[kvm-unit-tests PATCH v10 2/3] arm: pmu: Check cycle count increases

[Wei Huang]

From: Christopher Covington <cov@xxxxxxxxxxxxxx>

Ensure that reads of the PMCCNTR_EL0 are monotonically increasing,
even for the smallest delta of two subsequent reads.

Signed-off-by: Christopher Covington <cov@xxxxxxxxxxxxxx>
Signed-off-by: Wei Huang <wei@xxxxxxxxxx>
---
 arm/pmu.c | 156 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 156 insertions(+)

diff --git a/arm/pmu.c b/arm/pmu.c
index 9d9c53b..176b070 100644
--- a/arm/pmu.c
+++ b/arm/pmu.c
@@ -15,6 +15,9 @@
 #include "libcflat.h"
 #include "asm/barrier.h"
 
+#define PMU_PMCR_E         (1 << 0)
+#define PMU_PMCR_C         (1 << 2)
+#define PMU_PMCR_LC        (1 << 6)
 #define PMU_PMCR_N_SHIFT   11
 #define PMU_PMCR_N_MASK    0x1f
 #define PMU_PMCR_ID_SHIFT  16
@@ -22,6 +25,14 @@
 #define PMU_PMCR_IMP_SHIFT 24
 #define PMU_PMCR_IMP_MASK  0xff
 
+#define ID_DFR0_PERFMON_SHIFT 24
+#define ID_DFR0_PERFMON_MASK  0xf
+
+#define PMU_CYCLE_IDX         31
+
+#define NR_SAMPLES 10
+
+static unsigned int pmu_version;
 #if defined(__arm__)
 static inline uint32_t pmcr_read(void)
 {
@@ -30,6 +41,69 @@ static inline uint32_t pmcr_read(void)
 	asm volatile("mrc p15, 0, %0, c9, c12, 0" : "=r" (ret));
 	return ret;
 }
+
+static inline void pmcr_write(uint32_t value)
+{
+	asm volatile("mcr p15, 0, %0, c9, c12, 0" : : "r" (value));
+	isb();
+}
+
+static inline void pmselr_write(uint32_t value)
+{
+	asm volatile("mcr p15, 0, %0, c9, c12, 5" : : "r" (value));
+	isb();
+}
+
+static inline void pmxevtyper_write(uint32_t value)
+{
+	asm volatile("mcr p15, 0, %0, c9, c13, 1" : : "r" (value));
+}
+
+static inline uint64_t pmccntr_read(void)
+{
+	uint32_t lo, hi = 0;
+
+	if (pmu_version == 0x3)
+		asm volatile("mrrc p15, 0, %0, %1, c9" : "=r" (lo), "=r" (hi));
+	else
+		asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (lo));
+
+	return ((uint64_t)hi << 32) | lo;
+}
+
+static inline void pmccntr_write(uint64_t value)
+{
+	uint32_t lo, hi;
+
+	lo = value & 0xffffffff;
+	hi = (value >> 32) & 0xffffffff;
+
+	if (pmu_version == 0x3)
+		asm volatile("mcrr p15, 0, %0, %1, c9" : : "r" (lo), "r" (hi));
+	else
+		asm volatile("mcr p15, 0, %0, c9, c13, 0" : : "r" (lo));
+}
+
+static inline void pmcntenset_write(uint32_t value)
+{
+	asm volatile("mcr p15, 0, %0, c9, c12, 1" : : "r" (value));
+}
+
+/* PMCCFILTR is an obsolete name for PMXEVTYPER31 in ARMv7 */
+static inline void pmccfiltr_write(uint32_t value)
+{
+	pmselr_write(PMU_CYCLE_IDX);
+	pmxevtyper_write(value);
+	isb();
+}
+
+static inline uint32_t id_dfr0_read(void)
+{
+	uint32_t val;
+
+	asm volatile("mrc p15, 0, %0, c0, c1, 2" : "=r" (val));
+	return val;
+}
 #elif defined(__aarch64__)
 static inline uint32_t pmcr_read(void)
 {
@@ -38,6 +112,44 @@ static inline uint32_t pmcr_read(void)
 	asm volatile("mrs %0, pmcr_el0" : "=r" (ret));
 	return ret;
 }
+
+static inline void pmcr_write(uint32_t value)
+{
+	asm volatile("msr pmcr_el0, %0" : : "r" (value));
+	isb();
+}
+
+static inline uint64_t pmccntr_read(void)
+{
+	uint64_t cycles;
+
+	asm volatile("mrs %0, pmccntr_el0" : "=r" (cycles));
+	return cycles;
+}
+
+static inline void pmccntr_write(uint64_t value)
+{
+	asm volatile("msr pmccntr_el0, %0" : : "r" (value));
+}
+
+static inline void pmcntenset_write(uint32_t value)
+{
+	asm volatile("msr pmcntenset_el0, %0" : : "r" (value));
+}
+
+static inline void pmccfiltr_write(uint32_t value)
+{
+	asm volatile("msr pmccfiltr_el0, %0" : : "r" (value));
+	isb();
+}
+
+static inline uint32_t id_dfr0_read(void)
+{
+	uint32_t id;
+
+	asm volatile("mrs %0, id_dfr0_el1" : "=r" (id));
+	return id;
+}
 #endif
 
 /*
@@ -64,11 +176,55 @@ static bool check_pmcr(void)
 	return ((pmcr >> PMU_PMCR_IMP_SHIFT) & PMU_PMCR_IMP_MASK) != 0;
 }
 
+/*
+ * Ensure that the cycle counter progresses between back-to-back reads.
+ */
+static bool check_cycles_increase(void)
+{
+	bool success = true;
+
+	/* init before event access, this test only cares about cycle count */
+	pmcntenset_write(1 << PMU_CYCLE_IDX);
+	pmccfiltr_write(0); /* count cycles in EL0, EL1, but not EL2 */
+	pmccntr_write(0);
+
+	pmcr_write(pmcr_read() | PMU_PMCR_LC | PMU_PMCR_C | PMU_PMCR_E);
+
+	for (int i = 0; i < NR_SAMPLES; i++) {
+		uint64_t a, b;
+
+		a = pmccntr_read();
+		b = pmccntr_read();
+
+		if (a >= b) {
+			printf("Read %"PRId64" then %"PRId64".\n", a, b);
+			success = false;
+			break;
+		}
+	}
+
+	pmcr_write(pmcr_read() & ~PMU_PMCR_E);
+
+	return success;
+}
+
+void pmu_init(void)
+{
+	uint32_t dfr0;
+
+	/* probe pmu version */
+	dfr0 = id_dfr0_read();
+	pmu_version = (dfr0 >> ID_DFR0_PERFMON_SHIFT) & ID_DFR0_PERFMON_MASK;
+	printf("PMU version: %d\n", pmu_version);
+}
+
 int main(void)
 {
 	report_prefix_push("pmu");
 
+	pmu_init();
 	report("Control register", check_pmcr());
+	report("Monotonically increasing cycle count", check_cycles_increase());
 
 	return report_summary();
 }
-- 
1.8.3.1