Re: [Xen-devel] Re: computer stalls instead of reboot

[Heiko Wundram <modelnine@xxxxxxxxxxxxx>]

Am 09.09.2011 15:45, schrieb Sven Köhler:
> I wonder, what the disadvantage are.
> The hypervisor will still regulate CPU frequency, will it not?
No, it will not.

> Also, is the dom0 kernel doing something that it shouldn't do?
> (maybe something that collides with the ACPI-related activities of the
> hypervisor, if there are any?)
I guess the BIOS is simply reporting broken ACPI tables to the operating 
system (the board is a "consumer" board, so you can guess that the 
manufacturer only tests the ACPI-tables for compatability with Windows).
The ACPI tables (AFAIK, someone correct me) also contain a method for 
rebooting the system, which simply doesn't work/is broken when Xen is 
involved. Forcing acpi=off means that the normal triple-fault or 
kbd-controller reset machinery is always used, as ACPI isn't even 
initialized.
What struck me as odd, though: you can configure Linux to use "some 
other" form of hard reset through a kernel parameter, but setting that 
to explicitly use triple-faults didn't work, either (same hangs), so 
possibly it's some form of additional interaction between Xen, the board 
and the hypervisor. Anyway, the Hetzner "recommended" fix is just what I 
sent you, and I can confirm that works.
--
--- Heiko.

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