perf: offcore event monitoring patches

Hi, all

Sorry for late update, I was mostly on vacation in the past months.

FYI, the previous version at below link
http://marc.info/?l=linux-kernel&m=129346414407543&w=2
[PATCH 0/7] perf: offcore and load latency monitoring patches

I need some time to add userspace perf tool support for load latency monitoring, so for now I only post offcore patches here.

The most visible changes is adding a new field perf_event_attr::event_extra for extra MSR encoding, which is the first revision of the Andi's patch did. And also

Peter,
This version has addressed the comments against last version, could you please consider merging this series?

Thanks,
Lin Ming