Re: [RFC net-next v3 0/7] devmem/io_uring: allow more flexibility for ZC DMA devices
From: Stanislav Fomichev <hidden>
Date: 2025-08-15 15:31:07
Also in:
io-uring, linux-rdma, lkml
On 08/15, Dragos Tatulea wrote:
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@nvidia.com> ---- 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@nvidia.com/ (local) [2] v1: https://lore.kernel.org/all/20250709124059.516095-2-dtatulea@nvidia.com/ (local) [3] v2: https://lore.kernel.org/all/20250711092634.2733340-2-dtatulea@nvidia.com/ (local) --- Dragos Tatulea (7): queue_api: add support for fetching per queue DMA dev
[..]
io_uring/zcrx: add support for custom DMA devices
Did something happen to 2/7? I don't see it in my mailbox and in the lore..