From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757431Ab2DIPjg (ORCPT ); Mon, 9 Apr 2012 11:39:36 -0400 Received: from server1.neighborhoods.net ([207.154.13.48]:42022 "EHLO server1.neighborhoods.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753190Ab2DIPjf (ORCPT ); Mon, 9 Apr 2012 11:39:35 -0400 Message-ID: <4F8302B4.8040901@meetinghouse.net> Date: Mon, 09 Apr 2012 11:39:32 -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: linux-kernel@vger.kernel.org CC: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, peter.chubb@nicta.com.au, michael.d.labriola@gmail.com, mjg@redhat.com Subject: reboot via bios on X86_64? 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 [cc'd to maintainers of reboot.c] Re. the 2.6.32.5 kernel (currently used in Debian stable), and this seems to apply to later ones as well: The reboot code in arch/x86/kernel/reboot.c provides for rebooting through the bios by either a kernel option of "reboot=bios" or as automatically invoked by quite a few of the quirks case statements. But... reboot=bios is enabled only when configured for 32-bit mode - which just bit me when I moved from a 32bit kernel to a 64bit one on an old P4 box, which hangs on reboot for all reboot options except reboot=bios when running in 32 bit mode. Which leads to two questions: 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? 2. Anybody know a workaround, short of patching and compiling a custom kernel? Are there other paths through the reboot code that can invoke a bios reboot? [Note: someone suggested trying a kexec-reboot, but that's also not supported on my configuration (running over a Xen hypervisor).] Thank you very much, Miles Fidelman -- In theory, there is no difference between theory and practice. In practice, there is. .... Yogi Berra