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=-3.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 094C9C43463 for ; Sat, 19 Sep 2020 00:58:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A521321D43 for ; Sat, 19 Sep 2020 00:58:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ntl+DWhV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726054AbgISA6F (ORCPT ); Fri, 18 Sep 2020 20:58:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39994 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726009AbgISA6F (ORCPT ); Fri, 18 Sep 2020 20:58:05 -0400 Received: from mail-lj1-x241.google.com (mail-lj1-x241.google.com [IPv6:2a00:1450:4864:20::241]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E0D4FC0613CE for ; Fri, 18 Sep 2020 17:58:04 -0700 (PDT) Received: by mail-lj1-x241.google.com with SMTP id y4so6479414ljk.8 for ; Fri, 18 Sep 2020 17:58:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=pZ5wi8jIOWzLRpX0RYv1U5STsuvGrzwO5RB9BjjV5gY=; b=ntl+DWhVoWLZcFZOJ2kgm8kNEnhmil18Iz57OhyTPzQFTC+Seh0vRd/b2vK3rcktDs mTVJ/dRlmWUscy/QM3FHBcAbZmkOWWqqxFO12gxs/noIVVf/oI4u3tY6BxI/sNaCKCrQ KJMfO4WUQvaA/ziQm1bOCa6wq8rfApmfDjzZ7DXJ5eZmYd8bKWjNdge5dLgeyTJiwbkN XqDF0eBu/TcUZ7lViR/ji/hUivpqPVj/kS/ALkQThbkQ/h82NWB6RRX0iPWCl0CzGpJS dF5/3gYr0m7Nt+kcVOe0PanHocjhGXed15D+9WrrTt6iJPXVQvvTxSqxARWk6C826BdQ m11w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=pZ5wi8jIOWzLRpX0RYv1U5STsuvGrzwO5RB9BjjV5gY=; b=UeRg/Jr2/UKeP0O95HWiHHMhUDCh4BtbUD1kguPt1LJizn+Xfw+hQSIJh+sLYbZYud vXbKjT9f0NaIzTm+m0h/sPvF0Pfi8mXeHN6w5NIVybgENZYfVuiVloJliGfuMRrZUfWW F8vK9G7R7dUldW96Lu+k7SSwoOKCeljSVsNBOELs7CHDhefUB38/yMtAGD3UAp+/2uzf +LdNytPK7iYatiYKywlT4nir1eSpGjGA1JW2UnZwBd3tScW3g3vSmXpf3RtY+2qpFxZn T5mGWe8VoXkujrOQdkKrwPj5RmxKfMiyBSF520juDTdsUDTUn/KviIxsvbDsB6AxX2OJ lHJA== X-Gm-Message-State: AOAM532CHtU+rSdK6jmH7dckIDXbU3/F+WSazRi4JeWkCiDrjwkjE4iH T3ImTUCsGFjPpUJxNW4qQYL0gf1yVEtpZHRAxYE= X-Google-Smtp-Source: ABdhPJwbmgJP7037U4f9cFRaTQ21r3KHAevViiw65wV6N4x0LUmzECbp7Yeb+QqskOTg2aCDhkP4txUuit4u7/ryTPw= X-Received: by 2002:a2e:8593:: with SMTP id b19mr11823173lji.290.1600477082163; Fri, 18 Sep 2020 17:58:02 -0700 (PDT) MIME-Version: 1.0 References: <20200918204058.1030519-1-haoluo@google.com> In-Reply-To: <20200918204058.1030519-1-haoluo@google.com> From: Alexei Starovoitov Date: Fri, 18 Sep 2020 17:57:50 -0700 Message-ID: Subject: Re: [PATCH 0/2] pahole: Make encoding percpu vars into BTF optional. To: Hao Luo Cc: Arnaldo Carvalho de Melo , Andrii Nakryiko , Daniel Borkmann , dwarves@vger.kernel.org, Yonghong Song Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: dwarves@vger.kernel.org On Fri, Sep 18, 2020 at 1:41 PM Hao Luo wrote: > > Previous commit f3d9054ba8ff ("btf_encoder: Teach pahole to store > percpu variables in vmlinux BTF.") introduced a feature in btf_encoder > that encodes global symbols in BTF. However, this feature is not > protected by any flag. In order to avoid surprises after Pahole v1.18 > rolls out, make this feature off by default and enable only upon > request. On the kernel side, we can add a Kconfig to enable this > new capability on an opt-in pattern. I think I've missed some earlier discussions and motivation for opt-in. Why opt-out is a problem? I would think the kernel build should always include percpu vars.