diff --git a/qemu/exec.c b/qemu/exec.c
index 719895a3..2a664788 100644
--- a/qemu/exec.c
+++ b/qemu/exec.c
@@ -1087,8 +1087,12 @@ RAMBlock *qemu_ram_alloc_from_ptr(struct uc_struct *uc, ram_addr_t size, void *h
     RAMBlock *new_block;
     ram_addr_t max_size = size;
 
-    size = HOST_PAGE_ALIGN(uc, size);
-    max_size = HOST_PAGE_ALIGN(uc, max_size);
+    // Don't resize pre-alloced memory as they are given by users.
+    if (!host) {
+        size = HOST_PAGE_ALIGN(uc, size);
+        max_size = HOST_PAGE_ALIGN(uc, max_size);
+    }
+
     new_block = g_malloc0(sizeof(*new_block));
     if (new_block == NULL)
         return NULL;