Ingo Molnar wrote:
* H. Peter Anvin <hpa@xxxxxxxxx> 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
2007? Maybe 2002, a year after Windows XP was launched?
Windows XP uses ACPI by default. Not sure about reboot, but I wouldn't
be surprised if it did, since it's such a simple feature, not involving
AML etc.
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
Most likely ACPI uses port CF9 if it's available.
... 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.
What the vmx issues showed us is that keyboard reset is unreliable on
some machines, so reset was actually done by triple-fault, which doesn't
work well when vmx is enabled (if it's connected to INIT; note it won't
reset peripherals in that case).
--
error compiling committee.c: too many arguments to function
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