Forgot to add linuxppc-dev On Fri, Nov 06, 2026 at 09:01:31PM +0530, Gautam Menghani wrote: > 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 >
