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| Started by | Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> |
|---|---|
| First post | 2017-07-27 19:40 +0200 |
| Last post | 2017-07-30 01:40 +0200 |
| Articles | 2 — 2 participants |
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Re: [RFC v6 20/62] powerpc: store and restore the pkey state across context switches Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> - 2017-07-27 19:40 +0200
Re: [RFC v6 20/62] powerpc: store and restore the pkey state across context switches Ram Pai <linuxram@us.ibm.com> - 2017-07-30 01:40 +0200
| From | Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> |
|---|---|
| Date | 2017-07-27 19:40 +0200 |
| Subject | Re: [RFC v6 20/62] powerpc: store and restore the pkey state across context switches |
| Message-ID | <u7UVr-zr-1@gated-at.bofh.it> |
Ram Pai <linuxram@us.ibm.com> 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@us.ibm.com> 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? -- Thiago Jung Bauermann IBM Linux Technology Center
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| From | Ram Pai <linuxram@us.ibm.com> |
|---|---|
| Date | 2017-07-30 01:40 +0200 |
| Subject | Re: [RFC v6 20/62] powerpc: store and restore the pkey state across context switches |
| Message-ID | <u8JuV-Nu-1@gated-at.bofh.it> |
| In reply to | #1698211 |
On Thu, Jul 27, 2017 at 02:32:59PM -0300, Thiago Jung Bauermann wrote: > > Ram Pai <linuxram@us.ibm.com> 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@us.ibm.com> > > 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
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