From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756617Ab2GYQ5a (ORCPT ); Wed, 25 Jul 2012 12:57:30 -0400 Received: from terminus.zytor.com ([198.137.202.10]:57028 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756382Ab2GYQ53 (ORCPT ); Wed, 25 Jul 2012 12:57:29 -0400 Message-ID: <50102563.8090909@zytor.com> Date: Wed, 25 Jul 2012 09:57:07 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120717 Thunderbird/14.0 MIME-Version: 1.0 To: Jan Beulich CC: Yinghai Lu , mingo@elte.hu, tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: simplify mtrr_bp_init() References: <4FF70FDB020000780008E199@nat28.tlf.novell.com> <500FC39702000078000905AD@nat28.tlf.novell.com> In-Reply-To: <500FC39702000078000905AD@nat28.tlf.novell.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/25/2012 12:59 AM, Jan Beulich wrote: >> >> should drop all phys_addr assignment in this function. >> >> x86_phys_bits should have all correct value? > > Is it certain that all special cases (setting phys_addr to 32) are > covered by those CPUs not having PAE/PSE36? One would > think that this is valid to imply, but getting cpu_info's phys_bits > wrong isn't fatal as long as no addresses beyond 4G would ever > be encountered anywhere, whereas using too large an address > width here would result in the MTRR writes causing #GP. So > when I did this adjustment (a couple of years ago already - this > isn't the first submission), I decided to remain on the safe side. > > Does any of the maintainers have an opinion either way? > There are definitely CPUs which have PAE but only has a 32-bit address bus. On the other hand there are tons of chipsets which arbitrary address caps that almost nothing in the system knows about, so I don't think this matters. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.