> On Thu, Mar 24, 2011 at 03:18:14AM -0400, Len Brown wrote:
> > Is a CONFIG_XEN kernel supposed to use just HLT in idle?
>
> For right now..
> >
> > xen_arch_setup() does this:
> >
> > pm_idle = default_idle;
> > boot_option_idle_override = IDLE_HALT;
> >
> > which has that effect. I guess this makes sense b/c the
> > CONFIG_XEN kernel is Dom0 and the real C-sates are done
> > by the hypervisor?
>
> Correct. There are some patches that make the C-states
> be visible in the Linux kernel, but that hasn't been ported
> over yet.
The Xen Dom0 kernel will trap into the hypervisor
whenever it does a HLT or an MWAIT, yes?
What is the benefit of having Dom0 decided between
C-states that it can't actually enter?
What is the mechanism by which those C-states are
made visible to Dom0, and how are those states
related to the states that are supported on
the bare iron?
> > Would the same CONFIG_XEN kernel binary ever not
> > run xen_arch_setup(), run on raw hardware, and want
> > to use idle states other than HLT?
> ever not? I am not sure of the question, so let me state:
> The Linux kernel if compiled with CONFIG_XEN, and if run on
> native hardware, would _never_ run 'xen_arch_setup()'*. It would
> run the normal, native type setup.
Thanks, that clarifies.
-Len Brown, Intel Open Source Technolgy Center
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