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Date: Fri, 4 Apr 2014 19:40:29 +0200
From: Ingo Molnar <mingo@...nel.org>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Matthew Garrett <mjg59@...f.ucam.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"Li, Aubrey" <aubrey.li@...ux.intel.com>,
Steven Rostedt <rostedt@...dmis.org>,
LKML <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [BUG] x86: reboot doesn't reboot
* H. Peter Anvin <hpa@...or.com> wrote:
> On April 4, 2014 9:32:58 AM PDT, Matthew Garrett <mjg59@...f.ucam.org> wrote:
>
> > Windows does ACPI first, so no. And the Dells were broken even
> > before we moved ACPI up the list.
>
> That's not what you said a few posts ago.
Exactly, the claim ws:
"Windows hits the keyboard controller and then tries the ACPI vector."
Which is obviously not the same as 'Windows does ACPI first'.
So the first step _has_ to be to document exactly what Windows does,
because that's the hardware ABI that we cannot deviate from much. Or
if we don't know a detail, document the specific uncertainties, don't
pretend we know it!
The current documented sequence lists 0xcf9, which seems to be a lie:
/*
* 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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