memory: introduce memory_region_set_address()

Allow changing the address of a memory region while it is
in the memory hierarchy.

Signed-off-by: Avi Kivity <avi@redhat.com>

memory.c

@@ -1324,6 +1324,27 @@ void memory_region_set_enabled(MemoryRegion *mr, bool enabled)
     memory_region_update_topology(NULL);
 }
 
+void memory_region_set_address(MemoryRegion *mr, target_phys_addr_t addr)
+{
+    MemoryRegion *parent = mr->parent;
+    unsigned priority = mr->priority;
+    bool may_overlap = mr->may_overlap;
+
+    if (addr == mr->addr || !parent) {
+        mr->addr = addr;
+        return;
+    }
+
+    memory_region_transaction_begin();
+    memory_region_del_subregion(parent, mr);
+    if (may_overlap) {
+        memory_region_add_subregion_overlap(parent, addr, mr, priority);
+    } else {
+        memory_region_add_subregion(parent, addr, mr);
+    }
+    memory_region_transaction_commit();
+}
+
 void set_system_memory_map(MemoryRegion *mr)
 {
     address_space_memory.root = mr;

memory.h

@@ -518,6 +518,17 @@ void memory_region_del_subregion(MemoryRegion *mr,
  */
 void memory_region_set_enabled(MemoryRegion *mr, bool enabled);
 
+/*
+ * memory_region_set_address: dynamically update the address of a region
+ *
+ * Dynamically updates the address of a region, relative to its parent.
+ * May be used on regions are currently part of a memory hierarchy.
+ *
+ * @mr: the region to be updated
+ * @addr: new address, relative to parent region
+ */
+void memory_region_set_address(MemoryRegion *mr, target_phys_addr_t addr);
+
 /* Start a transaction; changes will be accumulated and made visible only
  * when the transaction ends.
  */