Re: About NetBSD and Xen (Was: Stability of -current for a Xen Dom0 machine)

[Stefano Marinelli <postnet%dragas.dyndns.org@localhost>]

> Power management under Xen requires ACPI support, as the hypervisor does not 
> implement extensive power management routines. Today's machines requires ACPI 
> parsing to query/obtain information regarding almost everything, including 
> PM, and this task is devoted to dom0. The support is missing for NetBSD.

Yes, that's why I was looking with interest at acpicpu(4) and was hoping it 
could be working on a XEN3_DOM0 kernel. AFAICT it seemed to do a very good job 
on non-XEN kernels.

> There are some quirks for playing with CPUs [1], but IMHO, it does not 
> qualify as power "management" :o
> 
> [1] http://mail-index.netbsd.org/port-xen/2010/05/22/msg006014.html

Thank you for the link. It was one of the first results that came up on google 
while searching for information about this thing. cpufreq=dom0-kernel gives the 
cpufreq control to Dom0. But my dom0 doesn't see any way of throttling the 
cpu/states, so nothing changes. My cpu is not recognised by the "powernow-k8", 
and the only way to have some power reduction is acpicpu.
Reading about your (committed) patch [1], I hoped I could be able to launch a 
Dom0 kernel with acpicpu support and Xen with cpufreq=dom0-kernel but it seems 
the acpicpu support is not still available on dom0 kernel. So it seems it's a 
no-go, for now.

[1] http://mail-index.netbsd.org/port-xen/2009/08/02/msg005213.html

Stefano