Messages in this thread Patch in this message | | | Date | Thu, 14 Jan 2010 15:04:53 -0800 | From | Greg KH <> | Subject | [5/6] powerpc: Disable VSX or current process in giveup_fpu/altivec |
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2.6.27-stable review patch. If anyone has any objections, please let us know.
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From: Michael Neuling <mikey@neuling.org>
commit 7e875e9dc8af70d126fa632446e967327ac3fdda upstream.
When we call giveup_fpu, we need to need to turn off VSX for the current process. If we don't, on return to userspace it may execute a VSX instruction before the next FP instruction, and not have its register state refreshed correctly from the thread_struct. Ditto for altivec.
This caused a bug where an unaligned lfs or stfs results in fix_alignment calling giveup_fpu so it can use the FPRs (in order to do a single <-> double conversion), and then returning 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, which overlap the FPRs.
Signed-off-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- arch/powerpc/kernel/fpu.S | 5 +++++ arch/powerpc/kernel/misc_64.S | 8 ++++++++ 2 files changed, 13 insertions(+)
--- a/arch/powerpc/kernel/fpu.S +++ b/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_VSX@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: --- a/arch/powerpc/kernel/misc_64.S +++ b/arch/powerpc/kernel/misc_64.S @@ -493,7 +493,15 @@ _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_VEC@h +ALT_FTR_SECTION_END_IFSET(CPU_FTR_VSX) +#else lis r3,MSR_VEC@h +#endif andc r4,r4,r3 /* disable FP for previous task */ std r4,_MSR-STACK_FRAME_OVERHEAD(r5) 1:
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