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=-6.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, 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 64750C43463 for ; Sun, 20 Sep 2020 18:59:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 14BE020897 for ; Sun, 20 Sep 2020 18:59:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="VNROPEgr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726316AbgITS7W (ORCPT ); Sun, 20 Sep 2020 14:59:22 -0400 Received: from mail.skyhub.de ([5.9.137.197]:50162 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726109AbgITS7V (ORCPT ); Sun, 20 Sep 2020 14:59:21 -0400 Received: from zn.tnic (p200300ec2f295d00c534af3fd805ebd6.dip0.t-ipconnect.de [IPv6:2003:ec:2f29:5d00:c534:af3f:d805:ebd6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 6CF4E1EC0269; Sun, 20 Sep 2020 20:59:20 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1600628360; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=UvXD3Q/TMABI41d+N90w8/mHRLoeW6vMnaSJGKGrbRc=; b=VNROPEgrxzET1pj/7t1nW7ippDsTCNLCBbd98ifrzv2xRuAg7RF3OjrmVGa3P8h+c5GXxF vYbZGUoYyPi1thJmbS9Hln7QaRF4MeYYWKGXQFDIKd72XJ152zNfKKvSUtV+Du+aziLhsJ TA21OZWi3QBfcTw8zDGlwcX3BZg2DGM= Date: Sun, 20 Sep 2020 20:59:14 +0200 From: Borislav Petkov To: Arvind Sankar Cc: x86-ml , lkml Subject: Re: [RFC PATCH] Use feature bit names in clearcpuid= Message-ID: <20200920185914.GD7473@zn.tnic> References: <20200920154228.GB7473@zn.tnic> <20200920161628.GA3951950@rani.riverdale.lan> <20200920172954.GC7473@zn.tnic> <20200920183527.GA3970023@rani.riverdale.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200920183527.GA3970023@rani.riverdale.lan> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Sep 20, 2020 at 02:35:27PM -0400, Arvind Sankar wrote: > Thanks. Maybe also mention in the documentation that names can now be > used. Already did it as an incremental ontop. Will merge later: --- diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index ffe864390c5a..49988e891d7f 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -577,12 +577,17 @@ loops can be debugged more effectively on production systems. - clearcpuid=BITNUM[,BITNUM...] [X86] + clearcpuid=X[,X...] [X86] Disable CPUID feature X for the kernel. See arch/x86/include/asm/cpufeatures.h for the valid bit - numbers. Note the Linux specific bits are not necessarily - stable over kernel options, but the vendor specific + numbers X. Note the Linux-specific bits are not necessarily + stable over kernel options, but the vendor-specific ones should be. + X can also be a string as appearing in the flags: line + in /proc/cpuinfo which does not have the above + instability issue. However, not all features have names + in /proc/cpuinfo. + Note that using this option will taint your kernel. Also note that user programs calling CPUID directly or using the feature without checking anything will still see it. This just prevents it from -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette