[POWERPC] Add 1TB workaround for PA6T

PA6T has a bug where the slbie instruction does not honor the large
segment bit.  As a result, we have to always use slbia when switching
context.

We don't have to worry about changing the slbie's during fault processing,
since they should never be replacing one VSID with another using the
same ESID.  I.e. there's no risk for inserting duplicate entries due to a
failed slbie of the old entry.  So as long as we clear it out on context
switch we should be fine.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 9 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 0ec134034899..148a3547c9aa 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -408,6 +408,12 @@ END_FTR_SECTION_IFSET(CPU_FTR_1T_SEGMENT)
         std     r7,SLBSHADOW_STACKVSID(r9)  /* Save VSID */
         std     r0,SLBSHADOW_STACKESID(r9)  /* Save ESID */
 
+        /* No need to check for CPU_FTR_NO_SLBIE_B here, since when
+         * we have 1TB segments, the only CPUs known to have the errata
+         * only support less than 1TB of system memory and we'll never
+         * actually hit this code path.
+         */
+
         slbie   r6
         slbie   r6              /* Workaround POWER5 < DD2.1 issue */
         slbmte  r7,r0
diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
index 09da90b53850..c78dc912411f 100644
--- a/arch/powerpc/mm/hash_utils_64.c
+++ b/arch/powerpc/mm/hash_utils_64.c
@@ -212,6 +212,7 @@ static int __init htab_dt_scan_seg_sizes(unsigned long node,
                         return 1;
                 }
         }
+        cur_cpu_spec->cpu_features &= ~CPU_FTR_NO_SLBIE_B;
         return 0;
 }
 
diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c
index 6c164cec9d2c..bbd2c512ee05 100644
--- a/arch/powerpc/mm/slb.c
+++ b/arch/powerpc/mm/slb.c
@@ -157,7 +157,8 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm)
         unsigned long stack = KSTK_ESP(tsk);
         unsigned long unmapped_base;
 
-        if (offset <= SLB_CACHE_ENTRIES) {
+        if (!cpu_has_feature(CPU_FTR_NO_SLBIE_B) &&
+            offset <= SLB_CACHE_ENTRIES) {
                 int i;
                 asm volatile("isync" : : : "memory");
                 for (i = 0; i < offset; i++) {