Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752662AbeADSek (ORCPT + 1 other); Thu, 4 Jan 2018 13:34:40 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58384 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750990AbeADSeh (ORCPT ); Thu, 4 Jan 2018 13:34:37 -0500 Date: Thu, 4 Jan 2018 19:34:35 +0100 From: Andrea Arcangeli To: Tim Chen Cc: Thomas Gleixner , Andy Lutomirski , Linus Torvalds , Greg KH , Dave Hansen , Andi Kleen , Arjan Van De Ven , linux-kernel@vger.kernel.org Subject: Re: [PATCH 6/7] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature Message-ID: <20180104183435.GK13348@redhat.com> References: <4d4b3752e8e533201c6983d8473eea95c747ea33.1515086770.git.tim.c.chen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4d4b3752e8e533201c6983d8473eea95c747ea33.1515086770.git.tim.c.chen@linux.intel.com> User-Agent: Mutt/1.9.2 (2017-12-15) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Thu, 04 Jan 2018 18:34:37 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Thu, Jan 04, 2018 at 09:56:47AM -0800, Tim Chen wrote: > There are 2 ways to control IBRS > > 1. At boot time > noibrs kernel boot parameter will disable IBRS usage > > Otherwise if the above parameters are not specified, the system > will enable ibrs and ibpb usage if the cpu supports it. > > 2. At run time > echo 0 > /sys/kernel/debug/ibrs_enabled will turn off IBRS > echo 1 > /sys/kernel/debug/ibrs_enabled will turn on IBRS in kernel > echo 2 > /sys/kernel/debug/ibrs_enabled will turn on IBRS in both userspace and kernel debug/x86/? Reviewed-by: Andrea Arcangeli Thanks, Andrea