powerpc: Clear RI and EE at the same time in system call exit

mtmsrd is an expensive instruction, we save a few cycles by
doing it once instead of twice.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 13 insertions, 12 deletions

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 5971c85df136..cf38a17ab28a 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -197,7 +197,16 @@ syscall_exit:
         wrteei  0
 #else
         ld      r10,PACAKMSR(r13)
-        mtmsrd  r10,1
+        /*
+         * For performance reasons we clear RI the same time that we
+         * clear EE. We only need to clear RI just before we restore r13
+         * below, but batching it with EE saves us one expensive mtmsrd call.
+         * We have to be careful to restore RI if we branch anywhere from
+         * here (eg syscall_exit_work).
+         */
+        li      r9,MSR_RI
+        andc    r11,r10,r9
+        mtmsrd  r11,1
 #endif /* CONFIG_PPC_BOOK3E */
 
         ld      r9,TI_FLAGS(r12)
@@ -214,17 +223,6 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
         andi.   r6,r8,MSR_PR
         ld      r4,_LINK(r1)
-        /*
-         * Clear RI before restoring r13.  If we are returning to
-         * userspace and we take an exception after restoring r13,
-         * we end up corrupting the userspace r13 value.
-         */
-#ifdef CONFIG_PPC_BOOK3S
-        /* No MSR:RI on BookE */
-        li      r12,MSR_RI
-        andc    r11,r10,r12
-        mtmsrd  r11,1                   /* clear MSR.RI */
-#endif /* CONFIG_PPC_BOOK3S */
 
         beq-    1f
         ACCOUNT_CPU_USER_EXIT(r11, r12)
@@ -271,6 +269,9 @@ syscall_enosys:
         b       syscall_exit
         
 syscall_exit_work:
+#ifdef CONFIG_PPC_BOOK3S
+        mtmsrd  r10,1           /* Restore RI */
+#endif
         /* If TIF_RESTOREALL is set, don't scribble on either r3 or ccr.
          If TIF_NOERROR is set, just save r3 as it is. */