From: Peilin Ye <yepeilin@google.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: bpf <bpf@vger.kernel.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
bpf@ietf.org, Xu Kuohai <xukuohai@huaweicloud.com>,
Eduard Zingerman <eddyz87@gmail.com>,
David Vernet <void@manifault.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
"Paul E. McKenney" <paulmck@kernel.org>,
Puranjay Mohan <puranjay@kernel.org>,
Ilya Leoshkevich <iii@linux.ibm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Quentin Monnet <qmo@kernel.org>,
Mykola Lysenko <mykolal@fb.com>, Shuah Khan <shuah@kernel.org>,
Ihor Solodrai <ihor.solodrai@linux.dev>,
Yingchi Long <longyingchi24s@ict.ac.cn>,
Josh Don <joshdon@google.com>, Barret Rhoden <brho@google.com>,
Neel Natu <neelnatu@google.com>,
Benjamin Segall <bsegall@google.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH bpf-next v2 4/9] bpf: Introduce load-acquire and store-release instructions
Date: Sun, 9 Feb 2025 23:41:56 +0000 [thread overview]
Message-ID: <Z6k9RELOQxp67rIn@google.com> (raw)
In-Reply-To: <CAADnVQLkHA9LGv99k2TZOJEGUU=dw=q6nVurJ=aoh0v6cFS6zQ@mail.gmail.com>
On Sat, Feb 08, 2025 at 07:46:54PM -0800, Alexei Starovoitov wrote:
> > > These values might imply that bpf infra is supposed to map all the values
> > > to cpu instructions, but that's not what we're doing here.
> > > We're only dealing with two specific instructions.
> > > We're not defining a memory model for all future new instructions.
> >
> > Got it! In v3, I'll change it back to:
> >
> > #define BPF_LOAD_ACQ 0x10
> > #define BPF_STORE_REL 0x20
>
> why not 1 and 2 ?
> All other bits are reserved and the verifier will make sure they're zero,
> so when/if we need to extend it then it wouldn't matter whether
> lower 4 bits are reserved or other bits.
> Say, we decide to support cmpwait_relaxed as a new insn.
> It can take the value 3 and arm64 JIT will map it to ldxr+wfe+...
>
> Then with this new load_acq and cmpwait_relaxed we can efficiently
> implement both smp_cond_load_relaxed and smp_cond_load_acquire.
Ah, I see. When you suggested "LOAD_ACQ=1 and STORE_REL=2" earlier, I
didn't realize you meant 1 and 2 in imm<0-3>.
Thanks,
Peilin Ye
next prev parent reply other threads:[~2025-02-09 23:42 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-07 2:04 [PATCH bpf-next v2 0/9] Introduce load-acquire and store-release BPF instructions Peilin Ye
2025-02-07 2:05 ` [PATCH bpf-next v2 1/9] bpf/verifier: Factor out atomic_ptr_type_ok() Peilin Ye
2025-02-07 2:05 ` [PATCH bpf-next v2 2/9] bpf/verifier: Factor out check_atomic_rmw() Peilin Ye
2025-02-07 2:05 ` [PATCH bpf-next v2 3/9] bpf/verifier: Factor out check_load_mem() and check_store_reg() Peilin Ye
2025-02-10 23:45 ` Eduard Zingerman
2025-02-07 2:05 ` [PATCH bpf-next v2 4/9] bpf: Introduce load-acquire and store-release instructions Peilin Ye
2025-02-07 11:28 ` Ilya Leoshkevich
2025-02-07 21:23 ` Peilin Ye
2025-02-08 21:30 ` Alexei Starovoitov
2025-02-09 2:21 ` Peilin Ye
2025-02-09 3:46 ` Alexei Starovoitov
2025-02-09 23:41 ` Peilin Ye [this message]
2025-02-10 22:51 ` Peilin Ye
2025-02-12 22:14 ` Peilin Ye
2025-02-13 5:55 ` Alexei Starovoitov
2025-02-13 11:41 ` Peilin Ye
2025-02-15 2:34 ` Peilin Ye
2025-02-15 3:04 ` Alexei Starovoitov
2025-02-15 6:17 ` Peilin Ye
2025-02-07 2:06 ` [PATCH bpf-next v2 5/9] arm64: insn: Add BIT(23) to {load,store}_ex's mask Peilin Ye
2025-02-07 2:06 ` [PATCH bpf-next v2 6/9] arm64: insn: Add load-acquire and store-release instructions Peilin Ye
2025-02-07 2:06 ` [PATCH bpf-next v2 7/9] bpf, arm64: Support " Peilin Ye
2025-02-07 2:06 ` [PATCH bpf-next v2 8/9] selftests/bpf: Add selftests for " Peilin Ye
2025-02-07 23:47 ` Peilin Ye
2025-02-08 0:20 ` Peilin Ye
2025-02-08 2:20 ` Peilin Ye
2025-02-11 0:20 ` Eduard Zingerman
2025-02-11 0:08 ` Eduard Zingerman
2025-02-11 19:09 ` Peilin Ye
2025-02-11 20:15 ` Eduard Zingerman
2025-02-11 20:51 ` Peilin Ye
2025-02-20 1:08 ` Peilin Ye
2025-02-20 1:21 ` Eduard Zingerman
2025-02-07 2:06 ` [PATCH bpf-next v2 9/9] bpf, docs: Update instruction-set.rst " Peilin Ye
2025-02-07 21:29 ` [PATCH bpf-next v2 0/9] Introduce load-acquire and store-release BPF instructions Peilin Ye
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