Re: [PATCHSET sched_ext/for-7.2] sched_ext: Topological CPU IDs and cid-form struct_ops

[Tejun Heo]

Hello, Cheng-Yang.

On Wed, Apr 22, 2026 at 02:18:56AM +0800, Cheng-Yang Chou wrote:
> Reviewed-by: Cheng-Yang Chou <yphbchou0911@xxxxxxxxx>

Thanks, applied.

> 1. Regarding the ext_cid feature (same as ext_idle), is it feasible to
>    implement this within the BPF arena instead of the current approach?

No - cid-form struct_ops translates cids <-> cpus at the ops boundary,
so the kernel needs direct access to the mapping. Building it also
pulls from cpu_to_node() / cacheinfo / sibling masks which aren't
reachable from BPF.

> 2. I noticed rust/kernel/cpumask.rs is already in tree. ... would it be
>    a good time to start adding Rust abstractions ...

I'd wait for a concrete in-tree consumer before growing Rust
wrappers speculatively.

Thanks.

--
tejun