KVM: riscv: selftests: Add a test for PMU snapshot functionality

Verify PMU snapshot functionality by setting up the shared memory
correctly and reading the counter values from the shared memory
instead of the CSR.
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20240420151741.962500-23-atishp@rivosinc.comSigned-off-by: Anup Patel <anup@brainfault.org>

tools/testing/selftests/kvm/include/riscv/sbi.h

@@ -8,6 +8,12 @@
 #ifndef SELFTEST_KVM_SBI_H
 #define SELFTEST_KVM_SBI_H
 
+/* SBI spec version fields */
+#define SBI_SPEC_VERSION_DEFAULT	0x1
+#define SBI_SPEC_VERSION_MAJOR_SHIFT	24
+#define SBI_SPEC_VERSION_MAJOR_MASK	0x7f
+#define SBI_SPEC_VERSION_MINOR_MASK	0xffffff
+
 /* SBI return error codes */
 #define SBI_SUCCESS				 0
 #define SBI_ERR_FAILURE				-1
@@ -33,6 +39,9 @@ enum sbi_ext_id {
 };
 
 enum sbi_ext_base_fid {
+	SBI_EXT_BASE_GET_SPEC_VERSION = 0,
+	SBI_EXT_BASE_GET_IMP_ID,
+	SBI_EXT_BASE_GET_IMP_VERSION,
 	SBI_EXT_BASE_PROBE_EXT = 3,
 };
 enum sbi_ext_pmu_fid {
@@ -60,6 +69,12 @@ union sbi_pmu_ctr_info {
 	};
 };
 
+struct riscv_pmu_snapshot_data {
+	u64 ctr_overflow_mask;
+	u64 ctr_values[64];
+	u64 reserved[447];
+};
+
 struct sbiret {
 	long error;
 	long value;
@@ -113,4 +128,14 @@ struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,
 
 bool guest_sbi_probe_extension(int extid, long *out_val);
 
+/* Make SBI version */
+static inline unsigned long sbi_mk_version(unsigned long major,
+					    unsigned long minor)
+{
+	return ((major & SBI_SPEC_VERSION_MAJOR_MASK) << SBI_SPEC_VERSION_MAJOR_SHIFT)
+		| (minor & SBI_SPEC_VERSION_MINOR_MASK);
+}
+
+unsigned long get_host_sbi_spec_version(void);
+
 #endif /* SELFTEST_KVM_SBI_H */

tools/testing/selftests/kvm/lib/riscv/processor.c

@@ -502,3 +502,15 @@ bool guest_sbi_probe_extension(int extid, long *out_val)
 
 	return true;
 }
+
+unsigned long get_host_sbi_spec_version(void)
+{
+	struct sbiret ret;
+
+	ret = sbi_ecall(SBI_EXT_BASE, SBI_EXT_BASE_GET_SPEC_VERSION, 0,
+		       0, 0, 0, 0, 0);
+
+	GUEST_ASSERT(!ret.error);
+
+	return ret.value;
+}

tools/testing/selftests/kvm/riscv/sbi_pmu_test.c

@@ -19,6 +19,11 @@
 #define RISCV_MAX_PMU_COUNTERS 64
 union sbi_pmu_ctr_info ctrinfo_arr[RISCV_MAX_PMU_COUNTERS];
 
+/* Snapshot shared memory data */
+#define PMU_SNAPSHOT_GPA_BASE		BIT(30)
+static void *snapshot_gva;
+static vm_paddr_t snapshot_gpa;
+
 /* Cache the available counters in a bitmask */
 static unsigned long counter_mask_available;
 
@@ -186,6 +191,32 @@ static unsigned long read_counter(int idx, union sbi_pmu_ctr_info ctrinfo)
 	return counter_val;
 }
 
+static inline void verify_sbi_requirement_assert(void)
+{
+	long out_val = 0;
+	bool probe;
+
+	probe = guest_sbi_probe_extension(SBI_EXT_PMU, &out_val);
+	GUEST_ASSERT(probe && out_val == 1);
+
+	if (get_host_sbi_spec_version() < sbi_mk_version(2, 0))
+		__GUEST_ASSERT(0, "SBI implementation version doesn't support PMU Snapshot");
+}
+
+static void snapshot_set_shmem(vm_paddr_t gpa, unsigned long flags)
+{
+	unsigned long lo = (unsigned long)gpa;
+#if __riscv_xlen == 32
+	unsigned long hi = (unsigned long)(gpa >> 32);
+#else
+	unsigned long hi = gpa == -1 ? -1 : 0;
+#endif
+	struct sbiret ret = sbi_ecall(SBI_EXT_PMU, SBI_EXT_PMU_SNAPSHOT_SET_SHMEM,
+				      lo, hi, flags, 0, 0, 0);
+
+	GUEST_ASSERT(ret.value == 0 && ret.error == 0);
+}
+
 static void test_pmu_event(unsigned long event)
 {
 	unsigned long counter;
@@ -234,6 +265,59 @@ static void test_pmu_event(unsigned long event)
 	stop_reset_counter(counter, 0);
 }
 
+static void test_pmu_event_snapshot(unsigned long event)
+{
+	unsigned long counter;
+	unsigned long counter_value_pre, counter_value_post;
+	unsigned long counter_init_value = 100;
+	struct riscv_pmu_snapshot_data *snapshot_data = snapshot_gva;
+
+	counter = get_counter_index(0, counter_mask_available, 0, event);
+	counter_value_pre = read_counter(counter, ctrinfo_arr[counter]);
+
+	/* Do not set the initial value */
+	start_counter(counter, 0, 0);
+	dummy_func_loop(10000);
+	stop_counter(counter, SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT);
+
+	/* The counter value is updated w.r.t relative index of cbase */
+	counter_value_post = READ_ONCE(snapshot_data->ctr_values[0]);
+	__GUEST_ASSERT(counter_value_post > counter_value_pre,
+		       "Event update verification failed: post [%lx] pre [%lx]\n",
+		       counter_value_post, counter_value_pre);
+
+	/*
+	 * We can't just update the counter without starting it.
+	 * Do start/stop twice to simulate that by first initializing to a very
+	 * high value and a low value after that.
+	 */
+	WRITE_ONCE(snapshot_data->ctr_values[0], ULONG_MAX/2);
+	start_counter(counter, SBI_PMU_START_FLAG_INIT_SNAPSHOT, 0);
+	stop_counter(counter, SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT);
+	counter_value_pre = READ_ONCE(snapshot_data->ctr_values[0]);
+
+	WRITE_ONCE(snapshot_data->ctr_values[0], counter_init_value);
+	start_counter(counter, SBI_PMU_START_FLAG_INIT_SNAPSHOT, 0);
+	stop_counter(counter, SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT);
+	counter_value_post = READ_ONCE(snapshot_data->ctr_values[0]);
+	__GUEST_ASSERT(counter_value_pre > counter_value_post,
+		       "Counter reinitialization verification failed : post [%lx] pre [%lx]\n",
+		       counter_value_post, counter_value_pre);
+
+	/* Now set the initial value and compare */
+	WRITE_ONCE(snapshot_data->ctr_values[0], counter_init_value);
+	start_counter(counter, SBI_PMU_START_FLAG_INIT_SNAPSHOT, 0);
+	dummy_func_loop(10000);
+	stop_counter(counter, SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT);
+
+	counter_value_post = READ_ONCE(snapshot_data->ctr_values[0]);
+	__GUEST_ASSERT(counter_value_post > counter_init_value,
+		       "Event update verification failed: post [%lx] pre [%lx]\n",
+		       counter_value_post, counter_init_value);
+
+	stop_reset_counter(counter, 0);
+}
+
 static void test_invalid_event(void)
 {
 	struct sbiret ret;
@@ -301,6 +385,34 @@ static void test_pmu_basic_sanity(void)
 	GUEST_DONE();
 }
 
+static void test_pmu_events_snaphost(void)
+{
+	int num_counters = 0;
+	struct riscv_pmu_snapshot_data *snapshot_data = snapshot_gva;
+	int i;
+
+	/* Verify presence of SBI PMU and minimum requrired SBI version */
+	verify_sbi_requirement_assert();
+
+	snapshot_set_shmem(snapshot_gpa, 0);
+
+	/* Get the counter details */
+	num_counters = get_num_counters();
+	update_counter_info(num_counters);
+
+	/* Validate shared memory access */
+	GUEST_ASSERT_EQ(READ_ONCE(snapshot_data->ctr_overflow_mask), 0);
+	for (i = 0; i < num_counters; i++) {
+		if (counter_mask_available & (BIT(i)))
+			GUEST_ASSERT_EQ(READ_ONCE(snapshot_data->ctr_values[i]), 0);
+	}
+	/* Only these two events are guranteed to be present */
+	test_pmu_event_snapshot(SBI_PMU_HW_CPU_CYCLES);
+	test_pmu_event_snapshot(SBI_PMU_HW_INSTRUCTIONS);
+
+	GUEST_DONE();
+}
+
 static void run_vcpu(struct kvm_vcpu *vcpu)
 {
 	struct ucall uc;
@@ -357,6 +469,35 @@ static void test_vm_events_test(void *guest_code)
 	test_vm_destroy(vm);
 }
 
+static void test_vm_setup_snapshot_mem(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
+{
+	/* PMU Snapshot requires single page only */
+	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, PMU_SNAPSHOT_GPA_BASE, 1, 1, 0);
+	/* PMU_SNAPSHOT_GPA_BASE is identity mapped */
+	virt_map(vm, PMU_SNAPSHOT_GPA_BASE, PMU_SNAPSHOT_GPA_BASE, 1);
+
+	snapshot_gva = (void *)(PMU_SNAPSHOT_GPA_BASE);
+	snapshot_gpa = addr_gva2gpa(vcpu->vm, (vm_vaddr_t)snapshot_gva);
+	sync_global_to_guest(vcpu->vm, snapshot_gva);
+	sync_global_to_guest(vcpu->vm, snapshot_gpa);
+}
+
+static void test_vm_events_snapshot_test(void *guest_code)
+{
+	struct kvm_vm *vm = NULL;
+	struct kvm_vcpu *vcpu;
+
+	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
+	__TEST_REQUIRE(__vcpu_has_sbi_ext(vcpu, KVM_RISCV_SBI_EXT_PMU),
+				   "SBI PMU not available, skipping test");
+
+	test_vm_setup_snapshot_mem(vm, vcpu);
+
+	run_vcpu(vcpu);
+
+	test_vm_destroy(vm);
+}
+
 int main(void)
 {
 	test_vm_basic_test(test_pmu_basic_sanity);
@@ -365,5 +506,8 @@ int main(void)
 	test_vm_events_test(test_pmu_events);
 	pr_info("SBI PMU event verification test : PASS\n");
 
+	test_vm_events_snapshot_test(test_pmu_events_snaphost);
+	pr_info("SBI PMU event verification with snapshot test : PASS\n");
+
 	return 0;
 }