perf: rdpmc and PERF_EVENT_IOC_RESET

[Vince Weaver]

Hello

so using rdpmc() and the mmap page to do fast perf_event reads seems to 
interact poorly with the PERF_EVENT_IOC_RESET ioctl.

>From what I can tell, on reset event->count is set to zero, but 
event->hw.prev_count is not, so the userpg->offset field ends up negative 
and weird things happen.

Shout reset just not be called if you are using the rdpmc() interface?

Vince