linux-kernel - Re: [PATCH bpf v3] powerpc/bpf: enforce full ordering for ATOMIC operations with BPF

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Date: Mon, 03 Jun 2024 12:45:11 +1000
From: Michael Ellerman <patch-notifications@...erman.id.au>
To: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, Yonghong Song <yonghong.song@...ux.dev>, 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>, "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>, Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, Christophe Leroy <christophe.leroy@...roup.eu>, "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>, Hari Bathini <hbathini@...ux.ibm.com>, bpf@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org, paulmck@...nel.org, Puranjay Mohan <puranjay@...nel.org>
Cc: Puranjay Mohan <puranjay@...nel.org>
Subject: Re: [PATCH bpf v3] powerpc/bpf: enforce full ordering for ATOMIC operations with BPF_FETCH

On Mon, 13 May 2024 10:02:48 +0000, Puranjay Mohan wrote:
> The Linux Kernel Memory Model [1][2] requires RMW operations that have a
> return value to be fully ordered.
> 
> BPF atomic operations with BPF_FETCH (including BPF_XCHG and
> BPF_CMPXCHG) return a value back so they need to be JITed to fully
> ordered operations. POWERPC currently emits relaxed operations for
> these.
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/bpf: enforce full ordering for ATOMIC operations with BPF_FETCH
      https://git.kernel.org/powerpc/c/b1e7cee96127468c2483cf10c2899c9b5cf79bf8

cheers