linux-kernel - Re: [PATCH 1/2] bpf, riscv: fix bugs in JIT for 32-bit ALU operations

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Date:   Fri, 31 May 2019 08:22:45 +0100
From:   Jiong Wang <jiong.wang@...ronome.com>
To:     Luke Nelson <luke.r.nels@...il.com>,
        Song Liu <liu.song.a23@...il.com>
Cc:     Xi Wang <xi.wang@...il.com>,
        Björn Töpel <bjorn.topel@...il.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Networking <netdev@...r.kernel.org>,
        linux-riscv@...ts.infradead.org, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] bpf, riscv: fix bugs in JIT for 32-bit ALU operations


Song Liu writes:

> On Thu, May 30, 2019 at 3:34 PM Luke Nelson <luke.r.nels@...il.com> wrote:
>>
>> On Thu, May 30, 2019 at 1:53 PM Song Liu <liu.song.a23@...il.com> wrote:
>> >
>> > This is a little messy. How about we introduce some helper function
>> > like:
>> >
>> > /* please find a better name... */
>> > emit_32_or_64(bool is64, const u32 insn_32, const u32 inst_64, struct
>> > rv_jit_context *ctx)
>> > {
>> >        if (is64)
>> >             emit(insn_64, ctx);
>> >        else {
>> >             emit(insn_32, ctx);
>> >            rd = xxxx;
>> >            emit_zext_32(rd, ctx);
>> >        }
>> > }
>>
>> This same check is used throughout the file, maybe clean it up in a
>> separate patch?

We also need to enable the recent 32-bit opt (on bpf-next) on these missing
insns, like what has been done at:

  https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=66d0d5a854a6625974e7de4b874e7934988b0ef8

Perhaps the best way is to wait this patch merged back to bpf-next, then we
do two patches, the first one to enable the opt, the second one then do the
re-factor. I guess this could avoid some code conflict.

Regards,
Jiong

>
> Yes, let's do follow up patch.
>
> Thanks,
> Song