[PATCH 2/4] selftests: KVM: Test reading a single stat

[Mingwei Zhang <mizhang@xxxxxxxxxx>]

From: Ben Gardon <bgardon@xxxxxxxxxx>

Retrieve the value of a single stat by name in the binary stats test to
ensure the kvm_util library functions work.

CC: Jing Zhang <jingzhangos@xxxxxxxxxx>
Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
---
 .../selftests/kvm/include/kvm_util_base.h     |  1 +
 .../selftests/kvm/kvm_binary_stats_test.c     |  3 ++
 tools/testing/selftests/kvm/lib/kvm_util.c    | 53 +++++++++++++++++++
 3 files changed, 57 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index 160b9ad8474a..a07964c95941 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -393,6 +393,7 @@ void assert_on_unhandled_exception(struct kvm_vm *vm, uint32_t vcpuid);
 int vm_get_stats_fd(struct kvm_vm *vm);
 int vcpu_get_stats_fd(struct kvm_vm *vm, uint32_t vcpuid);
 void dump_vm_stats(struct kvm_vm *vm);
+uint64_t vm_get_single_stat(struct kvm_vm *vm, const char *stat_name);
 
 uint32_t guest_get_vcpuid(void);
 
diff --git a/tools/testing/selftests/kvm/kvm_binary_stats_test.c b/tools/testing/selftests/kvm/kvm_binary_stats_test.c
index afc4701ce8dd..97bde355f105 100644
--- a/tools/testing/selftests/kvm/kvm_binary_stats_test.c
+++ b/tools/testing/selftests/kvm/kvm_binary_stats_test.c
@@ -177,6 +177,9 @@ static void vm_stats_test(struct kvm_vm *vm)
 
 	/* Dump VM stats */
 	dump_vm_stats(vm);
+
+	/* Read a single stat. */
+	printf("remote_tlb_flush: %lu\n", vm_get_single_stat(vm, "remote_tlb_flush"));
 }
 
 static void vcpu_stats_test(struct kvm_vm *vm, int vcpu_id)
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index d9c660913403..dad54f5d57e7 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -2660,3 +2660,56 @@ void dump_vm_stats(struct kvm_vm *vm)
 	close(stats_fd);
 }
 
+static int vm_get_stat_data(struct kvm_vm *vm, const char *stat_name,
+			    uint64_t **data)
+{
+	struct kvm_stats_desc *stats_desc;
+	struct kvm_stats_header *header;
+	struct kvm_stats_desc *desc;
+	size_t size_desc;
+	int stats_fd;
+	int ret = -EINVAL;
+	int i;
+
+	*data = NULL;
+
+	stats_fd = vm_get_stats_fd(vm);
+
+	header = read_vm_stats_header(stats_fd);
+
+	stats_desc = read_vm_stats_desc(stats_fd, header);
+
+	size_desc = stats_desc_size(header);
+
+	/* Read kvm stats data one by one */
+	for (i = 0; i < header->num_desc; ++i) {
+		desc = (void *)stats_desc + (i * size_desc);
+
+		if (strcmp(desc->name, stat_name))
+			continue;
+
+		ret = read_stat_data(stats_fd, header, desc, data);
+	}
+
+	free(stats_desc);
+	free(header);
+
+	close(stats_fd);
+
+	return ret;
+}
+
+uint64_t vm_get_single_stat(struct kvm_vm *vm, const char *stat_name)
+{
+	uint64_t *data;
+	uint64_t value;
+	int ret;
+
+	ret = vm_get_stat_data(vm, stat_name, &data);
+	TEST_ASSERT(ret == 1, "Stat %s expected to have 1 element, but has %d",
+		    stat_name, ret);
+	value = *data;
+	free(data);
+	return value;
+}
+
-- 
2.35.1.894.gb6a874cedc-goog