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=-2.8 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 E534AC4338F for ; Tue, 3 Aug 2021 15:13:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C52E2603E7 for ; Tue, 3 Aug 2021 15:13:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236293AbhHCPNO (ORCPT ); Tue, 3 Aug 2021 11:13:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41254 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235607AbhHCPNK (ORCPT ); Tue, 3 Aug 2021 11:13:10 -0400 Received: from mail-yb1-xb2f.google.com (mail-yb1-xb2f.google.com [IPv6:2607:f8b0:4864:20::b2f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA82BC061757; Tue, 3 Aug 2021 08:12:58 -0700 (PDT) Received: by mail-yb1-xb2f.google.com with SMTP id p145so19741390ybg.6; Tue, 03 Aug 2021 08:12:58 -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=0MA4yBUv23BbJVAOn10I0A8H8/n6Yml4qJZDjujIkSo=; b=JjNxfdKHLCtFD2XS5K70ZXQA2WcJLb5IdcPen4uyEfQUBbimCjc171tfxZeYtP8rM4 W9ZQg3+D+c81v3CGYG7ucquebzCRHerHH57GzrfHk1wx3KwcRf4KYl7iW0Y7hqH/f2yM s5FZcMsUo6tS4xeHdOwu9fUh0HRZH5bmNgcDsASGJ3zsGXSFfd5uEEv06J7Btj/OEz6B rNrGMnqAykS8PGrxzAAkX+eTBi5aZ87b3C0OXAs2KyndgwKGaO1IjkaEJu5tC0vmcGdI C0F6dweKUaDb/wqnP48Fxj+h4GmLm3pRWDpHPGgMvDmr9k81fuCq6T47L4XfkvWMSIZL zfCA== 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=0MA4yBUv23BbJVAOn10I0A8H8/n6Yml4qJZDjujIkSo=; b=lz2DsAw8cIouHxgFkixv3irzu0uBVZQwoVEFsOdww01kMnKqIzjgVndrFaygw6vUbf o4CMkCG7U1m6VhHjKGzbiLuGQEFcSxbE+3+4VejrDq3CrZEuWxM43f+6sQPwK6n794r6 LyMeCB0Ur0LOHeBX0e+hwOJfBkGX7+cyPmpvHq6r/G3ZYJFIF9H6eO2IExR/jiiMpvCC kI56guRT0SNcO4TkFudMl7nknFbBvMBxkkQCp3mvSK2qQoZkZ1+LdwbDCUQtF626w+zP QcV0VXOvrEOlsnnJoUC96j4Vevcku6wQ2Cvq1ZhHBan721EQ8pgR8VRP16rrfzfYc/Fp T9uQ== X-Gm-Message-State: AOAM533lGBPtTQy+xK2JDfM628Pk2vBb2jVZdsrJQJ3ntag3OFkaZWK7 WOlxVoIKjsjge/vZPSST8mVRPgpBkHNbNBuyjBs= X-Google-Smtp-Source: ABdhPJxLLhOuge4lnR2ARgHXuM36tY3HcPDFl47HIWEO4m4676WjV7JTLeLnfVbbWsXbk5W2gMxOcuEvnlYqvQJpYLA= X-Received: by 2002:a25:3046:: with SMTP id w67mr29095940ybw.134.1628003578010; Tue, 03 Aug 2021 08:12:58 -0700 (PDT) MIME-Version: 1.0 References: <20210803113531.30720-1-lukas.bulwahn@gmail.com> In-Reply-To: From: Lukas Bulwahn Date: Tue, 3 Aug 2021 17:12:47 +0200 Message-ID: Subject: Re: [PATCH 0/9] Kconfig symbol clean-up on ./arch/x86/ To: Dave Hansen Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , X86 ML , Randy Dunlap , "H . Peter Anvin" , Darren Hart , Andy Shevchenko , Lubomir Rintel , Pavel Machek , Lee Jones , "Rafael J . Wysocki" , Mika Westerberg , Linus Walleij , platform-driver-x86@vger.kernel.org, kernel-janitors , Linux Kernel Mailing List , Kees Cook Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 3, 2021 at 4:32 PM Dave Hansen wrote: > > On 8/3/21 4:35 AM, Lukas Bulwahn wrote: > > - a reference to STRICT_IOMEM in arch/x86/mm/init.c > > unclear to me: which exact config this refers to > > Are you referring to the reference in this comment? > > > + /* > > + * This must follow RAM test, since System RAM is considered a > > + * restricted resource under CONFIG_STRICT_IOMEM. > > + */ > > + if (iomem_is_exclusive(pagenr << PAGE_SHIFT)) { > > + /* Low 1MB bypasses iomem restrictions. */ > > + if (pagenr < 256) > > + return 1; > ... > Yes, that is what I referred to. > That came from here: > > > commit a4866aa812518ed1a37d8ea0c881dc946409de94 > > Author: Kees Cook > > Date: Wed Apr 5 09:39:08 2017 -0700 > > > > mm: Tighten x86 /dev/mem with zeroing reads > > Which also added this hunk: > > > #ifdef CONFIG_STRICT_DEVMEM > > +static inline int page_is_allowed(unsigned long pfn) > > +{ > > + return devmem_is_allowed(pfn); > > +} > > and talks about CONFIG_STRICT_DEVMEM in the changelog: > > > mm: Tighten x86 /dev/mem with zeroing reads > > > > Under CONFIG_STRICT_DEVMEM, reading System RAM through /dev/mem is > > disallowed. However, on x86, the first 1MB was always allowed for BIOS > ... > > It's a pretty safe guess that STRICT_IOMEM refers to CONFIG_STRICT_DEVMEM. Thanks, Dave. If the maintainers consider updates to comments making them consistent with the code as worth being picked, I will turn your analysis into a proper commit message and provide a patch to update that comment. Lukas