Message-ID: <1a02055f-deff-649f-9564-417ae916ddb3@huawei.com>
Date:   Tue, 21 Feb 2023 21:39:48 +0800
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Subject: Re: [PATCH bpf-next v2] riscv, bpf: Add kfunc support for RV64
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To:     =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>,
        Pu Lehui <pulehui@huaweicloud.com>, <bpf@vger.kernel.org>,
        <linux-riscv@lists.infradead.org>, <linux-kernel@vger.kernel.org>
CC:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>
References: <87h6vffqlo.fsf@all.your.base.are.belong.to.us>
From:   Pu Lehui <pulehui@huawei.com>
In-Reply-To: <87h6vffqlo.fsf@all.your.base.are.belong.to.us>
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On 2023/2/21 15:02, Björn Töpel wrote:
> Pu Lehui <pulehui@huaweicloud.com> writes:
> 
>> On 2023/2/20 22:34, Björn Töpel wrote:
>>> Pu Lehui <pulehui@huaweicloud.com> writes:
>>>
>>>> From: Pu Lehui <pulehui@huawei.com>
>>>>
>>>> As another important missing piece of RV64 JIT, kfunc allow bpf programs
>>>> call kernel functions. For now, RV64 is sufficient to enable it.
>>>
>>> Thanks Lehui!
>>>
>>> Maybe we can reword/massage the commit message a bit? What do you think
>>> about something like:
>>>
>>> "Now that the BPF trampoline is supported by RISC-V, it is possible to
>>> use BPF programs with kfunc calls.
>>>
>>
>> kfunc and bpf trampoline are functionally independent. kfunc [1], like
>> bpf helper functions, allows bpf programs to call exported kernel
>> functions, while bpf trampoline provides a more efficient way than
>> kprobe to act as a mediator between kernel functions and bpf programs,
>> and between bpf programs.
>>
>> In fact, it was already supported before the bpf trampoline
>> implementation, I just turned it on.
> 
> Good point. I guess my (incorrect) kfunc mental model was that
> struct_ops and kfunc were tightly coupled. (Then again, w/o struct_ops
> working kfunc is a bit half-working in my view.)
> 
> Fair enough. I'm still a bit confused about the commit message, but
> happy with the patch.
>  > Acked-by: Björn Töpel <bjorn@rivosinc.com>

Thanks Bjorn, will rewrite commit message to make more sense, and send 
new soon.