refactor: cleanup vsock DeviceError and QueueError

Add a #[from] to DeviceError to avoid a couple unnecessary map_err()
calls, remove an unneeded variant from QueueError, and delete two unused
functions.

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

Author: roypat

src/vmm/src/devices/mod.rs

@@ -45,7 +45,7 @@ pub enum DeviceError {
     /// Device received malformed descriptor.
     MalformedDescriptor,
     /// Error during queue processing: {0}
-    QueueError(QueueError),
+    QueueError(#[from] QueueError),
     /// Vsock device error: {0}
-    VsockError(VsockError),
+    VsockError(#[from] VsockError),
 }

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

@@ -701,19 +701,15 @@ impl Net {
             // are live at the same time, meaning this has exclusive ownership over the memory
             if unsafe { self.tx_buffer.load_descriptor_chain(mem, head).is_err() } {
                 self.metrics.tx_fails.inc();
-                tx_queue
-                    .add_used(head_index, 0)
-                    .map_err(DeviceError::QueueError)?;
+                tx_queue.add_used(head_index, 0)?;
                 continue;
             };
 
             // We only handle frames that are up to MAX_BUFFER_SIZE
             if self.tx_buffer.len() as usize > MAX_BUFFER_SIZE {
                 error!("net: received too big frame from driver");
                 self.metrics.tx_malformed_frames.inc();
-                tx_queue
-                    .add_used(head_index, 0)
-                    .map_err(DeviceError::QueueError)?;
+                tx_queue.add_used(head_index, 0)?;
                 continue;
             }
 
@@ -741,9 +737,7 @@ impl Net {
                 process_rx_for_mmds = true;
             }
 
-            tx_queue
-                .add_used(head_index, 0)
-                .map_err(DeviceError::QueueError)?;
+            tx_queue.add_used(head_index, 0)?;
             used_any = true;
         }
 

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

@@ -12,12 +12,11 @@ use std::str::FromStr;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex};
 
-use crate::devices::DeviceError;
 use crate::devices::virtio::net::Net;
 #[cfg(test)]
 use crate::devices::virtio::net::device::vnet_hdr_len;
 use crate::devices::virtio::net::tap::{IfReqBuilder, Tap};
-use crate::devices::virtio::queue::{Queue, QueueError};
+use crate::devices::virtio::queue::Queue;
 use crate::devices::virtio::test_utils::VirtQueue;
 use crate::mmds::data_store::Mmds;
 use crate::mmds::ns::MmdsNetworkStack;
@@ -265,25 +264,6 @@ pub(crate) fn inject_tap_tx_frame(net: &Net, len: usize) -> Vec<u8> {
     frame
 }
 
-pub fn write_element_in_queue(net: &Net, idx: u16, val: u64) -> Result<(), DeviceError> {
-    if idx as usize > net.queue_evts.len() {
-        return Err(DeviceError::QueueError(QueueError::DescIndexOutOfBounds(
-            idx,
-        )));
-    }
-    net.queue_evts[idx as usize].write(val).unwrap();
-    Ok(())
-}
-
-pub fn get_element_from_queue(net: &Net, idx: u16) -> Result<u64, DeviceError> {
-    if idx as usize > net.queue_evts.len() {
-        return Err(DeviceError::QueueError(QueueError::DescIndexOutOfBounds(
-            idx,
-        )));
-    }
-    Ok(u64::try_from(net.queue_evts[idx as usize].as_raw_fd()).unwrap())
-}
-
 pub fn default_guest_mac() -> MacAddr {
     MacAddr::from_str("11:22:33:44:55:66").unwrap()
 }

src/vmm/src/devices/virtio/queue.rs

@@ -28,8 +28,6 @@ pub(super) const FIRECRACKER_MAX_QUEUE_SIZE: u16 = 256;
 
 #[derive(Debug, thiserror::Error, displaydoc::Display)]
 pub enum QueueError {
-    /// Virtio queue number of available descriptors {0} is greater than queue size {1}.
-    InvalidQueueSize(u16, u16),
     /// Descriptor index out of bounds: {0}.
     DescIndexOutOfBounds(u16),
     /// Failed to write value into the virtio queue used ring: {0}