From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757650Ab2DISHY (ORCPT ); Mon, 9 Apr 2012 14:07:24 -0400 Received: from server1.neighborhoods.net ([207.154.13.48]:52676 "EHLO server1.neighborhoods.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757588Ab2DISHV (ORCPT ); Mon, 9 Apr 2012 14:07:21 -0400 Message-ID: <4F832557.6070109@meetinghouse.net> Date: Mon, 09 Apr 2012 14:07:19 -0400 From: Miles Fidelman User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:11.0) Gecko/20120312 Firefox/11.0 SeaMonkey/2.8 MIME-Version: 1.0 To: "H. Peter Anvin" CC: Matthew Garrett , linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, peter.chubb@nicta.com.au, michael.d.labriola@gmail.com Subject: Re: reboot via bios on X86_64? References: <4F8302B4.8040901@meetinghouse.net> <20120409155155.GA22974@srcf.ucam.org> <4F831BD0.3010707@meetinghouse.net> <4F832203.1010104@zytor.com> In-Reply-To: <4F832203.1010104@zytor.com> 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 H. Peter Anvin wrote: > On 04/09/2012 10:26 AM, Miles Fidelman wrote: >> Thanks for the quick response. >> >> Matthew Garrett wrote: >>> On Mon, Apr 09, 2012 at 11:39:32AM -0400, Miles Fidelman wrote: >>> >>>> 1. What's the logic behind this? Why not enable a bios reboot for 64bit >>>> kernels? Is there any reason why the machine_real_restart code wouldn't >>>> work just as well in 64bit mode? Anybody know the history? >>> The bios reboot code requires you to reprogram the CPU to real mode. I >>> don't think there's any fundamental reason you can't do that from 64-bit >>> mode, but nobody's ever written that code. >> That would explain it. I guess there's a little bit of trickiness >> involved in setting things up before >> switching to real mode. >> > Actually this code already exists; the difference is that we have to > return to 32-bit mode first. ahhh.... ain't things fun when one gets really close to the hardware -- In theory, there is no difference between theory and practice. In practice, there is. .... Yogi Berra