linux-kernel - [kvm-unit-tests Patch v3 04/11] x86: pmu: Switch instructions and core cycles events sequence

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Message-Id: <20240103031409.2504051-5-dapeng1.mi@linux.intel.com>
Date: Wed,  3 Jan 2024 11:14:02 +0800
From: Dapeng Mi <dapeng1.mi@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Jim Mattson <jmattson@...gle.com>
Cc: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Zhenyu Wang <zhenyuw@...ux.intel.com>,
	Zhang Xiong <xiong.y.zhang@...el.com>,
	Mingwei Zhang <mizhang@...gle.com>,
	Like Xu <like.xu.linux@...il.com>,
	Jinrong Liang <cloudliang@...cent.com>,
	Dapeng Mi <dapeng1.mi@...el.com>,
	Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: [kvm-unit-tests Patch v3 04/11] x86: pmu: Switch instructions and core cycles events sequence

When running pmu test on SPR, sometimes the following failure is
reported.

PMU version:         2
GP counters:         8
GP counter width:    48
Mask length:         8
Fixed counters:      3
Fixed counter width: 48
1000000 <= 55109398 <= 50000000
FAIL: Intel: core cycles-0
1000000 <= 18279571 <= 50000000
PASS: Intel: core cycles-1
1000000 <= 12238092 <= 50000000
PASS: Intel: core cycles-2
1000000 <= 7981727 <= 50000000
PASS: Intel: core cycles-3
1000000 <= 6984711 <= 50000000
PASS: Intel: core cycles-4
1000000 <= 6773673 <= 50000000
PASS: Intel: core cycles-5
1000000 <= 6697842 <= 50000000
PASS: Intel: core cycles-6
1000000 <= 6747947 <= 50000000
PASS: Intel: core cycles-7

The count of the "core cycles" on first counter would exceed the upper
boundary and leads to a failure, and then the "core cycles" count would
drop gradually and reach a stable state.

That looks reasonable. The "core cycles" event is defined as the 1st
event in xxx_gp_events[] array and it is always verified at first.
when the program loop() is executed at the first time it needs to warm
up the pipeline and cache, such as it has to wait for cache is filled.
All these warm-up work leads to a quite large core cycles count which
may exceeds the verification range.

The event "instructions" instead of "core cycles" is a good choice as
the warm-up event since it would always return a fixed count. Thus
switch instructions and core cycles events sequence in the
xxx_gp_events[] array.

Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
---
 x86/pmu.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/x86/pmu.c b/x86/pmu.c
index a42fff8d8b36..67ebfbe55b49 100644
--- a/x86/pmu.c
+++ b/x86/pmu.c
@@ -31,16 +31,16 @@ struct pmu_event {
 	int min;
 	int max;
 } intel_gp_events[] = {
-	{"core cycles", 0x003c, 1*N, 50*N},
 	{"instructions", 0x00c0, 10*N, 10.2*N},
+	{"core cycles", 0x003c, 1*N, 50*N},
 	{"ref cycles", 0x013c, 1*N, 30*N},
 	{"llc references", 0x4f2e, 1, 2*N},
 	{"llc misses", 0x412e, 1, 1*N},
 	{"branches", 0x00c4, 1*N, 1.1*N},
 	{"branch misses", 0x00c5, 0, 0.1*N},
 }, amd_gp_events[] = {
-	{"core cycles", 0x0076, 1*N, 50*N},
 	{"instructions", 0x00c0, 10*N, 10.2*N},
+	{"core cycles", 0x0076, 1*N, 50*N},
 	{"branches", 0x00c2, 1*N, 1.1*N},
 	{"branch misses", 0x00c3, 0, 0.1*N},
 }, fixed_events[] = {
@@ -307,7 +307,7 @@ static void check_counter_overflow(void)
 	int i;
 	pmu_counter_t cnt = {
 		.ctr = MSR_GP_COUNTERx(0),
-		.config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel /* instructions */,
+		.config = EVNTSEL_OS | EVNTSEL_USR | gp_events[0].unit_sel /* instructions */,
 	};
 	overflow_preset = measure_for_overflow(&cnt);
 
@@ -365,11 +365,11 @@ static void check_gp_counter_cmask(void)
 {
 	pmu_counter_t cnt = {
 		.ctr = MSR_GP_COUNTERx(0),
-		.config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel /* instructions */,
+		.config = EVNTSEL_OS | EVNTSEL_USR | gp_events[0].unit_sel /* instructions */,
 	};
 	cnt.config |= (0x2 << EVNTSEL_CMASK_SHIFT);
 	measure_one(&cnt);
-	report(cnt.count < gp_events[1].min, "cmask");
+	report(cnt.count < gp_events[0].min, "cmask");
 }
 
 static void do_rdpmc_fast(void *ptr)
@@ -446,7 +446,7 @@ static void check_running_counter_wrmsr(void)
 	uint64_t count;
 	pmu_counter_t evt = {
 		.ctr = MSR_GP_COUNTERx(0),
-		.config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel,
+		.config = EVNTSEL_OS | EVNTSEL_USR | gp_events[0].unit_sel,
 	};
 
 	report_prefix_push("running counter wrmsr");
@@ -455,7 +455,7 @@ static void check_running_counter_wrmsr(void)
 	loop();
 	wrmsr(MSR_GP_COUNTERx(0), 0);
 	stop_event(&evt);
-	report(evt.count < gp_events[1].min, "cntr");
+	report(evt.count < gp_events[0].min, "cntr");
 
 	/* clear status before overflow test */
 	if (this_cpu_has_perf_global_status())
@@ -493,7 +493,7 @@ static void check_emulated_instr(void)
 	pmu_counter_t instr_cnt = {
 		.ctr = MSR_GP_COUNTERx(1),
 		/* instructions */
-		.config = EVNTSEL_OS | EVNTSEL_USR | gp_events[1].unit_sel,
+		.config = EVNTSEL_OS | EVNTSEL_USR | gp_events[0].unit_sel,
 	};
 	report_prefix_push("emulated instruction");
 
-- 
2.34.1