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[Xen-devel] C-state detection (on Intel "Conroe", but possibly generic)

I have a Core 2 Duo "Conroe" box, and I just found and disabled
C2 support.  Output of the 'c' debug key is as follows:

(XEN) 'c' pressed -> printing ACPI Cx structures
(XEN) ==cpu0==
(XEN) active state:             C1
(XEN) max_cstate:               C7
(XEN) states:
(XEN)    *C1:   type[C1] latency[000] usage[00028463] duration[96334186317]
(XEN)     C0:   usage[00028463] duration[35090775621]
(XEN) ==cpu1==
(XEN) active state:             C1
(XEN) max_cstate:               C7
(XEN) states:
(XEN)    *C1:   type[C1] latency[000] usage[00013740] duration[103068828568]
(XEN)     C0:   usage[00013740] duration[28356147295]

This box is no longer capable of achieving a cstate
greater than 1, but max_cstate is still shown as C7.
This subverts some of the TSC logic, which measures
if the box can go into deep C-states.

I know I can override this with the Xen max_cstate boot
parameter but shouldn't Xen detect that the highest
C-state possible is 1?  (Linux 2.6.34 does.)


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