From: Lukas Bulwahn <lukas.bulwahn@gmail.com>
To: Brendan Jackman <jackmanb@google.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii.nakryiko@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Florent Revest <revest@chromium.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
Jonathan Corbet <corbet@lwn.net>
Subject: Re: [PATCH bpf-next v2 1/2] docs: bpf: Fixup atomics markup
Date: Mon, 18 Jan 2021 18:17:20 +0100 [thread overview]
Message-ID: <CAKXUXMytdMUT5FVtn=L4naMmbq14FXUEFqRTu3323ARKomJRJg@mail.gmail.com> (raw)
In-Reply-To: <20210118155735.532663-2-jackmanb@google.com>
On Mon, Jan 18, 2021 at 4:59 PM Brendan Jackman <jackmanb@google.com> wrote:
>
> This fixues up the markup to fix a warning, be more consistent with
s/fixues/fixes/ ?
> use of monospace, and use the correct .rst syntax for <em> (* instead
> of _).
>
> NB this conflicts with Lukas' patch at [1], which just fixes the
> warning. The scope of this one is a little broader.
>
> [1] https://lore.kernel.org/bpf/CA+i-1C3cEXqxcXfD4sibQfx+dtmmzvOzruhk8J5pAw3g5v=KgA@mail.gmail.com/T/#t
>
As I wrote in my patch, I did minimal changes. Your bit more extensive
changes make sense.
I suggest dropping this comment above starting from NB and the link;
it is not relevant for the history. You can of course move it below
the "---"; so it is not picked up into the git history.
Other than that:
Reviewed-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
> Signed-off-by: Brendan Jackman <jackmanb@google.com>
> ---
> Documentation/networking/filter.rst | 19 ++++++++++---------
> 1 file changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
> index f6d8f90e9a56..4c2bb4c6364d 100644
> --- a/Documentation/networking/filter.rst
> +++ b/Documentation/networking/filter.rst
> @@ -1048,12 +1048,12 @@ Unlike classic BPF instruction set, eBPF has generic load/store operations::
> Where size is one of: BPF_B or BPF_H or BPF_W or BPF_DW.
>
> It also includes atomic operations, which use the immediate field for extra
> -encoding.
> +encoding::
>
> .imm = BPF_ADD, .code = BPF_ATOMIC | BPF_W | BPF_STX: lock xadd *(u32 *)(dst_reg + off16) += src_reg
> .imm = BPF_ADD, .code = BPF_ATOMIC | BPF_DW | BPF_STX: lock xadd *(u64 *)(dst_reg + off16) += src_reg
>
> -The basic atomic operations supported are:
> +The basic atomic operations supported are::
>
> BPF_ADD
> BPF_AND
> @@ -1066,12 +1066,12 @@ memory location addresed by ``dst_reg + off`` is atomically modified, with
> immediate, then these operations also overwrite ``src_reg`` with the
> value that was in memory before it was modified.
>
> -The more special operations are:
> +The more special operations are::
>
> BPF_XCHG
>
> This atomically exchanges ``src_reg`` with the value addressed by ``dst_reg +
> -off``.
> +off``. ::
>
> BPF_CMPXCHG
>
> @@ -1081,18 +1081,19 @@ before is loaded back to ``R0``.
>
> Note that 1 and 2 byte atomic operations are not supported.
>
> -Except ``BPF_ADD`` _without_ ``BPF_FETCH`` (for legacy reasons), all 4 byte
> +Except ``BPF_ADD`` *without* ``BPF_FETCH`` (for legacy reasons), all 4 byte
> atomic operations require alu32 mode. Clang enables this mode by default in
> architecture v3 (``-mcpu=v3``). For older versions it can be enabled with
> ``-Xclang -target-feature -Xclang +alu32``.
>
> -You may encounter BPF_XADD - this is a legacy name for BPF_ATOMIC, referring to
> -the exclusive-add operation encoded when the immediate field is zero.
> +You may encounter ``BPF_XADD`` - this is a legacy name for ``BPF_ATOMIC``,
> +referring to the exclusive-add operation encoded when the immediate field is
> +zero.
>
> -eBPF has one 16-byte instruction: BPF_LD | BPF_DW | BPF_IMM which consists
> +eBPF has one 16-byte instruction: ``BPF_LD | BPF_DW | BPF_IMM`` which consists
> of two consecutive ``struct bpf_insn`` 8-byte blocks and interpreted as single
> instruction that loads 64-bit immediate value into a dst_reg.
> -Classic BPF has similar instruction: BPF_LD | BPF_W | BPF_IMM which loads
> +Classic BPF has similar instruction: ``BPF_LD | BPF_W | BPF_IMM`` which loads
> 32-bit immediate value into a register.
>
> eBPF verifier
> --
> 2.30.0.284.gd98b1dd5eaa7-goog
>
next prev parent reply other threads:[~2021-01-18 17:19 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-18 15:57 [PATCH bpf-next v2 0/2] BPF docs fixups Brendan Jackman
2021-01-18 15:57 ` [PATCH bpf-next v2 1/2] docs: bpf: Fixup atomics markup Brendan Jackman
2021-01-18 17:17 ` Lukas Bulwahn [this message]
2021-01-18 15:57 ` [PATCH bpf-next v2 2/2] docs: bpf: Clarify -mcpu=v3 requirement for atomic ops Brendan Jackman
2021-01-18 17:36 ` Yonghong Song
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