From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755553AbZBVDOQ (ORCPT ); Sat, 21 Feb 2009 22:14:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752493AbZBVDOA (ORCPT ); Sat, 21 Feb 2009 22:14:00 -0500 Received: from terminus.zytor.com ([198.137.202.10]:55710 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751483AbZBVDOA (ORCPT ); Sat, 21 Feb 2009 22:14:00 -0500 Message-ID: <49A0C2D4.20009@zytor.com> Date: Sat, 21 Feb 2009 19:13:24 -0800 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Vegard Nossum CC: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar , Pekka Enberg Subject: Re: [PATCH] kmemcheck: disable fast string operations on P4 CPUs References: <1235223364-2097-1-git-send-email-vegard.nossum@gmail.com> <1235223364-2097-2-git-send-email-vegard.nossum@gmail.com> In-Reply-To: <1235223364-2097-2-git-send-email-vegard.nossum@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Vegard Nossum wrote: > This patch may allow us to remove the REP emulation code from > kmemcheck. > +#ifdef CONFIG_KMEMCHECK > + /* > + * P4s have a "fast strings" feature which causes single- > + * stepping REP instructions to only generate a #DB on > + * cache-line boundaries. > + * > + * Ingo Molnar reported a Pentium D (model 6) and a Xeon > + * (model 2) with the same problem. > + */ > + if (c->x86 == 15) { If this is supposed to refer to the Intel P4 core, you should exclude the post-P4 cores that also have x86 == 15 (e.g. Core 2 and Core i7). If those are affected, too, they should be mentioned in the comment. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.