On Fri, Mar 12, 2021 at 02:22:07PM +0000, Vincenzo Frascino wrote: > diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h > index 9b557a457f24..8603c6636a7d 100644 > --- a/arch/arm64/include/asm/mte.h > +++ b/arch/arm64/include/asm/mte.h > @@ -90,5 +90,20 @@ static inline void mte_assign_mem_tag_range(void *addr, > size_t size) > > #endif /* CONFIG_ARM64_MTE */ > > +#ifdef CONFIG_KASAN_HW_TAGS > +/* Whether the MTE asynchronous mode is enabled. */ > +DECLARE_STATIC_KEY_FALSE(mte_async_mode); > + > +static inline bool system_uses_mte_async_mode(void) > +{ > + return static_branch_unlikely(&mte_async_mode); > +} > +#else > +static inline bool system_uses_mte_async_mode(void) > +{ > + return false; > +} > +#endif /* CONFIG_KASAN_HW_TAGS */
You can write this with fewer lines: DECLARE_STATIC_KEY_FALSE(mte_async_mode); static inline bool system_uses_mte_async_mode(void) { return IS_ENABLED(CONFIG_KASAN_HW_TAGS) && static_branch_unlikely(&mte_async_mode); } The compiler will ensure that mte_async_mode is not referred when !CONFIG_KASAN_HW_TAGS and therefore doesn't need to be defined. > diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c > index fa755cf94e01..9362928ba0d5 100644 > --- a/arch/arm64/kernel/mte.c > +++ b/arch/arm64/kernel/mte.c > @@ -26,6 +26,10 @@ u64 gcr_kernel_excl __ro_after_init; > > static bool report_fault_once = true; > > +/* Whether the MTE asynchronous mode is enabled. */ > +DEFINE_STATIC_KEY_FALSE(mte_async_mode); > +EXPORT_SYMBOL_GPL(mte_async_mode); Maybe keep these bracketed by #ifdef CONFIG_KASAN_HW_TAGS. I think the mte_enable_kernel_*() aren't needed either if KASAN_HW is disabled (you can do it with an additional patch). With these, you can add: Reviewed-by: Catalin Marinas <catalin.mari...@arm.com>