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

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Date:   Thu, 24 Sep 2020 01:20:56 +0000
From:   Song Liu <songliubraving@...com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
CC:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        "Kernel Team" <Kernel-team@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        "Daniel Borkmann" <daniel@...earbox.net>,
        john fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [PATCH v2 bpf-next 2/3] libbpf: introduce
 bpf_prog_test_run_xattr_opts



> On Sep 23, 2020, at 6:11 PM, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
> 
> On Wed, Sep 23, 2020 at 4:54 PM Song Liu <songliubraving@...com> wrote:
>> 
>> 
>> 
>>> On Sep 23, 2020, at 12:31 PM, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
>>> 
>>> On Wed, Sep 23, 2020 at 9:55 AM Song Liu <songliubraving@...com> wrote:
>>>> 
>>>> This API supports new field cpu_plus in bpf_attr.test.
>>>> 
>>>> Acked-by: John Fastabend <john.fastabend@...il.com>
>>>> Signed-off-by: Song Liu <songliubraving@...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?
>> 
> 
> I think it should be ok. opts are about passing optional things in a
> way that would be backward/forward compatible. Whether it's input
> only, output only, or input/output is secondary. We haven't had a need
> for output params yet, so this will be the first, but I think it fits
> here just fine. Just document it in the struct definition clearly and
> that's it. As for the mechanics, we might want to do OPTS_SET() macro,
> that will set some fields only if the user provided enough memory to
> fir that output parameter. That should work here pretty cleanly,
> right?

Yep, just sent v4 with OPTS_SET(). ;)

Thanks,
Song