From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753925Ab2DBR4B (ORCPT ); Mon, 2 Apr 2012 13:56:01 -0400 Received: from server1.neighborhoods.net ([207.154.13.48]:33115 "EHLO server1.neighborhoods.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753273Ab2DBR4A (ORCPT ); Mon, 2 Apr 2012 13:56:00 -0400 X-Greylist: delayed 364 seconds by postgrey-1.27 at vger.kernel.org; Mon, 02 Apr 2012 13:56:00 EDT Message-ID: <4F79E6BE.4030302@meetinghouse.net> Date: Mon, 02 Apr 2012 13:49:50 -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 Subject: QUESTION: reboot.c and X86-64 architectures References: In-Reply-To: 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 Hello Folks, I hope this is an appropriate question here, I've exhausted other resources: I've recently migrated from running a 32bit kernel to a 64bit one (specifically Debian Lenny 32bit environment to 2.6.32-5-xen-amd64 on top of xen-4.0-amd64 hypervisor build). This is a somewhat older, and apparently quirky, hardware box. I've found that the only way to reboot it, short of power cycling, is jumping through the bios - using the "reboot=bios" kernel option at boot time works just fine for an X86_32 kernel. But... this doesn't work with the 64bit kernel. Pouring through both the documentation and the code for linux /arch /x86 /kernel /reboot.c yields the very specific admonition "bios Reboot by jumping through the BIOS (only for X86_32)", and the code seems to support this (though I haven't quite waded through all the paths that might execute machine_real_restart). None of the other available command line options seem to work with this hardware, which leads to two questions: 1. What's the logic behind this? Why not enable a bios reboot for 64bit kernels? 2. Anybody know a workaround, short of patching and compiling a custom kernel? (Note: None of the available command line options seem to work on this particular box/bios combination, and kexec-reboot is not available for this combination of kernel and hypervisor). Thank you very much, Miles Fidelman -- In theory, there is no difference between theory and practice. In practice, there is. .... Yogi Berra