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MIPS: preserve scalar FP CSR when switching vector context

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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@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7301/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton 2014-07-11 16:44:29 +01:00 committed by Ralf Baechle
parent f7a46fa7bb
commit b83406735a
2 changed files with 8 additions and 1 deletions
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4
arch/mips/kernel/r4k_switch.S
View File

@ -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. */

5
arch/mips/kernel/traps.c
View File

@ -1154,6 +1154,11 @@ 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;
}