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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC2C7C43381 for ; Wed, 20 Jan 2021 20:10:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 843D3235E4 for ; Wed, 20 Jan 2021 20:10:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389725AbhATOFX (ORCPT ); Wed, 20 Jan 2021 09:05:23 -0500 Received: from mga17.intel.com ([192.55.52.151]:24322 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389668AbhATN0H (ORCPT ); Wed, 20 Jan 2021 08:26:07 -0500 IronPort-SDR: WimJPuLfOA9A9wPfQSoQxwiRlxK/ww+tZ2kvu7kgNSnBHuqXWby1XYeZ69QCGzkSFYRtFea0R9 pVzMzSA7VJOA== X-IronPort-AV: E=McAfee;i="6000,8403,9869"; a="158877893" X-IronPort-AV: E=Sophos;i="5.79,361,1602572400"; d="scan'208";a="158877893" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jan 2021 05:25:25 -0800 IronPort-SDR: HPzL6eB+vkLX+mVGosC2OWzaKNhF1iuzyuiiihb3ormJH/Vllh/ZMj3dTLlJL6EDFpkpmea90P 0Qtvn6ayMFMg== X-IronPort-AV: E=Sophos;i="5.79,361,1602572400"; d="scan'208";a="384834261" Received: from myegin-mobl1.ger.corp.intel.com (HELO btopel-mobl.ger.intel.com) ([10.249.42.133]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Jan 2021 05:25:19 -0800 Subject: Re: [PATCH bpf-next v2 5/8] libbpf, xsk: select AF_XDP BPF program based on kernel version To: =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org, bpf@vger.kernel.org Cc: magnus.karlsson@intel.com, maciej.fijalkowski@intel.com, kuba@kernel.org, jonathan.lemon@gmail.com, maximmi@nvidia.com, davem@davemloft.net, hawk@kernel.org, john.fastabend@gmail.com, ciara.loftus@intel.com, weqaar.a.janjua@intel.com, Marek Majtyka References: <20210119155013.154808-1-bjorn.topel@gmail.com> <20210119155013.154808-6-bjorn.topel@gmail.com> <875z3repng.fsf@toke.dk> From: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= Message-ID: <6c7da700-700d-c7f6-fe0a-c42e55e81c8a@intel.com> Date: Wed, 20 Jan 2021 14:25:15 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <875z3repng.fsf@toke.dk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 2021-01-20 13:52, Toke Høiland-Jørgensen wrote: > Björn Töpel writes: > >> From: Björn Töpel >> >> Add detection for kernel version, and adapt the BPF program based on >> kernel support. This way, users will get the best possible performance >> from the BPF program. > > Please do explicit feature detection instead of relying on the kernel > version number; some distro kernels are known to have a creative notion > of their own version, which is not really related to the features they > actually support (I'm sure you know which one I'm referring to ;)). > Right. For a *new* helper, like bpf_redirect_xsk, we rely on rejection from the verifier to detect support. What about "bpf_redirect_map() now supports passing return value as flags"? Any ideas how to do that in a robust, non-version number-based scheme? Thanks, Björn