Re: [PATCH v2 3/5] selftests/bpf: Use the new NMI_BITS definition

[Boqun Feng]

On Fri, Oct 02, 2026 at 02:24:11PM +0800, Leon Hwang wrote:
> On 1/10/26 21:13, Boqun Feng wrote:
> > On Thu, Oct 01, 2026 at 10:25:17AM +0200, Boqun Feng wrote:
> >> The definition of NMI_BITS was out of sync after the introduction of
> >> HAS_SEPARATE_PREEMPT_RESCHED_BITS, hence adjust it.
> >>
> >> Reported-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
> >> Reviewed-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
> >> Signed-off-by: Boqun Feng <boqun@xxxxxxxxxx>
> >> ---
> >>  tools/testing/selftests/bpf/bpf_experimental.h | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
> >> index 2893bf06ff25..4bf7390994bf 100644
> >> --- a/tools/testing/selftests/bpf/bpf_experimental.h
> >> +++ b/tools/testing/selftests/bpf/bpf_experimental.h
> > 
> > Per sashiko's report, seems I need the following to make it work:
> 
> Sashiko is correct.
> 
> BPF compilation context is different from kernel compilation context. It
> cannot directly use
> IS_ENABLED(CONFIG_HAS_SEPARATE_PREEMPT_RESCHED_BITS)) when compiling BPF
> objects.
> 
> > 
> > diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
> > index 4bf7390994bf..94143cf0ab0d 100644
> > --- a/tools/testing/selftests/bpf/bpf_experimental.h
> > +++ b/tools/testing/selftests/bpf/bpf_experimental.h
> > @@ -367,6 +367,9 @@ extern int bpf_cgroup_read_xattr(struct cgroup *cgroup, const char *name__str,
> >  extern int bpf_sock_read_xattr(struct socket *sock, const char *name__str,
> >                                struct bpf_dynptr *value_p) __weak __ksym;
> > 
> > +extern bool CONFIG_HAS_SEPARATE_PREEMPT_RESCHED_BITS __kconfig __weak;
> > +#define IS_ENABLED(cfg) (cfg)
> 
> Correct.
> 
> IS_ENABLED is unnecessary here.
> 
> The below patch passed the BPF ci [1].
> 
> [1] https://github.com/kernel-patches/bpf/pull/14197
> 

Thanks for the testing. I know that IS_ENABLED is not unnecessary, but I
put it there to make NMI_BITS definition stay the same as
include/linux/preempt.h.

> > +
> >  #define PREEMPT_BITS   8
> >  #define SOFTIRQ_BITS   8
> >  #define HARDIRQ_DISABLE_BITS   8
> > 
> > ?
> > 
> > [Cc Leon and Alexi]
> 
> Please cc BPF list, BPF maintainers, and me when respinning.
> 

Sure, will do.

Regards,
Boqun

> Thanks,
> Leon
> 
> > 
> > Regards,
> > Boqun
> > 
> ---
> 
> From 4c1b9a6f6404aa25d1d300465dba4bee9a139668 Mon Sep 17 00:00:00 2001
> From: Boqun Feng <boqun@xxxxxxxxxx>
> Date: Thu, 1 Oct 2026 10:25:17 +0200
> Subject: [PATCH 1/3] selftests/bpf: Use the new NMI_BITS definition
> 
> The definition of NMI_BITS was out of sync after the introduction of
> HAS_SEPARATE_PREEMPT_RESCHED_BITS, hence adjust it.
> 
> Reported-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
> Reviewed-by: Shrikanth Hegde <sshegde@xxxxxxxxxxxxx>
> Signed-off-by: Boqun Feng <boqun@xxxxxxxxxx>
> ---
>  tools/testing/selftests/bpf/bpf_experimental.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/bpf_experimental.h
> b/tools/testing/selftests/bpf/bpf_experimental.h
> index 2893bf06ff25..b567a48f1dce 100644
> --- a/tools/testing/selftests/bpf/bpf_experimental.h
> +++ b/tools/testing/selftests/bpf/bpf_experimental.h
> @@ -367,11 +367,13 @@ extern int bpf_cgroup_read_xattr(struct cgroup
> *cgroup, const char *name__str,
>  extern int bpf_sock_read_xattr(struct socket *sock, const char *name__str,
>  			       struct bpf_dynptr *value_p) __weak __ksym;
> 
> +extern bool CONFIG_HAS_SEPARATE_PREEMPT_RESCHED_BITS __weak __kconfig;
> +
>  #define PREEMPT_BITS	8
>  #define SOFTIRQ_BITS	8
>  #define HARDIRQ_DISABLE_BITS	8
>  #define HARDIRQ_BITS	4
> -#define NMI_BITS	1
> +#define NMI_BITS	(1 + 3*CONFIG_HAS_SEPARATE_PREEMPT_RESCHED_BITS)
> 
>  #define PREEMPT_SHIFT	0
>  #define SOFTIRQ_SHIFT	(PREEMPT_SHIFT + PREEMPT_BITS)
> -- 
> 2.55.0
> 
>