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

Eric W. Biederman
2008-11-11T20:35:32Z

"H. Peter Anvin" <hpa@zytor.com> writes:

> 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.

Yes. What we are guarding against in practice is a write that causes
the system to hang. Anything else and we will make it to the next
reset method.

Eric