Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761157AbYCERc0 (ORCPT ); Wed, 5 Mar 2008 12:32:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755330AbYCERcG (ORCPT ); Wed, 5 Mar 2008 12:32:06 -0500 Received: from terminus.zytor.com ([198.137.202.10]:43836 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757108AbYCERcB (ORCPT ); Wed, 5 Mar 2008 12:32:01 -0500 Message-ID: <47CED7F8.1060205@zytor.com> Date: Wed, 05 Mar 2008 09:27:20 -0800 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.12 (X11/20080226) MIME-Version: 1.0 To: Jeremy Fitzhardinge CC: Eduardo Habkost , Ian Campbell , Alexander van Heukelum , Ingo Molnar , Alexander van Heukelum , Andi Kleen , Thomas Gleixner , Mark McLoughlin , LKML Subject: Re: [RFC] use realmode code to reserve end-of-conventional-memory to 1MB References: <20080224174605.GA21661@mailshack.com> <47C22568.1010405@zytor.com> <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> <47CECC8D.9090507@goop.org> In-Reply-To: <47CECC8D.9090507@goop.org> 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: 1262 Lines: 28 Jeremy Fitzhardinge 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. > > For the moment that's true, but we should be able to release those > pages. On the other hand, there's been talk of making Xen hand out > memory in physically contigious 2M chunks, which means trying to unmap > 300k won't be possible or worthwhile. I suspect real hardware will just > waste this memory too (it won't remap that 320k of ram to somewhere > else; it will just be shadowed) - which is nothing compared to chipsets > which will just throw away 1G to make space for PCI... > Not that 384K is all that much to worry about, but you could just map memory from 2 MB upward, and set the kernel load address to 2 MB (which is good for performance anyway.) There has been talk of making the default kernel load address 16 MB, to keep the DMA zone free. -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/