refactor(virtio): converge kick methods to re-trigger queue events

Replace different `kick` implementations with a default implementation
in the `VirtioDevice` trait.
Change the `kick` logic to just re-trigger queue events instead of
manually calling different internal queue processing functions.

Signed-off-by: Egor Lazarchuk <yegorlz@amazon.co.uk>

Author: ShadowCurse

src/vmm/src/devices/virtio/balloon/device.rs

@@ -948,16 +948,16 @@ impl VirtioDevice for Balloon {
     }
 
     fn kick(&mut self) {
-        // If device is activated, kick the balloon queue(s) to make up for any
-        // pending or in-flight epoll events we may have not captured in snapshot.
-        // Stats queue doesn't need kicking as it is notified via a `timer_fd`.
         if self.is_activated() {
-            info!("kick balloon {}.", self.id());
             if self.free_page_hinting() {
-                // On restore we reset back to DONE to ensure everythign is freed
+                info!(
+                    "[{:?}:{}] resetting free page hinting to DONE",
+                    self.device_type(),
+                    self.id()
+                );
                 self.update_free_page_hint_cmd(FREE_PAGE_HINT_DONE);
             }
-            self.process_virtio_queues();
+            self.notify_queue_events();
         }
     }
 }

src/vmm/src/devices/virtio/block/device.rs

@@ -214,18 +214,6 @@ impl VirtioDevice for Block {
             Self::VhostUser(b) => b.device_state.is_activated(),
         }
     }
-
-    fn kick(&mut self) {
-        // If device is activated, kick the block queue(s) to make up for any
-        // pending or in-flight epoll events we may have not captured in
-        // snapshot. No need to kick Ratelimiters
-        // because they are restored 'unblocked' so
-        // any inflight `timer_fd` events can be safely discarded.
-        if self.is_activated() {
-            info!("kick block {}.", self.id());
-            self.process_virtio_queues();
-        }
-    }
 }
 
 impl MutEventSubscriber for Block {

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

@@ -17,7 +17,7 @@ use super::queue::{Queue, QueueError};
 use super::transport::VirtioInterrupt;
 use crate::devices::virtio::AsAny;
 use crate::devices::virtio::generated::virtio_ids;
-use crate::logger::warn;
+use crate::logger::{error, info, warn};
 use crate::vstate::memory::GuestMemoryMmap;
 
 /// State of an active VirtIO device
@@ -188,8 +188,28 @@ pub trait VirtioDevice: AsAny + Send {
         Ok(())
     }
 
+    /// Notify all queues by writing to the eventfds.
+    fn notify_queue_events(&mut self) {
+        info!("[{:?}:{}] notifying queues", self.device_type(), self.id());
+        for (i, eventfd) in self.queue_events().iter().enumerate() {
+            if let Err(err) = eventfd.write(1) {
+                error!(
+                    "[{:?}:{}] error notifying queue {}: {}",
+                    self.device_type(),
+                    self.id(),
+                    i,
+                    err
+                );
+            }
+        }
+    }
+
     /// Kick the device, as if it had received external events.
-    fn kick(&mut self) {}
+    fn kick(&mut self) {
+        if self.is_activated() {
+            self.notify_queue_events();
+        }
+    }
 }
 
 impl fmt::Debug for dyn VirtioDevice {

src/vmm/src/devices/virtio/net/device.rs

@@ -1056,17 +1056,6 @@ impl VirtioDevice for Net {
     fn is_activated(&self) -> bool {
         self.device_state.is_activated()
     }
-
-    fn kick(&mut self) {
-        // If device is activated, kick the net queue(s) to make up for any
-        // pending or in-flight epoll events we may have not captured in snapshot.
-        // No need to kick Ratelimiters because they are restored 'unblocked' so
-        // any inflight `timer_fd` events can be safely discarded.
-        if self.is_activated() {
-            info!("kick net {}.", self.id());
-            self.process_virtio_queues();
-        }
-    }
 }
 
 #[cfg(test)]

src/vmm/src/devices/virtio/rng/device.rs

@@ -312,13 +312,6 @@ impl VirtioDevice for Entropy {
         self.device_state = DeviceState::Activated(ActiveState { mem, interrupt });
         Ok(())
     }
-
-    fn kick(&mut self) {
-        if self.is_activated() {
-            info!("kick entropy {}.", self.id());
-            self.process_virtio_queues();
-        }
-    }
 }
 
 #[cfg(test)]

src/vmm/src/devices/virtio/vsock/device.rs

@@ -385,7 +385,11 @@ where
         // The only reason we still `kick` it is to make guest process
         // `TRANSPORT_RESET_EVENT` event we sent during snapshot creation.
         if self.is_activated() {
-            info!("kick vsock {}.", self.id());
+            info!(
+                "[{:?}:{}] signaling event queue",
+                self.device_type(),
+                self.id()
+            );
             self.signal_used_queue(EVQ_INDEX).unwrap();
         }
     }