On Thu, Jul 27, 2017 at 02:32:59PM -0300, Thiago Jung Bauermann wrote: > > Ram Pai <linuxram@xxxxxxxxxx> writes: > > > Store and restore the AMR, IAMR and UMOR register state of the task > > before scheduling out and after scheduling in, respectively. > > > > Signed-off-by: Ram Pai <linuxram@xxxxxxxxxx> > > s/UMOR/UAMOR/ > > > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c > > index 2ad725e..9429361 100644 > > --- a/arch/powerpc/kernel/process.c > > +++ b/arch/powerpc/kernel/process.c > > @@ -1096,6 +1096,11 @@ static inline void save_sprs(struct thread_struct *t) > > t->tar = mfspr(SPRN_TAR); > > } > > #endif > > +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS > > + t->amr = mfspr(SPRN_AMR); > > + t->iamr = mfspr(SPRN_IAMR); > > + t->uamor = mfspr(SPRN_UAMOR); > > +#endif > > } > > > > static inline void restore_sprs(struct thread_struct *old_thread, > > @@ -1131,6 +1136,14 @@ static inline void restore_sprs(struct thread_struct *old_thread, > > mtspr(SPRN_TAR, new_thread->tar); > > } > > #endif > > +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS > > + if (old_thread->amr != new_thread->amr) > > + mtspr(SPRN_AMR, new_thread->amr); > > + if (old_thread->iamr != new_thread->iamr) > > + mtspr(SPRN_IAMR, new_thread->iamr); > > + if (old_thread->uamor != new_thread->uamor) > > + mtspr(SPRN_UAMOR, new_thread->uamor); > > +#endif > > } > > Shouldn't the saving and restoring of the SPRs be guarded by a check for > whether memory protection keys are enabled? What happens when trying to > access these registers on a CPU which doesn't have them? Good point. need to guard it. However; i think, these registers have been available since power6. RP
