netdev - Re: [PATCH v1 10/15] io_uring/zcrx: add io_zcrx

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Message-ID: <CAHS8izNChXnQaMS5X=--e6Jz6OZGcJsgoSH4D6r4MEmFhxxdyQ@mail.gmail.com>
Date: Wed, 9 Oct 2024 14:29:41 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: David Wei <dw@...idwei.uk>
Cc: io-uring@...r.kernel.org, netdev@...r.kernel.org, 
	Jens Axboe <axboe@...nel.dk>, Pavel Begunkov <asml.silence@...il.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH v1 10/15] io_uring/zcrx: add io_zcrx_area

On Mon, Oct 7, 2024 at 3:16 PM David Wei <dw@...idwei.uk> wrote:
>
> From: David Wei <davidhwei@...a.com>
>
> Add io_zcrx_area that represents a region of userspace memory that is
> used for zero copy. During ifq registration, userspace passes in the
> uaddr and len of userspace memory, which is then pinned by the kernel.
> Each net_iov is mapped to one of these pages.
>
> The freelist is a spinlock protected list that keeps track of all the
> net_iovs/pages that aren't used.
>
> For now, there is only one area per ifq and area registration happens
> implicitly as part of ifq registration. There is no API for
> adding/removing areas yet. The struct for area registration is there for
> future extensibility once we support multiple areas and TCP devmem.
>
> Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
> Signed-off-by: David Wei <dw@...idwei.uk>

This patch, and the later patch to add the io_uring memory provider
are what I was referring to in the other thread as changes I would
like to reuse for a socket extension for this.

In my mind it would be nice to decouple the memory being bound to the
page_pool from io_uring, so I can bind a malloced/pinned block of
memory to the rx queue and use it with regular sockets. Seems a lot of
this patch and the provider can be reused. The biggest issue AFAICT I
see is that there are io_uring specific calls to set up the region
like io_buffer_validate/io_pin_pages, but these in turn seem to call
generic mm helpers and from a quick look I don't see much iouring
specific.

Seems fine to leave this to a future extension.

--
Thanks,
Mina