[POWERPC] Make sure interrupt enable gets restored properly

The lazy IRQ disable patch missed a couple of places where the
interrupt enable flags need to be restored correctly.  First, we
weren't restoring the paca->hard_enabled flag on interrupt exit.
Instead of saving it on entry, we compute it from the MSR_EE bit
in the MSR we are restoring at exit.  Secondly, the MMU hash miss
code was clearing both paca->soft_enabled and paca->hard_enabled
but not restoring them in the case where hash_page was able to
resolve the miss from the Linux page tables.

Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 23 insertions, 9 deletions

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index efda48741b29..86e2bdd5afd6 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -489,6 +489,10 @@ END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
         andi.   r0,r3,MSR_RI
         beq-    unrecov_restore
 
+        /* extract EE bit and use it to restore paca->hard_enabled */
+        rldicl  r4,r3,49,63             /* r0 = (r3 >> 15) & 1 */
+        stb     r4,PACAHARDIRQEN(r13)
+
         andi.   r0,r3,MSR_PR
 
         /*
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index c93d9f35a121..d2890050b7e0 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -961,10 +961,18 @@ bad_stack:
  * any task or sent any task a signal, you should use
  * ret_from_except or ret_from_except_lite instead of this.
  */
+fast_exc_return_irq:                    /* restores irq state too */
+        ld      r3,SOFTE(r1)
+        ld      r12,_MSR(r1)
+        stb     r3,PACASOFTIRQEN(r13)   /* restore paca->soft_enabled */
+        rldicl  r4,r12,49,63            /* get MSR_EE to LSB */
+        stb     r4,PACAHARDIRQEN(r13)   /* restore paca->hard_enabled */
+        b       1f
+
         .globl  fast_exception_return
 fast_exception_return:
         ld      r12,_MSR(r1)
-        ld      r11,_NIP(r1)
+1:      ld      r11,_NIP(r1)
         andi.   r3,r12,MSR_RI           /* check if RI is set */
         beq-    unrecov_fer
 
@@ -1361,6 +1369,16 @@ BEGIN_FW_FTR_SECTION
          * interrupts if necessary.
          */
         beq     .ret_from_except_lite
+END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
+#endif
+BEGIN_FW_FTR_SECTION
+        /*
+         * Here we have interrupts hard-disabled, so it is sufficient
+         * to restore paca->{soft,hard}_enable and get out.
+         */
+        beq     fast_exc_return_irq     /* Return from exception on success */
+END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES)
+
         /* For a hash failure, we don't bother re-enabling interrupts */
         ble-    12f
 
@@ -1372,14 +1390,6 @@ BEGIN_FW_FTR_SECTION
         ld      r3,SOFTE(r1)
         bl      .local_irq_restore
         b       11f
-END_FW_FTR_SECTION_IFSET(FW_FEATURE_ISERIES)
-#endif
-BEGIN_FW_FTR_SECTION
-        beq     fast_exception_return   /* Return from exception on success */
-        ble-    12f                     /* Failure return from hash_page */
-
-        /* fall through */
-END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISERIES)
 
 /* Here we have a page fault that hash_page can't handle. */
 _GLOBAL(handle_page_fault)