3.16.43-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Paul Burton <paul.burton@xxxxxxxxxx> commit b83406735a4ae0aff4b614664d6a64a0fd6b9917 upstream. Switching the vector context implicitly saves & restores the state of the aliased scalar FP data registers, however the scalar FP control & status register is distinct from the MSA control & status register. In order to allow scalar FP to function correctly in programs using MSA, the scalar CSR needs to be saved & restored along with the MSA vector context. Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx> Cc: linux-mips@xxxxxxxxxxxxxx Patchwork: https://patchwork.linux-mips.org/patch/7301/ Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> --- arch/mips/kernel/r4k_switch.S | 4 +++- arch/mips/kernel/traps.c | 5 +++++ 2 files changed, 8 insertions(+), 1 deletion(-) --- a/arch/mips/kernel/r4k_switch.S +++ b/arch/mips/kernel/r4k_switch.S @@ -64,8 +64,10 @@ /* Check whether we're saving scalar or vector context. */ bgtz a3, 1f - /* Save 128b MSA vector context. */ + /* Save 128b MSA vector context + scalar FP control & status. */ + cfc1 t1, fcr31 msa_save_all a0 + sw t1, THREAD_FCR31(a0) b 2f 1: /* Save 32b/64b scalar FP context. */ --- a/arch/mips/kernel/traps.c +++ b/arch/mips/kernel/traps.c @@ -1159,6 +1159,11 @@ static int enable_restore_fp_context(int /* We need to restore the vector context. */ restore_msa(current); + + /* Restore the scalar FP control & status register */ + if (!was_fpu_owner) + asm volatile("ctc1 %0, $31" : : "r"(current->thread.fpu.fcr31)); + return 0; }