From patchwork Wed Apr 17 21:34:11 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fenghua Yu X-Patchwork-Id: 1087228 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=fail (p=none dis=none) header.from=intel.com Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 44kwhW0mNfz9s4V for ; Thu, 18 Apr 2019 07:43:07 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387757AbfDQVnA (ORCPT ); Wed, 17 Apr 2019 17:43:00 -0400 Received: from mga12.intel.com ([192.55.52.136]:20177 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387667AbfDQVmd (ORCPT ); Wed, 17 Apr 2019 17:42:33 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Apr 2019 14:42:32 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,363,1549958400"; d="scan'208";a="224441229" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by orsmga001.jf.intel.com with ESMTP; 17 Apr 2019 14:42:31 -0700 From: Fenghua Yu To: "Thomas Gleixner" , "Ingo Molnar" , "Borislav Petkov" , "H Peter Anvin" , "Paolo Bonzini" , "Dave Hansen" , "Ashok Raj" , "Peter Zijlstra" , "Ravi V Shankar" , "Xiaoyao Li " , "Christopherson Sean J" , "Kalle Valo" , "Michael Chan" Cc: "linux-kernel" , "x86" , kvm@vger.kernel.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, Fenghua Yu Subject: [PATCH v7 21/21] x86/clearcpuid: Change document for kernel option clearcpuid Date: Wed, 17 Apr 2019 14:34:11 -0700 Message-Id: <1555536851-17462-22-git-send-email-fenghua.yu@intel.com> X-Mailer: git-send-email 2.5.0 In-Reply-To: <1555536851-17462-1-git-send-email-fenghua.yu@intel.com> References: <1555536851-17462-1-git-send-email-fenghua.yu@intel.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@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]]]