netdev - Re: [RFC net-next v3 0/7] devmem/io_uring: allow more flexibility for ZC DMA devices

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Message-ID: <aJ9SuemoS6n0GIBs@mini-arch>
Date: Fri, 15 Aug 2025 08:31:05 -0700
From: Stanislav Fomichev <stfomichev@...il.com>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: almasrymina@...gle.com, asml.silence@...il.com,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	Saeed Mahameed <saeedm@...dia.com>,
	Tariq Toukan <tariqt@...dia.com>, Mark Bloch <mbloch@...dia.com>,
	Leon Romanovsky <leon@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>, cratiu@...dia.com,
	parav@...dia.com, Christoph Hellwig <hch@...radead.org>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	io-uring@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [RFC net-next v3 0/7] devmem/io_uring: allow more flexibility
 for ZC DMA devices

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@...dia.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/
> [2]  v1: https://lore.kernel.org/all/20250709124059.516095-2-dtatulea@nvidia.com/
> [3]  v2: https://lore.kernel.org/all/20250711092634.2733340-2-dtatulea@nvidia.com/
> ---
> 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..