linux-kernel - Re: [PATCH bpf-next v3 05/14] bpf: Rename BPF_XADD and prepare to encode other atomics in .imm

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Message-ID: <33df38b3-60a6-9408-dfa7-f10b6273b226@fb.com>
Date:   Thu, 3 Dec 2020 20:49:49 -0800
From:   Yonghong Song <yhs@...com>
To:     Brendan Jackman <jackmanb@...gle.com>, <bpf@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        KP Singh <kpsingh@...omium.org>,
        Florent Revest <revest@...omium.org>,
        <linux-kernel@...r.kernel.org>, Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH bpf-next v3 05/14] bpf: Rename BPF_XADD and prepare to
 encode other atomics in .imm



On 12/3/20 8:02 AM, Brendan Jackman 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>

Acked-by: Yonghong Song <yhs@...com>

> Change-Id: Ib78f54acba37f7196cbf6c35ffa1c40805cb0d87

As pointed by Andrii earlier, this 'Change-Id' is weird. I didn't
see it in other submitted patches.