Implement the IOMMU performance monitor capability, which supports the
collection of information about key events occurring during operation of
the remapping hardware, to aid performance tuning and debug.

The IOMMU perfmon support is implemented as part of the IOMMU driver and
interfaces with the Linux perf subsystem.

The IOMMU PMU has the following unique features compared with the other
PMUs.
- Support counting. Not support sampling.
- Does not support per-thread counting. The scope is system-wide.
- Support per-counter capability register. The event constraints can be
  enumerated.
- The available event and event group can also be enumerated.
- Extra Enhanced Commands are introduced to control the counters.

Add a new variable, struct iommu_pmu *pmu, to in the struct intel_iommu
to track the PMU related information.

Add iommu_pmu_register() and iommu_pmu_unregister() to register and
unregister a IOMMU PMU. The register function setup the IOMMU PMU ops
and invoke the standard perf_pmu_register() interface to register a PMU
in the perf subsystem. This patch only exposes the functions. The
following patch will enable them in the IOMMU driver.

The IOMMU PMUs can be found under /sys/bus/event_source/devices/dmar*

The available filters and event format can be found at the format folder

 $ ls /sys/bus/event_source/devices/dmar1/format/
 event  event_group  filter_ats  filter_ats_en  filter_page_table
 filter_page_table_en

The supported events can be found at the events folder

 $ ls /sys/bus/event_source/devices/dmar1/events/
 ats_blocked        fs_nonleaf_hit           int_cache_hit_posted
 iommu_mem_blocked  iotlb_hit        pasid_cache_lookup  ss_nonleaf_hit
 ctxt_cache_hit     fs_nonleaf_lookup        int_cache_lookup
 iommu_mrds         iotlb_lookup     pg_req_posted    ss_nonleaf_lookup
 ctxt_cache_lookup  int_cache_hit_nonposted  iommu_clocks
 iommu_requests     pasid_cache_hit  pw_occupancy

The command below illustrates filter usage with a simple example.

 $ perf stat -e dmar1/iommu_requests,filter_ats_en=0x1,filter_ats=0x1/
   -a sleep 1

 Performance counter stats for 'system wide':

   368,947      dmar1/iommu_requests,filter_ats_en=0x1,filter_ats=0x1/

 1.002592074 seconds time elapsed
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Link: https://lore.kernel.org/r/20230128200428.1459118-5-kan.liang@linux.intel.comSigned-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>