[PATCH 2/3] KVM: LoongArch: selftests: Add basic PMU event counting test
From: Song Gao
Date: Tue Mar 10 2026 - 05:56:20 EST
Introduce a basic PMU test that verifies hardware event counting for
four performance counters. The test enables events for CPU cycles,
instructions retired, branch instructions, and branch misses, runs a
fixed number of loops, and checks that the counter values fall within
expected ranges. It also validates that the host supports PMU and that
the VM feature is enabled.
Signed-off-by: Song Gao <gaosong@xxxxxxxxxxx>
---
tools/testing/selftests/kvm/Makefile.kvm | 1 +
.../selftests/kvm/include/loongarch/pmu.h | 46 +++++
.../kvm/include/loongarch/processor.h | 1 +
.../selftests/kvm/lib/loongarch/processor.c | 6 +-
.../selftests/kvm/loongarch/guest_pmu_test.c | 171 ++++++++++++++++++
5 files changed, 224 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/kvm/include/loongarch/pmu.h
create mode 100644 tools/testing/selftests/kvm/loongarch/guest_pmu_test.c
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index fdec90e85467..137f97ad34c0 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -221,6 +221,7 @@ TEST_GEN_PROGS_riscv += rseq_test
TEST_GEN_PROGS_riscv += steal_time
TEST_GEN_PROGS_loongarch = arch_timer
+TEST_GEN_PROGS_loongarch += loongarch/guest_pmu_test
TEST_GEN_PROGS_loongarch += coalesced_io_test
TEST_GEN_PROGS_loongarch += demand_paging_test
TEST_GEN_PROGS_loongarch += dirty_log_perf_test
diff --git a/tools/testing/selftests/kvm/include/loongarch/pmu.h b/tools/testing/selftests/kvm/include/loongarch/pmu.h
new file mode 100644
index 000000000000..0d9ecb9de8c3
--- /dev/null
+++ b/tools/testing/selftests/kvm/include/loongarch/pmu.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * LoongArch PMU specific interface
+ */
+#ifndef SELFTEST_KVM_LOONGARCH_PMU_H
+#define SELFTEST_KVM_LOONGARCH_PMU_H
+
+#include "processor.h"
+
+/* Performance Counter registers */
+#define LOONGARCH_CSR_PERFCTRL0 0x200 /* perf event 0 config */
+#define LOONGARCH_CSR_PERFCNTR0 0x201 /* perf event 0 count value */
+#define LOONGARCH_CSR_PERFCTRL1 0x202 /* perf event 1 config */
+#define LOONGARCH_CSR_PERFCNTR1 0x203 /* perf event 1 count value */
+#define LOONGARCH_CSR_PERFCTRL2 0x204 /* perf event 2 config */
+#define LOONGARCH_CSR_PERFCNTR2 0x205 /* perf event 2 count value */
+#define LOONGARCH_CSR_PERFCTRL3 0x206 /* perf event 3 config */
+#define LOONGARCH_CSR_PERFCNTR3 0x207 /* perf event 3 count value */
+#define CSR_PERFCTRL_PLV0 BIT(16)
+#define CSR_PERFCTRL_PLV1 BIT(17)
+#define CSR_PERFCTRL_PLV2 BIT(18)
+#define CSR_PERFCTRL_PLV3 BIT(19)
+#define PMU_ENVENT_ENABLED (CSR_PERFCTRL_PLV0 | CSR_PERFCTRL_PLV1 |\
+ CSR_PERFCTRL_PLV2 | CSR_PERFCTRL_PLV3)
+
+#define LOONGARCH_CPUCFG6 0x6
+#define CPUCFG6_PMP BIT(0)
+#define CPUCFG6_PAMVER GENMASK(3, 1)
+#define CPUCFG6_PMNUM GENMASK(7, 4)
+#define CPUCFG6_PMNUM_SHIFT 4
+#define CPUCFG6_PMBITS GENMASK(13, 8)
+#define CPUCFG6_PMBITS_SHIFT 8
+#define CPUCFG6_UPM BIT(14)
+
+/* Hardware event codes (from LoongArch perf_event.c */
+#define LOONGARCH_PMU_EVENT_CYCLES 0x00 /* CPU cycles */
+#define LOONGARCH_PMU_EVENT_INSTR_RETIRED 0x01 /* Instructions retired */
+#define PERF_COUNT_HW_BRANCH_INSTRUCTIONS 0x02 /* Branch instructions */
+#define PERF_COUNT_HW_BRANCH_MISSES 0x03 /* Branch misses */
+
+#define NUM_LOOPS 1000
+#define EXPECTED_INSTR_MIN (NUM_LOOPS + 10) /* Loop + overhead */
+#define EXPECTED_CYCLES_MIN NUM_LOOPS /* At least 1 cycle per iteration */
+#define UPPER_BOUND (10 * NUM_LOOPS)
+
+#endif
diff --git a/tools/testing/selftests/kvm/include/loongarch/processor.h b/tools/testing/selftests/kvm/include/loongarch/processor.h
index b8f6c3348ddd..af8d05820961 100644
--- a/tools/testing/selftests/kvm/include/loongarch/processor.h
+++ b/tools/testing/selftests/kvm/include/loongarch/processor.h
@@ -189,6 +189,7 @@ struct handlers {
handler_fn exception_handlers[VECTOR_NUM];
};
+void loongarch_vcpu_setup(struct kvm_vcpu *vcpu);
void vm_init_descriptor_tables(struct kvm_vm *vm);
void vm_install_exception_handler(struct kvm_vm *vm, int vector, handler_fn handler);
diff --git a/tools/testing/selftests/kvm/lib/loongarch/processor.c b/tools/testing/selftests/kvm/lib/loongarch/processor.c
index 68eb34032a99..a64d47ad6ce8 100644
--- a/tools/testing/selftests/kvm/lib/loongarch/processor.c
+++ b/tools/testing/selftests/kvm/lib/loongarch/processor.c
@@ -7,6 +7,7 @@
#include "kvm_util.h"
#include "processor.h"
#include "ucall_common.h"
+#include "pmu.h"
#define LOONGARCH_PAGE_TABLE_PHYS_MIN 0x200000
#define LOONGARCH_GUEST_STACK_VADDR_MIN 0x200000
@@ -275,11 +276,12 @@ static void loongarch_set_cpucfg(struct kvm_vcpu *vcpu, uint64_t id, uint64_t va
__vcpu_set_reg(vcpu, cfgid, val);
}
-static void loongarch_vcpu_setup(struct kvm_vcpu *vcpu)
+void loongarch_vcpu_setup(struct kvm_vcpu *vcpu)
{
int width;
unsigned long val;
struct kvm_vm *vm = vcpu->vm;
+ uint32_t cfg6;
switch (vm->mode) {
case VM_MODE_P36V47_16K:
@@ -290,6 +292,8 @@ static void loongarch_vcpu_setup(struct kvm_vcpu *vcpu)
TEST_FAIL("Unknown guest mode, mode: 0x%x", vm->mode);
}
+ cfg6 = read_cpucfg(LOONGARCH_CPUCFG6);
+ loongarch_set_cpucfg(vcpu, LOONGARCH_CPUCFG6, cfg6);
/* kernel mode and page enable mode */
val = PLV_KERN | CSR_CRMD_PG;
loongarch_set_csr(vcpu, LOONGARCH_CSR_CRMD, val);
diff --git a/tools/testing/selftests/kvm/loongarch/guest_pmu_test.c b/tools/testing/selftests/kvm/loongarch/guest_pmu_test.c
new file mode 100644
index 000000000000..59ec945b6e05
--- /dev/null
+++ b/tools/testing/selftests/kvm/loongarch/guest_pmu_test.c
@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * LoongArch KVM PMU event counting test
+ *
+ * Test hardware event counting: CPU_CYCLES, INSTR_RETIRED,
+ * BRANCH_INSTRUCTIONS and BRANCH_MISSES.
+ *
+ */
+#include "kvm_util.h"
+#include "loongarch/processor.h"
+#include "pmu.h"
+#include <linux/bitops.h>
+
+/* Guest test code - runs inside VM */
+static void guest_pmu_base_test(void)
+{
+ uint64_t cnt[4];
+ int i;
+ uint32_t cfg6, pmnum;
+
+ cfg6 = read_cpucfg(LOONGARCH_CPUCFG6);
+ pmnum = (cfg6 >> 4) & 0xf;
+ GUEST_PRINTF("CPUCFG6 = 0x%x\n", cfg6);
+ GUEST_PRINTF("PMP enabled: %s\n", (cfg6 & 0x1) ? "YES" : "NO");
+ GUEST_PRINTF("Number of counters (PMNUM): %x\n", pmnum + 1);
+ GUEST_ASSERT(pmnum == 3);
+
+ GUEST_PRINTF("Clean csr_perfcntr0-3\n");
+ csr_write(0, LOONGARCH_CSR_PERFCNTR0);
+ csr_write(0, LOONGARCH_CSR_PERFCNTR1);
+ csr_write(0, LOONGARCH_CSR_PERFCNTR2);
+ csr_write(0, LOONGARCH_CSR_PERFCNTR3);
+ GUEST_PRINTF("Set csr_perfctrl0 for cycles event\n");
+ csr_write(PMU_ENVENT_ENABLED |
+ LOONGARCH_PMU_EVENT_CYCLES, LOONGARCH_CSR_PERFCTRL0);
+ GUEST_PRINTF("Set csr_perfctrl1 for instr_retired event\n");
+ csr_write(PMU_ENVENT_ENABLED |
+ LOONGARCH_PMU_EVENT_INSTR_RETIRED, LOONGARCH_CSR_PERFCTRL1);
+ GUEST_PRINTF("Set csr_perfctrl2 for branch_instructions event\n");
+ csr_write(PMU_ENVENT_ENABLED |
+ PERF_COUNT_HW_BRANCH_INSTRUCTIONS, LOONGARCH_CSR_PERFCTRL2);
+ GUEST_PRINTF("Set csr_perfctrl3 for branch_misses event\n");
+ csr_write(PMU_ENVENT_ENABLED |
+ PERF_COUNT_HW_BRANCH_MISSES, LOONGARCH_CSR_PERFCTRL3);
+
+ for (i = 0; i < NUM_LOOPS; i++)
+ cpu_relax();
+
+ cnt[0] = csr_read(LOONGARCH_CSR_PERFCNTR0);
+ GUEST_PRINTF("csr_perfcntr0 is %lx\n", cnt[0]);
+ cnt[1] = csr_read(LOONGARCH_CSR_PERFCNTR1);
+ GUEST_PRINTF("csr_perfcntr1 is %lx\n", cnt[1]);
+ cnt[2] = csr_read(LOONGARCH_CSR_PERFCNTR2);
+ GUEST_PRINTF("csr_perfcntr2 is %lx\n", cnt[2]);
+ cnt[3] = csr_read(LOONGARCH_CSR_PERFCNTR3);
+ GUEST_PRINTF("csr_perfcntr3 is %lx\n", cnt[3]);
+
+ GUEST_PRINTF("assert csr_perfcntr0 >EXPECTED_CYCLES_MIN && csr_perfcntr0 < UPPER_BOUND\n");
+ GUEST_ASSERT(cnt[0] > EXPECTED_CYCLES_MIN && cnt[0] < UPPER_BOUND);
+ GUEST_PRINTF("assert csr_perfcntr1 > EXPECTED_INSTR_MIN && csr_perfcntr1 < UPPER_BOUND\n");
+ GUEST_ASSERT(cnt[1] > EXPECTED_INSTR_MIN && cnt[1] < UPPER_BOUND);
+ GUEST_PRINTF("assert csr_perfcntr2 > 0 && csr_perfcntr2 < UPPER_BOUND\n");
+ GUEST_ASSERT(cnt[2] > 0 && cnt[2] < UPPER_BOUND);
+ GUEST_PRINTF("assert csr_perfcntr3 > 0 && csr_perfcntr3 < UPPER_BOUND\n");
+ GUEST_ASSERT(cnt[3] > 0 && cnt[3] < UPPER_BOUND);
+
+}
+
+static void guest_code(void)
+{
+ guest_pmu_base_test();
+
+ GUEST_DONE();
+}
+
+/* check PMU support */
+static bool kvm_has_pmu_support(void)
+{
+ uint32_t cfg6;
+
+ /* Read CPUCFG6 to check PMU */
+ cfg6 = read_cpucfg(LOONGARCH_CPUCFG6);
+
+ /* Check PMU present bit */
+ if (!(cfg6 & CPUCFG6_PMP))
+ return false;
+
+ /* Check that at least one counter exists */
+ if (((cfg6 & CPUCFG6_PMNUM) >> CPUCFG6_PMNUM_SHIFT) == 0)
+ return false;
+
+ return true;
+}
+/* Dump PMU capabilities */
+static void dump_pmu_caps(void)
+{
+ uint32_t cfg6;
+ int nr_counters, counter_bits;
+
+ cfg6 = read_cpucfg(LOONGARCH_CPUCFG6);
+ nr_counters = ((cfg6 & CPUCFG6_PMNUM) >> CPUCFG6_PMNUM_SHIFT) + 1;
+ counter_bits = ((cfg6 & CPUCFG6_PMBITS) >> CPUCFG6_PMBITS_SHIFT) + 1;
+
+ pr_info("PMU capabilities:\n");
+ pr_info(" Counters present: %s\n", cfg6 & CPUCFG6_PMP ? "yes" : "no");
+ pr_info(" Number of counters: %d\n", nr_counters);
+ pr_info(" Counter width: %d bits\n", counter_bits);
+}
+
+int main(int argc, char *argv[])
+{
+ struct kvm_device_attr attr;
+ struct kvm_vcpu *vcpu;
+ struct kvm_vm *vm;
+ int ret = 0;
+ struct ucall uc;
+
+ /* Check host KVM PMU support */
+ if (!kvm_has_pmu_support()) {
+ print_skip("PMU not supported by host hardware\n");
+ dump_pmu_caps();
+ return KSFT_SKIP;
+ }
+ pr_info("Host support PMU\n");
+
+ /* Dump PMU capabilities */
+ dump_pmu_caps();
+
+ vm = vm_create(VM_MODE_P47V47_16K);
+ vcpu = vm_vcpu_add(vm, 0, guest_code);
+
+ vm_init_descriptor_tables(vm);
+ loongarch_vcpu_setup(vcpu);
+
+ attr.group = KVM_LOONGARCH_VM_FEAT_CTRL,
+ attr.attr = KVM_LOONGARCH_VM_FEAT_PMU,
+
+ ret = ioctl(vm->fd, KVM_HAS_DEVICE_ATTR, &attr);
+
+ if (ret == 0) {
+ pr_info("PMU is enabled in VM\n");
+ } else {
+ print_skip("PMU not enabled by VM config\n");
+ return KSFT_SKIP;
+ }
+
+ while (1) {
+ vcpu_run(vcpu);
+ switch (get_ucall(vcpu, &uc)) {
+ case UCALL_PRINTF:
+ printf("%s", (const char *)uc.buffer);
+ break;
+ case UCALL_DONE:
+ printf("PMU test PASSED\n");
+ goto done;
+ case UCALL_ABORT:
+ printf("PMU test FAILED\n");
+ ret = -1;
+ goto done;
+ default:
+ printf("Unexpected exit\n");
+ ret = -1;
+ goto done;
+ }
+ }
+
+done:
+ kvm_vm_free(vm);
+ return ret;
+}
+
--
2.47.3