diff --git a/drivers/virt/acrn/acrn_drv.h b/drivers/virt/acrn/acrn_drv.h
index 5663c17ad37c..fb8438094f6f 100644
--- a/drivers/virt/acrn/acrn_drv.h
+++ b/drivers/virt/acrn/acrn_drv.h
@@ -60,7 +60,7 @@ struct vm_memory_region_batch {
 	u16			   reserved[3];
 	u32			   regions_num;
 	u64			   regions_gpa;
-	struct vm_memory_region_op regions_op[];
+	struct vm_memory_region_op regions_op[] __counted_by(regions_num);
 };
 
 /**
diff --git a/drivers/virt/acrn/mm.c b/drivers/virt/acrn/mm.c
index b4ad8d452e9a..fa5d9ca6be57 100644
--- a/drivers/virt/acrn/mm.c
+++ b/drivers/virt/acrn/mm.c
@@ -250,11 +250,11 @@ int acrn_vm_ram_map(struct acrn_vm *vm, struct acrn_vm_memmap *memmap)
 		ret = -ENOMEM;
 		goto unmap_kernel_map;
 	}
+	regions_info->regions_num = nr_regions;
 
 	/* Fill each vm_memory_region_op */
 	vm_region = regions_info->regions_op;
 	regions_info->vmid = vm->vmid;
-	regions_info->regions_num = nr_regions;
 	regions_info->regions_gpa = virt_to_phys(vm_region);
 	user_vm_pa = memmap->user_vm_pa;
 	i = 0;