perf, x86: P4 PMU -- redesign cache events

To support cache events we have reserved the low 6 bits in
hw_perf_event::config (which is a part of CCCR register
configuration actually).

These bits represent Replay Event mertic enumerated in
enum P4_PEBS_METRIC. The caller should not care about
which exact bits should be set and how -- the caller
just chooses one P4_PEBS_METRIC entity and puts it into
the config. The kernel will track it and set appropriate
additional MSR registers (metrics) when needed.

The reason for this redesign was the PEBS enable bit, which
should not be set until DS (and PEBS sampling) support will
be implemented properly.

TODO
====

 - PEBS sampling (note it's tricky and works with _one_ counter only
   so for HT machines it will be not that easy to handle both threads)

 - tracking of PEBS registers state, a user might need to turn
   PEBS off completely (ie no PEBS enable, no UOP_tag) but some
   other event may need it, such events clashes and should not
   run simultaneously, at moment we just don't support such events

 - eventually export user space bits in separate header which will
   allow user apps to configure raw events more conveniently.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1278295769.9540.15.camel@minggr.sh.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>