Re: [MAINTAINERS / KERNEL SUMMIT] AI patch review tools

[Chris Mason <clm@meta.com>]

On 10/8/25 2:33 PM, Sasha Levin wrote:
> On Wed, Oct 08, 2025 at 01:04:54PM -0400, Chris Mason wrote:
>> Hi everyone,
>>
>> Depending on how you look at things, this is potentially a topic for
>> either MS or KS.
>>
>> One way to lower the load on maintainers is to make it easier for
>> contributors to send higher quality patches, and to catch errors before
>> they land in various git trees.
>>
>> Along those lines, when the AI code submission thread started over the
>> summer, I decided to see if it was possible to get reasonable code
>> reviews out of AI.
> 
> This is a really great subject to discuss.
> 
> IMO when the AI topic initially came up the concerns around AI drowned
> discussions of finding places where AI could be useful and provide
> support for
> maintainers struggling under the load.
> 
>> There are certainly false positives, but Alexei and the BPF developers
>> wired up my prompts into the BPF CI, and you can find the results in
>> their github CI.  Everything in red is a bug the AI review found:
>>
>> https://github.com/kernel-patches/bpf/actions/workflows/ai-code-
>> review.yml
>> My goal for KS/MS is to discuss how to enable maintainers to use review
>> automation tools to lower their workload.  I don't want to build new CI
>> here, so the goal would be enabling integration with existing CI.
> 
> This is great to see!
> 
> I think that AUTOSEL is already a large scale kernel patch review
> workflow and
> I'd love to work more towards a unified kernel patch AI review story that
> community members could use.
> 
> I've gotten good feedback[1] from Linus about the AI AUTOSEL workflow
> and his
> idea around expanding our AI tooling to help with maintainer workflows
> sounds
> in line with what you're describing here.

Fantastic.

> 
>> My question for everyone is what would it take to make all of this
>> useful?  I'm working on funding for API access, so hopefully that part
>> won't be a problem.
> 
> I've been playing with extending[2] b4 (unofficially) with AI workflows
> that
> are useful for myself. The patches themselves aren't too interesting,
> but what
> I found exciting is expanding b4 with tooling that maintainers can run
> locally
> and which will save them a good amound of time/effort.
> 
> Something along the lines of "b4 ai review [commit]" or "b4 ai style
> [patch]".

Yeah, I think that'll really help as well.

> 
>> There's definitely overlap between the bugs I'm finding and the bugs Dan
>> Carpenter finds, so I'm hoping he and I can team up as well.
>>
>> In terms of actual review details, the reviews have two parts:
>>
>> 1) The review prompts.  These are stand alone and can just work on any
>> kernel tree.  This is what BPF CI is currently using:
>>
>> https://github.com/masoncl/review-prompts/ 
> 
> I think I'll borrow some of these :)
> 
> It was interesting to read through some of the prompts and see where you
> had
> good and bad experience with the AI ("You're not smart enough to understand
> smp_mb()" :D )

If I'm being honest, I'm probably not smart enough to teach AI about
smp_mb(), but that's a different problem.

> 
>> These prompts can also debug oopsen or syzbot reports (with varying
>> success).
>>
>> 2) A code indexing tool with MCP server that Claude can use to find
>> functions, types, and call chains more effectively.  This makes it more
>> likely Claude can trace complex relationships in the code:
>>
>> https://github.com/facebookexperimental/semcode
>> Asking claude to produce a callgraph for btrfs_search_slot() consumes
>> ~444K tokens.  With semcode installed, the same query produces better
>> results and uses 25K tokens. (btrfs_search_slot() has a huge callchain)
> 
> Also very interesting! AUTOSEL is a token eating machine. Reducing token
> counts
> while still getting the same (or better) quality of outputs is really
> great.

I think/hope the extra context will make a huge difference, and I want
to add indexing for git history and lore archives as well.

-chris