sched_cpu_cache_wiped(int llc)
that would be very nice for this; the menuidle side knows this for some cases and thus can just call it. This would be a very small and minimal change
What do you mean by "menuidle side knows this for some cases" ? You mean you know that some C-state entries imply llc clean/invalidate ?
in the architectural idle code we can know if the llc got flushed there's also the per core flags where we know with reasonable certainty that the per core caches got flushed.