device_manager: Store the subscriber IDs returned by EventManager

So far we haven't been storing the subscriber IDs returned by the event
manager because we didn't need to use it.

Subsequent commits will add support for device hot-unplug for virtio-pci
devices, and therefore we need to store the IDs so that we can remove
the objects from the event manager. We also need to store it for
virtio-mmio devices to support device reset.

Signed-off-by: Ilias Stamatis <ilstam@amazon.com>

Author: ilstam

src/vmm/src/device_manager/mmio.rs

@@ -114,6 +114,8 @@ pub struct MMIODevice<T> {
     pub(crate) resources: MMIODeviceInfo,
     /// The actual device
     pub(crate) inner: Arc<Mutex<T>>,
+    /// The subscriber ID returned by the EventManager
+    pub(crate) sub_id: Option<event_manager::SubscriberId>,
 }
 
 /// Manages the complexities of registering a MMIO device.
@@ -175,7 +177,7 @@ impl MMIODeviceManager {
         &mut self,
         vm: &Vm,
         device_id: String,
-        device: MMIODevice<MmioTransport>,
+        mut device: MMIODevice<MmioTransport>,
         event_manager: &mut EventManager,
     ) -> Result<(), MmioError> {
         // Our virtio devices are currently hardcoded to use a single IRQ.
@@ -204,7 +206,9 @@ impl MMIODeviceManager {
             device.resources.len,
         )?;
 
-        event_manager.add_subscriber(device.inner.lock().expect("Poisoned lock").device());
+        let sub_id =
+            event_manager.add_subscriber(device.inner.lock().expect("Poisoned lock").device());
+        device.sub_id = Some(sub_id);
 
         self.virtio_devices.insert(identifier, device);
 
@@ -245,6 +249,7 @@ impl MMIODeviceManager {
         let device = MMIODevice {
             resources: self.allocate_mmio_resources(&mut vm.resource_allocator(), 1)?,
             inner: Arc::new(Mutex::new(mmio_device)),
+            sub_id: None,
         };
 
         #[cfg(target_arch = "x86_64")]
@@ -294,6 +299,7 @@ impl MMIODeviceManager {
         let device = MMIODevice {
             resources: device_info,
             inner: serial,
+            sub_id: None,
         };
 
         vm.common.mmio_bus.insert(
@@ -347,6 +353,7 @@ impl MMIODeviceManager {
         let device = MMIODevice {
             resources: device_info,
             inner: rtc,
+            sub_id: None,
         };
 
         vm.common.mmio_bus.insert(
@@ -374,6 +381,7 @@ impl MMIODeviceManager {
         let device = MMIODevice {
             resources: device_info,
             inner: boot_timer,
+            sub_id: None,
         };
 
         mmio_bus.insert(

src/vmm/src/device_manager/pci_mngr.rs

@@ -126,12 +126,12 @@ impl PciDevices {
             .insert((device_type, id), virtio_device.clone());
 
         Self::register_bars_with_bus(vm, &virtio_device)?;
-        virtio_device
-            .lock()
-            .expect("Poisoned lock")
-            .register_notification_ioevent(vm)?;
 
-        event_manager.add_subscriber(virtio_device.lock().expect("Poisoned lock").virtio_device());
+        let mut device = virtio_device.lock().expect("Poisoned lock");
+        device.register_notification_ioevent(vm)?;
+
+        let sub_id = event_manager.add_subscriber(device.virtio_device());
+        device.sub_id = Some(sub_id);
 
         Ok(())
     }

src/vmm/src/device_manager/persist.rs

@@ -358,6 +358,7 @@ impl<'a> Persist<'a> for MMIODeviceManager {
                 MMIODevice {
                     resources: *device_info,
                     inner: mmio_transport,
+                    sub_id: None,
                 },
                 event_manager,
             )?;

src/vmm/src/devices/virtio/transport/pci/device.rs

@@ -258,6 +258,9 @@ pub enum VirtioPciDeviceError {
 pub struct VirtioPciDevice {
     id: String,
 
+    // The subscriber ID returned by the EventManager
+    pub sub_id: Option<event_manager::SubscriberId>,
+
     // BDF assigned to the device
     pci_device_bdf: PciBdf,
 
@@ -398,6 +401,7 @@ impl VirtioPciDevice {
 
         let virtio_pci_device = VirtioPciDevice {
             id,
+            sub_id: None,
             pci_device_bdf: pci_device_bdf.into(),
             configuration: pci_config,
             common_config: virtio_common_config,
@@ -442,6 +446,7 @@ impl VirtioPciDevice {
 
         let virtio_pci_device = VirtioPciDevice {
             id,
+            sub_id: None,
             pci_device_bdf: state.pci_device_bdf,
             configuration: pci_config,
             common_config: virtio_common_config,