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=-5.2 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 D6716C43603 for ; Tue, 2 Mar 2021 10:39:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9A46B64F0A for ; Tue, 2 Mar 2021 10:39:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1578076AbhCBKf3 (ORCPT ); Tue, 2 Mar 2021 05:35:29 -0500 Received: from mga03.intel.com ([134.134.136.65]:14921 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1381609AbhCBIGO (ORCPT ); Tue, 2 Mar 2021 03:06:14 -0500 IronPort-SDR: DKLZvsxwWIiBb/kHAMe1JaB0tFh7jv4UTzxqepl1R6dBlimw5kVXTht3Gk6fq0T2zyHstM7LMZ cuLDvrcwbLeA== X-IronPort-AV: E=McAfee;i="6000,8403,9910"; a="186785815" X-IronPort-AV: E=Sophos;i="5.81,216,1610438400"; d="scan'208";a="186785815" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Mar 2021 00:05:20 -0800 IronPort-SDR: sw2rsKQqdZjtGURCfIUjJ+SdN7iPxlLGUoaT0a/bgRr/3agl4H7BR1FC+Zn1s2SW81VeV1Jqe/ sZiWgvwKQgfQ== X-IronPort-AV: E=Sophos;i="5.81,216,1610438400"; d="scan'208";a="398278563" Received: from ilick-mobl1.ger.corp.intel.com (HELO btopel-mobl.ger.intel.com) ([10.249.41.237]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Mar 2021 00:05:17 -0800 Subject: Re: [PATCH bpf-next 2/2] libbpf, xsk: add libbpf_smp_store_release libbpf_smp_load_acquire 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, jonathan.lemon@gmail.com, maximmi@nvidia.com, andrii@kernel.org, will@kernel.org References: <20210301104318.263262-1-bjorn.topel@gmail.com> <20210301104318.263262-3-bjorn.topel@gmail.com> <87k0qqx3be.fsf@toke.dk> From: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= Message-ID: Date: Tue, 2 Mar 2021 09:05:15 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <87k0qqx3be.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 2021-03-01 17:10, Toke Høiland-Jørgensen wrote: > Björn Töpel writes: > >> From: Björn Töpel >> >> Now that the AF_XDP rings have load-acquire/store-release semantics, >> move libbpf to that as well. >> >> The library-internal libbpf_smp_{load_acquire,store_release} are only >> valid for 32-bit words on ARM64. >> >> Also, remove the barriers that are no longer in use. > > So what happens if an updated libbpf is paired with an older kernel (or > vice versa)? > "This is fine." ;-) This was briefly discussed in [1], outlined by the previous commit! ...even on POWER. Björn [1] https://lore.kernel.org/bpf/20200316184423.GA14143@willie-the-truck/ > -Toke >