diff --git a/misc/acrn-config/board_config/misc_cfg_h.py b/misc/acrn-config/board_config/misc_cfg_h.py
index c80ec90a0..8edf63ef6 100644
--- a/misc/acrn-config/board_config/misc_cfg_h.py
+++ b/misc/acrn-config/board_config/misc_cfg_h.py
@@ -106,8 +106,8 @@ def find_hi_mmio_window(config):
 
     print("", file=config)
     if is_hi_mmio:
-        print("#define HI_MMIO_START\t\t0x%xUL" % mmio_min, file=config)
-        print("#define HI_MMIO_END\t\t0x%xUL" % mmio_max, file=config)
+        print("#define HI_MMIO_START\t\t0x%xUL" % common.round_down(mmio_min, common.SIZE_G), file=config)
+        print("#define HI_MMIO_END\t\t0x%xUL" % common.round_up(mmio_max, common.SIZE_G), file=config)
     else:
         print("#define HI_MMIO_START\t\t~0UL", file=config)
         print("#define HI_MMIO_END\t\t0UL", file=config)
diff --git a/misc/acrn-config/library/common.py b/misc/acrn-config/library/common.py
index 765e7c3ee..316bceaa3 100644
--- a/misc/acrn-config/library/common.py
+++ b/misc/acrn-config/library/common.py
@@ -466,6 +466,9 @@ def undline_name(name):
 
     return name_str
 
+def round_down(addr, mem_align):
+    """Keep memory align"""
+    return (addr & (~(mem_align - 1)))
 
 def round_up(addr, mem_align):
     """Keep memory align"""