Re: [PATCH 1/4] arm64: percpu: Always inline helpers used by noinstr code

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] arm64: percpu: __PERCPU_OP_CASE() and sibling helpers not marked
  __always_inline
--

commit 3a2df0916b5200b227df21487897e171275b29f4
Author: Jisheng Zhang <jszhang@kernel.org>

arm64: percpu: Always inline helpers used by noinstr code

This commit marks __hyp_my_cpu_offset(), __kern_my_cpu_offset(), and
__percpu_read_##sz() as __always_inline so they are not emitted out of line
when called from non-instrumentable code.

> diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
> index 3cc316091d665..7c344de5052d5 100644
> --- a/arch/arm64/include/asm/percpu.h
> +++ b/arch/arm64/include/asm/percpu.h

[ ... ]

> @@ -129,7 +129,7 @@ static inline unsigned long __kern_my_cpu_offset(void)
>  #endif
>  
>  #define PERCPU_RW_OPS(w, sfx, sz)						\
> -static inline unsigned long __percpu_read_##sz(void __percpu *pcp)		\
> +static __always_inline unsigned long __percpu_read_##sz(void __percpu *pcp)		\
>  {										\
>  	u16 *gprs = &current_thread_info()->pcpu_gprs;				\
>  	unsigned long off;							\

[Severity: Low]
Should __PERCPU_OP_CASE() and the remaining __percpu_* helpers in this header
(__percpu_write_##sz(), __PERCPU_RET_OP_CASE(), PERCPU_XCHG_OP(),
PERCPU_CMPXCHG_OP(), and __percpu_cmpxchg_128()) also be marked
__always_inline?

The noinstr function lockdep_hardirqs_on() calls
__debug_atomic_inc(redundant_hardirqs_on), which under CONFIG_DEBUG_LOCKDEP=y
expands to this_cpu_inc(lockdep_stats.redundant_hardirqs_on) ->
__percpu_add_case_64().  Because __PERCPU_OP_CASE() still uses plain static
inline and is also called from instrumentable lockdep functions, builds with
CONFIG_CC_OPTIMIZE_FOR_SIZE=y can emit __percpu_add_case_64() out of line in
.text and call it from .noinstr.text before RCU and lockdep state are ready
for instrumentation.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261107071339.17467-1-jszhang@kernel.org?part=1