feat(devices): add debug logging for device activation

Add informative debug logs when virtio devices are activated:

1. net_windows: Logs MAC address and backend connection status
2. vsock_windows: Logs CID, active streams, and pending RX count
3. balloon_windows: Logs num_pages and actual page count

These logs help with debugging device initialization and provide
visibility into the device state at activation time. Useful for
troubleshooting guest driver issues or verifying device configuration.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: hikejs

src/devices/src/virtio/balloon_windows.rs

@@ -305,6 +305,13 @@ impl VirtioDevice for Balloon {
         self.activate_evt
             .write(1)
             .map_err(|_| super::ActivateError::BadActivate)?;
+
+        let num_pages = self.config.num_pages;
+        let actual = self.config.actual;
+        debug!(
+            "balloon(windows): device activated, num_pages={}, actual={}",
+            num_pages, actual
+        );
         Ok(())
     }
 

src/devices/src/virtio/net_windows.rs

@@ -460,6 +460,12 @@ impl VirtioDevice for Net {
         self.activate_evt
             .write(1)
             .map_err(|_| ActivateError::BadActivate)?;
+
+        debug!(
+            "net(windows): device activated, MAC={:02x}:{:02x}:{:02x}:{:02x}:{:02x}:{:02x}, backend={}",
+            self.mac[0], self.mac[1], self.mac[2], self.mac[3], self.mac[4], self.mac[5],
+            if self.backend.is_some() { "connected" } else { "none" }
+        );
         Ok(())
     }
 

src/devices/src/virtio/vsock_windows.rs

@@ -1010,12 +1010,18 @@ impl VirtioDevice for Vsock {
 
     fn activate(&mut self, mem: GuestMemoryMmap, interrupt: InterruptTransport) -> ActivateResult {
         if self.queues.len() != NUM_QUEUES {
+            error!("vsock(windows): expected {NUM_QUEUES} queues, got {}", self.queues.len());
             return Err(ActivateError::BadActivate);
         }
         self.state = DeviceState::Activated(mem, interrupt);
         self.activate_evt
             .write(1)
             .map_err(|_| ActivateError::BadActivate)?;
+
+        debug!(
+            "vsock(windows): device activated, CID={}, streams={}, pending_rx={}",
+            self.cid, self.streams.len(), self.pending_rx.len()
+        );
         Ok(())
     }