Implement a perf PMU to handle IOMMU performance counters and events.
The PMU only supports counting mode (e.g. perf stat). Since the counters
are shared across all cores, the PMU is implemented as "system-wide" mode.

To invoke the AMD IOMMU PMU, issue a perf tool command such as:

  ./perf stat -a -e amd_iommu/<events>/ <command>

or:

  ./perf stat -a -e amd_iommu/config=<config-data>,config1=<config1-data>/ <command>

For example:

  ./perf stat -a -e amd_iommu/mem_trans_total/ <command>

The resulting count will be how many IOMMU total peripheral memory
operations were performed during the command execution window.
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1370466709-3212-3-git-send-email-suravee.suthikulpanit@amd.comSigned-off-by: Ingo Molnar <mingo@kernel.org>