On Wed, Mar 30, 2022 at 10:46:13AM -0700, Ben Gardon wrote:
> 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 4783fd1cd4cf..78c4407f36b4 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util_base.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
> @@ -402,6 +402,7 @@ 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 f87df68b150d..9c4574381daa 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -2705,3 +2705,56 @@ 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);
Allocating temporary storage for the data is unnecessary. Just read the
stat directly into &value. You'll need to change read_stat_data() to
accept another parameter that defines the number of elements the caller
wants to read. Otherwise botched stats could trigger a buffer overflow.
> + return value;
> +}
> +
> --
> 2.35.1.1021.g381101b075-goog
>
