Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759567AbYGJSHp (ORCPT ); Thu, 10 Jul 2008 14:07:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760355AbYGJSHE (ORCPT ); Thu, 10 Jul 2008 14:07:04 -0400 Received: from terminus.zytor.com ([198.137.202.10]:40404 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759102AbYGJSHD (ORCPT ); Thu, 10 Jul 2008 14:07:03 -0400 Message-ID: <48764E31.4010408@zytor.com> Date: Thu, 10 Jul 2008 14:00:17 -0400 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Christoph Lameter CC: Jeremy Fitzhardinge , Mike Travis , "Eric W. Biederman" , Arjan van de Ven , Ingo Molnar , Andrew Morton , Jack Steiner , linux-kernel@vger.kernel.org, Rusty Russell Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses References: <20080709165129.292635000@polaris-admin.engr.sgi.com> <20080709200757.GD14009@elte.hu> <48751B57.8030605@goop.org> <20080709133958.612635f0@infradead.org> <4875231F.1020506@zytor.com> <487524A0.6020304@goop.org> <487529AE.3060505@zytor.com> <48753A71.2030006@zytor.com> <48763732.7020805@sgi.com> <487637DE.1050706@zytor.com> <48763A5E.7080105@linux-foundation.org> <48763B36.80104@zytor.com> <48763D1C.8040206@linux-foundation.org> <48764530.7000909@goop.org> <48764783.6030201@linux-foundation.org> In-Reply-To: <48764783.6030201@linux-foundation.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: 980 Lines: 20 Christoph Lameter wrote: > > Right. The problem is with the percpu area handled by the linker. That percpu area is used by the boot cpu and later we setup other additional per cpu areas. Those can be placed in an arbitrary way if one goes through a table of pointers to these areas. > > However, that does not work if one calculates the virtual address instead of looking up a physical address. > As far as the linker is concerned, there are two address spaces: VMA, which is the offset, and LMA, which is the physical address on where to load. The linker doesn't give a flying hoot about the virtual address, since it's completely irrelevant as far as it is concerned; it's nothing but a kernel-internal abstraction. -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/