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Mon, 09 Nov 2026 10:29:17 -0800 (PST) Received: from localhost ([2a03:2880:9ff:6f::]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b3b5890e04sm722817c88.2.2026.11.09.10.29.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Nov 2026 10:29:17 -0800 (PST) Date: Mon, 09 Nov 2026 10:29:16 -0800 Message-ID: <3d2b8463b7ea74cde9327a3b8678f1e5@gmail.com> From: Stanislav Fomichev 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, michael.chan@broadcom.com, pavan.chebbi@broadcom.com, 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, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kselftest@vger.kernel.org, leon@kernel.org In-Reply-To: <179418738408.994134.12387400537759262351@kernel.org> Subject: Re: [PATCH net-next v3 8/9] net: devmem: size TX net_iovs from the dmabuf sg table Content-Type: text/plain; charset="utf-8" X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > [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/