When we call giveup_fpu, we need to need to turn off VSX in current.
If we don't, on return to current it may execute a VSX instruction
(before the next FP), and not have it's register state refreshed
correctly from the thread_struct. Ditto for altivec.
This caused a bug where an unaligned lfs or stfs (which calls
giveup_fpu so it can use the FPRs) to return to userspace with FP off
but VSX on. Then if a VSX instruction is executed, before another FP
instruction, it will proceed without another exception and hence have
the incorrect register state for VSX registers 0-31.
lfs unaligned <- alignment exception turns FP off but leaves VSX on
VSX instruction <- no exception since VSX on, hence we get the
wrong VSX register values for VSX registers 0-31
(overlapping the FPRs)
Signed-off-by: Michael Neuling <mi...@neuling.org>
---
arch/powerpc/kernel/fpu.S | 5 +++++
arch/powerpc/kernel/misc_64.S | 8 ++++++++
2 files changed, 13 insertions(+)
Index: linux-2.6-ozlabs/arch/powerpc/kernel/fpu.S
===================================================================
--- linux-2.6-ozlabs.orig/arch/powerpc/kernel/fpu.S
+++ linux-2.6-ozlabs/arch/powerpc/kernel/fpu.S
@@ -145,6 +145,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_VSX)
beq 1f
PPC_LL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
li r3,MSR_FP|MSR_FE0|MSR_FE1
+#ifdef CONFIG_VSX
+BEGIN_FTR_SECTION
+ oris r3,r3,msr_...@h
+END_FTR_SECTION_IFSET(CPU_FTR_VSX)
+#endif
andc r4,r4,r3 /* disable FP for previous task */
PPC_STL r4,_MSR-STACK_FRAME_OVERHEAD(r5)
1:
Index: linux-2.6-ozlabs/arch/powerpc/kernel/misc_64.S
===================================================================
--- linux-2.6-ozlabs.orig/arch/powerpc/kernel/misc_64.S
+++ linux-2.6-ozlabs/arch/powerpc/kernel/misc_64.S
@@ -495,7 +495,15 @@ _GLOBAL(giveup_altivec)
stvx vr0,r4,r3
beq 1f
ld r4,_MSR-STACK_FRAME_OVERHEAD(r5)
+#ifdef CONFIG_VSX
+BEGIN_FTR_SECTION
+ lis r3,(MSR_VEC|MSR_VSX)@h
+FTR_SECTION_ELSE
+ lis r3,msr_...@h
+ALT_FTR_SECTION_END_IFSET(CPU_FTR_VSX)
+#else
lis r3,msr_...@h
+#endif
andc r4,r4,r3 /* disable FP for previous task */
std r4,_MSR-STACK_FRAME_OVERHEAD(r5)
1:
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