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-rw-r--r--arch/powerpc/include/asm/mmu_context.h18
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 0c76675394c5..35bec1c5bd5a 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -90,6 +90,24 @@ static inline void switch_mm_irqs_off(struct mm_struct *prev,
/* Mark this context has been used on the new CPU */
if (!cpumask_test_cpu(smp_processor_id(), mm_cpumask(next))) {
cpumask_set_cpu(smp_processor_id(), mm_cpumask(next));
+
+ /*
+ * This full barrier orders the store to the cpumask above vs
+ * a subsequent operation which allows this CPU to begin loading
+ * translations for next.
+ *
+ * When using the radix MMU that operation is the load of the
+ * MMU context id, which is then moved to SPRN_PID.
+ *
+ * For the hash MMU it is either the first load from slb_cache
+ * in switch_slb(), and/or the store of paca->mm_ctx_id in
+ * copy_mm_to_paca().
+ *
+ * On the read side the barrier is in pte_xchg(), which orders
+ * the store to the PTE vs the load of mm_cpumask.
+ */
+ smp_mb();
+
new_on_cpu = true;
}