Re: [PATCH v2 bpf-next 2/3] libbpf: introduce bpf_prog_test_run_xattr_opts

[Song Liu <songliubraving@fb.com>]

> On Sep 23, 2020, at 12:31 PM, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
> 
> On Wed, Sep 23, 2020 at 9:55 AM Song Liu <songliubraving@fb.com> wrote:
>> 
>> This API supports new field cpu_plus in bpf_attr.test.
>> 
>> Acked-by: John Fastabend <john.fastabend@gmail.com>
>> Signed-off-by: Song Liu <songliubraving@fb.com>
>> ---
>> tools/lib/bpf/bpf.c      | 13 ++++++++++++-
>> tools/lib/bpf/bpf.h      | 11 +++++++++++
>> tools/lib/bpf/libbpf.map |  1 +
>> 3 files changed, 24 insertions(+), 1 deletion(-)
>> 
>> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
>> index 2baa1308737c8..3228dd60fa32f 100644
>> --- a/tools/lib/bpf/bpf.c
>> +++ b/tools/lib/bpf/bpf.c
>> @@ -684,7 +684,8 @@ int bpf_prog_test_run(int prog_fd, int repeat, void *data, __u32 size,
>>        return ret;
>> }
>> 
>> -int bpf_prog_test_run_xattr(struct bpf_prog_test_run_attr *test_attr)
>> +int bpf_prog_test_run_xattr_opts(struct bpf_prog_test_run_attr *test_attr,
>> +                                const struct bpf_prog_test_run_opts *opts)
> 
> opts are replacement for test_attr, not an addition to it. We chose to
> use _xattr suffix for low-level APIs previously, but it's already
> "taken". So I'd suggest to go with just  bpf_prog_test_run_ops and
> have prog_fd as a first argument and then put all the rest of
> test_run_attr into opts.

One question on this: from the code, most (if not all) of these xxx_opts
are used as input only. For example:

LIBBPF_API int bpf_prog_bind_map(int prog_fd, int map_fd,
                                 const struct bpf_prog_bind_opts *opts);

However, bpf_prog_test_run_attr contains both input and output. Do you
have any concern we use bpf_prog_test_run_opts for both input and output?

Thanks,
Song


> BTW, it's also probably overdue to have a higher-level
> bpf_program__test_run(), which can re-use the same
> bpf_prog_test_run_opts options struct. It would be more convenient to
> use it with libbpf bpf_object/bpf_program APIs.
> 
>> {
>>        union bpf_attr attr;
>>        int ret;
>> @@ -693,6 +694,11 @@ int bpf_prog_test_run_xattr(struct bpf_prog_test_run_attr *test_attr)
>>                return -EINVAL;
>> 
>>        memset(&attr, 0, sizeof(attr));
>> +       if (opts) {
> 
> you don't need to check opts for being not NULL, OPTS_VALID handle that already.
> 
>> +               if (!OPTS_VALID(opts, bpf_prog_test_run_opts))
>> +                       return -EINVAL;
>> +               attr.test.cpu_plus = opts->cpu_plus;
> 
> And here you should use OPTS_GET(), please see other examples in
> libbpf for proper usage.
> 
> 
>> +       }
>>        attr.test.prog_fd = test_attr->prog_fd;
>>        attr.test.data_in = ptr_to_u64(test_attr->data_in);
>>        attr.test.data_out = ptr_to_u64(test_attr->data_out);
>> @@ -712,6 +718,11 @@ int bpf_prog_test_run_xattr(struct bpf_prog_test_run_attr *test_attr)
>>        return ret;
>> }
>> 
> 
> [...]