[kvm-unit-tests PATCH v2 0/2] arm: pmu-overflow-interrupt: Fix failures on Amberwing

[Eric Auger <eric.auger@redhat.com>]

On Qualcomm Amberwing, some pmu-overflow-interrupt failures can be observed.
Although the even counter overflows, the interrupt is not seen as
expected on guest side. This happens in the subtest after "promote to 64-b"
comment.

After analysis, the PMU overflow interrupt actually hits, ie.
kvm_pmu_perf_overflow() gets called and KVM_REQ_IRQ_PENDING is set,
as expected. However the PMCR.E is reset by the handle_exit path, at
kvm_pmu_handle_pmcr() before the next guest entry and
kvm_pmu_flush_hwstate/kvm_pmu_update_state subsequent call.
There, since the enable bit has been reset, kvm_pmu_update_state() does
not inject the interrupt into the guest.

This does not seem to be a KVM bug but rather an unfortunate
scenario where the test disables the PMCR.E too closely to the
advent of the overflow interrupt.

Since it looks like a benign and inlikely case, let's resize the number
of iterations to prevent the PMCR enable bit from being resetted
immediately at the same time as the actual overflow event.

Also make pmu_stats volatile to prevent any optimizations.

Eric Auger (2):
  arm: pmu: Declare pmu_stats as volatile
  arm: pmu-overflow-interrupt: Increase count values

 arm/pmu.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

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2.41.0