |
https://lore.kernel.org/all/cover.1725362773.git.leon@kernel.org/ | 8439662f6f16 | Introduce mlx5 data direct placement (DDP) | 6.13 |
https://lore.kernel.org/all/828d57444a0a41042556bb0a4394ecf2fcaed639.1730368052.git.leon@kernel.org/ | eb3d354efb39 | RDMA/mlx5: Support querying per-plane IB PortCounters | 6.13 |
https://lore.kernel.org/all/20250106151145.908217414@linuxfoundation.org/ | 45d339fefaa3 | RDMA/mlx5: Enable multiplane mode only when it is supported | 6.13 |