3.16.55-rc1 review patch. If anyone has any objections, please let me know.
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From: James Hogan james.hogan@imgtec.com
commit acaf6a97d623af123314c2f8ce4cf7254f6b2fc1 upstream.
The lose_fpu() function only disables the FPU in CP0_Status.CU1 if the FPU is in use and MSA isn't enabled.
This isn't necessarily a problem because KSTK_STATUS(current), the version of CP0_Status stored on the kernel stack on entry from user mode, does always get updated and gets restored when returning to user mode, but I don't think it was intended, and it is inconsistent with the case of only the FPU being in use. Sometimes leaving the FPU enabled may also mask kernel bugs where FPU operations are executed when the FPU might not be enabled.
So lets disable the FPU in the MSA case too.
Fixes: 33c771ba5c5d ("MIPS: save/disable MSA in lose_fpu") Signed-off-by: James Hogan james.hogan@imgtec.com Cc: Ralf Baechle ralf@linux-mips.org Cc: Paul Burton paul.burton@imgtec.com Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/9323/ Signed-off-by: Ralf Baechle ralf@linux-mips.org Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/mips/include/asm/fpu.h | 1 + 1 file changed, 1 insertion(+)
--- a/arch/mips/include/asm/fpu.h +++ b/arch/mips/include/asm/fpu.h @@ -150,6 +150,7 @@ static inline void lose_fpu(int save) } disable_msa(); clear_thread_flag(TIF_USEDMSA); + __disable_fpu(); } else if (is_fpu_owner()) { if (save) _save_fp(current);