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

[Ben Gardon]

On Tue, Apr 5, 2022 at 3:19 PM David Matlack <dmatlack@xxxxxxxxxx> wrote:
>
> 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@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    | 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.

It could, but I think the duplicate code in that test has value in
being verbose and well commented and having a bunch of checks to
assert things the regular library function isn't interested in.
I'd prefer to keep the duplication as-is.

>
> > +
> > +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
> >