Re: [PATCH stable 6.6.y v3 0/4] bpf: linked scalar precision fixes

[Paul Chaignon]

On Mon, Jun 15, 2026 at 12:58:37AM +0800, Zhenzhong Wu wrote:
> Hi,
> 
> This v3 targets 6.6.y and changes the backport strategy based on review
> feedback on v2.

[...]

> Relevant QEMU selftest results on 6.6.y with this backport:
> 
>   verifier_scalar_ids passed all 18 subtests, including the newly
>   backported linked-scalar precision tests and the related
>   check_ids_in_regsafe tests.

The first patch in this backport series is actually breaking the
"precise: test 1" selftest from test_verifier. You can see the full
error at [1]. I haven't yet checked if it's the test or the backport
that needs to be adjusted.

1: https://github.com/shunghsiyu/libbpf/actions/runs/27575831217/job/81523786835

> 
> Thanks to Shung-Hsi Yu for reviewing v2 and suggesting the upstream
> linked-scalar precision series as the preferred backport direction.
> 
> Eduard Zingerman (4):
>   bpf: Track equal scalars history on per-instruction level
>   bpf: Remove mark_precise_scalar_ids()
>   selftests/bpf: Tests for per-insn sync_linked_regs() precision
>     tracking
>   selftests/bpf: Update comments find_equal_scalars->sync_linked_regs
> 
>  include/linux/bpf_verifier.h                  |   4 +
>  kernel/bpf/verifier.c                         | 367 +++++++++++-------
>  .../selftests/bpf/progs/verifier_scalar_ids.c | 253 ++++++++----
>  .../selftests/bpf/progs/verifier_spill_fill.c |   4 +-
>  .../bpf/progs/verifier_subprog_precision.c    |   2 +-
>  .../testing/selftests/bpf/verifier/precise.c  |   2 +-
>  6 files changed, 417 insertions(+), 215 deletions(-)
> 
> 
> base-commit: 924b4a879cbb75aef37c160b955b92f6894b11a4
> -- 
> 2.43.0