Re: [PATCH 10/10] x86, ACPI: default to reboot via ACPI (again)

[Ingo Molnar <mingo@elte.hu>]

* H. Peter Anvin <hpa@zytor.com> wrote:

> Avi Kivity wrote:
> > 
> > I think the sequence should be acpi -> kbd -> triple fault.  Given that
> > Windows uses ACPI, the number of machines that support it is much larger
> > (and growing daily) than the number of machines that do not.
> > 
> 
> Like with many other things ACPI, there probably should be an ACPI 
> date cutoff for using it by default.  There is also port CF9 reboot 
> (often incorrectly described as "PCI reboot", but it has nothing to 
> do with the PCI standard.)

so, the sequence should be:

 [ acpi if date > 2007 ] -> kbd -> triple fault

Where in this sequence should we insert port-CF9 reboot? We have no 
discovery of it, etc. The KGDB reboot will do _something_ on most 
boxes, so inserting it like this:

 [ acpi	if date	> 2007 ] -> kbd -> port-CF9 -> triple fault

... will likely have no practical impact as we rarely get to the 
triple fault method to begin with. So the reboot chain we'd like to 
have is:

 [ acpi	if date	> 2007 ] -> safe-port-CF9 -> kbd -> triple fault

... where safe-port-CF9 is something that can be done safely on all 
x86 boxes.

Anyway, safe-port-CF9 aside, the ACPI sequence should definitely be 
cutoff based, so the plain re-introduction of the patch that changes 
the default is not acceptable.

	Ingo