powerpc/process: Fix altivec SPR not being saved

oohal · mpe · commit 01d7c2a2de47 · 2016-03-29T12:08:08.000+11:00
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. Fixes: 152d523 ("powerpc: Create context switch helpers save_sprs() and restore_sprs()") Cc: stable@vger.kernel.org Signed-off-by: Oliver O'Halloran <oohall@gmail.com> Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
@@ -983,7 +983,7 @@ 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

Original file line number	Diff line number	Diff line change
`@@ -983,7 +983,7 @@ void restore_tm_state(struct pt_regs *regs)`
`983`	`983`	`static inline void save_sprs(struct thread_struct *t)`
`984`	`984`	`{`
`985`	`985`	`#ifdef CONFIG_ALTIVEC`
`986`		`- if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC)))`
	`986`	`+ if (cpu_has_feature(CPU_FTR_ALTIVEC))`
`987`	`987`	`t->vrsave = mfspr(SPRN_VRSAVE);`
`988`	`988`	`#endif`
`989`	`989`	`#ifdef CONFIG_PPC_BOOK3S_64`