access to tsc calibration info

[Steven Harp]

x86-specific question: Is there a generic way to get access to the
TSC frequency calibration information, as provided by modern x86
CPUs in MSRs?  (User mode components cannot directly read these.)

 The information is readily available in Nova's hypervisor
information page (Hip), conveniently exported as a ROM. But I
am not spotting a similar export for (e.g.) seL4.  The data
is present in the sel4 boot info structure (in core)--maybe this
is accessible to components in some manner?  Suggests a possible
platform API, if not already present...

Suggestions?

// Steve Harp