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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 00:39:48 +0000	[thread overview]
Message-ID: <Z8ZL1L69z8XWm8vl@google.com> (raw)
In-Reply-To: <CAADnVQKX+PoSUqPBB2+eZrR7wdq-8EVaMxy_Wur7g8wyy3Dcmg@mail.gmail.com>

Hi Alexei,

On Mon, Mar 03, 2025 at 04:24:12PM -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 ?

Thanks,
Peilin Ye



  reply	other threads:[~2025-03-04  0:41 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 [this message]
2025-03-04  0:45       ` Alexei Starovoitov
2025-03-04  0:49         ` Peilin Ye
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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