iommu/vt-d: Add IOMMU perfmon support

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.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

iommu/vt-d: Retrieve IOMMU perfmon capability information

The performance monitoring infrastructure, perfmon, is to support
collection of information about key events occurring during operation of
the remapping hardware, to aid performance tuning and debug. Each
remapping hardware unit has capability registers that indicate support
for performance monitoring features and enumerate the capabilities.

Add alloc_iommu_pmu() to retrieve IOMMU perfmon capability information
for each iommu unit. The information is stored in the iommu->pmu data
structure. Capability registers are read-only, so it's safe to prefetch
and store them in the pmu structure. This could avoid unnecessary VMEXIT
when this code is running in the virtualization environment.

Add free_iommu_pmu() to free the saved capability information when
freeing the iommu unit.

Add a kernel config option for the IOMMU perfmon feature. Unless a user
explicitly uses the perf tool to monitor the IOMMU perfmon event, there
isn't any impact for the existing IOMMU. Enable it by default.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Link: https://lore.kernel.org/r/20230128200428.1459118-3-kan.liang@linux.intel.com
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>