From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755255AbXKEAXt (ORCPT ); Sun, 4 Nov 2007 19:23:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752867AbXKEAXl (ORCPT ); Sun, 4 Nov 2007 19:23:41 -0500 Received: from smtp2.linux-foundation.org ([207.189.120.14]:47117 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752168AbXKEAXk (ORCPT ); Sun, 4 Nov 2007 19:23:40 -0500 Date: Sun, 4 Nov 2007 16:23:11 -0800 (PST) From: Linus Torvalds To: "H. Peter Anvin" cc: Jeremy Fitzhardinge , Mikael Pettersson , linux-kernel@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de Subject: Re: [PATCH] fix i486 boot failure due to stale %ds In-Reply-To: Message-ID: References: <200711042158.lA4Lwv9S014628@harpo.it.uu.se> <472E50C5.5020201@goop.org> <472E5AB6.40509@zytor.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 4 Nov 2007, Linus Torvalds wrote: > > So I'd suggest having both jumps back-to-back, but realistically, the > first regular short jump is actually the one that is more important. > That's the one that really matters on i386/i486 class machines, and later > CPU's will generally do the right thing even with _neither_ jump there. That's obviously badly phrased. The far jump is obviously required on all CPU's in order for us to actually finally get to 32-bit protected mode and reload CS, but what I *meant* was that we certainly also know that "unreal mode" works and is used by various strange DOS extenders, and that not doing the far jump isn't really required for having a "working setup" - it's just going to be a rather limited mode. So the short jump is required for the code to *work*. The long jump is required only to get us the 32-bit mode we *want* and out of the odd "half-way" state. Two different issues. Linus