All of lore.kernel.org
 help / color / mirror / Atom feed
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: Wed, 12 Feb 2025 22:14:19 +0000	[thread overview]
Message-ID: <Z60dO2sV6VIVNE6t@google.com> (raw)
In-Reply-To: <Z6qC303CzfUMN8nV@google.com>

On Mon, Feb 10, 2025 at 10:51:11PM +0000, Peilin Ye wrote:
> > >   #define BPF_LOAD_ACQ   0x10
> > >   #define BPF_STORE_REL  0x20
> > 
> > why not 1 and 2 ?
> 
> I just realized that we can't do 1 and 2 because BPF_ADD | BPF_FETCH
> also equals 1.
> 
> > All other bits are reserved and the verifier will make sure they're zero
> 
> IOW, we can't tell if imm<4-7> is reserved or BPF_ADD (0x00).  What
> would you suggest?  Maybe:
> 
>   #define BPF_ATOMIC_LD_ST 0x10
> 
>   #define BPF_LOAD_ACQ      0x1
>   #define BPF_STORE_REL     0x2
> 
> ?

Or, how about reusing 0xb in imm<4-7>:

  #define BPF_ATOMIC_LD_ST 0xb0

  #define BPF_LOAD_ACQ      0x1
  #define BPF_STORE_REL     0x2

0xb is BPF_MOV in BPFArithOp<>, and we'll never need it for BPF_ATOMIC.
Instead of moving values between registers, we now "move" values from/to
the memory - if I can think of it that way.

- - -
Or, do we want to start to use the remaining bits of the imm field (i.e.
imm<8-31>) ?

Thanks,
Peilin Ye


  reply	other threads:[~2025-02-12 22:14 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
2025-02-10 22:51         ` Peilin Ye
2025-02-12 22:14           ` Peilin Ye [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=Z60dO2sV6VIVNE6t@google.com \
    --to=yepeilin@google.com \
    --cc=alexei.starovoitov@gmail.com \
    --cc=andrii@kernel.org \
    --cc=ast@kernel.org \
    --cc=bpf@ietf.org \
    --cc=bpf@vger.kernel.org \
    --cc=brho@google.com \
    --cc=bsegall@google.com \
    --cc=catalin.marinas@arm.com \
    --cc=corbet@lwn.net \
    --cc=daniel@iogearbox.net \
    --cc=eddyz87@gmail.com \
    --cc=gor@linux.ibm.com \
    --cc=haoluo@google.com \
    --cc=hca@linux.ibm.com \
    --cc=ihor.solodrai@linux.dev \
    --cc=iii@linux.ibm.com \
    --cc=john.fastabend@gmail.com \
    --cc=jolsa@kernel.org \
    --cc=joshdon@google.com \
    --cc=kpsingh@kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=longyingchi24s@ict.ac.cn \
    --cc=martin.lau@linux.dev \
    --cc=mykolal@fb.com \
    --cc=neelnatu@google.com \
    --cc=paulmck@kernel.org \
    --cc=puranjay@kernel.org \
    --cc=qmo@kernel.org \
    --cc=sdf@fomichev.me \
    --cc=shuah@kernel.org \
    --cc=song@kernel.org \
    --cc=void@manifault.com \
    --cc=will@kernel.org \
    --cc=xukuohai@huaweicloud.com \
    --cc=yonghong.song@linux.dev \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.