| Message ID | 1457303588-29173-1-git-send-email-oohall@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Mon, 2016-03-07 at 09:33 +1100, Oliver O'Halloran wrote: > In save_sprs() in process.c contains the following test: > > if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC))) > t->vrsave = mfspr(SPRN_VRSAVE); > > CPU feature with the mask 0x1 is CPU_FTR_COHERENT_ICACHE so the test > is equivilent to: > > if (cpu_has_feature(CPU_FTR_ALTIVEC) && > cpu_has_feature(CPU_FTR_COHERENT_ICACHE)) > > On CPUs without support for both (i.e G5) this results in vrsave not > being > saved between context switches. The vector register save/restore code > doesn't use VRSAVE to determine which registers to save/restore, > but the value of VRSAVE is used to determine if altivec is being used > in several code paths. Nice one, should probably go to stable ! > Signed-off-by: Oliver O'Halloran <oohall@gmail.com> > --- > arch/powerpc/kernel/process.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/process.c > b/arch/powerpc/kernel/process.c > index 8224852..5a4d4d1 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -855,7 +855,7 @@ void restore_tm_state(struct pt_regs *regs) > static inline void save_sprs(struct thread_struct *t) > { > #ifdef CONFIG_ALTIVEC > - if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC))) > + if (cpu_has_feature(CPU_FTR_ALTIVEC)) > t->vrsave = mfspr(SPRN_VRSAVE); > #endif > #ifdef CONFIG_PPC_BOOK3S_64
Hi Oliver, > In save_sprs() in process.c contains the following test: > > if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC))) > t->vrsave = mfspr(SPRN_VRSAVE); > > CPU feature with the mask 0x1 is CPU_FTR_COHERENT_ICACHE so the test > is equivilent to: > > if (cpu_has_feature(CPU_FTR_ALTIVEC) && > cpu_has_feature(CPU_FTR_COHERENT_ICACHE)) > > On CPUs without support for both (i.e G5) this results in vrsave not > being saved between context switches. The vector register > save/restore code doesn't use VRSAVE to determine which registers to > save/restore, but the value of VRSAVE is used to determine if altivec > is being used in several code paths. Nice catch, not sure how I missed that. As Ben suggests, it should definitely go to -stable as well. Feel free to add my sign off: Signed-off-by: Anton Blanchard <anton@samba.org> Anton > Signed-off-by: Oliver O'Halloran <oohall@gmail.com> > --- > arch/powerpc/kernel/process.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/process.c > b/arch/powerpc/kernel/process.c index 8224852..5a4d4d1 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -855,7 +855,7 @@ void restore_tm_state(struct pt_regs *regs) > static inline void save_sprs(struct thread_struct *t) > { > #ifdef CONFIG_ALTIVEC > - if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC))) > + if (cpu_has_feature(CPU_FTR_ALTIVEC)) > t->vrsave = mfspr(SPRN_VRSAVE); > #endif > #ifdef CONFIG_PPC_BOOK3S_64
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 8224852..5a4d4d1 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -855,7 +855,7 @@ void restore_tm_state(struct pt_regs *regs) static inline void save_sprs(struct thread_struct *t) { #ifdef CONFIG_ALTIVEC - if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC))) + if (cpu_has_feature(CPU_FTR_ALTIVEC)) t->vrsave = mfspr(SPRN_VRSAVE); #endif #ifdef CONFIG_PPC_BOOK3S_64
In save_sprs() in process.c contains the following test: if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC))) t->vrsave = mfspr(SPRN_VRSAVE); CPU feature with the mask 0x1 is CPU_FTR_COHERENT_ICACHE so the test is equivilent to: if (cpu_has_feature(CPU_FTR_ALTIVEC) && cpu_has_feature(CPU_FTR_COHERENT_ICACHE)) On CPUs without support for both (i.e G5) this results in vrsave not being saved between context switches. The vector register save/restore code doesn't use VRSAVE to determine which registers to save/restore, but the value of VRSAVE is used to determine if altivec is being used in several code paths. Signed-off-by: Oliver O'Halloran <oohall@gmail.com> --- arch/powerpc/kernel/process.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)