netdev - Re: [PATCH bpf-next v1 0/4] Support bpf trampoline for RV64

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Date:   Thu, 16 Feb 2023 09:23:02 +0800
From:   Pu Lehui <pulehui@...weicloud.com>
To:     Björn Töpel <bjorn@...nel.org>,
        bpf@...r.kernel.org, linux-riscv@...ts.infradead.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Guo Ren <guoren@...nel.org>,
        Luke Nelson <luke.r.nels@...il.com>,
        Xi Wang <xi.wang@...il.com>, Pu Lehui <pulehui@...wei.com>
Subject: Re: [PATCH bpf-next v1 0/4] Support bpf trampoline for RV64



On 2023/2/15 22:45, Björn Töpel wrote:
> Hi Lehui,
> 
> Pu Lehui <pulehui@...weicloud.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