For TCP zerocopy rx (io_uring, devmem), there is an assumption that the parent device can do DMA. However that is not always the case: - Scalable Function netdevs [1] have the DMA device in the grandparent. - For Multi-PF netdevs [2] queues can be associated to different DMA devices. The series adds an API for getting the DMA device for a netdev queue. Drivers that have special requirements can implement the newly added queue management op. Otherwise the parent will still be used as before. This series continues with switching to this API for io_uring zcrx and devmem and adds a ndo_queue_dma_dev op for mlx5. The last part of the series changes devmem rx bind to get the DMA device per queue and blocks the case when multiple queues use different DMA devices. The tx bind is left as is. [1] Documentation/networking/device_drivers/ethernet/mellanox/mlx5/switchdev.rst [2] Documentation/networking/multi-pf-netdev.rst Signed-off-by: Dragos Tatulea <dtatulea@xxxxxxxxxx> ---- Changes sice v3 [4]: - Moved ndo_queue_get_dma_dev() from header to own file (patch 1). - Used real_num_rx_queues for queue bitmap (patch 6). - Allocate zeroed bitmap (patch 6). - Validate queue index (patch 6). - Forward errors from netdev_nl_read_rxq_bitmap() (patch 6). - Dropped rxq_dma_dev check (patch 7). - Fixed incorrect handling of extack message on bad dma dev (patch 7). - Added conflicting queues in error message (patch 7). - Dropped RFC status as feedback was mostly positive. Changes sice v2 [3]: - Downgraded to RFC status until consensus is reached. - Implemented more generic approach as discussed during v2 review. - Refactor devmem to get DMA device for multiple rx queues for multi PF netdev support. - Renamed series with a more generic name. Changes since v1 [2]: - Dropped the Fixes tag. - Added more documentation as requeseted. - Renamed the patch title to better reflect its purpose. Changes since RFC [1]: - Upgraded from RFC status. - Dropped driver specific bits for generic solution. - Implemented single patch as a fix as requested in RFC. - Handling of multi-PF netdevs will be handled in a subsequent patch series. [1] RFC: https://lore.kernel.org/all/20250702172433.1738947-2-dtatulea@xxxxxxxxxx/ [2] v1: https://lore.kernel.org/all/20250709124059.516095-2-dtatulea@xxxxxxxxxx/ [3] v2: https://lore.kernel.org/all/20250711092634.2733340-2-dtatulea@xxxxxxxxxx/ [4] v3: https://lore.kernel.org/all/20250815110401.2254214-2-dtatulea@xxxxxxxxxx/#t --- Dragos Tatulea (7): queue_api: add support for fetching per queue DMA dev io_uring/zcrx: add support for custom DMA devices net: devmem: get netdev DMA device via new API net/mlx5e: add op for getting netdev DMA device net: devmem: pull out dma_dev out of net_devmem_bind_dmabuf net: devmem: pre-read requested rx queues during bind net: devmem: allow binding on rx queues with same DMA devices .../net/ethernet/mellanox/mlx5/core/en_main.c | 24 ++++ include/net/netdev_queues.h | 8 ++ io_uring/zcrx.c | 3 +- net/core/Makefile | 1 + net/core/devmem.c | 8 +- net/core/devmem.h | 2 + net/core/netdev-genl.c | 123 +++++++++++++----- net/core/netdev_queues.c | 25 ++++ 8 files changed, 163 insertions(+), 31 deletions(-) create mode 100644 net/core/netdev_queues.c -- 2.50.1
