linux-kernel - Re: Machine reboot

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Message-ID: <20061008185125.GE4033@ucw.cz>
Date:	Sun, 8 Oct 2006 18:51:25 +0000
From:	Pavel Machek <pavel@...e.cz>
To:	Lukas Hejtmanek <xhejtman@...l.muni.cz>
Cc:	Magnus Damm <magnus.damm@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: Machine reboot

On Thu 05-10-06 18:05:18, Lukas Hejtmanek wrote:
> On Thu, Oct 05, 2006 at 08:58:22PM +0900, Magnus Damm wrote:
> > A long shot, but switching to real mode does not work if the cpu is
> > running in VMX root mode ie on hardware with Intel VT extensions
> > enabled. So if you are using some kind of kernel virtualization module
> > on rather new hardware, consider rmmod:ing the module before
> > rebooting.
> > 
> > I'm about to post patches for kexec that fixes this problem, but I'm
> > not sure about the current reboot status.
> 
> You are right, I'm using Intel Core 2 Duo processor with DP965LT board that is
> capable of VT extensions. However, I'm using vanilla 2.6.18 kernel in X86_64,
> no additional patches, nor XEN or VMWARE is running (even their modules are
> not loaded). Moreover, SYSRQ-B (emergency reboot) works fine. System graceful
> reboot does not work.

Of course... copy/paste pieces of sysrq-b sequence into regular
sequence to find out what the critical difference is... no, it will
not be easy.

Perhaps your box *likes* to reboot with apic on or something? Perhaps
device_shutdown() breaks your ability to reboot?

-- 
Thanks for all the (sleeping) penguins.
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