From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=74.125.82.195 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794248963; b=1gsJ7cyNQ3os8DHqY1xz4S+jhbvNl7Uu4bsNg7bZ1kPnKv14GuDLuXE09ZzCL9x1wAL5 luGcKs/InJzbftKH5X+ksj3NN6zZu+o6H3SiJ2iWE1N9E5x1SjEZTOaBqqG4DMgfjr3cJ K4yXHYu5COHYdPvOUnteyBKSUB2jADVMNFIQoaPcGEVkzPLxP55D3b2E9cdr+RgcNeF64 Qkgw0J9mY2wngPfIkAA11HfSJkpIkslr5IrpTBDj38CAeD47srF+enPLub7g0vTAggFXz ARLy8J49xKtr+S31Wxpqjl2F86EsRHN0waPhJaAa6uI4RTLEq0tBLQm6NUrcI66RIAQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794248963; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: Date:Message-ID:From:To:Cc:In-Reply-To:Subject:Content-Type; bh=KcVmoMQgperP1wPlpI/4lZIUWk5pcHjD9u34purQ6ks=; b=A2NhTO41rJ6ZFwBQh6laBdyuSYL8lJsJqkmt9m/otSoZ1dgaN92OBO1e2yV51gwYUdRo UKcvaK4DOpKgnq2fVGN0BVZss7g16lZY9lI9Z5Rw2GeYHOPfsO0xBGZ41QOxxko2fPYjp xkTIPXzcOq+kaaAyZn0bXkk0EJdwbNg5fxkmI1O5F2AdVNGGxfGtxLUPeT48EgArCW9Ya WzvEaDRmPyKO9a6rjeeNl6JQDm28nDreIOPk/U6D/LgL1NA9wRjmc8GxYHApnWSGG+xu4 6HoochO5L993Zjq935K2SAnLuQ8Sa5Q1RFsFi4lQLO8j1pIr8uozD9/wOSXWZR3bfcQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=X7wedxBS; arc=none smtp.remote-ip=74.125.82.195 Received: from mail-dy1-f195.google.com (mail-dy1-f195.google.com [74.125.82.195]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 68A4A60A383E for ; Mon, 9 Nov 2026 18:29:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 68A4A60A383E Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=X7wedxBS Received: by mail-dy1-f195.google.com with SMTP id 5a478bee46e88-36fb88ea38cso1498209eec.1 for ; Mon, 09 Nov 2026 10:29:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20260707; t=1794248962; x=1794853762; darn=vger.kernel.org; h=content-type:subject:in-reply-to:cc:to:from:message-id:date:from:to :cc:subject:date:message-id:reply-to:content-type; bh=KcVmoMQgperP1wPlpI/4lZIUWk5pcHjD9u34purQ6ks=; b=X7wedxBSS8iZNbIq3uVV6Lk387o+XeGOfTW6Zk2cySFVKqEWn7Djj69lXsU8s/kpKz tJiJ1NC1pNUqxiy43lTvIzQnaR1XWltnvNswRXYTYKvJhMy1Ym9sy/gLTRWhTzeoZy/r kf9IurJNAyUB0JwvE50fsKX5uraHf+5WXfCjtNq7xr/i9v+AGqhqYTaRQLpfpje/s44G JAaCcBLIk5pgtY0fMS2yln/+byA2YY2Cjh8Vsy4CPhQB/kcoPBKf8PLdF0pQZM0hwa2X mCEmy0QrvQXIQcY0xkadgOuk8+FykA/urSyQYxogIANNQn5HVGBPGbcSPTXfDKNUDh9f 93Pw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1794248962; x=1794853762; h=content-type:subject:in-reply-to:cc:to:from:message-id:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=KcVmoMQgperP1wPlpI/4lZIUWk5pcHjD9u34purQ6ks=; b=V+bqn6Q1PS5ZQNlgfSxMxS2lP62Vt07Xh5OG/Z70yl50RQH4rXvDAqimuAEGwpuKLu hdPls26yfuFjNfuBT1HtzTGoED/sai5mNrf8Bf5Joympf2CTXHaHMcpUgIVcIB/obQ56 z09011cOWRVvz/zP7dxissd5ffv7Ak6uSfffeq2lzkAVzfsP8mv1CSoj6VwCDtI8bA61 2pWh6DMpqU0fN+fbN4m+lntMcxRiFmMZLhpX6qFV0M4hCFn0KcFVy/wkcqhxXEzx8KdM O1W8aoODIJC4qZT/+B/DQXETIyhqyX8zuUaYDGhr0rGpMOE4Uw/tdbnWjH1OpKQGYJod eEdQ== X-Forwarded-Encrypted: i=1; AL+hErFAo9BcWWmSrwyjiY8X0Bs7qwHw/lQqo8Rm6f0Jp7RdqBYT6C8t1Dte58dJPjpivMqiHXLxK8wa5y+dd/39mTE=@vger.kernel.org X-Gm-Message-State: APuU4Z8klfpDAmwNTgL6o80nRX0FbEJsrtGXsaFj7OOnWVZSwf5z/SSu fvLfTQXKvotXiaKMyCWVTEwNWau2Kodj9xRV0TshOSQm/bTKzmDFF9rh X-Gm-Gg: AYBFou18uL4zkCTx9mWvbDbDYifNLULqxoTyR0MW520AuuFCA/kEDqq8Vym8nbPkmtm I8Hmm1A+K3HPx7E4qV7UV5LMIX5WTOdRJAHmklLVawi+GbcXDaq/5MUWBcKuFaaspBoDQUYIhK3 zW0kIy8D3OmTxxJFzKGDzJZE1mPJTRvm5+bsGStUl+mqqI0SaAE8uET3BatjKJOXtAvKpXcRxWr M/jQL5wUHpjQk0kgtk2Ewl1hC7kRIx/AdveWM9YtDuZNQEP8B+Ln4pAH/Vijy0QIkU1CCD99ALi dHv4lcaB1Rpty1BUmskbRyRWssxL3VK0LDYxjAgZ/I7EPlFdgbNkdNIvGhnBGTAXDb81lGCDNu+ /ZdpLKdDI0J5Is7/71SzBQv8hwIn65DVoHFJ17PtGgNqzmVihKha3pGK+2iloxqK8EV79tUAU3J LroJHoKhSgJ8cweHVTseV4dEwgjjzDjknltnOYgor7Cy3cVUxdrO2LE77KbeliZ/Rz7DKWihV5e yeXemfSC+zMa6aq48qAr3zvAv9gQiaH7WXldygkw1pZ7cSTpXe4YsBk2NEVwcuHvzrsRNI42G3G e1yZAvs6OdcPH8aMzQsdDx4= X-Received: by 2002:a05:693c:8312:b0:36a:2473:9b2f with SMTP id 5a478bee46e88-3750a20b93bmr299470eec.23.1794248962308; Mon, 09 Nov 2026 10:29:22 -0800 (PST) Received: from localhost ([2a03:2880:9ff:73::]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3752060c4b6sm117168eec.15.2026.11.09.10.29.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Nov 2026 10:29:21 -0800 (PST) Date: Mon, 09 Nov 2026 10:29:21 -0800 Message-ID: <86219505a92ebc720950d87dc76662f3@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: <179418737701.994134.5100743053640770189@kernel.org> Subject: Re: [PATCH net-next v3 4/9] net: devmem: add a per-device netmem TX frag size limit Content-Type: text/plain; charset="utf-8" X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > > @@ -734,6 +734,7 @@ zerocopy_fill_skb_from_devmem(struct sk_buff *skb, struct iov_iter *from, > > > > size = min_t(size_t, size, length); > > size = min_t(size_t, size, iter_iov_len(from)); > > + size = min_t(size_t, size, binding->tx_max_frag_size); > > [Severity: Medium] > Is this the only place the new cap is enforced? The netmem.rst text added > by this patch says "Devmem TX frags are capped at > netdev->netmem_tx_max_frag_size". TCP MTU probing looks like it can merge > the capped frags back together later. [..] > Could tcp_clone_payload() compare skb_frag_netmem() and stop merging once > the binding cap is reached? Another option is to skip MTU probe > coalescing for unreadable skbs. Hmm, let me comment on Mina's patches, might be easier not to merge netmems in tcp_clone_payload at all? > [Severity: High] > This isn't a bug introduced by this patch, but the same merge check in > tcp_clone_payload() looks like it can also combine frags from different > net_iovs. skb_frag_page() returns NULL for both frags, so the page > comparison always passes and only the offsets are compared. [..] > Should the merge test compare skb_frag_netmem(), the way > skb_can_coalesce_netmem() does? Nothing later in the series changes > tcp_output.c. Mina is gonna take care of this: https://lore.kernel.org/netdev/20261108013838.1454450-3-almasrymina@google.com/