powerpc: Fix ppc32 mm_struct CPU tracking in SMP

The 32-bit hash code didn't need it so far so we don't update
mm->cpu_vm_mask on context switch.  This however will break when we
merge the RCU based page table freeing patch and other upcoming 32-bit
embedded SMP work, so this adds the update.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 6b993ef452ff..b570209b71a8 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -180,6 +180,9 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 
         tsk->thread.pgdir = next->pgd;
 
+        if (!cpu_isset(smp_processor_id(), next->cpu_vm_mask))
+                cpu_set(smp_processor_id(), next->cpu_vm_mask);
+
         /* No need to flush userspace segments if the mm doesnt change */
         if (prev == next)
                 return;