Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758927AbYCERdi (ORCPT ); Wed, 5 Mar 2008 12:33:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755183AbYCERdN (ORCPT ); Wed, 5 Mar 2008 12:33:13 -0500 Received: from terminus.zytor.com ([198.137.202.10]:34558 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757296AbYCERdJ (ORCPT ); Wed, 5 Mar 2008 12:33:09 -0500 Message-ID: <47CED853.6030909@zytor.com> Date: Wed, 05 Mar 2008 09:28:51 -0800 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.12 (X11/20080226) MIME-Version: 1.0 To: Eduardo Habkost CC: Ian Campbell , Alexander van Heukelum , Ingo Molnar , Alexander van Heukelum , Andi Kleen , Thomas Gleixner , Jeremy Fitzhardinge , Mark McLoughlin , LKML Subject: Re: [RFC] use realmode code to reserve end-of-conventional-memory to 1MB References: <1203958478.20033.1239002461@webmail.messagingengine.com> <20080225170134.GA15839@elte.hu> <20080225180750.GA31054@mailshack.com> <20080228131341.GA25213@mailshack.com> <20080228132822.GA25278@mailshack.com> <1204233131.28798.12.camel@cthulhu.hellion.org.uk> <47C72432.3010606@zytor.com> <1204240609.28798.33.camel@cthulhu.hellion.org.uk> <20080305155930.GI20230@blackpad> <47CEC561.6050008@zytor.com> <20080305165320.GJ20230@blackpad> In-Reply-To: <20080305165320.GJ20230@blackpad> 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 Content-Length: 1132 Lines: 28 Eduardo Habkost wrote: >>> >>> I am aware that it would take more work to tell all kernel code that it >>> shouldn't look for BIOS data on this region when running as a domU guest, >>> but it seems that it would be a better solution. >>> >> No, the right thing is for Xen to not try to map RAM in this area. > > Why? If the Xen host is telling us there is valid RAM in this area, > why can't we use it? > > Existing Xen hosts use those physical address ranges for RAM. We can't > fix this on the e820 map on the guest side without making otherwise-valid > RAM unused. > x86 has a number of historical assumptions, both in kernel and in userspace (consider dmidecode!) Trying to go against them is a losing proposition, *AND* a headache for the maintainers, which will have to consider "oh yes, and Xen does this dumb thing which goes against what all the hardware does." -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/