diff --git a/crates/vm-core/src/cpu/vm_exit.rs b/crates/vm-core/src/cpu/vm_exit.rs
index 1971c1d..632065f 100644
--- a/crates/vm-core/src/cpu/vm_exit.rs
+++ b/crates/vm-core/src/cpu/vm_exit.rs
@@ -1,8 +1,5 @@
 use thiserror::Error;
 
-#[cfg(target_arch = "aarch64")]
-use crate::arch::aarch64::vcpu::AArch64Vcpu;
-
 #[derive(Error, Debug)]
 pub enum VmExitHandlerError {
     #[error("no device found for port 0x{0:#x}")]
@@ -37,5 +34,8 @@ pub trait VmExit: Send + Sync {
     fn in_mmio_region(&self, addr: u64) -> bool;
 
     #[cfg(target_arch = "aarch64")]
-    fn call_smc(&self, vcpu: &mut dyn AArch64Vcpu) -> Result<(), VmExitHandlerError>;
+    fn call_smc(
+        &self,
+        vcpu: &mut dyn crate::arch::aarch64::vcpu::AArch64Vcpu,
+    ) -> Result<(), VmExitHandlerError>;
 }
diff --git a/crates/vm-core/src/monitor.rs b/crates/vm-core/src/monitor.rs
index 16bcc05..60fccaf 100644
--- a/crates/vm-core/src/monitor.rs
+++ b/crates/vm-core/src/monitor.rs
@@ -12,9 +12,6 @@ pub enum MonitorError {
     #[error("{0}")]
     Serde(#[from] serde_json::Error),
 
-    #[error("Unknown cmd {0}")]
-    UnknownCmd(String),
-
     #[error("unknown subcommand {0:?}")]
     UnknownSubcommand(Vec<String>),
 
@@ -23,6 +20,6 @@ pub enum MonitorError {
 }
 
 #[async_trait]
-pub trait MonitorCommand: Send + Sync {
+pub trait MonitorCommandOps: Send + Sync {
     async fn handle_command(&self, subcommands: &[&str]) -> Result<String, MonitorError>;
 }
diff --git a/crates/vm-device/src/device/virtio/virtio_balloon_traditional/monitor.rs b/crates/vm-device/src/device/virtio/virtio_balloon_traditional/monitor.rs
index bfb989c..fc60dce 100644
--- a/crates/vm-device/src/device/virtio/virtio_balloon_traditional/monitor.rs
+++ b/crates/vm-device/src/device/virtio/virtio_balloon_traditional/monitor.rs
@@ -3,7 +3,7 @@ use std::sync::Mutex;
 
 use async_trait::async_trait;
 use serde::Serialize;
-use vm_core::monitor::MonitorCommand;
+use vm_core::monitor::MonitorCommandOps;
 use vm_core::monitor::MonitorError;
 use vm_virtio::transport::VirtioDev;
 
@@ -27,7 +27,7 @@ impl VirtioBalloonMonitor {
 }
 
 #[async_trait]
-impl MonitorCommand for VirtioBalloonMonitor {
+impl MonitorCommandOps for VirtioBalloonMonitor {
     async fn handle_command(&self, subcommands: &[&str]) -> Result<String, MonitorError> {
         match *subcommands {
             ["info"] => {
diff --git a/crates/vm-vmm/src/error.rs b/crates/vm-vmm/src/error.rs
index c49cdad..f296cba 100644
--- a/crates/vm-vmm/src/error.rs
+++ b/crates/vm-vmm/src/error.rs
@@ -42,9 +42,6 @@ pub enum Error {
     #[error("Failed to setup with bootloader, error: {0}")]
     Bootloader(#[from] vm_bootloader::boot_loader::Error),
 
-    #[error("gdb_stub failed, error: {0}")]
-    GdbStub(String),
-
     #[error("monitor error: {0}")]
     Monitor(#[from] MonitorError),
 }
diff --git a/crates/vm-vmm/src/firmware.rs b/crates/vm-vmm/src/firmware.rs
index fa0b5b8..d4ca20e 100644
--- a/crates/vm-vmm/src/firmware.rs
+++ b/crates/vm-vmm/src/firmware.rs
@@ -1,3 +1,3 @@
 #[allow(warnings)]
 #[cfg(target_arch = "x86_64")]
-pub mod bios;
+pub(crate) mod bios;
diff --git a/crates/vm-vmm/src/service.rs b/crates/vm-vmm/src/service.rs
index ce0f625..e9eaf45 100644
--- a/crates/vm-vmm/src/service.rs
+++ b/crates/vm-vmm/src/service.rs
@@ -1,2 +1,2 @@
-pub mod gdbstub;
-pub mod monitor;
+pub(crate) mod gdbstub;
+pub(crate) mod monitor;
diff --git a/crates/vm-vmm/src/service/monitor/builder.rs b/crates/vm-vmm/src/service/monitor/builder.rs
index ce6582c..fb4a87f 100644
--- a/crates/vm-vmm/src/service/monitor/builder.rs
+++ b/crates/vm-vmm/src/service/monitor/builder.rs
@@ -1,18 +1,18 @@
 use std::collections::HashMap;
 
-use vm_core::monitor::MonitorCommand;
+use vm_core::monitor::MonitorCommandOps;
 use vm_core::monitor::MonitorError;
 
 #[derive(Default)]
 pub struct MonitorServerBuilder {
-    pub components: HashMap<String, Box<dyn MonitorCommand>>,
+    pub components: HashMap<String, Box<dyn MonitorCommandOps>>,
 }
 
 impl MonitorServerBuilder {
     pub fn register_command_handler(
         &mut self,
         name: &str,
-        handler: Box<dyn MonitorCommand>,
+        handler: Box<dyn MonitorCommandOps>,
     ) -> Result<(), MonitorError> {
         let name = name.to_string();
 
diff --git a/crates/vm-vmm/src/vm.rs b/crates/vm-vmm/src/vm.rs
index fe05ca3..a4e2163 100644
--- a/crates/vm-vmm/src/vm.rs
+++ b/crates/vm-vmm/src/vm.rs
@@ -25,7 +25,7 @@ use vm_core::arch::x86_64::layout::RAM_BASE;
 use vm_core::cpu::vcpu_manager::VcpuManager;
 use vm_core::device::mmio::layout::MmioLayout;
 use vm_core::device_manager::DeviceManager;
-use vm_core::monitor::MonitorCommand;
+use vm_core::monitor::MonitorCommandOps;
 use vm_core::virtualization::hypervisor::Hypervisor;
 use vm_core::virtualization::vm::HypervisorVm;
 use vm_core::virtualization::vm::SetUserMemoryRegionFlags;
@@ -47,7 +47,7 @@ use crate::vmm::handler::VmmCommand;
 
 pub mod config;
 
-pub(crate) mod vm_exit_handler;
+mod vm_exit_handler;
 
 const PAGE_SIZE: usize = 4 << 10;
 
@@ -58,7 +58,7 @@ pub struct Vm {
     _irq_chip: Arc<dyn InterruptController>,
     _device_manager: Arc<DeviceManager>,
     gdb_stub: Option<VmGdbStubConnector>,
-    monitor_handlers: HashMap<String, Box<dyn MonitorCommand>>,
+    monitor_handlers: HashMap<String, Box<dyn MonitorCommandOps>>,
     _vm_config: VmConfig,
     #[cfg(target_arch = "aarch64")]
     start_pc: u64,
@@ -113,11 +113,11 @@ impl Vm {
             vcpu_manager: vcpu_manager.clone(),
         };
 
-        let vm_exit_handler = Arc::new(VmExitHandler {
-            device_manager: device_manager.clone(),
+        let vm_exit_handler = Arc::new(VmExitHandler::new(
+            device_manager.clone(),
             #[cfg(target_arch = "aarch64")]
             psci,
-        });
+        ));
 
         {
             let mut vcpu_manager = vcpu_manager.lock().await;
@@ -180,7 +180,7 @@ impl Vm {
         self.memory_address_space.as_ref()
     }
 
-    pub fn monitor_handlers(&self) -> &HashMap<String, Box<dyn MonitorCommand>> {
+    pub fn monitor_handlers(&self) -> &HashMap<String, Box<dyn MonitorCommandOps>> {
         &self.monitor_handlers
     }
 
diff --git a/crates/vm-vmm/src/vm/vm_exit_handler.rs b/crates/vm-vmm/src/vm/vm_exit_handler.rs
index 81f6b17..901015d 100644
--- a/crates/vm-vmm/src/vm/vm_exit_handler.rs
+++ b/crates/vm-vmm/src/vm/vm_exit_handler.rs
@@ -11,9 +11,22 @@ use vm_core::cpu::vm_exit::VmExitHandlerError;
 use vm_core::device_manager::DeviceManager;
 
 pub struct VmExitHandler {
-    pub device_manager: Arc<DeviceManager>,
+    device_manager: Arc<DeviceManager>,
     #[cfg(target_arch = "aarch64")]
-    pub psci: Psci02,
+    psci: Psci02,
+}
+
+impl VmExitHandler {
+    pub fn new(
+        device_manager: Arc<DeviceManager>,
+        #[cfg(target_arch = "aarch64")] psci: Psci02,
+    ) -> Self {
+        VmExitHandler {
+            device_manager,
+            #[cfg(target_arch = "aarch64")]
+            psci,
+        }
+    }
 }
 
 impl VmExit for VmExitHandler {
diff --git a/crates/vm-vmm/src/vmm.rs b/crates/vm-vmm/src/vmm.rs
index 5766e95..f752bdd 100644
--- a/crates/vm-vmm/src/vmm.rs
+++ b/crates/vm-vmm/src/vmm.rs
@@ -11,7 +11,7 @@ use crate::vm::Vm;
 use crate::vm::config::VmConfig;
 use crate::vmm::handler::VmmCommand;
 
-pub mod handler;
+pub(crate) mod handler;
 
 mod service;