From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752369Ab0DLOhx (ORCPT ); Mon, 12 Apr 2010 10:37:53 -0400 Received: from terminus.zytor.com ([198.137.202.10]:43982 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752123Ab0DLOhv (ORCPT ); Mon, 12 Apr 2010 10:37:51 -0400 Message-ID: <4BC33022.3000608@zytor.com> Date: Mon, 12 Apr 2010 07:37:22 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: Andi Kleen CC: Colin King , Ingo Molnar , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: Disable 4MB page tables for Atom, work around errata AAE44 References: <1269271251-19775-1-git-send-email-colin.king@canonical.com> <87633xayk4.fsf@basil.nowhere.org> In-Reply-To: <87633xayk4.fsf@basil.nowhere.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/12/2010 01:02 AM, Andi Kleen wrote: > Colin King writes: >> >> +static void __init check_atom(void) >> +{ >> + >> + /* >> + * Disable 4MB page tables to work around Intel errata AAE44 for >> + * Atom. We cannot guarantee stopping undefined processor behaviour >> + * when two pageing structure translations differ with respect to >> + * page frame sizes. Hence, for Atoms we disable the PSE. >> + */ >> + if (boot_cpu_data.x86_model == 0x1c) { > > Perhaps someone else pointed that out already, but you obviously > need to check for x86_vendor == X86_VENDOR_INTEL and x86_family == 6 too, > otherwise you'll get false positives. > > Besides such workarounds are normally in arch/x86/kernel/cpu/intel.c. > bugs.c is really obsolete. > Much more than that, the constraint is clearly not strict enough. I'm currently trying to work out internally what the actual constraint should be (it's a bit of a documentation hole at the moment.) -hpa