Re: [PATCH] Use correct x86 reboot vector

From: ebiederm@xmission.com (Eric W. Biederman)
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: CaT <cat@zip.com.au>, Andi Kleen <ak@muc.de>,
	Linus Torvalds <torvalds@transmeta.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Use correct x86 reboot vector
Date: 11 May 2003 12:01:57 -0600	[thread overview]
Message-ID: <m1bry9746i.fsf@frodo.biederman.org> (raw)
In-Reply-To: <1052578182.16166.6.camel@dhcp22.swansea.linux.org.uk>

Alan Cox <alan@lxorguk.ukuu.org.uk> writes:

> On Sad, 2003-05-10 at 04:35, CaT wrote:
> > On Sat, May 10, 2003 at 04:56:34AM +0200, Andi Kleen wrote:
> > > Extensive discussion by various experts on the discuss@x86-64.org
> > > mailing list concluded that the correct vector to restart an 286+ 
> > > CPU is f000:fff0, not ffff:0000. Both seem to work on current systems, 
> > > but the first is correct.
> > 
> > Could this bug, by any chance, cause a system to shutdown instead of
> > rebooting? This is what happens to me at the moment but not each and
> > every time.
> 
> Unlikely. But try it and see 8)
> 
> At least some SMP boxes freak if you do a poweroff request on CPU != 0

As per the MP spec.  The system should reboot on the bootstrap cpu.
smp_processor_id() == 0 on x86.  apicid??

I have a patch for this as part my kexec stuff as the kernel freaks
when it doesn't start up on the bootstrap cpu as well.  I am busily
cleaning it up so it works in interrupt context as well.

Alan if you want it holler and I can send it to you as well.

Eric