From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753039AbaBYLfb (ORCPT ); Tue, 25 Feb 2014 06:35:31 -0500 Received: from mail.skyhub.de ([78.46.96.112]:44326 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751164AbaBYLf2 (ORCPT ); Tue, 25 Feb 2014 06:35:28 -0500 Date: Tue, 25 Feb 2014 12:35:24 +0100 From: Borislav Petkov To: "H. Peter Anvin" Cc: Chris Bainbridge , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: set Pentium M as PAE capable Message-ID: <20140225113524.GA23256@pd.tnic> References: <20140225060146.GA4339@debian.local> <530C7465.2080600@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <530C7465.2080600@zytor.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 25, 2014 at 02:45:57AM -0800, H. Peter Anvin wrote: > 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. Right, I was about to say that. And since there's no special bit for running "out-of-spec", we could probably repurpose TAINT_UNSAFE_SMP - 'S' - SMP with CPUs not designed for SMP. to TAINT_UNSAFE_OUT_OF_SPEC (the letter S fits still) and add that taint everytime we're enforcing functionality against doctor's orders, so to speak. :-) Hmm. -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. --