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xen-devel
RE: [Xen-devel] cpufreq support status
> Could anyone summarize what the support status of cpu
> frequency changes is at present. I don't seem to
> recall generic changes to the hpyervisor in
> that respect, but the linux tree has fairly extensive
> changes to the powernow-k8 driver
Keir rewrote and committed patches from me that:
* allow the dom0 kernel to write to the
fid/vid k8 pstate control and status MSRs if and
only if "cpufreq=dom0-kernel" is passed on the
Xen command line
* modify time-xen.c to add cpufreq notifier
support, and to modify the clock frequency
of the hypervisor through a platform hypercall
* add platform hypercalls to change the
hypervisor clock frequency and to get the idle
ticks of all the physical processors
* make powernow-k8 use the _PSD structure to
determine what cores in the system share frequencies
still to be done:
* allow the dom0 kernel to write to the
architectural pstate control MSR (Opteron 3rd gen
and later processors)
* modify the cpufreq ondemand governor to use
the platform hypercall to get the idle load. I'm
working on this now, but Xen and Linux have different
ideas of what a "tick" is, so it wasn't as simple as
I'd hoped.
* add the patch to have powernow-k8 only use the
architectural registers for pstate control for
Opteron 3rd gen and later processors
* get the _PSD mods accepted into the mainstream
kernel; they were submitted but Dave Jones didn't
commit them for some reason.
> (which would make sense to me only if all other cpufreq
> drivers are fully supported now, too).
I don't understand this; the changes I made in the
Linux tree were not prompted by the Xen code. What
are you trying to say?
-Mark Langsdorf
Operating System Research Center
AMD
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