vmm: api: Introduce new "add-device" HTTP endpoint

This commit introduces the new command "add-device" that will let a user
hotplug a VFIO PCI device to an already running VM.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/api/mod.rs

@@ -99,6 +99,9 @@ pub enum ApiError {
 
     /// The VM could not be resized
     VmResize(VmError),
+
+    /// The device could not be added to the VM.
+    VmAddDevice(VmError),
 }
 pub type ApiResult<T> = std::result::Result<T, ApiError>;
 
@@ -119,6 +122,11 @@ pub struct VmResizeData {
     pub desired_ram: Option<u64>,
 }
 
+#[derive(Clone, Deserialize, Serialize)]
+pub struct VmAddDeviceData {
+    pub path: String,
+}
+
 pub enum ApiResponsePayload {
     /// No data is sent on the channel.
     Empty,
@@ -179,8 +187,11 @@ pub enum ApiRequest {
     /// VMM process.
     VmmShutdown(Sender<ApiResponse>),
 
-    /// Resize the VMM
+    /// Resize the VM.
     VmResize(Arc<VmResizeData>, Sender<ApiResponse>),
+
+    /// Add a device to the VM.
+    VmAddDevice(Arc<VmAddDeviceData>, Sender<ApiResponse>),
 }
 
 pub fn vm_create(
@@ -333,3 +344,21 @@ pub fn vm_resize(
 
     Ok(())
 }
+
+pub fn vm_add_device(
+    api_evt: EventFd,
+    api_sender: Sender<ApiRequest>,
+    data: Arc<VmAddDeviceData>,
+) -> ApiResult<()> {
+    let (response_sender, response_receiver) = channel();
+
+    // Send the VM add-device request.
+    api_sender
+        .send(ApiRequest::VmAddDevice(data, response_sender))
+        .map_err(ApiError::RequestSend)?;
+    api_evt.write(1).map_err(ApiError::EventFdWrite)?;
+
+    response_receiver.recv().map_err(ApiError::ResponseRecv)??;
+
+    Ok(())
+}