From: Stanislav Fomichev <sdf.kernel@gmail.com>
To: netdev-bot+sashiko@kernel.org
Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, andrew+netdev@lunn.ch,
edumazet@kernel.org, horms@kernel.org, corbet@lwn.net,
skhan@linuxfoundation.org, rdunlap@infradead.org,
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saeedm@nvidia.com, tariqt@nvidia.com, mbloch@nvidia.com,
alexanderduyck@fb.com, kernel-team@meta.com, sdf@fomichev.me,
dimitri.daskalakis1@gmail.com, almasrymina@google.com,
dtatulea@nvidia.com, bobbyeshleman@meta.com,
asml.silence@gmail.com, daniel@iogearbox.net,
razor@blackwall.org, leitao@debian.org,
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linux-rdma@vger.kernel.org, linux-kselftest@vger.kernel.org,
leon@kernel.org
Subject: Re: [PATCH net-next v3 8/9] net: devmem: size TX net_iovs from the dmabuf sg table
Date: Mon, 09 Nov 2026 10:29:16 -0800 [thread overview]
Message-ID: <3d2b8463b7ea74cde9327a3b8678f1e5@gmail.com> (raw)
In-Reply-To: <179418738408.994134.12387400537759262351@kernel.org>
> [Severity: Medium]
> netdev_nl_bind_tx_doit() now passes niov_shift == 0, so a hugepage-backed
> dmabuf gets 2MB TX net_iovs. Can a devmem TX frag then end up larger than
> dev->netmem_tx_max_frag_size?
[..]
> Is a cap applied only at build time enough to keep that contract?
It's not, same as reported for patch 4. In v4 tcp_clone_payload()
won't merge net_iov frags, which keeps the cap with large net_iovs.
> There is also a related issue in the same code. It is pre-existing and
> was not introduced by this patch.
[..]
> Would either of these fix both problems:
>
> - compare skb_frag_netmem() and apply binding->tx_max_frag_size in
> tcp_clone_payload()
> - don't coalesce unreadable skbs when building MTU probes
Not merging net_iov frags in tcp_clone_payload() fixes both. Mina's
series also compares skb_frag_netmem() there:
https://lore.kernel.org/netdev/20261108013838.1454450-3-almasrymina@google.com/
next prev parent reply other threads:[~2026-11-09 18:29 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-05 22:20 [PATCH net-next v3 0/9] net: devmem: size TX net_iovs from the dmabuf layout Stanislav Fomichev
2026-11-05 22:20 ` [PATCH net-next v3 1/9] bnxt_en: let the stack segment GSO skbs with too many frags Stanislav Fomichev
2026-11-09 1:22 ` netdev-bot+sashiko
2026-11-09 18:29 ` Stanislav Fomichev
2026-11-10 22:37 ` Jakub Kicinski
2026-11-05 22:20 ` [PATCH net-next v3 2/9] net: devmem: charge the frag length to TX skb truesize Stanislav Fomichev
2026-11-09 1:22 ` netdev-bot+sashiko
2026-11-09 10:59 ` Breno Leitao
2026-11-05 22:20 ` [PATCH net-next v3 3/9] net: devmem: use niov_shift in net_devmem_get_niov_at() Stanislav Fomichev
2026-11-05 22:20 ` [PATCH net-next v3 4/9] net: devmem: add a per-device netmem TX frag size limit Stanislav Fomichev
2026-11-09 1:22 ` netdev-bot+sashiko
2026-11-09 18:29 ` Stanislav Fomichev
2026-11-10 22:36 ` Jakub Kicinski
2026-11-11 21:50 ` Stanislav Fomichev
2026-11-05 22:20 ` [PATCH net-next v3 5/9] bnxt_en: set the netmem TX frag size limit to 32KB Stanislav Fomichev
2026-11-09 1:22 ` netdev-bot+sashiko
2026-11-09 18:29 ` Stanislav Fomichev
2026-11-05 22:20 ` [PATCH net-next v3 6/9] eth: fbnic: " Stanislav Fomichev
2026-11-05 22:20 ` [PATCH net-next v3 7/9] net/mlx5e: lift the netmem TX frag size limit Stanislav Fomichev
2026-11-09 1:23 ` netdev-bot+sashiko
2026-11-09 18:29 ` Stanislav Fomichev
2026-11-05 22:20 ` [PATCH net-next v3 8/9] net: devmem: size TX net_iovs from the dmabuf sg table Stanislav Fomichev
2026-11-09 1:23 ` netdev-bot+sashiko
2026-11-09 18:29 ` Stanislav Fomichev [this message]
2026-11-05 22:20 ` [PATCH net-next v3 9/9] selftests: drv-net: devmem: TX from a hugepage-backed dmabuf Stanislav Fomichev
2026-11-09 1:23 ` netdev-bot+sashiko
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