On Wed, Jun 19, 2024 at 05:44:11PM +0200, Ilya Leoshkevich wrote: Hi Ilya, > +static inline bool is_lowcore_addr(void *addr) > +{ > + return addr >= (void *)&S390_lowcore && > + addr < (void *)(&S390_lowcore + 1); > +} > + > +static inline void *arch_kmsan_get_meta_or_null(void *addr, bool is_origin) > +{ > + if (is_lowcore_addr(addr)) { > + /* > + * Different lowcores accessed via S390_lowcore are described > + * by the same struct page. Resolve the prefix manually in > + * order to get a distinct struct page. > + */ > + addr += (void *)lowcore_ptr[raw_smp_processor_id()] - > + (void *)&S390_lowcore; If I am not mistaken neither raw_smp_processor_id() itself, nor lowcore_ptr[raw_smp_processor_id()] are atomic. Should the preemption be disabled while the addr is calculated? But then the question arises - how meaningful the returned value is? AFAICT kmsan_get_metadata() is called from a preemptable context. So if the CPU is changed - how useful the previous CPU lowcore meta is? Is it a memory block that needs to be ignored instead? > + if (WARN_ON_ONCE(is_lowcore_addr(addr))) > + return NULL; lowcore_ptr[] pointing into S390_lowcore is rather a bug. > + return kmsan_get_metadata(addr, is_origin); > + } > + return NULL; > +} Thanks!