memory: handle alias in memory_region_is_iommu()

Cc: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NJason Wang <jasowang@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: NPeter Xu <peterx@redhat.com>

include/exec/memory.h

@@ -628,6 +628,9 @@ static inline bool memory_region_is_romd(MemoryRegion *mr)
  */
 static inline bool memory_region_is_iommu(MemoryRegion *mr)
 {
+    if (mr->alias) {
+        return memory_region_is_iommu(mr->alias);
+    }
     return mr->iommu_ops;
 }