linux-kernel - Re: [BUG] x86: reboot doesn't reboot

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Date:	Fri, 04 Apr 2014 10:37:07 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...nel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>
CC:	"Li, Aubrey" <aubrey.li@...ux.intel.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [BUG] x86: reboot doesn't reboot

The comment header is bogus... it describes what we do, not what Windows does.

On April 4, 2014 10:34:31 AM PDT, Ingo Molnar <mingo@...nel.org> wrote:
>
>* Matthew Garrett <mjg59@...f.ucam.org> wrote:
>
>> On Fri, Apr 04, 2014 at 08:13:48AM -0700, H. Peter Anvin wrote:
>> > On 04/04/2014 08:12 AM, Matthew Garrett wrote:
>> > > On Fri, Apr 04, 2014 at 09:27:48AM +0800, Li, Aubrey wrote:
>> > > 
>> > >> The current situation is,
>> > >> - we have one(do we know more?) preproduction machine hangs by
>CF9.
>> > >> - We have more than one(could be thousand known) production
>machine
>> > >> works by CF9.
>> > > 
>> > > Production hardware should never require CF9.
>> > > 
>> > 
>> > There are a lot of things that shouldn't be.
>> 
>> Windows doesn't hit CF9, and production hardware is always tested
>with 
>> Windows, so. [...]
>
>So why the hell does the reboot function comment claim that the 
>Windows reboot sequence (which is the de facto hardware standard)
>uses 0xcf9:
>
>/*
> * Windows compatible x86 hardware expects the following on reboot:
> *
> * 1) If the FADT has the ACPI reboot register flag set, try it
> * 2) If still alive, write to the keyboard controller
> * 3) If still alive, write to the ACPI reboot register again
> * 4) If still alive, write to the keyboard controller again
> * 5) If still alive, call the EFI runtime service to reboot
> * 6) If still alive, write to the PCI IO port 0xCF9 to reboot
> * 7) If still alive, inform BIOS to do a proper reboot
> *
>
>??
>
>Thanks,
>
>	Ingo

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