memory: add memory_region_ram_resize

This is a simple MemoryRegion wrapper for qemu_ram_resize.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

include/exec/memory.h

@@ -605,6 +605,18 @@ int memory_region_get_fd(MemoryRegion *mr);
  */
 void *memory_region_get_ram_ptr(MemoryRegion *mr);
 
+/* memory_region_ram_resize: Resize a RAM region.
+ *
+ * Only legal before guest might have detected the memory size: e.g. on
+ * incoming migration, or right after reset.
+ *
+ * @mr: a memory region created with @memory_region_init_resizeable_ram.
+ * @newsize: the new size the region
+ * @errp: pointer to Error*, to store an error if it happens.
+ */
+void memory_region_ram_resize(MemoryRegion *mr, ram_addr_t newsize,
+                              Error **errp);
+
 /**
  * memory_region_set_log: Turn dirty logging on or off for a region.
  *

memory.c

@@ -1452,6 +1452,13 @@ void *memory_region_get_ram_ptr(MemoryRegion *mr)
     return qemu_get_ram_ptr(mr->ram_addr & TARGET_PAGE_MASK);
 }
 
+void memory_region_ram_resize(MemoryRegion *mr, ram_addr_t newsize, Error **errp)
+{
+    assert(mr->terminates);
+
+    qemu_ram_resize(mr->ram_addr, newsize, errp);
+}
+
 static void memory_region_update_coalesced_range_as(MemoryRegion *mr, AddressSpace *as)
 {
     FlatView *view;