From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755500AbYD2Wzj (ORCPT ); Tue, 29 Apr 2008 18:55:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751027AbYD2Wzb (ORCPT ); Tue, 29 Apr 2008 18:55:31 -0400 Received: from www.tglx.de ([62.245.132.106]:46602 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750698AbYD2Wza (ORCPT ); Tue, 29 Apr 2008 18:55:30 -0400 Date: Wed, 30 Apr 2008 00:54:28 +0200 (CEST) From: Thomas Gleixner To: "Eric W. Biederman" cc: Yinghai Lu , Andrew Morton , Ingo Molnar , "H. Peter Anvin" , Gabriel C , "linux-kernel@vger.kernel.org" , Mika Fischer Subject: Re: [PATCH] x86: mtrr cleanup for converting continuous to discrete layout v5 In-Reply-To: Message-ID: References: <200804272337.40130.yhlu.kernel@gmail.com> <200804281244.56938.yhlu.kernel@gmail.com> <200804281316.14168.yhlu.kernel@gmail.com> <200804281505.05764.yhlu.kernel@gmail.com> <86802c440804291304r7ff169f6k9132f98761ecef42@mail.gmail.com> <86802c440804291457k79099d84w53110fabf59e9e37@mail.gmail.com> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 29 Apr 2008, Eric W. Biederman wrote: > Think of SMM mode is a lightweight hypervisor that we can't get rid > of, if you want to understand the worst case. > > In theory SMM mode is completely unnecessary as soon as we enable > ACPI. In practice ACPI appears to frequently trap into SMM mode. SMM does more than that. It emulates legacy hardware and fixes chip(set) bugs as well. Disabling it just makes your box stop working. There are certain types of systems where essential safety nets rely on SMIs (you can deep-fry P4s by disabling SMIs). Thanks, tglx