[kvm-unit-tests PATCH v2 3/7] x86: pmu: Test perfctr overflow after WRMSR on a running counter

Bill Wendling
2020-02-26T09:44:54Z

From: Eric Hankland <ehankland@google.com>

Ensure that a WRMSR on a running counter will correctly update when the
counter should overflow (similar to the existing overflow test case but
with the counter being written to while it is running).

Signed-off-by: Eric Hankland <ehankland@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Bill Wendling <morbo@google.com>
---
x86/pmu.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/x86/pmu.c b/x86/pmu.c
index c8096b8..f45621a 100644
--- a/x86/pmu.c
+++ b/x86/pmu.c
@@ -422,17 +422,34 @@ static void check_rdpmc(void)

static void check_running_counter_wrmsr(void)
{
+ uint64_t status;
pmu_counter_t evt = {
.ctr = MSR_IA32_PERFCTR0,
.config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel,
.count = 0,
};

+ report_prefix_push("running counter wrmsr");
+
start_event(&evt);
loop();
wrmsr(MSR_IA32_PERFCTR0, 0);
stop_event(&evt);
- report(evt.count < gp_events[1].min, "running counter wrmsr");
+ report(evt.count < gp_events[1].min, "cntr");
+
+ /* clear status before overflow test */
+ wrmsr(MSR_CORE_PERF_GLOBAL_OVF_CTRL,
+ rdmsr(MSR_CORE_PERF_GLOBAL_STATUS));
+
+ evt.count = 0;
+ start_event(&evt);
+ wrmsr(MSR_IA32_PERFCTR0, -1);
+ loop();
+ stop_event(&evt);
+ status = rdmsr(MSR_CORE_PERF_GLOBAL_STATUS);
+ report(status & 1, "status");
+
+ report_prefix_pop();
}

int main(int ac, char **av)
--
2.25.0.265.gbab2e86ba0-goog