[PATCH v3 0/3] powerpc/perf: Fix vpa-pmu driver to report correct numbers

[Gautam Menghani <gautam@linux.ibm.com>]

The vpa-pmu driver can sometimes report incorrect context switch latency
numbers:

$ perf stat -e vpa_pmu/l1_to_l2_lat/  --tid=2061  -I 1000
           time             counts unit events
     1.001022517 18,446,744,073,708,177,408      vpa_pmu/l1_to_l2_lat/
     2.002120674            345,092      vpa_pmu/l1_to_l2_lat/
     3.003171582            406,342      vpa_pmu/l1_to_l2_lat/
     4.004234838            340,836      vpa_pmu/l1_to_l2_lat/

These invalid numbers are observed because of 2 issues:

1. The PACA never points to the correct vCPU running on a host vCPU when
vpa_pmu_add() is called.

2. When get_counter_data() reads the PACA counter values, it does not
update the event->hw.prev_count.


Changes in V3:
1. Drop the usage of the PACA's vCPU pointer.
2. Introduce a new patch to fix an issue seen when a tracepoint and vpa-pmu
driver concurrently enable/disable access to latency counters in VPA.


Gautam Menghani (3):
  Revert "powerpc/perf: Add per-task/process monitoring to vpa_pmu
    driver"
  powerpc/perf: Update prev_count of event to get accurate values
  KVM: PPC: Book3s HV: Ensure reliable usage of latency counters

 arch/powerpc/include/asm/kvm_book3s_64.h |  3 --
 arch/powerpc/kvm/book3s_hv.c             | 54 +++---------------------
 arch/powerpc/perf/vpa-pmu.c              | 16 ++-----
 3 files changed, 11 insertions(+), 62 deletions(-)

-- 
2.56.0