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

Wei Huang
2016-11-21T20:24:54Z

From: Christopher Covington <cov@codeaurora.org>

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@codeaurora.org>
Signed-off-by: Wei Huang <wei@redhat.com>
---
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