linux-kernel - [kvm-unit-tests PATCH] x86: pmu: Test WRMSR on a running counter

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Date:   Mon,  3 Feb 2020 17:25:04 -0800
From:   Eric Hankland <ehankland@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Peter Shier <pshier@...gle.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Eric Hankland <ehankland@...gle.com>
Subject: [kvm-unit-tests PATCH] x86: pmu: Test WRMSR on a running counter

Ensure that the value of the counter was successfully set to 0 after
writing it while the counter was running.

Signed-off-by: Eric Hankland <ehankland@...gle.com>
---
 x86/pmu.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/x86/pmu.c b/x86/pmu.c
index cb8c9e3..8a77993 100644
--- a/x86/pmu.c
+++ b/x86/pmu.c
@@ -419,6 +419,21 @@ static void check_rdpmc(void)
 	report_prefix_pop();
 }
 
+static void check_running_counter_wrmsr(void)
+{
+	pmu_counter_t evt = {
+		.ctr = MSR_IA32_PERFCTR0,
+		.config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel,
+		.count = 0,
+	};
+
+	start_event(&evt);
+	loop();
+	wrmsr(MSR_IA32_PERFCTR0, 0);
+	stop_event(&evt);
+	report("running counter wrmsr", evt.count < gp_events[1].min);
+}
+
 int main(int ac, char **av)
 {
 	struct cpuid id = cpuid(10);
@@ -453,6 +468,7 @@ int main(int ac, char **av)
 	check_counters_many();
 	check_counter_overflow();
 	check_gp_counter_cmask();
+	check_running_counter_wrmsr();
 
 	return report_summary();
 }