[kvm-ppc-devel] [PATCH] Add idle power save for ppc 4xx

[Josh Boyer]

On Tue, 2008-04-01 at 08:01 -0400, Jimi Xenidis wrote:
> On Mar 31, 2008, at 11:15 PM, Josh Boyer wrote:
> 
> > On Tue, 2008-04-01 at 12:04 +1100, Michael Ellerman wrote:
> >>>>> I'm assuming you pass a dtb to the virtual guest when you start  
> >>>>> it up.
> >>>>> Could you define a property in the CPU node there that can be  
> >>>>> parsed to
> >>>>> use the power_save function instead of always making it the  
> >>>>> default?
> >>>>
> >>>> Actually, you probably don't want this as a property in the device
> >>>> tree.  It doesn't describe hardware.  A Kconfig option might be
> >>>> warranted though.
> >>>
> >>> I'll go with the Kconfig option.
> >>
> >> Go with a device-tree check. The pseries kernel supports both bare- 
> >> metal
> >> and hypervisor in the same kernel image, and it works out which it's
> >> running on by looking at the device-tree. This seems equivalent to  
> >> me?
> >
> > After some back and forth on IRC, we decided on that as well.  I love
> > being right, then wrong, then right again.
> 
> Awesome, can you summarize for the rest of us?

A node or property will be in the device tree that the guests can use to
determine if it's running under a hypervisor or not.

The details are yet to be worked out, so there isn't much more of a
summary yet.  There was also some conversation about having an "idle="
kernel parameter similar to the PA-Semi port that would allow toggling
of it as well.

josh