From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752635AbaBYKqJ (ORCPT ); Tue, 25 Feb 2014 05:46:09 -0500 Received: from terminus.zytor.com ([198.137.202.10]:52720 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750735AbaBYKqI (ORCPT ); Tue, 25 Feb 2014 05:46:08 -0500 Message-ID: <530C7465.2080600@zytor.com> Date: Tue, 25 Feb 2014 02:45:57 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Chris Bainbridge , x86@kernel.org CC: linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: set Pentium M as PAE capable References: <20140225060146.GA4339@debian.local> In-Reply-To: <20140225060146.GA4339@debian.local> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/24/2014 10:01 PM, Chris Bainbridge wrote: > Pentium M is PAE capable but does not indicate so in the CPUID response. > This is an issue now that some distributions are no longer shipping > non-PAE kernels (those distributions no longer boot on Pentium M). This > small patch fixes the issue by forcing the PAE capability on Pentium M. > > For more discussion see https://bugs.launchpad.net/baltix/+bug/930447 > 1. This patch doesn't match the discussion in the link. 2. You would have to also enable this in the cpu testing code in arch/x86/boot. 3. At the very least we need to print a serious warning that the CPU is being run outside its specifications. I have no personal information about why this CPUID bit was disabled, but it could be that it was discovered in testing that it didn't work correctly in all circumstances (e.g. high temperature.) This is very much "use at your own risk..."; you could get data corruption or even hardware damage. We should probably also taint the kernel. -hpa