linux-kernel - Re: [PATCH] riscv, bpf: try RVC for reg move within BPF

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Message-ID: <87a5kjdsx0.fsf@all.your.base.are.belong.to.us>
Date: Tue, 21 May 2024 18:35:39 +0200
From: Björn Töpel <bjorn@...nel.org>
To: Xiao Wang <xiao.w.wang@...el.com>, paul.walmsley@...ive.com,
 palmer@...belt.com, aou@...s.berkeley.edu, luke.r.nels@...il.com,
 xi.wang@...il.com
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
 martin.lau@...ux.dev, eddyz87@...il.com, song@...nel.org,
 yonghong.song@...ux.dev, john.fastabend@...il.com, kpsingh@...nel.org,
 sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org, pulehui@...wei.com, haicheng.li@...el.com, Xiao Wang
 <xiao.w.wang@...el.com>
Subject: Re: [PATCH] riscv, bpf: try RVC for reg move within BPF_CMPXCHG JIT

Xiao Wang <xiao.w.wang@...el.com> writes:

> We could try to emit compressed insn for reg move operation during CMPXCHG
> JIT, the instruction compression has no impact on the jump offsets of
> following forward and backward jump instructions.

..and at some point we should start supporting Zacas and friends,
instead of lr/sc.

> Signed-off-by: Xiao Wang <xiao.w.wang@...el.com>

Acked-by: Björn Töpel <bjorn@...nel.org>