From: John Fastabend <john.fastabend@gmail.com>
To: Brendan Jackman <jackmanb@google.com>,
John Fastabend <john.fastabend@gmail.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Yonghong Song <yhs@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>,
KP Singh <kpsingh@chromium.org>,
Florent Revest <revest@chromium.org>,
linux-kernel@vger.kernel.org, Jann Horn <jannh@google.com>
Subject: Re: [PATCH bpf-next v4 04/11] bpf: Rename BPF_XADD and prepare to encode other atomics in .imm
Date: Tue, 08 Dec 2020 21:40:03 -0800 [thread overview]
Message-ID: <5fd06333d11ff_50ce2082d@john-XPS-13-9370.notmuch> (raw)
In-Reply-To: <X89G2kItO2o60+A6@google.com>
Brendan Jackman wrote:
> Hi John, thanks a lot for the reviews!
>
> On Mon, Dec 07, 2020 at 01:56:53PM -0800, John Fastabend wrote:
> > Brendan Jackman wrote:
> > > A subsequent patch will add additional atomic operations. These new
> > > operations will use the same opcode field as the existing XADD, with
> > > the immediate discriminating different operations.
> > >
> > > In preparation, rename the instruction mode BPF_ATOMIC and start
> > > calling the zero immediate BPF_ADD.
> > >
> > > This is possible (doesn't break existing valid BPF progs) because the
> > > immediate field is currently reserved MBZ and BPF_ADD is zero.
> > >
> > > All uses are removed from the tree but the BPF_XADD definition is
> > > kept around to avoid breaking builds for people including kernel
> > > headers.
> > >
> > > Signed-off-by: Brendan Jackman <jackmanb@google.com>
> > > ---
[...]
> > > + case BPF_STX | BPF_ATOMIC | BPF_W:
> > > + case BPF_STX | BPF_ATOMIC | BPF_DW:
> > > + if (insn->imm != BPF_ADD) {
> > > + pr_err("bpf-jit: not supported: atomic operation %02x ***\n",
> > > + insn->imm);
> > > + return -EINVAL;
> > > + }
> >
> > Can we standardize the error across jits and the error return code? It seems
> > odd that we use pr_err, pr_info_once, pr_err_ratelimited and then return
> > ENOTSUPP, EFAULT or EINVAL.
>
> That would be a noble cause but I don't think it makes sense in this
> patchset: they are already inconsistent, so here I've gone for intra-JIT
> consistency over inter-JIT consistency.
>
> I think it would be more annoying, for example, if the s390 JIT returned
> -EOPNOTSUPP for a bad atomic but -1 for other unsupported ops, than it
> is already that the s390 JIT returns -1 where the MIPS returns -EINVAL.
ok works for me thanks for the explanation.
next prev parent reply other threads:[~2020-12-09 5:40 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-07 16:07 [PATCH bpf-next v4 00/11] Atomics for eBPF Brendan Jackman
2020-12-07 16:07 ` [PATCH bpf-next v4 01/11] bpf: x86: Factor out emission of ModR/M for *(reg + off) Brendan Jackman
2020-12-07 21:04 ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 02/11] bpf: x86: Factor out emission of REX byte Brendan Jackman
2020-12-07 21:07 ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 03/11] bpf: x86: Factor out a lookup table for some ALU opcodes Brendan Jackman
2020-12-07 21:08 ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 04/11] bpf: Rename BPF_XADD and prepare to encode other atomics in .imm Brendan Jackman
2020-12-07 21:56 ` John Fastabend
2020-12-08 9:26 ` Brendan Jackman
2020-12-09 5:40 ` John Fastabend [this message]
2020-12-07 16:07 ` [PATCH bpf-next v4 05/11] bpf: Move BPF_STX reserved field check into BPF_STX verifier code Brendan Jackman
2020-12-08 1:35 ` Yonghong Song
2020-12-08 5:13 ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 06/11] bpf: Add BPF_FETCH field / create atomic_fetch_add instruction Brendan Jackman
2020-12-08 1:41 ` Yonghong Song
2020-12-08 9:31 ` Brendan Jackman
2020-12-08 5:31 ` John Fastabend
2020-12-08 9:59 ` Brendan Jackman
2020-12-07 16:07 ` [PATCH bpf-next v4 07/11] bpf: Add instructions for atomic_[cmp]xchg Brendan Jackman
2020-12-08 1:44 ` Yonghong Song
2020-12-08 6:37 ` John Fastabend
2020-12-14 15:39 ` Brendan Jackman
2020-12-08 6:42 ` John Fastabend
2020-12-07 16:07 ` [PATCH bpf-next v4 08/11] bpf: Pull out a macro for interpreting atomic ALU operations Brendan Jackman
2020-12-07 16:07 ` [PATCH bpf-next v4 09/11] bpf: Add bitwise atomic instructions Brendan Jackman
2020-12-08 1:47 ` Yonghong Song
2020-12-10 0:22 ` kernel test robot
2020-12-07 16:07 ` [PATCH bpf-next v4 10/11] bpf: Add tests for new BPF atomic operations Brendan Jackman
2020-12-08 3:18 ` Yonghong Song
2020-12-08 12:41 ` Brendan Jackman
2020-12-08 16:38 ` Yonghong Song
2020-12-08 16:59 ` Brendan Jackman
2020-12-08 18:15 ` Yonghong Song
2020-12-15 11:12 ` Brendan Jackman
2020-12-16 7:18 ` Yonghong Song
2020-12-16 11:51 ` Brendan Jackman
2020-12-16 20:00 ` Yonghong Song
2020-12-07 16:07 ` [PATCH bpf-next v4 11/11] bpf: Document new atomic instructions Brendan Jackman
2020-12-08 3:25 ` Yonghong Song
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=5fd06333d11ff_50ce2082d@john-XPS-13-9370.notmuch \
--to=john.fastabend@gmail.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=jackmanb@google.com \
--cc=jannh@google.com \
--cc=kpsingh@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=revest@chromium.org \
--cc=yhs@fb.com \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®