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, Alexei Starovoitov <ast@kernel.org>,
Xu Kuohai <xukuohai@huaweicloud.com>,
Eduard Zingerman <eddyz87@gmail.com>,
David Vernet <void@manifault.com>,
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 v5 1/6] bpf: Introduce load-acquire and store-release instructions
Date: Tue, 4 Mar 2025 00:49:26 +0000 [thread overview]
Message-ID: <Z8ZOFuipuznnOD-7@google.com> (raw)
In-Reply-To: <CAADnVQKB-9q6fxcVPbd7Ee+QBH=_ySv2EyULkgFhv_n2i07L1A@mail.gmail.com>
On Mon, Mar 03, 2025 at 04:45:45PM -0800, Alexei Starovoitov wrote:
> > > > switch (insn->imm) {
> > > > @@ -7780,6 +7813,24 @@ static int check_atomic(struct bpf_verifier_env *env, struct bpf_insn *insn)
> > > > case BPF_XCHG:
> > > > case BPF_CMPXCHG:
> > > > return check_atomic_rmw(env, insn);
> > > > + case BPF_LOAD_ACQ:
> > > > +#ifndef CONFIG_64BIT
> > > > + if (BPF_SIZE(insn->code) == BPF_DW) {
> > > > + verbose(env,
> > > > + "64-bit load-acquires are only supported on 64-bit arches\n");
> > > > + return -EOPNOTSUPP;
> > > > + }
> > > > +#endif
> > >
> > > Your earlier proposal of:
> > > if (BPF_SIZE(insn->code) == BPF_DW && BITS_PER_LONG != 64) {
> > >
> > > was cleaner.
> > > Why did you pick ifndef ?
> >
> > Likely overthinking, but I wanted to avoid this check at all for 64-bit
> > arches, so it's just a little bit faster. Should I change it back to
> > checking BITS_PER_LONG ?
>
> In general #ifdef in .c is the last resort.
> We avoid it when possible.
Got it.
> In core.c we probably cannot, but here we can.
> So yes. please respin.
Sure!
> I bet the compiler will produce the exact same code.
Thanks,
Peilin Ye
next prev parent reply other threads:[~2025-03-04 0:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-04 0:13 [PATCH bpf-next v5 0/6] Introduce load-acquire and store-release BPF instructions Peilin Ye
2025-03-04 0:13 ` [PATCH bpf-next v5 1/6] bpf: Introduce load-acquire and store-release instructions Peilin Ye
2025-03-04 0:24 ` Alexei Starovoitov
2025-03-04 0:39 ` Peilin Ye
2025-03-04 0:45 ` Alexei Starovoitov
2025-03-04 0:49 ` Peilin Ye [this message]
2025-03-04 0:13 ` [PATCH bpf-next v5 2/6] arm64: insn: Add BIT(23) to {load,store}_ex's mask Peilin Ye
2025-03-04 0:13 ` [PATCH bpf-next v5 3/6] arm64: insn: Add load-acquire and store-release instructions Peilin Ye
2025-03-04 0:14 ` [PATCH bpf-next v5 4/6] bpf, arm64: Support " Peilin Ye
2025-03-04 0:14 ` [PATCH bpf-next v5 5/6] bpf, x86: " Peilin Ye
2025-03-04 0:14 ` [PATCH bpf-next v5 6/6] selftests/bpf: Add selftests for " Peilin Ye
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