From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fout-a5-smtp.messagingengine.com (fout-a5-smtp.messagingengine.com [103.168.172.148]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AFC1341F37A; Mon, 17 Aug 2026 12:59:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=103.168.172.148 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786971588; cv=none; b=MEEzOA/5kA41SHSV1geEFt8Uj4vAF9HkscJIK9BIvM/pOtOE52Nrzfm9RZ/mTEUy7iQTfrQYiEdfGoQ56cA3QtLSDsbWF9tJOhygvB27r3mIAi+W934PYU8L0RFM//i5oyE15EH73nI6gzjtCigLLE23XrYMJioWI6q891EmamE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786971588; c=relaxed/simple; bh=DRyKZDUerO4XoZiKd0/UMs68uPcTpzCDEqnmCAFZfJw=; h=MIME-Version:Date:From:To:Cc:Message-Id:In-Reply-To:References: Subject:Content-Type; b=LgcZjqZM1HK+pGVMFXEsW0szJP+eGQHUHEJwJPOZhNc9JaEmKQhBS3PRIgEgO5NkxYmBcQFk+TgfELQsZF8Zk/ojHB3pyrmUoY5Kq0UGRd+PTWiThHdsUHDtjbdj6ArpGPujA1XgM0EHBXSDrAlhhFkKMosNyhp9ebLH/fwhIoc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arndb.de; spf=pass smtp.mailfrom=arndb.de; dkim=pass (2048-bit key) header.d=arndb.de header.i=@arndb.de header.b=GXRjuXp7; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b=iqk0ZZGL; arc=none smtp.client-ip=103.168.172.148 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arndb.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arndb.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=arndb.de header.i=@arndb.de header.b="GXRjuXp7"; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="iqk0ZZGL" Received: from ams-compute-02.internal (ams-compute-02.internal [10.64.2.62]) by mailfout.phl.internal (Postfix) with ESMTP id 9E27EEC023A; Mon, 17 Aug 2026 08:59:42 -0400 (EDT) Received: from ams-imap-03 ([10.64.2.23]) by ams-compute-02.internal (MEProxy); Mon, 17 Aug 2026 08:59:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arndb.de; h=cc :cc:content-transfer-encoding:content-type:content-type:date :date:from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to; s=fm2; t=1786971581; x=1787057981; bh=bQ68rGWO5+XJK8Ee7Y4MpJFQgMAvX184NdiLnRVSkzI=; b= GXRjuXp7Jv+3Fds7JDBpdOJL6G1CE4gD9Q/IqnxqxWBRPIq0Lw84CWRLF1bvVJGr xmPYDAXG2rH1cW433tXlnm/j93zkl3UKZWysNLFOHI45DOSgXBmvGOxR4RnRX/lp B7GUXiC/8udS4NoK+K4ISch9RsEnC/24wPiBlTl+k763cvBIuP/nZF0FQom1/5uX YxUf/+31mfneVrsawfhBf3bqRkFv03L3YSUzAkvuRfDSZw2MoP5vgu6FHLW56CK4 PrGCtNqWYU2ENGUaGwx1fKBnXG2CN5DUb97CtJQsTTEbn5GEXwQHEc+URYSWmpOW tUrajbGLLfx3JDSiwbcq6g== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:content-type:date:date:feedback-id:feedback-id :from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm3; t=1786971581; x= 1787057981; bh=bQ68rGWO5+XJK8Ee7Y4MpJFQgMAvX184NdiLnRVSkzI=; b=i qk0ZZGLQPfTfh2kptC750VNH9PmChyfYQx5a5sa2HUzx390rfuMo+KPS5/ep4zMG LMBsJxY9WnhwQBRB909OWefFpqnZ5zJ+Dblok3DBePsj2WpSshvae5Oh3c7wmow5 eAQYz91n+DdXshP3Z/giKu5eYAUIzRpGD6BeAGYMrH9tY/11aWGfjyrvbYATtLG1 wRWVlDVK248PFhnrjrF18HilhDan0U6HknNojhtHPgzPUZwROpH/Fn90ewOUFE4l 6ER2ou/yIflu00LYZ0KLCXI5ymoXCVIMCmFSc8C2+yxVSgPBFgWeYPLYPHYxx9C/ ZCtW3z6pBHYEhqo1hdtdQ== X-ME-Sender: X-ME-Proxy-Cause: dmFkZTFrJQquK4O/Ss9PIUnA61QMTKUxplzDdeAV+mGJHm6az6ApcdUzgLb4ocbjXBTFEQ 5ZIKh+gRdwlURyM1BOZsyjg3BxgSAv9jwi31hDOmEcJFGkpWNl0sok7rBC3wSehXCV6Gcd budBvHA5eC+q9TOcRGZPvDE4DVSXy3T7vhgLk6sFJ94H0eJL0jnslBuB3FSILMtRZlFAYQ 3zD7qDx+GwpfSiV+tmkDGSn7hVAwA0Km7hBXyITvN8slYbT4kTN2IlGcCesnDzxGm6hE8C 8uoQeNiOVoRRyEGlVYl/E1aRIeYW6CczUWjdYlcaXU6UiTG2IHG3NaqTZV3ij0f/mFK9tZ sDMwl00WCYHSE2mF4xDuFUlGcdM/kJShAvBgye9OftzsK1LkfEas2LA64uZZaEwvzL1Opw qWsrsuzES5iljhkKU7/9VVHzMPCGSGkFFtyFG4W60Y/fyqzM9DlYA7Yeh3H+HnBKmIhxiz eDbyotJI3ZlN4G2pIJIHrODsDnfClP65xHYvCqQNewEare2JOBXlatPbzd2D5ducAH2C49 NPmXvbXIotr4tQ4v3ZU4LiGzEa/lYEmy8eQXrm48CQFUwp5Y/mWYene0Vs4ctJdQSiKgVm m2b+evTH2uotPBCeFVTIIZa7LOWED6upQNzX/x3CJoJPJWBs16qXr0181kpQ X-ME-Proxy: Feedback-ID: i56a14606:Fastmail Received: by mailuser.ams.internal (Postfix, from userid 501) id 21A9432A0070; Mon, 17 Aug 2026 08:59:30 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: AdWx15gK6UpR Date: Mon, 17 Aug 2026 14:59:09 +0200 From: "Arnd Bergmann" To: "Stanislav Fomichev" , Netdev Cc: "David S . Miller" , "Eric Dumazet" , "Jakub Kicinski" , "Paolo Abeni" , "Anthony L Nguyen" , "Przemek Kitszel" , andrew+netdev@lunn.ch, "Saeed Mahameed" , "Tariq Toukan" , "Mark Bloch" , "Maxime Chevallier" , "Maxime Coquelin" , "Alexandre Torgue" , "Alexander Lobakin" , "Simon Horman" , magnus.karlsson@intel.com, "Maciej Fijalkowski" , "Stanislav Fomichev" , "Alexei Starovoitov" , "Daniel Borkmann" , "Jesper Dangaard Brouer" , "John Fastabend" , witu@nvidia.com, "Martin KaFai Lau" , yoong.siang.song@intel.com, rohan.g.thomas@intel.com, "intel-wired-lan@lists.osuosl.org" , linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, bpf@vger.kernel.org, "Leon Romanovsky" Message-Id: <06f8153d-2156-4e7d-9d49-006db4b2cec4@app.fastmail.com> In-Reply-To: <20260813190800.222527-2-sdf@fomichev.me> References: <20260813190800.222527-1-sdf@fomichev.me> <20260813190800.222527-2-sdf@fomichev.me> Subject: Re: [PATCH net v2 1/3] xsk: align TX metadata layout across ABIs Content-Type: text/plain Content-Transfer-Encoding: 7bit On Thu, Aug 13, 2026, at 21:07, Stanislav Fomichev wrote: > Add explicit padding before launch_time so xsk_tx_metadata has the same > layout on 32-bit and 64-bit systems. > > On i386 and m68k, the old native 32-bit layout put launch_time at offset 12 > and had a natural size of 20 bytes. Using sizeof(struct xsk_tx_metadata) as > tx_metadata_len was already rejected because the length must be a multiple > of eight, so the straightforward use of the interface was broken on those > ABIs. Userspace could still register a padded length of 24 bytes, though; > mixing the old and new layouts then silently reads launch_time from the > wrong offset and misprograms packet launch times. This intentionally > replaces that incompatible layout while the interface is still new. > > Fixes: ca4419f15abd ("xsk: Add launch time hardware offload support to > XDP Tx metadata") > Signed-off-by: Stanislav Fomichev This is probably the right approach, given lack of alternatives. In the changelog text, it may be worth noting a few more points: - A few additional architectures have the same issue: csky, nios2, openrisc and sh. - the commit that introduced the mistake was part of linux-6.15, so the 6.18-lts release also needs an ABI change. I don't think the "while the interface is still new" wording makes sense here. - what actually saves us here is that none of the affected architectures are likely to have notable use cases for xdp that would care about the ABI break. The one that is most likely to have affected users is x86-compat, and that is also the only one that is broken right now. Arnd From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 240D2C5DF66 for ; Mon, 17 Aug 2026 13:06:24 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id C38B160783; Mon, 17 Aug 2026 13:06:23 +0000 (UTC) X-Virus-Scanned: amavis at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavis, port 10024) with ESMTP id wpYLMYpe6lEY; Mon, 17 Aug 2026 13:06:23 +0000 (UTC) X-Comment: SPF check N/A for local connections - client-ip=140.211.166.142; helo=lists1.osuosl.org; envelope-from=intel-wired-lan-bounces@osuosl.org; receiver= DKIM-Filter: OpenDKIM Filter v2.11.0 smtp3.osuosl.org 1C3F260777 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osuosl.org; s=default; t=1786971983; bh=bQ68rGWO5+XJK8Ee7Y4MpJFQgMAvX184NdiLnRVSkzI=; h=Date:From:To:Cc:In-Reply-To:References:Subject:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=9E0Fu5vyrvV4i7CwgYi4UKKB4diDmmunzOC34EpchTUdMqTfLnG73kHTs0mODLAMY FXsI/U1IKBOfmdcsTGAJyY5vy6w8gs32l6rmUsvpPQXbQ4Z2QW8Y7gIL2DnlHFPCRB YWz4dlVFYcTT2gMGwGYVX+Y4qVHyDTCmnJoc7CRa4q3KYnaP+vRk4eAwjlIMaOt2Ru jCL4buj65OOVrWklw1Ty5BfvG7ysJQZwj6iJ+W5RhLkvoRijNZ21VGiBBjbVclF9TT UuQaofLSLfXeebzRwadiPNQPOUnHE69RUFCJlVgrnZPgPt86HQD65bMzOTVlo8gtIj 0OMdNvp0a3/dA== Received: from lists1.osuosl.org (lists1.osuosl.org [140.211.166.142]) by smtp3.osuosl.org (Postfix) with ESMTP id 1C3F260777; Mon, 17 Aug 2026 13:06:23 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists1.osuosl.org (Postfix) with ESMTP id BA52C147 for ; Mon, 17 Aug 2026 13:06:21 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id AC5A780EE3 for ; Mon, 17 Aug 2026 13:06:21 +0000 (UTC) X-Virus-Scanned: amavis at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavis, port 10024) with ESMTP id JNszWezUGmPR for ; Mon, 17 Aug 2026 13:06:20 +0000 (UTC) X-Greylist: delayed 393 seconds by postgrey-1.37 at util1.osuosl.org; Mon, 17 Aug 2026 13:06:19 UTC DMARC-Filter: OpenDMARC Filter v1.4.2 smtp1.osuosl.org 050C980EDF Authentication-Results: smtp1.osuosl.org; dmarc=pass (p=none dis=none) header.from=arndb.de DKIM-Filter: OpenDKIM Filter v2.11.0 smtp1.osuosl.org 050C980EDF Authentication-Results: smtp1.osuosl.org; dkim=pass (2048-bit key, unprotected) header.d=arndb.de header.i=@arndb.de header.a=rsa-sha256 header.s=fm2 header.b=GXRjuXp7; dkim=pass (2048-bit key, unprotected) header.d=messagingengine.com header.i=@messagingengine.com header.a=rsa-sha256 header.s=fm3 header.b=iqk0ZZGL Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=103.168.172.148; helo=fout-a5-smtp.messagingengine.com; envelope-from=arnd@arndb.de; receiver= Received: from fout-a5-smtp.messagingengine.com (fout-a5-smtp.messagingengine.com [103.168.172.148]) by smtp1.osuosl.org (Postfix) with ESMTPS id 050C980EDF for ; Mon, 17 Aug 2026 13:06:19 +0000 (UTC) Received: from ams-compute-02.internal (ams-compute-02.internal [10.64.2.62]) by mailfout.phl.internal (Postfix) with ESMTP id 9E27EEC023A; Mon, 17 Aug 2026 08:59:42 -0400 (EDT) Received: from ams-imap-03 ([10.64.2.23]) by ams-compute-02.internal (MEProxy); Mon, 17 Aug 2026 08:59:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arndb.de; h=cc :cc:content-transfer-encoding:content-type:content-type:date :date:from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to; s=fm2; t=1786971581; x=1787057981; bh=bQ68rGWO5+XJK8Ee7Y4MpJFQgMAvX184NdiLnRVSkzI=; b= GXRjuXp7Jv+3Fds7JDBpdOJL6G1CE4gD9Q/IqnxqxWBRPIq0Lw84CWRLF1bvVJGr xmPYDAXG2rH1cW433tXlnm/j93zkl3UKZWysNLFOHI45DOSgXBmvGOxR4RnRX/lp B7GUXiC/8udS4NoK+K4ISch9RsEnC/24wPiBlTl+k763cvBIuP/nZF0FQom1/5uX YxUf/+31mfneVrsawfhBf3bqRkFv03L3YSUzAkvuRfDSZw2MoP5vgu6FHLW56CK4 PrGCtNqWYU2ENGUaGwx1fKBnXG2CN5DUb97CtJQsTTEbn5GEXwQHEc+URYSWmpOW tUrajbGLLfx3JDSiwbcq6g== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:content-type:date:date:feedback-id:feedback-id :from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm3; t=1786971581; x= 1787057981; bh=bQ68rGWO5+XJK8Ee7Y4MpJFQgMAvX184NdiLnRVSkzI=; b=i qk0ZZGLQPfTfh2kptC750VNH9PmChyfYQx5a5sa2HUzx390rfuMo+KPS5/ep4zMG LMBsJxY9WnhwQBRB909OWefFpqnZ5zJ+Dblok3DBePsj2WpSshvae5Oh3c7wmow5 eAQYz91n+DdXshP3Z/giKu5eYAUIzRpGD6BeAGYMrH9tY/11aWGfjyrvbYATtLG1 wRWVlDVK248PFhnrjrF18HilhDan0U6HknNojhtHPgzPUZwROpH/Fn90ewOUFE4l 6ER2ou/yIflu00LYZ0KLCXI5ymoXCVIMCmFSc8C2+yxVSgPBFgWeYPLYPHYxx9C/ ZCtW3z6pBHYEhqo1hdtdQ== X-ME-Sender: X-ME-Proxy-Cause: dmFkZTFrJQquK4O/Ss9PIUnA61QMTKUxplzDdeAV+mGJHm6az6ApcdUzgLb4ocbjXBTFEQ 5ZIKh+gRdwlURyM1BOZsyjg3BxgSAv9jwi31hDOmEcJFGkpWNl0sok7rBC3wSehXCV6Gcd budBvHA5eC+q9TOcRGZPvDE4DVSXy3T7vhgLk6sFJ94H0eJL0jnslBuB3FSILMtRZlFAYQ 3zD7qDx+GwpfSiV+tmkDGSn7hVAwA0Km7hBXyITvN8slYbT4kTN2IlGcCesnDzxGm6hE8C 8uoQeNiOVoRRyEGlVYl/E1aRIeYW6CczUWjdYlcaXU6UiTG2IHG3NaqTZV3ij0f/mFK9tZ sDMwl00WCYHSE2mF4xDuFUlGcdM/kJShAvBgye9OftzsK1LkfEas2LA64uZZaEwvzL1Opw qWsrsuzES5iljhkKU7/9VVHzMPCGSGkFFtyFG4W60Y/fyqzM9DlYA7Yeh3H+HnBKmIhxiz eDbyotJI3ZlN4G2pIJIHrODsDnfClP65xHYvCqQNewEare2JOBXlatPbzd2D5ducAH2C49 NPmXvbXIotr4tQ4v3ZU4LiGzEa/lYEmy8eQXrm48CQFUwp5Y/mWYene0Vs4ctJdQSiKgVm m2b+evTH2uotPBCeFVTIIZa7LOWED6upQNzX/x3CJoJPJWBs16qXr0181kpQ X-ME-Proxy: Feedback-ID: i56a14606:Fastmail Received: by mailuser.ams.internal (Postfix, from userid 501) id 21A9432A0070; Mon, 17 Aug 2026 08:59:30 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface MIME-Version: 1.0 X-ThreadId: AdWx15gK6UpR Date: Mon, 17 Aug 2026 14:59:09 +0200 From: "Arnd Bergmann" To: "Stanislav Fomichev" , Netdev Cc: "David S . Miller" , "Eric Dumazet" , "Jakub Kicinski" , "Paolo Abeni" , "Anthony L Nguyen" , "Przemek Kitszel" , andrew+netdev@lunn.ch, "Saeed Mahameed" , "Tariq Toukan" , "Mark Bloch" , "Maxime Chevallier" , "Maxime Coquelin" , "Alexandre Torgue" , "Alexander Lobakin" , "Simon Horman" , magnus.karlsson@intel.com, "Maciej Fijalkowski" , "Stanislav Fomichev" , "Alexei Starovoitov" , "Daniel Borkmann" , "Jesper Dangaard Brouer" , "John Fastabend" , witu@nvidia.com, "Martin KaFai Lau" , yoong.siang.song@intel.com, rohan.g.thomas@intel.com, "intel-wired-lan@lists.osuosl.org" , linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, bpf@vger.kernel.org, "Leon Romanovsky" Message-Id: <06f8153d-2156-4e7d-9d49-006db4b2cec4@app.fastmail.com> In-Reply-To: <20260813190800.222527-2-sdf@fomichev.me> References: <20260813190800.222527-1-sdf@fomichev.me> <20260813190800.222527-2-sdf@fomichev.me> Content-Type: text/plain Content-Transfer-Encoding: 7bit Subject: Re: [Intel-wired-lan] [PATCH net v2 1/3] xsk: align TX metadata layout across ABIs X-BeenThere: intel-wired-lan@osuosl.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Intel Wired Ethernet Linux Kernel Driver Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-wired-lan-bounces@osuosl.org Sender: "Intel-wired-lan" On Thu, Aug 13, 2026, at 21:07, Stanislav Fomichev wrote: > Add explicit padding before launch_time so xsk_tx_metadata has the same > layout on 32-bit and 64-bit systems. > > On i386 and m68k, the old native 32-bit layout put launch_time at offset 12 > and had a natural size of 20 bytes. Using sizeof(struct xsk_tx_metadata) as > tx_metadata_len was already rejected because the length must be a multiple > of eight, so the straightforward use of the interface was broken on those > ABIs. Userspace could still register a padded length of 24 bytes, though; > mixing the old and new layouts then silently reads launch_time from the > wrong offset and misprograms packet launch times. This intentionally > replaces that incompatible layout while the interface is still new. > > Fixes: ca4419f15abd ("xsk: Add launch time hardware offload support to > XDP Tx metadata") > Signed-off-by: Stanislav Fomichev This is probably the right approach, given lack of alternatives. In the changelog text, it may be worth noting a few more points: - A few additional architectures have the same issue: csky, nios2, openrisc and sh. - the commit that introduced the mistake was part of linux-6.15, so the 6.18-lts release also needs an ABI change. I don't think the "while the interface is still new" wording makes sense here. - what actually saves us here is that none of the affected architectures are likely to have notable use cases for xdp that would care about the ABI break. The one that is most likely to have affected users is x86-compat, and that is also the only one that is broken right now. Arnd