netdev - Re: [PATCH/RFC v2 bpf-next 11/19] libbpf: new global variable "libbpf_test

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Date:   Thu, 11 Apr 2019 15:32:37 +0100
From:   Jiong Wang <jiong.wang@...ronome.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        daniel@...earbox.net, bpf@...r.kernel.org, netdev@...r.kernel.org,
        oss-drivers@...ronome.com
Subject: Re: [PATCH/RFC v2 bpf-next 11/19] libbpf: new global variable
 "libbpf_test_mode"

> On 11 Apr 2019, at 04:19, Jakub Kicinski <jakub.kicinski@...ronome.com> wrote:
> 
> On Wed, 10 Apr 2019 20:50:25 +0100, Jiong Wang wrote:
>> Enable BPF_F_TEST_RND_HI32 for all existing bpf selftests or other
>> independent tests could involve quite a few changes to make sure all bpf
>> prog load places has BPF_F_TEST_RND_HI32 set.
>> 
>> Given most of the tests are using libbpf, this patch introduces a new
>> global variable "libbpf_test_mode" into libbpf, once which is set, all bpf
>> prog load issued through libbpf will have BPF_F_TEST_RND_HI32 set
>> automatically, this could minimize changes required from testsuite.
>> 
>> The other way might be introducing new load function like
>> "bpf_prog_test_load", which will set BPF_F_TEST_RND_HI32. But there are
>> several prog load APIs, and we need minor changes on some parameters.
>> 
>> The global variable approach seems to be a proper first step for easy
>> testsuite porting.
>> 
>> Signed-off-by: Jiong Wang <jiong.wang@...ronome.com>
> 
> Can we perhaps make it per-object by setting it after
> bpf_object__open() but before bpf_object__load(), or add 
> it to struct bpf_object_open_attr?

Not sure I followed the meaning correctly. My read is you mean it would
better if there is more accurate and fine control on this feature, especially
if prog_flags could become an API parameter during file/obj/prog load?

As mentioned in the cover letter, I tried to implement bpf_prog_test_load
In parallel with existing bpf_prog_test_run, but then found there are
also similar APIs for bpf_object__open, and raw insn load “bpf_load_progams”
etc and they may involve extending bpf_prog_load_attr/bpf_load_program_attr
etc. I thought the change is a little bit heavy. I could go further if it
is thought to be the correct way or there is any other suggestion on nicely
passing “prog_flags” to low level bpf syscall in libbpf.

Regards,
Jiong