chore: Eliminate miscellaneous .unwraps()s

Removes a handful of unwraps by slightly rearranging code (e.g. by using
pattern matching to combine the fallible operation with the check that
ensures it won't actually fail).

Signed-off-by: Patrick Roy <roypat@amazon.co.uk>

Author: roypat

src/vmm/src/devices/virtio/vsock/unix/muxer_killq.rs

@@ -106,7 +106,7 @@ impl MuxerKillQ {
     pub fn pop(&mut self) -> Option<ConnMapKey> {
         if let Some(item) = self.q.front() {
             if Instant::now() > item.kill_time {
-                return Some(self.q.pop_front().unwrap().key);
+                return self.q.pop_front().map(|entry| entry.key);
             }
         }
         None

src/vmm/src/dumbo/tcp/connection.rs

@@ -714,13 +714,9 @@ impl Connection {
 
             // We check this here because if a valid payload has been received, then we must have
             // set enqueue_ack = true earlier.
-            if payload_len > 0 {
+            if let Some(payload_len) = NonZeroUsize::new(payload_len.into()) {
                 buf[..payload_len.into()].copy_from_slice(s.payload());
-                // The unwrap is safe because payload_len > 0.
-                return Ok((
-                    Some(NonZeroUsize::new(payload_len.into()).unwrap()),
-                    recv_status_flags,
-                ));
+                return Ok((Some(payload_len), recv_status_flags));
             }
         }
 

src/vmm/src/vmm_config/net.rs

@@ -109,20 +109,20 @@ impl NetBuilder {
         &mut self,
         netif_config: NetworkInterfaceConfig,
     ) -> Result<Arc<Mutex<Net>>, NetworkInterfaceError> {
-        let mac_conflict = |net: &Arc<Mutex<Net>>| {
-            let net = net.lock().expect("Poisoned lock");
-            // Check if another net dev has same MAC.
-            netif_config.guest_mac.is_some()
-                && netif_config.guest_mac.as_ref() == net.guest_mac()
-                && &netif_config.iface_id != net.id()
-        };
-        // Validate there is no Mac conflict.
-        // No need to validate host_dev_name conflict. In such a case,
-        // an error will be thrown during device creation anyway.
-        if self.net_devices.iter().any(mac_conflict) {
-            return Err(NetworkInterfaceError::GuestMacAddressInUse(
-                netif_config.guest_mac.unwrap().to_string(),
-            ));
+        if let Some(ref mac_address) = netif_config.guest_mac {
+            let mac_conflict = |net: &Arc<Mutex<Net>>| {
+                let net = net.lock().expect("Poisoned lock");
+                // Check if another net dev has same MAC.
+                Some(mac_address) == net.guest_mac() && &netif_config.iface_id != net.id()
+            };
+            // Validate there is no Mac conflict.
+            // No need to validate host_dev_name conflict. In such a case,
+            // an error will be thrown during device creation anyway.
+            if self.net_devices.iter().any(mac_conflict) {
+                return Err(NetworkInterfaceError::GuestMacAddressInUse(
+                    mac_address.to_string(),
+                ));
+            }
         }
 
         // If this is an update, just remove the old one.

src/vmm/src/vstate/vm.rs

@@ -235,10 +235,10 @@ impl Vm {
         }
         guest_mem
             .iter()
-            .enumerate()
-            .try_for_each(|(index, region)| {
+            .zip(0u32..)
+            .try_for_each(|(region, slot)| {
                 let memory_region = kvm_userspace_memory_region {
-                    slot: u32::try_from(index).unwrap(),
+                    slot,
                     guest_phys_addr: region.start_addr().raw_value(),
                     memory_size: region.len(),
                     // It's safe to unwrap because the guest address is valid.