Re: [PATCH v3 02/11] KVM: selftests: Dump VM stats in binary stats test

[David Matlack <dmatlack@google.com>]

On Wed, Mar 30, 2022 at 10:46:12AM -0700, Ben Gardon wrote:
> Add kvm_util library functions to read KVM stats through the binary
> stats interface and then dump them to stdout when running the binary
> stats test. Subsequent commits will extend the kvm_util code and use it
> to make assertions in a test for NX hugepages.
> 
> CC: Jing Zhang <jingzhangos@google.com>
> Signed-off-by: Ben Gardon <bgardon@google.com>
> ---
>  .../selftests/kvm/include/kvm_util_base.h     |   1 +
>  .../selftests/kvm/kvm_binary_stats_test.c     |   3 +
>  tools/testing/selftests/kvm/lib/kvm_util.c    | 143 ++++++++++++++++++
>  3 files changed, 147 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
> index 976aaaba8769..4783fd1cd4cf 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util_base.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
> @@ -401,6 +401,7 @@ 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);
>  
>  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 17f65d514915..afc4701ce8dd 100644
> --- a/tools/testing/selftests/kvm/kvm_binary_stats_test.c
> +++ b/tools/testing/selftests/kvm/kvm_binary_stats_test.c
> @@ -174,6 +174,9 @@ static void vm_stats_test(struct kvm_vm *vm)
>  	stats_test(stats_fd);
>  	close(stats_fd);
>  	TEST_ASSERT(fcntl(stats_fd, F_GETFD) == -1, "Stats fd not freed");
> +
> +	/* Dump VM stats */
> +	dump_vm_stats(vm);
>  }
>  
>  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 11a692cf4570..f87df68b150d 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -2562,3 +2562,146 @@ int vcpu_get_stats_fd(struct kvm_vm *vm, uint32_t vcpuid)
>  
>  	return ioctl(vcpu->fd, KVM_GET_STATS_FD, NULL);
>  }
> +
> +/* Caller is responsible for freeing the returned kvm_stats_header. */
> +static struct kvm_stats_header *read_vm_stats_header(int stats_fd)
> +{
> +	struct kvm_stats_header *header;
> +	ssize_t ret;
> +
> +	/* Read kvm stats header */
> +	header = malloc(sizeof(*header));
> +	TEST_ASSERT(header, "Allocate memory for stats header");
> +
> +	ret = read(stats_fd, header, sizeof(*header));
> +	TEST_ASSERT(ret == sizeof(*header), "Read stats header");
> +
> +	return header;
> +}

It seems like this helper could be used in kvm_binary_stats_test.c to
eliminate duplicate code.

> +
> +static void dump_header(int stats_fd, struct kvm_stats_header *header)
> +{
> +	ssize_t ret;
> +	char *id;
> +
> +	printf("flags: %u\n", header->flags);
> +	printf("name size: %u\n", header->name_size);
> +	printf("num_desc: %u\n", header->num_desc);
> +	printf("id_offset: %u\n", header->id_offset);
> +	printf("desc_offset: %u\n", header->desc_offset);
> +	printf("data_offset: %u\n", header->data_offset);
> +
> +	/* Read kvm stats id string */
> +	id = malloc(header->name_size);
> +	TEST_ASSERT(id, "Allocate memory for id string");
> +	ret = pread(stats_fd, id, header->name_size, header->id_offset);
> +	TEST_ASSERT(ret == header->name_size, "Read id string");
> +
> +	printf("id: %s\n", id);
> +
> +	free(id);
> +}
> +
> +static ssize_t stats_desc_size(struct kvm_stats_header *header)
> +{
> +	return sizeof(struct kvm_stats_desc) + header->name_size;
> +}
> +
> +/* Caller is responsible for freeing the returned kvm_stats_desc. */
> +static struct kvm_stats_desc *read_vm_stats_desc(int stats_fd,
> +						 struct kvm_stats_header *header)
> +{
> +	struct kvm_stats_desc *stats_desc;
> +	size_t size_desc;
> +	ssize_t ret;
> +
> +	size_desc = header->num_desc * stats_desc_size(header);
> +
> +	/* Allocate memory for stats descriptors */
> +	stats_desc = malloc(size_desc);
> +	TEST_ASSERT(stats_desc, "Allocate memory for stats descriptors");
> +
> +	/* Read kvm stats descriptors */
> +	ret = pread(stats_fd, stats_desc, size_desc, header->desc_offset);
> +	TEST_ASSERT(ret == size_desc, "Read KVM stats descriptors");
> +
> +	return stats_desc;
> +}

Same with this helper.

> +
> +/* Caller is responsible for freeing the memory *data. */
> +static int read_stat_data(int stats_fd, struct kvm_stats_header *header,
> +			  struct kvm_stats_desc *desc, uint64_t **data)
> +{
> +	u64 *stats_data;
> +	ssize_t ret;
> +
> +	stats_data = malloc(desc->size * sizeof(*stats_data));
> +
> +	ret = pread(stats_fd, stats_data, desc->size * sizeof(*stats_data),
> +		    header->data_offset + desc->offset);
> +
> +	/* ret is in bytes. */
> +	ret = ret / sizeof(*stats_data);
> +
> +	TEST_ASSERT(ret == desc->size,
> +		    "Read data of KVM stats: %s", desc->name);
> +
> +	*data = stats_data;
> +
> +	return ret;
> +}

Same with this helper.

> +
> +static void dump_stat(int stats_fd, struct kvm_stats_header *header,
> +		      struct kvm_stats_desc *desc)
> +{
> +	u64 *stats_data;
> +	ssize_t ret;
> +	int i;
> +
> +	printf("\tflags: %u\n", desc->flags);
> +	printf("\texponent: %u\n", desc->exponent);
> +	printf("\tsize: %u\n", desc->size);
> +	printf("\toffset: %u\n", desc->offset);
> +	printf("\tbucket_size: %u\n", desc->bucket_size);
> +	printf("\tname: %s\n", (char *)&desc->name);
> +
> +	ret = read_stat_data(stats_fd, header, desc, &stats_data);
> +
> +	printf("\tdata: %lu", *stats_data);
> +	for (i = 1; i < ret; i++)
> +		printf(", %lu", *(stats_data + i));
> +	printf("\n\n");
> +
> +	free(stats_data);
> +}
> +
> +void dump_vm_stats(struct kvm_vm *vm)
> +{
> +	struct kvm_stats_desc *stats_desc;
> +	struct kvm_stats_header *header;
> +	struct kvm_stats_desc *desc;
> +	size_t size_desc;
> +	int stats_fd;
> +	int i;
> +
> +	stats_fd = vm_get_stats_fd(vm);
> +
> +	header = read_vm_stats_header(stats_fd);
> +	dump_header(stats_fd, header);
> +
> +	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);
> +		dump_stat(stats_fd, header, desc);
> +	}
> +
> +	free(stats_desc);
> +	free(header);
> +
> +	close(stats_fd);
> +}
> +
> -- 
> 2.35.1.1021.g381101b075-goog
>