linux-kernel - Re: [PATCH bpf-next v5 04/11] bpf: Rename BPF_XADD and prepare to encode other atomics in .imm

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Message-ID: <CAJ+HfNieDqvamAzZfp36_yZHzsnwkeaARwedQaiFjaEu5Cn1tQ@mail.gmail.com>
Date:   Tue, 15 Dec 2020 15:05:36 +0100
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Brendan Jackman <jackmanb@...gle.com>
Cc:     bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Florent Revest <revest@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v5 04/11] bpf: Rename BPF_XADD and prepare to
 encode other atomics in .imm

On Tue, 15 Dec 2020 at 13:25, Brendan Jackman <jackmanb@...gle.com> wrote:
>
> A subsequent patch will add additional atomic operations. These new
> operations will use the same opcode field as the existing XADD, with
> the immediate discriminating different operations.
>
> In preparation, rename the instruction mode BPF_ATOMIC and start
> calling the zero immediate BPF_ADD.
>
> This is possible (doesn't break existing valid BPF progs) because the
> immediate field is currently reserved MBZ and BPF_ADD is zero.
>
> All uses are removed from the tree but the BPF_XADD definition is
> kept around to avoid breaking builds for people including kernel
> headers.
>
> Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
> ---
>  Documentation/networking/filter.rst           | 30 +++++++-----
>  arch/arm/net/bpf_jit_32.c                     |  7 ++-
>  arch/arm64/net/bpf_jit_comp.c                 | 16 +++++--
>  arch/mips/net/ebpf_jit.c                      | 11 +++--
>  arch/powerpc/net/bpf_jit_comp64.c             | 25 ++++++++--
>  arch/riscv/net/bpf_jit_comp32.c               | 20 ++++++--
>  arch/riscv/net/bpf_jit_comp64.c               | 16 +++++--

For RISC-V:

Acked-by: Björn Töpel <bjorn.topel@...il.com>