Re: [PATCH bpf-next v2] bpf, docs: add LOAD_ACQUIRE and STORE_RELEASE instructions

["Alexis Lothoré" <alexis.lothore@bootlin.com>]

Hi David,

On Thu May 21, 2026 at 4:17 AM CEST, David Vernet wrote:
> On Thu, May 21, 2026 at 12:09:11AM +0200, Alexis Lothoré (eBPF Foundation) wrote:
>
> Hi Alexis,
>
> Thanks for working on this.
>
>> Commit 880442305a39 ("bpf: Introduce load-acquire and store-release
>> instructions") instroduced the LOAD_ACQUIRE and STORE_RELEASE atomic
>
> introduced
>
>> instructions modifiers. Those are currently not described in the
>> documentation, despite being used in the verifier and the various JIT
>> compilers supporting them.
>> 
>> Add the missing entries in the instruction set documentation.
>> 
>> Signed-off-by: Alexis Lothoré (eBPF Foundation) <alexis.lothore@bootlin.com>
>
> Alexei et al -- if you plan to do a subsequent RFC, it will influence
> how this document needs to be structured. [0] explains the process for
> adding new instructions. To quote:
>
>> Once a conformance group is registered with a set of instructions, no
>> further instructions can be added to that conformance group. A
>> specification should instead create a new conformance group that
>> includes the original conformance group, plus any newly added
>> instructions. Inclusion of the original conformance group is done via
>> the "includes" column of the BPF Instruction Conformance Groups
>> registry, and inclusion of newly added instructions is done via the
>> "groups" column of the BPF Instruction Set registry.
>
> So you would have to create a new conformance group for these new
> atomics -- you can't just add them to the existing one. In general it
> might be easier / advised to snapshot this file to RFC 9669 and create a
> new one for the new instructions to make it easier to tease this stuff
> apart later. If that's something you want, I'm happy to get us started
> with a skeleton file. Again, though, that's only necessary if you plan
> to submit a new document to the IETF WG.
>
> [0]: https://www.rfc-editor.org/rfc/rfc9669.html#name-adding-instructions

I don't know how heavy/long the process is to submit this kind of RFC
update, but your point makes it sound like it makes more sense to just
go directly for the proper way, ie adding the conformance group and then
adding those new ops in there, rather than updating the kernel doc as my
series is proposing, and then later reverting to a proper conformance
group.

-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com