Maybe there is some other way to handle asymmetry ??
I mis-spoke on asymmetry.
Moorestown is already an example of an asymmetric system,
since its deepest c-state is available on cpu0, but not on cpu1.
So it needs different tables for each cpu.
I think what would work is a default c-state table for the system,
and the ability of a per-cpu override table. I think that would
gracefully handle the case of many identical cpus, and also systems
with different tables per cpu.
The same goes for write-access to the tables.
In the typical case, a single table can be shared for the entire system
and nobody will be writing to it. However, with the governor changes
to call dev->prepare and sift through all the states to find the
legal one with the lowest power_usage... There is software today
out of tree that updates that power_usage entry from prepare().
As I mentioned, I'm not fond of that mechanism - it looks racey
to me. I'd rather see the capability of a drivers idle handler
to demote to another handler in the driver and for the accounting
to not get messed up when that happens. I think the way to do that
is to let the driver do the accounting rather than doing it in
the cpuidle caller.