From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764699Ab3DDU0y (ORCPT ); Thu, 4 Apr 2013 16:26:54 -0400 Received: from terminus.zytor.com ([198.137.202.10]:57404 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763121Ab3DDU0x (ORCPT ); Thu, 4 Apr 2013 16:26:53 -0400 Message-ID: <515DE1C1.6080000@zytor.com> Date: Thu, 04 Apr 2013 13:25:37 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: Pekka Enberg CC: Yinghai Lu , Thomas Gleixner , Ingo Molnar , Andrew Morton , Tejun Heo , Thomas Renninger , Tang Chen , linux-kernel@vger.kernel.org, Jacob Shin , "Rafael J. Wysocki" , linux-acpi@vger.kernel.org Subject: Re: [PATCH v2 08/20] x86, ACPI: Find acpi tables in initrd early from head_32.S/head64.c References: <1362897887-30808-1-git-send-email-yinghai@kernel.org> <1362897887-30808-9-git-send-email-yinghai@kernel.org> In-Reply-To: X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/10/2013 03:25 AM, Pekka Enberg wrote: > > What is preventing us from making the 64-bit variant also work in flat > mode to make the code consistent and not hiding the differences under > the rug? What am I missing here? > There is no such thing as "flat mode" in 64-bit mode. We use a #PF handler to emulate it, but we add the normal kernel offset when doing so. In the 32-bit case the problem is that the kernel offset is not available while in linear mode. It *could* be created using segment bases, but that would break Xen, I'm pretty sure, and possibly some other too-clever environments. -hpa