[POWERPC] Fix small race in 44x tlbie function

The 440 family of processors don't have a tlbie instruction.  So, we
implement TLB invalidates by explicitly searching the TLB with tlbsx.,
then clobbering the relevant entry, if any.  Unfortunately the PID for
the search needs to be stored in the MMUCR register, which is also
used by the TLB miss handler.  Interrupts were enabled in _tlbie(), so
an interrupt between loading the MMUCR and the tlbsx could cause
incorrect search results, and thus a failure to invalide TLB entries
which needed to be invalidated.

This fixes the problem in both arch/ppc and arch/powerpc by inhibiting
interrupts (even critical and debug interrupts) across the relevant
instructions.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 22 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index e708ab7ca9e8..8533de50347d 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -301,9 +301,19 @@ _GLOBAL(_tlbie)
         mfspr   r4,SPRN_MMUCR
         mfspr   r5,SPRN_PID                     /* Get PID */
         rlwimi  r4,r5,0,24,31                   /* Set TID */
-        mtspr   SPRN_MMUCR,r4
 
+        /* We have to run the search with interrupts disabled, even critical
+         * and debug interrupts (in fact the only critical exceptions we have
+         * are debug and machine check).  Otherwise  an interrupt which causes
+         * a TLB miss can clobber the MMUCR between the mtspr and the tlbsx. */
+        mfmsr   r5
+        lis     r6,(MSR_EE|MSR_CE|MSR_ME|MSR_DE)@ha
+        addi    r6,r6,(MSR_EE|MSR_CE|MSR_ME|MSR_DE)@l
+        andc    r6,r5,r6
+        mtmsr   r6
+        mtspr   SPRN_MMUCR,r4
         tlbsx.  r3, 0, r3
+        mtmsr   r5
         bne     10f
         sync
         /* There are only 64 TLB entries, so r3 < 64,
diff --git a/arch/ppc/kernel/misc.S b/arch/ppc/kernel/misc.S
index 0da55368655c..a22e1f4d94c8 100644
--- a/arch/ppc/kernel/misc.S
+++ b/arch/ppc/kernel/misc.S
@@ -237,9 +237,19 @@ _GLOBAL(_tlbie)
         mfspr   r4,SPRN_MMUCR
         mfspr   r5,SPRN_PID                     /* Get PID */
         rlwimi  r4,r5,0,24,31                   /* Set TID */
-        mtspr   SPRN_MMUCR,r4
 
+        /* We have to run the search with interrupts disabled, even critical
+         * and debug interrupts (in fact the only critical exceptions we have
+         * are debug and machine check).  Otherwise  an interrupt which causes
+         * a TLB miss can clobber the MMUCR between the mtspr and the tlbsx. */
+        mfmsr   r5
+        lis     r6,(MSR_EE|MSR_CE|MSR_ME|MSR_DE)@ha
+        addi    r6,r6,(MSR_EE|MSR_CE|MSR_ME|MSR_DE)@l
+        andc    r6,r5,r6
+        mtmsr   r6
+        mtspr   SPRN_MMUCR,r4
         tlbsx.  r3, 0, r3
+        mtmsr   r5
         bne     10f
         sync
         /* There are only 64 TLB entries, so r3 < 64,