Hi All,
as I had guessed for long time the PMV primitive is actually the on-chip oscillator, most likely it is the same oscillator that is used for configuration. And it can be used from user designs as well. PMV is present in all recent FPGAs.
When I opened webcase about the issue that Xilinx tools made fatal failure when I tried to use the PMV from an hard macro the response was that, "you dont need to know" - well now I know :)
Antti