virtio-devices, net_util: Migrate virtio-net to EpollHelper

EpollHelper allows the removal of much duplicated loop handling code and
instead the device specific even handling is delegated via an
implementation of EpollHelperHandler.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

net_util/src/lib.rs

@@ -32,10 +32,7 @@ use std::{io, mem, net};
 
 pub use mac::{MacAddr, MAC_ADDR_LEN};
 pub use open_tap::{open_tap, Error as OpenTapError};
-pub use queue_pair::{
+pub use queue_pair::{NetCounters, NetQueuePair, NetQueuePairError, RxVirtio, TxVirtio};
-    NetCounters, NetQueuePair, NetQueuePairError, RxVirtio, TxVirtio, RX_QUEUE_EVENT, RX_TAP_EVENT,
-    TX_QUEUE_EVENT,
-};
 pub use tap::{Error as TapError, Tap};
 
 #[derive(Debug)]

net_util/src/queue_pair.rs

@@ -216,16 +216,9 @@ pub struct NetQueuePair {
     pub epoll_fd: Option<RawFd>,
     pub rx_tap_listening: bool,
     pub counters: NetCounters,
+    pub tap_event_id: u16,
 }
 
-pub type DeviceEventT = u16;
-// The guest has made a buffer available to receive a frame into.
-pub const RX_QUEUE_EVENT: DeviceEventT = 0;
-// The transmit queue has a frame that is ready to send from the guest.
-pub const TX_QUEUE_EVENT: DeviceEventT = 1;
-// A frame is available for reading from the tap device to receive in the guest.
-pub const RX_TAP_EVENT: DeviceEventT = 2;
-
 impl NetQueuePair {
     // Copies a single frame from `self.rx.frame_buf` into the guest. Returns true
     // if a buffer was used, and false if the frame must be deferred until a buffer
@@ -245,7 +238,7 @@ impl NetQueuePair {
                     self.epoll_fd.unwrap(),
                     self.tap.as_raw_fd(),
                     epoll::Events::EPOLLIN,
-                    u64::from(RX_TAP_EVENT),
+                    u64::from(self.tap_event_id),
                 )
                 .map_err(NetQueuePairError::UnregisterListener)?;
                 self.rx_tap_listening = false;
@@ -314,7 +307,7 @@ impl NetQueuePair {
                 self.epoll_fd.unwrap(),
                 self.tap.as_raw_fd(),
                 epoll::Events::EPOLLIN,
-                u64::from(RX_TAP_EVENT),
+                u64::from(self.tap_event_id),
             )
             .map_err(NetQueuePairError::RegisterListener)?;
             self.rx_tap_listening = true;

vhost_user_net/src/lib.rs

@@ -110,6 +110,7 @@ impl VhostUserNetThread {
                 rx_tap_listening: false,
                 epoll_fd: None,
                 counters: NetCounters::default(),
+                tap_event_id: 2,
             },
         })
     }

virtio-devices/src/net.rs

@@ -7,25 +7,23 @@
 
 use super::net_util::{
     build_net_config_space, build_net_config_space_with_mq, CtrlVirtio, NetCtrlEpollHandler,
-    VirtioNetConfig, KILL_EVENT, NET_EVENTS_COUNT, PAUSE_EVENT,
+    VirtioNetConfig,
 };
 use super::Error as DeviceError;
 use super::{
-    ActivateError, ActivateResult, Queue, VirtioDevice, VirtioDeviceType, VirtioInterruptType,
+    ActivateError, ActivateResult, EpollHelper, EpollHelperError, EpollHelperHandler, Queue,
+    VirtioDevice, VirtioDeviceType, VirtioInterruptType, EPOLL_HELPER_EVENT_LAST,
 };
 use crate::VirtioInterrupt;
 use anyhow::anyhow;
 use libc::EFD_NONBLOCK;
 use net_util::{
     open_tap, MacAddr, NetCounters, NetQueuePair, OpenTapError, RxVirtio, Tap, TxVirtio,
-    RX_QUEUE_EVENT, RX_TAP_EVENT, TX_QUEUE_EVENT,
 };
 use std::collections::HashMap;
-use std::fs::File;
-use std::io;
 use std::net::Ipv4Addr;
 use std::num::Wrapping;
-use std::os::unix::io::{AsRawFd, FromRawFd};
+use std::os::unix::io::AsRawFd;
 use std::result;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
@@ -40,6 +38,13 @@ use vm_migration::{
 };
 use vmm_sys_util::eventfd::EventFd;
 
+// The guest has made a buffer available to receive a frame into.
+pub const RX_QUEUE_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 1;
+// The transmit queue has a frame that is ready to send from the guest.
+pub const TX_QUEUE_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 2;
+// A frame is available for reading from the tap device to receive in the guest.
+pub const RX_TAP_EVENT: u16 = EPOLL_HELPER_EVENT_LAST + 3;
+
 #[derive(Debug)]
 pub enum Error {
     /// Failed to open taps.
@@ -53,7 +58,8 @@ struct NetEpollHandler {
     interrupt_cb: Arc<dyn VirtioInterrupt>,
     kill_evt: EventFd,
     pause_evt: EventFd,
-
+    queue_pair: Vec<Queue>,
+    queue_evt_pair: Vec<EventFd>,
     // Always generate interrupts until the driver has signalled to the device.
     // This mitigates a problem with interrupts from tap events being "lost" upon
     // a restore as the vCPU thread isn't ready to handle the interrupt. This causes
@@ -71,22 +77,19 @@ impl NetEpollHandler {
             })
     }
 
-    fn handle_rx_event(
+    fn handle_rx_event(&mut self) -> result::Result<(), DeviceError> {
-        &mut self,
+        let queue_evt = &self.queue_evt_pair[0];
-        mut queue: &mut Queue,
-        queue_evt: &EventFd,
-    ) -> result::Result<(), DeviceError> {
         if let Err(e) = queue_evt.read() {
             error!("Failed to get rx queue event: {:?}", e);
         }
 
         if self
             .net
-            .resume_rx(&mut queue)
+            .resume_rx(&mut self.queue_pair[0])
             .map_err(DeviceError::NetQueuePair)?
             || !self.driver_awake
         {
-            self.signal_used_queue(queue)?;
+            self.signal_used_queue(&self.queue_pair[0])?;
             info!("Signalling RX queue");
         } else {
             info!("Not signalling RX queue");
@@ -95,21 +98,18 @@ impl NetEpollHandler {
         Ok(())
     }
 
-    fn handle_tx_event(
+    fn handle_tx_event(&mut self) -> result::Result<(), DeviceError> {
-        &mut self,
+        let queue_evt = &self.queue_evt_pair[1];
-        mut queue: &mut Queue,
-        queue_evt: &EventFd,
-    ) -> result::Result<(), DeviceError> {
         if let Err(e) = queue_evt.read() {
             error!("Failed to get tx queue event: {:?}", e);
         }
         if self
             .net
-            .process_tx(&mut queue)
+            .process_tx(&mut self.queue_pair[1])
             .map_err(DeviceError::NetQueuePair)?
             || !self.driver_awake
         {
-            self.signal_used_queue(queue)?;
+            self.signal_used_queue(&self.queue_pair[1])?;
             info!("Signalling TX queue");
         } else {
             info!("Not signalling TX queue");
@@ -117,14 +117,14 @@ impl NetEpollHandler {
         Ok(())
     }
 
-    fn handle_rx_tap_event(&mut self, queue: &mut Queue) -> result::Result<(), DeviceError> {
+    fn handle_rx_tap_event(&mut self) -> result::Result<(), DeviceError> {
         if self
             .net
-            .process_rx_tap(queue)
+            .process_rx_tap(&mut self.queue_pair[0])
             .map_err(DeviceError::NetQueuePair)?
             || !self.driver_awake
         {
-            self.signal_used_queue(queue)?;
+            self.signal_used_queue(&self.queue_pair[0])?;
             info!("Signalling RX queue");
         } else {
             info!("Not signalling RX queue");
@@ -132,134 +132,60 @@ impl NetEpollHandler {
         Ok(())
     }
 
-    fn run(
+    fn run(&mut self, paused: Arc<AtomicBool>) -> result::Result<(), EpollHelperError> {
-        &mut self,
+        let mut helper = EpollHelper::new(&self.kill_evt, &self.pause_evt)?;
-        paused: Arc<AtomicBool>,
+        helper.add_event(self.queue_evt_pair[0].as_raw_fd(), RX_QUEUE_EVENT)?;
-        mut queues: Vec<Queue>,
+        helper.add_event(self.queue_evt_pair[1].as_raw_fd(), TX_QUEUE_EVENT)?;
-        queue_evts: Vec<EventFd>,
-    ) -> result::Result<(), DeviceError> {
-        // Create the epoll file descriptor
-        let epoll_fd = epoll::create(true).map_err(DeviceError::EpollCreateFd)?;
-        // Use 'File' to enforce closing on 'epoll_fd'
-        let epoll_file = unsafe { File::from_raw_fd(epoll_fd) };
-        self.net.epoll_fd = Some(epoll_fd);
-
-        // Add events
-        epoll::ctl(
-            epoll_file.as_raw_fd(),
-            epoll::ControlOptions::EPOLL_CTL_ADD,
-            queue_evts[0].as_raw_fd(),
-            epoll::Event::new(epoll::Events::EPOLLIN, u64::from(RX_QUEUE_EVENT)),
-        )
-        .map_err(DeviceError::EpollCtl)?;
-        epoll::ctl(
-            epoll_file.as_raw_fd(),
-            epoll::ControlOptions::EPOLL_CTL_ADD,
-            queue_evts[1].as_raw_fd(),
-            epoll::Event::new(epoll::Events::EPOLLIN, u64::from(TX_QUEUE_EVENT)),
-        )
-        .map_err(DeviceError::EpollCtl)?;
-        epoll::ctl(
-            epoll_file.as_raw_fd(),
-            epoll::ControlOptions::EPOLL_CTL_ADD,
-            self.kill_evt.as_raw_fd(),
-            epoll::Event::new(epoll::Events::EPOLLIN, u64::from(KILL_EVENT)),
-        )
-        .map_err(DeviceError::EpollCtl)?;
-        epoll::ctl(
-            epoll_file.as_raw_fd(),
-            epoll::ControlOptions::EPOLL_CTL_ADD,
-            self.pause_evt.as_raw_fd(),
-            epoll::Event::new(epoll::Events::EPOLLIN, u64::from(PAUSE_EVENT)),
-        )
-        .map_err(DeviceError::EpollCtl)?;
 
         // If there are some already available descriptors on the RX queue,
         // then we can start the thread while listening onto the TAP.
-        if queues[0]
+        if self.queue_pair[0]
             .available_descriptors(&self.net.mem.as_ref().unwrap().memory())
             .unwrap()
         {
-            epoll::ctl(
+            helper.add_event(self.net.tap.as_raw_fd(), RX_TAP_EVENT)?;
-                epoll_file.as_raw_fd(),
-                epoll::ControlOptions::EPOLL_CTL_ADD,
-                self.net.tap.as_raw_fd(),
-                epoll::Event::new(epoll::Events::EPOLLIN, u64::from(RX_TAP_EVENT)),
-            )
-            .map_err(DeviceError::EpollCtl)?;
             self.net.rx_tap_listening = true;
-            error!("Listener registered at start");
+            info!("Listener registered at start");
         }
 
-        let mut events = vec![epoll::Event::new(epoll::Events::empty(), 0); NET_EVENTS_COUNT];
+        // The NetQueuePair needs the epoll fd.
+        self.net.epoll_fd = Some(helper.as_raw_fd());
 
-        // Before jumping into the epoll loop, check if the device is expected
+        helper.run(paused, self)?;
-        // to be in a paused state. This is helpful for the restore code path
+
-        // as the device thread should not start processing anything before the
+        Ok(())
-        // device has been resumed.
-        while paused.load(Ordering::SeqCst) {
-            thread::park();
     }
+}
 
-        'epoll: loop {
+impl EpollHelperHandler for NetEpollHandler {
-            let num_events = match epoll::wait(epoll_file.as_raw_fd(), -1, &mut events[..]) {
+    fn handle_event(&mut self, _helper: &mut EpollHelper, event: u16) -> bool {
-                Ok(res) => res,
+        match event {
-                Err(e) => {
-                    if e.kind() == io::ErrorKind::Interrupted {
-                        // It's well defined from the epoll_wait() syscall
-                        // documentation that the epoll loop can be interrupted
-                        // before any of the requested events occurred or the
-                        // timeout expired. In both those cases, epoll_wait()
-                        // returns an error of type EINTR, but this should not
-                        // be considered as a regular error. Instead it is more
-                        // appropriate to retry, by calling into epoll_wait().
-                        continue;
-                    }
-                    return Err(DeviceError::EpollWait(e));
-                }
-            };
-
-            for event in events.iter().take(num_events) {
-                let ev_type = event.data as u16;
-
-                match ev_type {
             RX_QUEUE_EVENT => {
                 self.driver_awake = true;
-                        self.handle_rx_event(&mut queues[0], &queue_evts[0])?;
+                if let Err(e) = self.handle_rx_event() {
+                    error!("Error processing RX queue: {:?}", e);
+                    return true;
+                }
             }
             TX_QUEUE_EVENT => {
                 self.driver_awake = true;
-                        self.handle_tx_event(&mut queues[1], &queue_evts[1])?;
+                if let Err(e) = self.handle_tx_event() {
+                    error!("Error processing TX queue: {:?}", e);
+                    return true;
+                }
             }
             RX_TAP_EVENT => {
-                        self.handle_rx_tap_event(&mut queues[0])?;
+                if let Err(e) = self.handle_rx_tap_event() {
+                    error!("Error processing tap queue: {:?}", e);
+                    return true;
                 }
-                    KILL_EVENT => {
-                        debug!("KILL_EVENT received, stopping epoll loop");
-                        break 'epoll;
-                    }
-                    PAUSE_EVENT => {
-                        debug!("PAUSE_EVENT received, pausing virtio-net epoll loop");
-
-                        // We loop here to handle spurious park() returns.
-                        // Until we have not resumed, the paused boolean will
-                        // be true.
-                        while paused.load(Ordering::SeqCst) {
-                            thread::park();
-                        }
-
-                        // Drain pause event after the device has been resumed.
-                        // This ensures the pause event has been seen by each
-                        // and every thread related to this virtio device.
-                        let _ = self.pause_evt.read();
             }
             _ => {
-                        error!("Unknown event for virtio-net");
+                error!("Unknown event: {}", event);
+                return true;
             }
         }
-            }
+        false
-        }
-        Ok(())
     }
 }
 
@@ -273,7 +199,7 @@ pub struct Net {
     config: VirtioNetConfig,
     queue_evts: Option<Vec<EventFd>>,
     interrupt_cb: Option<Arc<dyn VirtioInterrupt>>,
-    epoll_threads: Option<Vec<thread::JoinHandle<result::Result<(), DeviceError>>>>,
+    epoll_threads: Option<Vec<thread::JoinHandle<result::Result<(), EpollHelperError>>>>,
     ctrl_queue_epoll_thread: Option<thread::JoinHandle<result::Result<(), DeviceError>>>,
     paused: Arc<AtomicBool>,
     queue_size: Vec<u16>,
@@ -515,7 +441,10 @@ impl VirtioDevice for Net {
                         epoll_fd: None,
                         rx_tap_listening,
                         counters: self.counters.clone(),
+                        tap_event_id: RX_TAP_EVENT,
                     },
+                    queue_pair,
+                    queue_evt_pair,
                     interrupt_cb: interrupt_cb.clone(),
                     kill_evt: kill_evt.try_clone().unwrap(),
                     pause_evt: pause_evt.try_clone().unwrap(),
@@ -525,7 +454,7 @@ impl VirtioDevice for Net {
                 let paused = self.paused.clone();
                 thread::Builder::new()
                     .name("virtio_net".to_string())
-                    .spawn(move || handler.run(paused, queue_pair, queue_evt_pair))
+                    .spawn(move || handler.run(paused))
                     .map(|thread| epoll_threads.push(thread))
                     .map_err(|e| {
                         error!("failed to clone queue EventFd: {}", e);