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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 C44A1C10F06 for ; Wed, 3 Apr 2019 21:30:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9B75A2082C for ; Wed, 3 Apr 2019 21:30:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726948AbfDCVa1 (ORCPT ); Wed, 3 Apr 2019 17:30:27 -0400 Received: from mga05.intel.com ([192.55.52.43]:37312 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726825AbfDCVaW (ORCPT ); Wed, 3 Apr 2019 17:30:22 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Apr 2019 14:30:13 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,306,1549958400"; d="scan'208";a="334754289" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by fmsmga005.fm.intel.com with ESMTP; 03 Apr 2019 14:30:13 -0700 From: Fenghua Yu To: "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "H Peter Anvin" , "Dave Hansen" , "Paolo Bonzini" , "Ashok Raj" , "Peter Zijlstra" , "Kalle Valo" , "Xiaoyao Li " , "Michael Chan" , "Ravi V Shankar" Cc: "linux-kernel" , "x86" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, kvm@vger.kernel.org, Fenghua Yu Subject: [PATCH v6 20/20] x86/clearcpuid: Change document for kernel option clearcpuid Date: Wed, 3 Apr 2019 14:22:06 -0700 Message-Id: <1554326526-172295-21-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1554326526-172295-1-git-send-email-fenghua.yu@intel.com> References: <1554326526-172295-1-git-send-email-fenghua.yu@intel.com> Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org Since kernel option clearcpuid now supports multiple options and CPU capability flags, the document needs to be changed. Signed-off-by: Fenghua Yu --- .../admin-guide/kernel-parameters.txt | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 2b8ee90bb644..0cbeda6d7f16 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -563,17 +563,21 @@ loops can be debugged more effectively on production systems. - clearcpuid=BITNUM [X86] + clearcpuid=BITNUM | FLAG [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 + numbers or /proc/cpuinfo for valid CPU flags. + Multiple options can be used to disable a few features. + This prevents the feature from being used by the + kernel or shown in /proc/cpuinfo or shown in CPUID + called directly by user programs. + A few notes: + - The Linux specific bits are not necessarily stable over kernel options, but the vendor specific ones should be. - Also note that user programs calling CPUID directly - or using the feature without checking anything - will still see it. This just prevents it from - being used by the kernel or shown in /proc/cpuinfo. - Also note the kernel might malfunction if you disable + - User programs using the feature without checking + anything will still use it. + - The kernel might malfunction if you disable some critical bits. cma=nn[MG]@[start[MG][-end[MG]]] -- 2.19.1