From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755484Ab2LNAvf (ORCPT ); Thu, 13 Dec 2012 19:51:35 -0500 Received: from terminus.zytor.com ([198.137.202.10]:41349 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753410Ab2LNAve (ORCPT ); Thu, 13 Dec 2012 19:51:34 -0500 Message-ID: <50CA7808.7090307@zytor.com> Date: Thu, 13 Dec 2012 16:51:20 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Yinghai Lu CC: Thomas Gleixner , Ingo Molnar , "Eric W. Biederman" , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 19/27] x86, boot: update comments about entries for 64bit image References: <1355436141-8668-1-git-send-email-yinghai@kernel.org> <1355436141-8668-20-git-send-email-yinghai@kernel.org> <50CA6478.20008@zytor.com> <50CA7515.9080701@zytor.com> In-Reply-To: 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 12/13/2012 04:44 PM, Yinghai Lu wrote: > On Thu, Dec 13, 2012 at 4:38 PM, H. Peter Anvin wrote: >> On 12/13/2012 04:13 PM, Yinghai Lu wrote: >> >> It is definitely the minmum we can rely on, and so is the minimum we should >> rely on. In fact, we don't even need .bss/.brk to be mapped, but we >> probably should require that as a matter of protocol. > > in my version of arch/x86/kernel/head_64.S is using BRK to do > ident/kernel high mapping > for kernel that is above 4G. > so .brk is needed. > Yes, with the page fault approach we wouldn't need to do that, so that version is the minimum that can, practically, be required (one can constrain that even further, down to only needing a handful of pages, but that gets progressively more painful for little to no gain.) However, as I said, rather than tying our hands for the future we should include .bss/.brk in the requirement. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.