Support graceful single VM exit (#130)

* support graceful single vm exit

* update axvm and x86_vcpu

* fix doc typo in src/vmm/vcpus.rs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* update comment for clarity

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: aarkegz

Cargo.lock

@@ -6,7 +6,7 @@ use crate::vmm::{VCpuRef, VMRef};
 pub struct TaskExt {
     /// The VM.
     pub vm: VMRef,
-    /// The virtual memory address space.
+    /// The virtual CPU.
     pub vcpu: VCpuRef,
 }
 

src/task.rs

@@ -30,7 +30,7 @@ pub fn init_guest_vms() {
             AxVMCrateConfig::from_toml(raw_cfg_str).expect("Failed to resolve VM config");
         let vm_config = AxVMConfig::from(vm_create_config.clone());
 
-        info!("Creating VM [{}] {:?}", vm_config.id(), vm_config.name());
+        info!("Creating VM[{}] {:?}", vm_config.id(), vm_config.name());
 
         // Create VM.
         let vm = VM::new(vm_config).expect("Failed to create VM");

src/vmm/config.rs

@@ -7,21 +7,26 @@ mod vm_list;
 
 use std::os::arceos::api::task::{self, AxWaitQueueHandle};
 
-use core::sync::atomic::AtomicUsize;
-use core::sync::atomic::Ordering;
+use core::sync::atomic::{AtomicUsize, Ordering};
 
 use crate::hal::{AxVCpuHalImpl, AxVMHalImpl};
 pub use timer::init_percpu as init_timer_percpu;
 
+/// The instantiated VM type.
 pub type VM = axvm::AxVM<AxVMHalImpl, AxVCpuHalImpl>;
+/// The instantiated VM ref type (by `Arc`).
 pub type VMRef = axvm::AxVMRef<AxVMHalImpl, AxVCpuHalImpl>;
-
+/// The instantiated VCpu ref type (by `Arc`).
 pub type VCpuRef = axvm::AxVCpuRef<AxVCpuHalImpl>;
 
 static VMM: AxWaitQueueHandle = AxWaitQueueHandle::new();
 
+/// The number of running VMs. This is used to determine when to exit the VMM.
 static RUNNING_VM_COUNT: AtomicUsize = AtomicUsize::new(0);
 
+/// Initialize the VMM.
+///
+/// This function creates the VM structures and sets up the primary VCpu for each VM.
 pub fn init() {
     // Initialize guest VM according to config file.
     config::init_guest_vms();
@@ -33,6 +38,7 @@ pub fn init() {
     }
 }
 
+/// Start the VMM.
 pub fn start() {
     info!("VMM starting, booting VMs...");
     for vm in vm_list::get_vm_list() {
@@ -47,5 +53,13 @@ pub fn start() {
     }
 
     // Do not exit until all VMs are stopped.
-    task::ax_wait_queue_wait_until(&VMM, || RUNNING_VM_COUNT.load(Ordering::Acquire) == 0, None);
+    task::ax_wait_queue_wait_until(
+        &VMM,
+        || {
+            let vm_count = RUNNING_VM_COUNT.load(Ordering::Acquire);
+            info!("a VM exited, current running VM count: {}", vm_count);
+            vm_count == 0
+        },
+        None,
+    );
 }