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Message-ID: <20240903145150.4ffee51b@kernel.org>
Date: Tue, 3 Sep 2024 14:51:50 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Mina Almasry <almasrymina@...gle.com>
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Subject: Re: [PATCH net-next v24 11/13] net: add devmem TCP documentation
On Sat, 31 Aug 2024 00:43:11 +0000 Mina Almasry wrote:
> +The socket must be flow steered to the dmabuf bound RX queue::
> +
> + ethtool -N eth1 flow-type tcp4 ... queue 15,
nit: tailing comma here
> +Devmem payloads are inaccessible to the kernel processing the packets. This
> +results in a few quirks for payloads of devmem skbs:
> +
> +- Loopback is not functional. Loopback relies on copying the payload, which is
> + not possible with devmem skbs.
> +
> +- Software checksum calculation fails.
Speaking of which, I think we need to add readability check to
skb_checksum_help(). Shouldn't the check in __skb_checksum()
have a WARN_ON_ONCE() around it? It's impossible to return
an error from there.
> +- TCP Dump and bpf can't access devmem packet payloads.
> +
> +
> +Testing
> +=======
> +
> +More realistic example code can be found in the kernel source under
> +tools/testing/selftests/net/ncdevmem.c
looks like HTML output wraps the file path, maybe quote it as
``tools/testing/selftests/net/ncdevmem.c`` ?
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