fix: propagate Err(InvalidAvailIdx) out of Vsock::notify_backend

turns out that when driving the vsock device from test code using fake
descriptors placed in guest memory, calling this function is the only
way to get it to process new connections, etc. So avoid it panicking.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

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

@@ -33,6 +33,7 @@ use vmm_sys_util::epoll::EventSet;
 use super::VsockBackend;
 use super::device::{EVQ_INDEX, RXQ_INDEX, TXQ_INDEX, Vsock};
 use crate::devices::virtio::device::VirtioDevice;
+use crate::devices::virtio::queue::InvalidAvailIdx;
 use crate::devices::virtio::vsock::metrics::METRICS;
 use crate::logger::IncMetric;
 
@@ -107,7 +108,7 @@ where
     }
 
     /// Notify backend of new events.
-    pub fn notify_backend(&mut self, evset: EventSet) -> bool {
+    pub fn notify_backend(&mut self, evset: EventSet) -> Result<bool, InvalidAvailIdx> {
         self.backend.notify(evset);
         // After the backend has been kicked, it might've freed up some resources, so we
         // can attempt to send it more data to process.
@@ -116,11 +117,11 @@ where
         // TX queue again.
         // OK to unwrap: Only QueueError::InvalidAvailIdx is returned, and we explicitly
         // want to panic on that one.
-        let mut raise_irq = self.process_tx().unwrap();
+        let mut raise_irq = self.process_tx()?;
         if self.backend.has_pending_rx() {
-            raise_irq |= self.process_rx().unwrap();
+            raise_irq |= self.process_rx()?;
         }
-        raise_irq
+        Ok(raise_irq)
     }
 
     fn register_runtime_events(&self, ops: &mut EventOps) {
@@ -194,7 +195,7 @@ where
                 Self::PROCESS_RXQ => raise_irq = self.handle_rxq_event(evset),
                 Self::PROCESS_TXQ => raise_irq = self.handle_txq_event(evset),
                 Self::PROCESS_EVQ => raise_irq = self.handle_evq_event(evset),
-                Self::PROCESS_NOTIFY_BACKEND => raise_irq = self.notify_backend(evset),
+                Self::PROCESS_NOTIFY_BACKEND => raise_irq = self.notify_backend(evset).unwrap(),
                 _ => warn!("Unexpected vsock event received: {:?}", source),
             }
             if raise_irq {
@@ -394,7 +395,7 @@ mod tests {
             ctx.mock_activate(test_ctx.mem.clone());
 
             ctx.device.backend.set_pending_rx(true);
-            ctx.device.notify_backend(EventSet::IN);
+            ctx.device.notify_backend(EventSet::IN).unwrap();
 
             // The backend should've received this event.
             assert_eq!(ctx.device.backend.evset, Some(EventSet::IN));
@@ -413,7 +414,7 @@ mod tests {
             ctx.mock_activate(test_ctx.mem.clone());
 
             ctx.device.backend.set_pending_rx(false);
-            ctx.device.notify_backend(EventSet::IN);
+            ctx.device.notify_backend(EventSet::IN).unwrap();
 
             // The backend should've received this event.
             assert_eq!(ctx.device.backend.evset, Some(EventSet::IN));