Better ACPI C-state support

[Sepherosa Ziehau]

Hi all,

I have made good progress to improve ACPI C-state support on Intel
CPUs (x86_64).  All necessary bits are pushed to master.  Please test.

For many Intel CPU based boxes, which only had C1, now more C-states
should be available.  And for CPUs' which have ARAT, i8254 is no
longer required to enter C3+ states.

If possible, please post the bootversbose dmesg and output of 'sysctl
machdep.mwait'.  For laptops, you may need to plug/unplug power cable
to get more C-states.

I am still looking for native C1 state :)

Best Regards,
sephe

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Tomorrow Will Never Die