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

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Date:   Sat, 18 Feb 2023 09:30:44 +0800
From:   Pu Lehui <pulehui@...wei.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Björn Töpel <bjorn@...nel.org>,
        Pu Lehui <pulehui@...weicloud.com>, <bpf@...r.kernel.org>,
        <linux-riscv@...ts.infradead.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...nel.org>,
        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>
Subject: Re: [PATCH bpf-next v1 0/4] Support bpf trampoline for RV64



On 2023/2/18 4:49, Daniel Borkmann wrote:
> On 2/16/23 10:56 AM, Björn Töpel wrote:
>> 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.
>>>
>>> As most of riscv cpu support unaligned memory accesses,
>>> we temporarily use patch [1] to facilitate testing. The
>>> test results are as follow, and test_verifier with no
>>> new failure ceses.
>>>
>>> - fexit_bpf2bpf:OK
>>> - dummy_st_ops:OK
>>> - xdp_bpf2bpf:OK
>>>
>>> [1] 
>>> https://lore.kernel.org/linux-riscv/20210916130855.4054926-2-chenhuang5@huawei.com/
>>>
>>> v1:
>>> - Remove the logic of bpf_arch_text_poke supported for
>>>    kernel functions. (Kuohai and Björn)
>>> - Extend patch_text for multiple instructions. (Björn)
>>> - Fix OOB issue when image too big. (Björn)
>>
>> This series is ready to go in as is.
> 
> Ok.
> 
>> @Palmer I'd like to take this series via the bpf-next tree (as usual),
>> but note that there are some non-BPF changes as well, related to text
>> poking.
>>
>> @Lehui I'd like to see two follow-up patches:
>>
>> 1. Enable kfunc for RV64, by adding:
>>   | bool bpf_jit_supports_kfunc_call(void)
>>   | {
>>   |         return true;
>>   | }
>>
>> 2. Remove the checkpatch warning on patch 4:
>>   | WARNING: kfree(NULL) is safe and this check is probably not required
>>   | #313: FILE: arch/riscv/net/bpf_jit_comp64.c:984:
>>   | +    if (branches_off)
>>   | +        kfree(branches_off);
>>
>>
>> For the series:
>>
>> Tested-by: Björn Töpel <bjorn@...osinc.com>
>> Acked-by: Björn Töpel <bjorn@...osinc.com>
> 
> Thanks, I fixed up issue 2 and cleaned up the commit msgs while applying.
> For issue 1, pls send a follow-up.

Thank you both, will handle this.