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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D0C9BC433E0 for ; Wed, 6 Jan 2021 11:28:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B170221EA for ; Wed, 6 Jan 2021 11:28:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726258AbhAFL2D (ORCPT ); Wed, 6 Jan 2021 06:28:03 -0500 Received: from foss.arm.com ([217.140.110.172]:39612 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726216AbhAFL2C (ORCPT ); Wed, 6 Jan 2021 06:28:02 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 974F1106F; Wed, 6 Jan 2021 03:27:16 -0800 (PST) Received: from e107158-lin (e107158-lin.cambridge.arm.com [10.1.194.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1337B3F719; Wed, 6 Jan 2021 03:27:14 -0800 (PST) Date: Wed, 6 Jan 2021 11:27:12 +0000 From: Qais Yousef To: Alexei Starovoitov Cc: bpf , Daniel Borkmann , Andrii Nakryiko , Phil Auld , "Peter Zijlstra (Intel)" , Dietmar Eggemann , vincent.donnefort@arm.com, Ingo Molnar , vincent.guittot@linaro.org, LKML , Valentin Schneider Subject: Re: [PATCH v2] sched/debug: Add new tracepoint to track cpu_capacity Message-ID: <20210106112712.6ec7yejhidauo432@e107158-lin> References: <1e806d48-fd54-fd86-5b3a-372d9876f360@arm.com> <20200828172658.dxygk7j672gho4ax@e107158-lin.cambridge.arm.com> <58f5d2e8-493b-7ce1-6abd-57705e5ab437@arm.com> <20200902135423.GB93959@lorien.usersys.redhat.com> <20200907110223.gtdgqod2iv2w7xmg@e107158-lin.cambridge.arm.com> <20200908131954.GA147026@lorien.usersys.redhat.com> <20210104182642.xglderapsfrop6pi@e107158-lin> <20210105113857.gzqaiuhxsxdtu474@e107158-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/05/21 08:44, Alexei Starovoitov wrote: > > Any pointer to an example test I could base this on? > > selftests/bpf/ I was hoping for something more elaborate. I thought there's something already there that do some verification for raw tracepoint that I could either extend or replicate. Otherwise this could end up being a time sink for me and I'm not keen on jumping down this rabbit hole. > > > - add a doc with contents from commit log. > > > > You're referring to the ABI part of the changelog, right? > > > > > The "Does bpf make things into an abi ?" question keeps coming back > > > over and over again. > > > Everytime we have the same answer that No, bpf cannot bake things into abi. > > > I think once it's spelled out somewhere in Documentation/ it would be easier to > > > repeat this message. > > > > How about a new Documentation/bpf/ABI.rst? I can write something up initially > > for us to discuss in detail when I post. > > There is Documentation/bpf/bpf_design_QA.rst > and we already have this text in there that was added back in 2017: > > Q: Does BPF have a stable ABI? > ------------------------------ > A: YES. BPF instructions, arguments to BPF programs, set of helper > functions and their arguments, recognized return codes are all part > of ABI. However there is one specific exception to tracing programs > which are using helpers like bpf_probe_read() to walk kernel internal > data structures and compile with kernel internal headers. Both of these > kernel internals are subject to change and can break with newer kernels > such that the program needs to be adapted accordingly. > > I'm suggesting to add an additional section to this Q/A doc to include > more or less > the same text you had in the commit log. Works for me. Thanks -- Qais Yousef