MIPS: Don't save/restore OCTEON wide multiplier state on syscalls.

The ABI allows these to be clobbered on syscalls, so only save and
restore the multiplier state when the temporary registers need to be
preserved.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Cc: David Daney <david.daney@cavium.com>
Patchwork: https://patchwork.linux-mips.org/patch/5540/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/include/asm/stackframe.h b/arch/mips/include/asm/stackframe.h
index a89d1b1..23fc95e 100644 (file)
--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -69,6 +69,14 @@
                LONG_S  $24, PT_R24(sp)
 #ifndef CONFIG_CPU_HAS_SMARTMIPS
                LONG_S  v1, PT_LO(sp)
+#endif
+#ifdef CONFIG_CPU_CAVIUM_OCTEON
+               /*
+                * The Octeon multiplier state is affected by general
+                * multiply instructions. It must be saved before and
+                * kernel code might corrupt it
+                */
+               jal     octeon_mult_save
 #endif
                .endm
 
@@ -218,17 +226,8 @@
                ori     $28, sp, _THREAD_MASK
                xori    $28, _THREAD_MASK
 #ifdef CONFIG_CPU_CAVIUM_OCTEON
-               .set    mips64
-               pref    0, 0($28)       /* Prefetch the current pointer */
-               pref    0, PT_R31(sp)   /* Prefetch the $31(ra) */
-               /* The Octeon multiplier state is affected by general multiply
-                   instructions. It must be saved before and kernel code might
-                   corrupt it */
-               jal     octeon_mult_save
-               LONG_L  v1, 0($28)  /* Load the current pointer */
-                        /* Restore $31(ra) that was changed by the jal */
-               LONG_L  ra, PT_R31(sp)
-               pref    0, 0(v1)    /* Prefetch the current thread */
+               .set    mips64
+               pref    0, 0($28)       /* Prefetch the current pointer */
 #endif
                .set    pop
                .endm
@@ -248,6 +247,10 @@
                .endm
 
                .macro  RESTORE_TEMP
+#ifdef CONFIG_CPU_CAVIUM_OCTEON
+               /* Restore the Octeon multiplier state */
+               jal     octeon_mult_restore
+#endif
 #ifdef CONFIG_CPU_HAS_SMARTMIPS
                LONG_L  $24, PT_ACX(sp)
                mtlhx   $24
@@ -360,10 +363,6 @@
                DVPE    5                               # dvpe a1
                jal     mips_ihb
 #endif /* CONFIG_MIPS_MT_SMTC */
-#ifdef CONFIG_CPU_CAVIUM_OCTEON
-               /* Restore the Octeon multiplier state */
-               jal     octeon_mult_restore
-#endif
                mfc0    a0, CP0_STATUS
                ori     a0, STATMASK
                xori    a0, STATMASK