powerpc/perf: Add perf interface to expose vpa counters

powerpc/perf: Add perf interface to expose vpa counters

To support performance measurement for KVM on PowerVM(KoP)
feature, PowerVM hypervisor has added couple of new software
counters in Virtual Process Area(VPA) of the partition.

Commit e1f288d2f9c69 ("KVM: PPC: Book3S HV nestedv2: Add
support for reading VPA counters for pseries guests")
have updated the paca fields with corresponding changes.

Proposed perf interface is to expose these new software
counters for monitoring of context switch latencies and
runtime aggregate. Perf interface driver is called
"vpa_pmu" and it has dependency on KVM and perf, hence
added new config called "VPA_PMU" which depends on
"CONFIG_KVM_BOOK3S_64_HV" and "CONFIG_HV_PERF_CTRS".
Since, kvm and kvm_host are currently compiled as built-in
modules, this perf interface takes the same path and
registered as a module.

vpa_pmu perf interface needs access to some of the kvm
functions and structures like kvmhv_get_l2_counters_status(),
hence kvm_book3s_64.h and kvm_ppc.h are included.
Below are the events added to monitor KoP:

  vpa_pmu/l1_to_l2_lat/
  vpa_pmu/l2_to_l1_lat/
  vpa_pmu/l2_runtime_agg/

and vpa_pmu driver supports only per-cpu monitoring with this patch.
Example usage:

[command]# perf stat -e vpa_pmu/l1_to_l2_lat/ -a -I 1000
     1.001017682            727,200      vpa_pmu/l1_to_l2_lat/
     2.003540491          1,118,824      vpa_pmu/l1_to_l2_lat/
     3.005699458          1,919,726      vpa_pmu/l1_to_l2_lat/
     4.007827011          2,364,630      vpa_pmu/l1_to_l2_lat/

Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Co-developed-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241118114114.208964-1-kjain@linux.ibm.com