pmu-basic-event-count in ubuntu_kvm_unit_tests failed on B-4.15 ARM64 (FAIL: pmu: pmu-basic-event-count: check overflow happened on #0 only)

Issue found on 4.15.0-157.164 with ARM64 node appleton-kernel

Test failed with:
  FAIL: pmu: pmu-basic-event-count: check overflow happened on #0 only

Test log:
Running '/home/ubuntu/autotest/client/tmp/ubuntu_kvm_unit_tests/src/kvm-unit-tests/tests/pmu-basic-event-count'
 BUILD_HEAD=1593e88a
 timeout -k 1s --foreground 90s /usr/bin/qemu-system-aarch64 -nodefaults -machine virt,gic-version=host,accel=kvm -cpu host -device virtio-serial-device -device virtconsole,chardev=ctd -chardev testdev,id=ctd -device pci-testdev -display none -serial stdio -kernel /tmp/tmp.taHLHqkXUx -smp 1 -append pmu-basic-event-count # -initrd /tmp/tmp.hdwyLnSKoE
 INFO: PMU version: 0x1
 INFO: PMU implementer/ID code: 0x41("A")/0x2
 INFO: Implements 6 event counters
 PASS: pmu: pmu-basic-event-count: pmcntenclr: disable all counters
 PASS: pmu: pmu-basic-event-count: pmcr: reset counters
 PASS: pmu: pmu-basic-event-count: counter #0 preset to pre-overflow value
 PASS: pmu: pmu-basic-event-count: counter #1 is 0
 PASS: pmu: pmu-basic-event-count: pmcntenset: enabled implemented_counters
 PASS: pmu: pmu-basic-event-count: pmcntenset: just enabled #0 and #1
 PASS: pmu: pmu-basic-event-count: check overflow reg is 0
 PASS: pmu: pmu-basic-event-count: pmintenclr_el1=0, all interrupts disabled
 PASS: pmu: pmu-basic-event-count: overflow interrupts enabled on all implemented counters
 INFO: pmu: pmu-basic-event-count: counter #0 is 0x120d (CPU_CYCLES)
 INFO: pmu: pmu-basic-event-count: counter #1 is 0xaa8 (INST_RETIRED)
 INFO: pmu: pmu-basic-event-count: overflow reg = 0x0
 FAIL: pmu: pmu-basic-event-count: check overflow happened on #0 only
 SUMMARY: 10 tests, 1 unexpected failures
 FAIL pmu-basic-event-count (10 tests, 1 unexpected failures)

This issue can be found with 4.15.0-156.163 / 4.15.0-154.161 as well. Not a regression.