Re: [PATCH v3] selftests/bpf: Use the new NMI_BITS definition

[Boqun Feng <boqun@kernel.org>]

On Fri, Oct 02, 2026 at 09:50:02PM +0800, Leon Hwang wrote:
> On 2026/10/2 18:29, 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@linux.ibm.com>
> > Fixes: 3b0e2a22d408 ("preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS")
> > Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> > Cc: Leon Hwang <leon.hwang@linux.dev>
> > Cc: Alexei Starovoitov <ast@kernel.org>
> > Signed-off-by: Boqun Feng <boqun@kernel.org>
> 
> lgtm,
> 
> Acked-by: Leon Hwang <leon.hwang@linux.dev>
> 
> One nit below.
> 
> > ---
> > v2: https://lore.kernel.org/lkml/20261001082519.16195-4-boqun@kernel.org/
> > v2 -> v3:
> > 
> > * Add Fixes tag.
> > * Add CONFIG_HAS_SEPARATE_PREEMPT_RESCHED_BITS weak symbol because
> >   CONFIG_* is not available in bpf programs.
> > 
> > 
> >  tools/testing/selftests/bpf/bpf_experimental.h | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
> > index 2893bf06ff25..a09448347966 100644
> > --- a/tools/testing/selftests/bpf/bpf_experimental.h
> > +++ b/tools/testing/selftests/bpf/bpf_experimental.h
> > @@ -367,11 +367,16 @@ 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;
> > +
> > +/* A trivial macro to make NMI_BITS exactly the same as in <linux/preempt.h> */
> > +#define IS_ENABLED(cfg)	(cfg)
> 
> NIT: change this to ((cfg) ? 1 : 0) to match IS_ENABLED() semantics.
> 

Seems reasonable.

Regards,
Boqun

> Thanks,
> Leon
> 
> > +
> >  #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*IS_ENABLED(CONFIG_HAS_SEPARATE_PREEMPT_RESCHED_BITS))
> >  
> >  #define PREEMPT_SHIFT	0
> >  #define SOFTIRQ_SHIFT	(PREEMPT_SHIFT + PREEMPT_BITS)
>