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>
---
arch/mips/kernel/r4k_switch.S | 4 +++-
arch/mips/kernel/traps.c | 5 +++++
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/mips/kernel/r4k_switch.S b/arch/mips/kernel/r4k_switch.S
index 81ca3f7..1a1aef0 100644
--- 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. */
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 51706d6..4792fd7 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1153,6 +1153,11 @@ static int enable_restore_fp_context(int msa)
/* 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;
}
--
2.0.1
