Message-ID: <f4f01d2a-666b-58a1-cf76-84541643bdc3@huaweicloud.com>
Date:   Thu, 16 Feb 2023 09:23:02 +0800
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Subject: Re: [PATCH bpf-next v1 0/4] Support bpf trampoline for RV64
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To:     =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn@kernel.org>,
        bpf@vger.kernel.org, linux-riscv@lists.infradead.org,
        netdev@vger.kernel.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>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Conor Dooley <conor.dooley@microchip.com>,
        Guo Ren <guoren@kernel.org>,
        Luke Nelson <luke.r.nels@gmail.com>,
        Xi Wang <xi.wang@gmail.com>, Pu Lehui <pulehui@huawei.com>
References: <20230215135205.1411105-1-pulehui@huaweicloud.com>
 <87mt5ft2bx.fsf@all.your.base.are.belong.to.us>
From:   Pu Lehui <pulehui@huaweicloud.com>
In-Reply-To: <87mt5ft2bx.fsf@all.your.base.are.belong.to.us>
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On 2023/2/15 22:45, Björn Töpel wrote:
> Hi Lehui,
> 
> Pu Lehui <pulehui@huaweicloud.com> writes:
> 
>> BPF trampoline is the critical infrastructure of the bpf
>> subsystem, acting as a mediator between kernel functions
>> and BPF programs. Numerous important features, such as
>> using ebpf program for zero overhead kernel introspection,
>> rely on this key component. We can't wait to support bpf
>> trampoline on RV64. Since RV64 does not support ftrace
>> direct call yet, the current RV64 bpf trampoline is only
>> used in bpf context.
> 
> Thanks a lot for continuing this work. I agree with you that it's
> valuable to have BPF trampoline support, even without proper direct call
> support (we'll get there soon). The trampoline enables kfunc calls. On
> that note; I don't see that you enable "bpf_jit_supports_kfunc_call()"
> anywhere in the series.  With BPF trampoline support, the RISC-V BPF
> finally can support kfunc calls!
> 
> I'd add the following to bpf_jit_comp64.c:
> 

happy to hear that，let's make it more completeable.

> bool bpf_jit_supports_kfunc_call(void)
> {
>          return true;
> }
> 
> :-)
> 
> I'll do a review ASAP.
> 
> 
> Björn