[Qemu-devel] [kvm-unit-tests PATCHv2] arm: Add PMU test

[Christopher Covington <cov@codeaurora.org>]

Add test the ARM Performance Monitors Unit (PMU). The informational
fields from the control register are printed, but not checked, and
the number of cycles it takes to run a known-instruction-count loop
is printed, but not checked. Once QEMU is fixed, we can at least
begin to check for IPC == 1 when using -icount.

Signed-off-by: Christopher Covington <cov@codeaurora.org>
---
 arm/pmu.c               | 89 +++++++++++++++++++++++++++++++++++++++++++++++++
 arm/unittests.cfg       | 11 ++++++
 config/config-arm64.mak |  4 ++-
 3 files changed, 103 insertions(+), 1 deletion(-)
 create mode 100644 arm/pmu.c

diff --git a/arm/pmu.c b/arm/pmu.c
new file mode 100644
index 0000000..f724c2c
--- /dev/null
+++ b/arm/pmu.c
@@ -0,0 +1,89 @@
+/*
+ * Test the ARM Performance Monitors Unit (PMU).
+ *
+ * Copyright 2015 The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License version 2.1 and
+ * only version 2.1 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ */
+#include "libcflat.h"
+
+struct pmu_data {
+	union {
+		uint32_t pmcr_el0;
+		struct {
+			unsigned int enable:1;
+			unsigned int event_counter_reset:1;
+			unsigned int cycle_counter_reset:1;
+			unsigned int cycle_counter_clock_divider:1;
+			unsigned int event_counter_export:1;
+			unsigned int cycle_counter_disable_when_prohibited:1;
+			unsigned int cycle_counter_long:1;
+			unsigned int zeros:4;
+			unsigned int num_counters:5;
+			unsigned int identification_code:8;
+			unsigned int implementor:8;
+		};
+	};
+};
+
+/* Execute a known number of guest instructions. Only odd instruction counts
+ * greater than or equal to 3 are supported. The control register (PMCR) is
+ * initialized with the provided value (allowing for example for the cycle
+ * counter or eventer count to be reset if needed). After the known instruction
+ * count loop, zero is written to the PMCR to disable counting, allowing the
+ * cycle counter or event counters to be read as needed at a later time.
+ */
+static void measure_instrs(int len, struct pmu_data pmcr)
+{
+	int i = (len - 1) / 2;
+
+	if (len < 3 || ((len - 1) % 2))
+		abort();
+
+	asm volatile(
+		"msr pmcr_el0, %[pmcr]\n"
+		"1: subs %[i], %[i], #1\n"
+		"b.gt 1b\n"
+		"msr pmcr_el0, xzr"
+	: [i] "+r" (i) : [pmcr] "r" (pmcr) : "cc");
+}
+
+int main()
+{
+	struct pmu_data pmcr;
+	const int samples = 10;
+
+	asm volatile("mrs %0, pmcr_el0" : "=r" (pmcr));
+
+	printf("PMU implementor:     %c\n", pmcr.implementor);
+	printf("Identification code: 0x%x\n", pmcr.identification_code);
+	printf("Event counters:      %d\n", pmcr.num_counters);
+
+	pmcr.cycle_counter_reset = 1;
+	pmcr.enable = 1;
+
+	printf("\ninstructions : cycles0 cycles1 ...\n");
+
+	for (int i = 3; i < 300; i += 32) {
+		int avg, sum = 0;
+		printf("%d :", i);
+		for (int j = 0; j < samples; j++) {
+			int val;
+			measure_instrs(i, pmcr);
+			asm volatile("mrs %0, pmccntr_el0" : "=r" (val));
+			sum += val;
+			printf(" %d", val);
+		}
+		avg = sum / samples;
+		printf(" sum=%d avg=%d avg_ipc=%d avg_cpi=%d\n", sum, avg, i / avg, avg / i);
+	}
+
+	return report_summary();
+}
diff --git a/arm/unittests.cfg b/arm/unittests.cfg
index e068a0c..b3b7ff4 100644
--- a/arm/unittests.cfg
+++ b/arm/unittests.cfg
@@ -35,3 +35,14 @@ file = selftest.flat
 smp = `getconf _NPROCESSORS_CONF`
 extra_params = -append 'smp'
 groups = selftest
+
+# Test PMU support without -icount
+[pmu]
+file = pmu.flat
+groups = pmu
+
+# Test PMU support with -icount
+[pmu-icount]
+file = pmu.flat
+groups = pmu
+extra_params = -icount 0
diff --git a/config/config-arm64.mak b/config/config-arm64.mak
index d61b703..140b611 100644
--- a/config/config-arm64.mak
+++ b/config/config-arm64.mak
@@ -12,9 +12,11 @@ cflatobjs += lib/arm64/processor.o
 cflatobjs += lib/arm64/spinlock.o
 
 # arm64 specific tests
-tests =
+tests = $(TEST_DIR)/pmu.flat
 
 include config/config-arm-common.mak
 
 arch_clean: arm_clean
 	$(RM) lib/arm64/.*.d
+
+$(TEST_DIR)/pmu.elf: $(cstart.o) $(TEST_DIR)/pmu.o
-- 
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