diff mbox

powerpc/process: fix altivec SPR not being saved

Message ID 1457388527-14575-1-git-send-email-oohall@gmail.com (mailing list archive)
State Accepted
Headers show

Commit Message

Oliver O'Halloran March 7, 2016, 10:08 p.m. UTC 
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(-)

Comments

Michael Ellerman March 30, 2016, 11:29 p.m. UTC | #1 
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
diff mbox

Patch

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