Re: [PATCH v2 5/5] KVM: selftests: Relax branches event count check for event_filter test

Sean Christopherson
2025-09-10T23:52:13Z

On Fri, Jul 18, 2025, Dapeng Mi wrote:
> As the branches event overcount issue on Atom platforms, once there are
> VM-Exits triggered (external interrupts) in the guest loop, the measured
> branch event count could be larger than NUM_BRANCHES, this would lead to
> the pmu_event_filter_test print warning to info the measured branches
> event count is mismatched with expected number (NUM_BRANCHES).
>
> To eliminate this warning, relax the branches event count check on the
> Atom platform which have the branches event overcount issue.
>
> Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
> Tested-by: Yi Lai <yi1.lai@intel.com>
> ---

This can be squashed with the previous patch, "workaround errata" is a single
logical change as far as I'm concerned.

> tools/testing/selftests/kvm/x86/pmu_event_filter_test.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/x86/pmu_event_filter_test.c b/tools/testing/selftests/kvm/x86/pmu_event_filter_test.c
> index c15513cd74d1..9c1a92f05786 100644
> --- a/tools/testing/selftests/kvm/x86/pmu_event_filter_test.c
> +++ b/tools/testing/selftests/kvm/x86/pmu_event_filter_test.c
> @@ -60,6 +60,8 @@ struct {
> uint64_t instructions_retired;
> } pmc_results;
>
> +static uint8_t inst_overcount_flags;
> +
> /*
> * If we encounter a #GP during the guest PMU sanity check, then the guest
> * PMU is not functional. Inform the hypervisor via GUEST_SYNC(0).
> @@ -214,8 +216,10 @@ static void remove_event(struct __kvm_pmu_event_filter *f, uint64_t event)
> do { \
> uint64_t br = pmc_results.branches_retired; \
> uint64_t ir = pmc_results.instructions_retired; \
> + bool br_matched = inst_overcount_flags & BR_RETIRED_OVERCOUNT ? \
> + br >= NUM_BRANCHES : br == NUM_BRANCHES; \
> \
> - if (br && br != NUM_BRANCHES) \
> + if (br && !br_matched) \
> pr_info("%s: Branch instructions retired = %lu (expected %u)\n", \
> __func__, br, NUM_BRANCHES); \
> TEST_ASSERT(br, "%s: Branch instructions retired = %lu (expected > 0)", \
> @@ -850,6 +854,9 @@ int main(int argc, char *argv[])
> if (use_amd_pmu())
> test_amd_deny_list(vcpu);
>
> + if (use_intel_pmu())

Checking for an Intel CPU should be done by the library.