From: Peter Xu <peterx@redhat.com>

Add a bool for MR to mark whether this MR is a root MR of an AS.  We bail out
asap if this MR is added as a subregion of another MR.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/exec/memory.h | 1 +
 softmmu/memory.c      | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 5728a681b27..83ac86525b2 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -477,6 +477,7 @@ struct MemoryRegion {
     bool ram_device;
     bool enabled;
     bool warning_printed; /* For reservations */
+    bool is_root_mr;
     uint8_t vga_logging_count;
     MemoryRegion *alias;
     hwaddr alias_offset;
diff --git a/softmmu/memory.c b/softmmu/memory.c
index d4493ef9e43..409bcaec7f5 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -2443,6 +2443,7 @@ static void memory_region_add_subregion_common(MemoryRegion *mr,
                                                MemoryRegion *subregion)
 {
     assert(!subregion->container);
+    assert(!subregion->is_root_mr);
     subregion->container = mr;
     subregion->addr = offset;
     memory_region_update_container_subregions(subregion);
@@ -2820,6 +2821,7 @@ void address_space_init(AddressSpace *as, MemoryRegion *root, const char *name)
 {
     memory_region_ref(root);
     as->root = root;
+    root->is_root_mr = true;
     as->current_map = NULL;
     as->ioeventfd_nb = 0;
     as->ioeventfds = NULL;
-- 
2.26.3