vmm: Implement VM resume

To resume a VM, we unpark all its vCPU threads.

Fixes: #333

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

vmm/src/api/http.rs

@@ -59,6 +59,7 @@ lazy_static! {
         r.routes.insert(endpoint!("/vm.delete"), Box::new(VmActionHandler::new(VmAction::Delete)));
         r.routes.insert(endpoint!("/vm.info"), Box::new(VmInfo {}));
         r.routes.insert(endpoint!("/vm.pause"), Box::new(VmActionHandler::new(VmAction::Pause)));
+        r.routes.insert(endpoint!("/vm.resume"), Box::new(VmActionHandler::new(VmAction::Resume)));
         r.routes.insert(endpoint!("/vm.shutdown"), Box::new(VmActionHandler::new(VmAction::Shutdown)));
         r.routes.insert(endpoint!("/vm.reboot"), Box::new(VmActionHandler::new(VmAction::Reboot)));
         r.routes.insert(endpoint!("/vmm.shutdown"), Box::new(VmmShutdown {}));

vmm/src/api/http_endpoint.rs

@@ -5,8 +5,8 @@
 
 use crate::api::http::EndpointHandler;
 use crate::api::{
-    vm_boot, vm_create, vm_delete, vm_info, vm_pause, vm_reboot, vm_shutdown, vmm_shutdown,
+    vm_boot, vm_create, vm_delete, vm_info, vm_pause, vm_reboot, vm_resume, vm_shutdown,
-    ApiError, ApiRequest, ApiResult, VmAction, VmConfig,
+    vmm_shutdown, ApiError, ApiRequest, ApiResult, VmAction, VmConfig,
 };
 use micro_http::{Body, Method, Request, Response, StatusCode, Version};
 use serde_json::Error as SerdeError;
@@ -32,6 +32,9 @@ pub enum HttpError {
     /// Could not pause the VM
     VmPause(ApiError),
 
+    /// Could not pause the VM
+    VmResume(ApiError),
+
     /// Could not shut a VM down
     VmShutdown(ApiError),
 
@@ -107,6 +110,7 @@ impl VmActionHandler {
             VmAction::Shutdown => vm_shutdown,
             VmAction::Reboot => vm_reboot,
             VmAction::Pause => vm_pause,
+            VmAction::Resume => vm_resume,
         });
 
         VmActionHandler { action_fn }
@@ -127,6 +131,7 @@ impl EndpointHandler for VmActionHandler {
                     ApiError::VmShutdown(_) => HttpError::VmShutdown(e),
                     ApiError::VmReboot(_) => HttpError::VmReboot(e),
                     ApiError::VmPause(_) => HttpError::VmPause(e),
+                    ApiError::VmResume(_) => HttpError::VmResume(e),
                     _ => HttpError::VmAction(e),
                 }) {
                     Ok(_) => Response::new(Version::Http11, StatusCode::OK),

vmm/src/api/mod.rs

@@ -79,6 +79,9 @@ pub enum ApiError {
     /// The VM could not be paused.
     VmPause(VmError),
 
+    /// The VM could not resume.
+    VmResume(VmError),
+
     /// The VM is not booted.
     VmNotBooted,
 
@@ -138,6 +141,9 @@ pub enum ApiRequest {
     /// Pause a VM.
     VmPause(Sender<ApiResponse>),
 
+    /// Resume a VM.
+    VmResume(Sender<ApiResponse>),
+
     /// Shut the previously booted virtual machine down.
     /// If the VM was not previously booted or created, the VMM API server
     /// will send a VmShutdown error back.
@@ -190,6 +196,9 @@ pub enum VmAction {
 
     /// Pause a VM
     Pause,
+
+    /// Resume a VM
+    Resume,
 }
 
 fn vm_action(api_evt: EventFd, api_sender: Sender<ApiRequest>, action: VmAction) -> ApiResult<()> {
@@ -201,6 +210,7 @@ fn vm_action(api_evt: EventFd, api_sender: Sender<ApiRequest>, action: VmAction)
         VmAction::Shutdown => ApiRequest::VmShutdown(response_sender),
         VmAction::Reboot => ApiRequest::VmReboot(response_sender),
         VmAction::Pause => ApiRequest::VmPause(response_sender),
+        VmAction::Resume => ApiRequest::VmResume(response_sender),
     };
 
     // Send the VM request.
@@ -232,6 +242,10 @@ pub fn vm_pause(api_evt: EventFd, api_sender: Sender<ApiRequest>) -> ApiResult<(
     vm_action(api_evt, api_sender, VmAction::Pause)
 }
 
+pub fn vm_resume(api_evt: EventFd, api_sender: Sender<ApiRequest>) -> ApiResult<()> {
+    vm_action(api_evt, api_sender, VmAction::Resume)
+}
+
 pub fn vm_info(api_evt: EventFd, api_sender: Sender<ApiRequest>) -> ApiResult<VmInfo> {
     let (response_sender, response_receiver) = channel();
 

vmm/src/api/openapi/cloud-hypervisor.yaml

@@ -95,6 +95,21 @@ paths:
           description: The VM instance could not pause because it is not booted.
           content: {}
 
+  /vm.resume:
+    put:
+      summary: Resume a previously paused VM instance.
+      operationId: resumeVM
+      responses:
+        201:
+          description: The VM instance successfully paused.
+          content: {}
+        404:
+          description: The VM instance could not resume because it is not booted yet
+          content: {}
+        405:
+          description: The VM instance could not resume because it is not paused.
+          content: {}
+
   /vm.shutdown:
     put:
       summary: Shut the VM instance down.

vmm/src/lib.rs

@@ -235,6 +235,14 @@ impl Vmm {
         }
     }
 
+    fn vm_resume(&mut self) -> result::Result<(), VmError> {
+        if let Some(ref mut vm) = self.vm {
+            vm.resume()
+        } else {
+            Err(VmError::VmNotBooted)
+        }
+    }
+
     fn vm_shutdown(&mut self) -> result::Result<(), VmError> {
         if let Some(ref mut vm) = self.vm.take() {
             vm.shutdown()
@@ -430,6 +438,14 @@ impl Vmm {
 
                                     sender.send(response).map_err(Error::ApiResponseSend)?;
                                 }
+                                ApiRequest::VmResume(sender) => {
+                                    let response = self
+                                        .vm_resume()
+                                        .map_err(ApiError::VmResume)
+                                        .map(|_| ApiResponsePayload::Empty);
+
+                                    sender.send(response).map_err(Error::ApiResponseSend)?;
+                                }
                                 ApiRequest::VmmShutdown(sender) => {
                                     let response = self
                                         .vmm_shutdown()

vmm/src/vm.rs

@@ -831,6 +831,25 @@ impl Vm {
         Ok(())
     }
 
+    pub fn resume(&mut self) -> Result<()> {
+        // Toggle the vCPUs pause boolean
+        self.vcpus_pause_signalled.store(false, Ordering::SeqCst);
+
+        // Unpark all the VCPU threads.
+        // Once unparked, the next thing they will do is checking for the pause
+        // boolean. Since it'll be set to false, they will exit their pause loop
+        // and go back to vmx root.
+        for vcpu_thread in self.threads.iter() {
+            vcpu_thread.thread().unpark();
+        }
+
+        // And we're back to Booted state.
+        let mut state = self.state.try_write().map_err(|_| Error::PoisonedState)?;
+        *state = VmState::Booted;
+
+        Ok(())
+    }
+
     fn os_signal_handler(signals: Signals, console_input_clone: Arc<Console>) {
         for signal in signals.forever() {
             if signal == SIGWINCH {