Re: [PATCH] powerpc/process: fix altivec SPR not being saved
From: Benjamin Herrenschmidt <hidden>
Date: 2016-03-07 03:52:02
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 !
quoted hunk ↗ jump to hunk
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.cb/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