* [PATCH] powerpc/process: fix altivec SPR not being saved
@ 2016-03-06 22:33 Oliver O'Halloran
2016-03-07 3:51 ` Benjamin Herrenschmidt
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Oliver O'Halloran @ 2016-03-06 22:33 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Oliver O'Halloran
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(-)
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
--
2.5.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] powerpc/process: fix altivec SPR not being saved
2016-03-06 22:33 [PATCH] powerpc/process: fix altivec SPR not being saved Oliver O'Halloran
@ 2016-03-07 3:51 ` Benjamin Herrenschmidt
2016-03-07 4:19 ` Anton Blanchard
2016-03-07 22:08 ` Oliver O'Halloran
2 siblings, 0 replies; 5+ messages in thread
From: Benjamin Herrenschmidt @ 2016-03-07 3:51 UTC (permalink / raw)
To: Oliver O'Halloran, linuxppc-dev
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
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] powerpc/process: fix altivec SPR not being saved
2016-03-06 22:33 [PATCH] powerpc/process: fix altivec SPR not being saved Oliver O'Halloran
2016-03-07 3:51 ` Benjamin Herrenschmidt
@ 2016-03-07 4:19 ` Anton Blanchard
2016-03-07 22:08 ` Oliver O'Halloran
2 siblings, 0 replies; 5+ messages in thread
From: Anton Blanchard @ 2016-03-07 4:19 UTC (permalink / raw)
To: Oliver O'Halloran; +Cc: linuxppc-dev
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
^ permalink raw reply [flat|nested] 5+ messages in thread* [PATCH] powerpc/process: fix altivec SPR not being saved
2016-03-06 22:33 [PATCH] powerpc/process: fix altivec SPR not being saved Oliver O'Halloran
2016-03-07 3:51 ` Benjamin Herrenschmidt
2016-03-07 4:19 ` Anton Blanchard
@ 2016-03-07 22:08 ` Oliver O'Halloran
2016-03-30 23:29 ` Michael Ellerman
2 siblings, 1 reply; 5+ messages in thread
From: Oliver O'Halloran @ 2016-03-07 22:08 UTC (permalink / raw)
To: linuxppc-dev; +Cc: Oliver O'Halloran, Anton Blanchard
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>
Signed-off-by: Anton Blanchard <anton@samba.org>
Fixes: 152d523e6307 ("powerpc: Create context switch helpers save_sprs() and restore_sprs()")
Cc: stable@vger.kernel.org
---
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 dccc87e8fee5..bc6aa87a3b12 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -854,7 +854,7 @@ 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
--
2.5.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: powerpc/process: fix altivec SPR not being saved
2016-03-07 22:08 ` Oliver O'Halloran
@ 2016-03-30 23:29 ` Michael Ellerman
0 siblings, 0 replies; 5+ messages in thread
From: Michael Ellerman @ 2016-03-30 23:29 UTC (permalink / raw)
To: Oliver O'Halloran, linuxppc-dev
Cc: Oliver O'Halloran, Anton Blanchard
On Mon, 2016-07-03 at 22:08:47 UTC, 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.
>
> Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
> Signed-off-by: Anton Blanchard <anton@samba.org>
> Fixes: 152d523e6307 ("powerpc: Create context switch helpers save_sprs() and restore_sprs()")
> Cc: stable@vger.kernel.org
Applied to powerpc fixes, thanks.
https://git.kernel.org/powerpc/c/01d7c2a2de47890934faba91a7
cheers
^ permalink raw reply [flat|nested] 5+ messages in thread
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2016-03-06 22:33 [PATCH] powerpc/process: fix altivec SPR not being saved Oliver O'Halloran
2016-03-07 3:51 ` Benjamin Herrenschmidt
2016-03-07 4:19 ` Anton Blanchard
2016-03-07 22:08 ` Oliver O'Halloran
2016-03-30 23:29 ` Michael Ellerman
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