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| author | Michael Neuling <mikey@neuling.org> | 2009-04-01 18:02:42 +0000 |
|---|---|---|
| committer | Paul Mackerras <paulus@samba.org> | 2009-04-07 15:18:59 +1000 |
| commit | 7e875e9dc8af70d126fa632446e967327ac3fdda (patch) | |
| tree | 22757e6faff097d01931194c4af051017cb1c359 /arch/powerpc | |
| parent | 4c6cf42843e924fd2f71439d87e85b739b2aa973 (diff) | |
| download | lwn-7e875e9dc8af70d126fa632446e967327ac3fdda.tar.gz lwn-7e875e9dc8af70d126fa632446e967327ac3fdda.zip | |
powerpc: Disable VSX or current process in giveup_fpu/altivec
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>
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/kernel/fpu.S | 5 | ||||
| -rw-r--r-- | arch/powerpc/kernel/misc_64.S | 8 |
2 files changed, 13 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/fpu.S b/arch/powerpc/kernel/fpu.S index a088c064ae40..2436df33c6f4 100644 --- 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: diff --git a/arch/powerpc/kernel/misc_64.S b/arch/powerpc/kernel/misc_64.S index 3053fe5c62f2..b9530b2395a2 100644 --- a/arch/powerpc/kernel/misc_64.S +++ b/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_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: |