[PATCHSET v4 sched_ext/for-7.2] bpf/arena: Direct kernel-side access

[Alexei Starovoitov]

On Fri, May 22, 2026 at 10:22 AM Tejun Heo <tj at kernel.org> wrote:
>
> Patches 1-2 (atomic PTE install + arena scratch-page recovery)
> --------------------------------------------------------------
>
>   mm: Add ptep_try_set() for lockless empty-slot installs
>   bpf: Recover arena kernel faults with scratch page
>
> Patches 3-5 (helpers used by struct_ops registration)
> -----------------------------------------------------
>
>   bpf: Add sleepable variant of bpf_arena_alloc_pages for kernel callers
>   bpf: Add bpf_struct_ops_for_each_prog()
>   bpf/arena: Add bpf_arena_map_kern_vm_start() and bpf_prog_arena()
>
> Patches 6-8 (sched_ext: arena auto-discovery, allocator, set_cmask)
> -------------------------------------------------------------------
>
>   sched_ext: Require an arena for cid-form schedulers
>   sched_ext: Sub-allocator over kernel-claimed BPF arena pages
>   sched_ext: Convert ops.set_cmask() to arena-resident cmask
>
> Patch 6 reads each member prog's prog->aux->arena via bpf_prog_arena() and
> requires the cid-form struct_ops to reference exactly one arena. Patch 7
> builds a gen_pool sub-allocator inside that arena. Patch 8 converts
> set_cmask() to write into arena memory. BPF dereferences via __arena like
> any other arena struct, no probe-reads.
>
> Base
> ----
>
> sched_ext/for-7.2 (f31e89a8f583)
>
> Git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git arena-direct-v4

I created a stable branch bpf-next/arena_direct_access
with the first 5 patches and merged it into bpf-next/master.

Tejun,
please pull it into sched-ext tree as well.

Let's do any follow ups on top.

Thanks everyone!