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

H. Peter Anvin
2008-11-11T18:27:16Z

Ingo Molnar wrote:
>
> well then we could insert CF9 to before the triple fault, and solve
> some of the problems as well, without unnecessary risks.
>
> This is a separate patch from ACPI reboot itself, naturally.
>

This is a pretty good point. There is extremely low risk of being
something at port CF9 that is something other than the reset register.
It may not be there, but if it isn't, the worst thing that happened is
we confused a device right before reset.

Even better if we condition the port CF9 write on existence a PCI bus
(or even more specifically PCI Configuration Method #1 or #2). Port CF9
is extremely unlikely to exist on a machine without a PCI bus, and
extremely unlikely to conflict with anything else on a machine with a
PCI bus.

-hpa