virtio-devices: vhost_user: Refactor through VhostUserCommon

Introducing a new structure VhostUserCommon allowing to factorize a lot
of the code shared between the vhost-user devices (block, fs and net).

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

virtio-devices/src/vhost_user/blk.rs

@@ -6,30 +6,28 @@ use super::super::{
 };
 use super::vu_common_ctrl::{VhostUserConfig, VhostUserHandle};
 use super::{Error, Result, DEFAULT_VIRTIO_FEATURES};
-use crate::vhost_user::{Inflight, VhostUserEpollHandler};
+use crate::vhost_user::VhostUserCommon;
 use crate::VirtioInterrupt;
 use crate::{GuestMemoryMmap, GuestRegionMmap};
-use anyhow::anyhow;
 use block_util::VirtioBlockConfig;
 use std::mem;
-use std::ops::Deref;
-use std::os::unix::io::AsRawFd;
 use std::result;
 use std::sync::{Arc, Barrier, Mutex};
 use std::thread;
 use std::vec::Vec;
 use versionize::{VersionMap, Versionize, VersionizeResult};
 use versionize_derive::Versionize;
-use vhost::vhost_user::message::VhostUserConfigFlags;
+use vhost::vhost_user::message::{
-use vhost::vhost_user::message::VHOST_USER_CONFIG_OFFSET;
+    VhostUserConfigFlags, VhostUserProtocolFeatures, VhostUserVirtioFeatures,
-use vhost::vhost_user::message::{VhostUserProtocolFeatures, VhostUserVirtioFeatures};
+    VHOST_USER_CONFIG_OFFSET,
+};
 use vhost::vhost_user::{MasterReqHandler, VhostUserMaster, VhostUserMasterReqHandler};
 use virtio_bindings::bindings::virtio_blk::{
     VIRTIO_BLK_F_BLK_SIZE, VIRTIO_BLK_F_CONFIG_WCE, VIRTIO_BLK_F_DISCARD, VIRTIO_BLK_F_FLUSH,
     VIRTIO_BLK_F_GEOMETRY, VIRTIO_BLK_F_MQ, VIRTIO_BLK_F_RO, VIRTIO_BLK_F_SEG_MAX,
     VIRTIO_BLK_F_SIZE_MAX, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_WRITE_ZEROES,
 };
-use vm_memory::{Address, ByteValued, GuestAddressSpace, GuestMemory, GuestMemoryAtomic};
+use vm_memory::{ByteValued, GuestMemoryAtomic};
 use vm_migration::{
     protocol::MemoryRangeTable, Migratable, MigratableError, Pausable, Snapshot, Snapshottable,
     Transportable, VersionMapped,
@@ -54,15 +52,11 @@ impl VhostUserMasterReqHandler for SlaveReqHandler {}
 
 pub struct Blk {
     common: VirtioCommon,
+    vu_common: VhostUserCommon,
     id: String,
-    vu: Option<Arc<Mutex<VhostUserHandle>>>,
     config: VirtioBlockConfig,
     guest_memory: Option<GuestMemoryAtomic<GuestMemoryMmap>>,
-    acked_protocol_features: u64,
-    socket_path: String,
     epoll_thread: Option<thread::JoinHandle<()>>,
-    vu_num_queues: usize,
-    migration_started: bool,
 }
 
 impl Blk {
@@ -75,7 +69,6 @@ impl Blk {
             // enough to handle all the potential queues. VirtioPciDevice::new()
             // will create the actual queues based on this information.
             return Ok(Blk {
-                id,
                 common: VirtioCommon {
                     device_type: VirtioDeviceType::Block as u32,
                     queue_sizes: vec![vu_cfg.queue_size; num_queues],
@@ -83,14 +76,15 @@ impl Blk {
                     min_queues: DEFAULT_QUEUE_NUMBER as u16,
                     ..Default::default()
                 },
-                vu: None,
+                vu_common: VhostUserCommon {
+                    socket_path: vu_cfg.socket,
+                    vu_num_queues: num_queues,
+                    ..Default::default()
+                },
+                id,
                 config: VirtioBlockConfig::default(),
                 guest_memory: None,
-                acked_protocol_features: 0,
-                socket_path: vu_cfg.socket,
                 epoll_thread: None,
-                vu_num_queues: num_queues,
-                migration_started: false,
             });
         }
 
@@ -166,15 +160,17 @@ impl Blk {
                 min_queues: DEFAULT_QUEUE_NUMBER as u16,
                 ..Default::default()
             },
+            vu_common: VhostUserCommon {
+                vu: Some(Arc::new(Mutex::new(vu))),
+                acked_protocol_features,
+                socket_path: vu_cfg.socket,
+                vu_num_queues: num_queues,
+                ..Default::default()
+            },
             id,
-            vu: Some(Arc::new(Mutex::new(vu))),
             config,
             guest_memory: None,
-            acked_protocol_features,
-            socket_path: vu_cfg.socket,
             epoll_thread: None,
-            vu_num_queues: num_queues,
-            migration_started: false,
         })
     }
 
@@ -183,8 +179,8 @@ impl Blk {
             avail_features: self.common.avail_features,
             acked_features: self.common.acked_features,
             config: self.config,
-            acked_protocol_features: self.acked_protocol_features,
+            acked_protocol_features: self.vu_common.acked_protocol_features,
-            vu_num_queues: self.vu_num_queues,
+            vu_num_queues: self.vu_common.vu_num_queues,
         }
     }
 
@@ -192,31 +188,18 @@ impl Blk {
         self.common.avail_features = state.avail_features;
         self.common.acked_features = state.acked_features;
         self.config = state.config;
-        self.acked_protocol_features = state.acked_protocol_features;
+        self.vu_common.acked_protocol_features = state.acked_protocol_features;
-        self.vu_num_queues = state.vu_num_queues;
+        self.vu_common.vu_num_queues = state.vu_num_queues;
 
-        let mut vu = match VhostUserHandle::connect_vhost_user(
+        if let Err(e) = self
-            false,
+            .vu_common
-            &self.socket_path,
+            .restore_backend_connection(self.common.acked_features)
-            self.vu_num_queues as u64,
+        {
-            false,
+            error!(
-        ) {
+                "Failed restoring connection with vhost-user backend: {:?}",
-            Ok(r) => r,
+                e
-            Err(e) => {
+            );
-                error!("Failed connecting vhost-user backend: {:?}", e);
-                return;
-            }
-        };
-
-        if let Err(e) = vu.set_protocol_features_vhost_user(
-            self.common.acked_features,
-            self.acked_protocol_features,
-        ) {
-            error!("Failed setting up vhost-user backend: {:?}", e);
-            return;
         }
-
-        self.vu = Some(Arc::new(Mutex::new(vu)));
     }
 }
 
@@ -266,7 +249,7 @@ impl VirtioDevice for Blk {
         }
 
         self.config.writeback = data[0];
-        if let Some(vu) = &self.vu {
+        if let Some(vu) = &self.vu_common.vu {
             if let Err(e) = vu
                 .lock()
                 .unwrap()
@@ -297,51 +280,20 @@ impl VirtioDevice for Blk {
         let backend_acked_features = self.common.acked_features
             | (self.common.avail_features & VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits());
 
-        let mut inflight: Option<Inflight> =
-            if self.acked_protocol_features & VhostUserProtocolFeatures::INFLIGHT_SHMFD.bits() != 0
-            {
-                Some(Inflight::default())
-            } else {
-                None
-            };
-
-        if self.vu.is_none() {
-            error!("Missing vhost-user handle");
-            return Err(ActivateError::BadActivate);
-        }
-        let vu = self.vu.as_ref().unwrap();
-        vu.lock()
-            .unwrap()
-            .setup_vhost_user(
-                &mem.memory(),
-                queues.clone(),
-                queue_evts.iter().map(|q| q.try_clone().unwrap()).collect(),
-                &interrupt_cb,
-                backend_acked_features,
-                &slave_req_handler,
-                inflight.as_mut(),
-            )
-            .map_err(ActivateError::VhostUserBlkSetup)?;
-
         // Run a dedicated thread for handling potential reconnections with
         // the backend.
         let (kill_evt, pause_evt) = self.common.dup_eventfds();
 
-        let mut handler: VhostUserEpollHandler<SlaveReqHandler> = VhostUserEpollHandler {
+        let mut handler = self.vu_common.activate(
-            vu: vu.clone(),
             mem,
-            kill_evt,
-            pause_evt,
             queues,
             queue_evts,
-            virtio_interrupt: interrupt_cb,
+            interrupt_cb,
-            acked_features: backend_acked_features,
+            backend_acked_features,
-            acked_protocol_features: self.acked_protocol_features,
+            slave_req_handler,
-            socket_path: self.socket_path.clone(),
+            kill_evt,
-            server: false,
+            pause_evt,
-            slave_req_handler: None,
+        )?;
-            inflight,
-        };
 
         let paused = self.common.paused.clone();
         let paused_sync = self.common.paused_sync.clone();
@@ -368,7 +320,7 @@ impl VirtioDevice for Blk {
             self.common.resume().ok()?;
         }
 
-        if let Some(vu) = &self.vu {
+        if let Some(vu) = &self.vu_common.vu {
             if let Err(e) = vu
                 .lock()
                 .unwrap()
@@ -391,47 +343,20 @@ impl VirtioDevice for Blk {
     }
 
     fn shutdown(&mut self) {
-        if let Some(vu) = &self.vu {
+        self.vu_common.shutdown()
-            let _ = unsafe { libc::close(vu.lock().unwrap().socket_handle().as_raw_fd()) };
-        }
     }
 
     fn add_memory_region(
         &mut self,
         region: &Arc<GuestRegionMmap>,
     ) -> std::result::Result<(), crate::Error> {
-        if let Some(vu) = &self.vu {
+        self.vu_common.add_memory_region(&self.guest_memory, region)
-            if self.acked_protocol_features & VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS.bits()
-                != 0
-            {
-                return vu
-                    .lock()
-                    .unwrap()
-                    .add_memory_region(region)
-                    .map_err(crate::Error::VhostUserAddMemoryRegion);
-            } else if let Some(guest_memory) = &self.guest_memory {
-                return vu
-                    .lock()
-                    .unwrap()
-                    .update_mem_table(guest_memory.memory().deref())
-                    .map_err(crate::Error::VhostUserUpdateMemory);
-            }
-        }
-        Ok(())
     }
 }
 
 impl Pausable for Blk {
     fn pause(&mut self) -> result::Result<(), MigratableError> {
-        if let Some(vu) = &self.vu {
+        self.vu_common.pause()?;
-            vu.lock()
-                .unwrap()
-                .pause_vhost_user(self.vu_num_queues)
-                .map_err(|e| {
-                    MigratableError::Pause(anyhow!("Error pausing vhost-user-blk backend: {:?}", e))
-                })?;
-        }
-
         self.common.pause()
     }
 
@@ -442,19 +367,7 @@ impl Pausable for Blk {
             epoll_thread.thread().unpark();
         }
 
-        if let Some(vu) = &self.vu {
+        self.vu_common.resume()
-            vu.lock()
-                .unwrap()
-                .resume_vhost_user(self.vu_num_queues)
-                .map_err(|e| {
-                    MigratableError::Resume(anyhow!(
-                        "Error resuming vhost-user-blk backend: {:?}",
-                        e
-                    ))
-                })
-        } else {
-            Ok(())
-        }
     }
 }
 
@@ -464,13 +377,7 @@ impl Snapshottable for Blk {
     }
 
     fn snapshot(&mut self) -> std::result::Result<Snapshot, MigratableError> {
-        let snapshot = Snapshot::new_from_versioned_state(&self.id(), &self.state())?;
+        self.vu_common.snapshot(&self.id(), &self.state())
-
-        if self.migration_started {
-            self.shutdown();
-        }
-
-        Ok(snapshot)
     }
 
     fn restore(&mut self, snapshot: Snapshot) -> std::result::Result<(), MigratableError> {
@@ -482,77 +389,19 @@ impl Transportable for Blk {}
 
 impl Migratable for Blk {
     fn start_dirty_log(&mut self) -> std::result::Result<(), MigratableError> {
-        self.migration_started = true;
+        self.vu_common.start_dirty_log(&self.guest_memory)
-        if let Some(vu) = &self.vu {
-            if let Some(guest_memory) = &self.guest_memory {
-                let last_ram_addr = guest_memory.memory().last_addr().raw_value();
-                vu.lock()
-                    .unwrap()
-                    .start_dirty_log(last_ram_addr)
-                    .map_err(|e| {
-                        MigratableError::StartDirtyLog(anyhow!(
-                            "Error starting migration for vhost-user-blk backend: {:?}",
-                            e
-                        ))
-                    })
-            } else {
-                Err(MigratableError::StartDirtyLog(anyhow!(
-                    "Missing guest memory"
-                )))
-            }
-        } else {
-            Ok(())
-        }
     }
 
     fn stop_dirty_log(&mut self) -> std::result::Result<(), MigratableError> {
-        self.migration_started = false;
+        self.vu_common.stop_dirty_log()
-        if let Some(vu) = &self.vu {
-            vu.lock().unwrap().stop_dirty_log().map_err(|e| {
-                MigratableError::StopDirtyLog(anyhow!(
-                    "Error stopping migration for vhost-user-blk backend: {:?}",
-                    e
-                ))
-            })
-        } else {
-            Ok(())
-        }
     }
 
     fn dirty_log(&mut self) -> std::result::Result<MemoryRangeTable, MigratableError> {
-        if let Some(vu) = &self.vu {
+        self.vu_common.dirty_log(&self.guest_memory)
-            if let Some(guest_memory) = &self.guest_memory {
-                let last_ram_addr = guest_memory.memory().last_addr().raw_value();
-                vu.lock().unwrap().dirty_log(last_ram_addr).map_err(|e| {
-                    MigratableError::DirtyLog(anyhow!(
-                        "Error retrieving dirty ranges from vhost-user-blk backend: {:?}",
-                        e
-                    ))
-                })
-            } else {
-                Err(MigratableError::DirtyLog(anyhow!("Missing guest memory")))
-            }
-        } else {
-            Ok(MemoryRangeTable::default())
-        }
     }
 
     fn complete_migration(&mut self) -> std::result::Result<(), MigratableError> {
-        // Make sure the device thread is killed in order to prevent from
+        self.vu_common
-        // reconnections to the socket.
+            .complete_migration(self.common.kill_evt.take())
-        if let Some(kill_evt) = self.common.kill_evt.take() {
-            kill_evt.write(1).map_err(|e| {
-                MigratableError::CompleteMigration(anyhow!(
-                    "Error killing vhost-user-blk thread: {:?}",
-                    e
-                ))
-            })?;
-        }
-
-        // Drop the vhost-user handler to avoid further calls to fail because
-        // the connection with the backend has been closed.
-        self.vu = None;
-
-        Ok(())
     }
 }

virtio-devices/src/vhost_user/fs.rs

@@ -4,17 +4,15 @@
 use super::vu_common_ctrl::VhostUserHandle;
 use super::{Error, Result, DEFAULT_VIRTIO_FEATURES};
 use crate::seccomp_filters::{get_seccomp_filter, Thread};
-use crate::vhost_user::{Inflight, VhostUserEpollHandler};
+use crate::vhost_user::VhostUserCommon;
 use crate::{
     ActivateError, ActivateResult, Queue, UserspaceMapping, VirtioCommon, VirtioDevice,
     VirtioDeviceType, VirtioInterrupt, VirtioSharedMemoryList,
 };
 use crate::{GuestMemoryMmap, GuestRegionMmap, MmapRegion};
-use anyhow::anyhow;
 use libc::{self, c_void, off64_t, pread64, pwrite64};
 use seccomp::{SeccompAction, SeccompFilter};
 use std::io;
-use std::ops::Deref;
 use std::os::unix::io::AsRawFd;
 use std::result;
 use std::sync::{Arc, Barrier, Mutex};
@@ -300,8 +298,8 @@ unsafe impl ByteValued for VirtioFsConfig {}
 
 pub struct Fs {
     common: VirtioCommon,
+    vu_common: VhostUserCommon,
     id: String,
-    vu: Option<Arc<Mutex<VhostUserHandle>>>,
     config: VirtioFsConfig,
     // Hold ownership of the memory that is allocated for the device
     // which will be automatically dropped when the device is dropped
@@ -309,11 +307,7 @@ pub struct Fs {
     slave_req_support: bool,
     seccomp_action: SeccompAction,
     guest_memory: Option<GuestMemoryAtomic<GuestMemoryMmap>>,
-    acked_protocol_features: u64,
-    socket_path: String,
     epoll_thread: Option<thread::JoinHandle<()>>,
-    vu_num_queues: usize,
-    migration_started: bool,
 }
 
 impl Fs {
@@ -339,7 +333,6 @@ impl Fs {
             // enough to handle all the potential queues. VirtioPciDevice::new()
             // will create the actual queues based on this information.
             return Ok(Fs {
-                id,
                 common: VirtioCommon {
                     device_type: VirtioDeviceType::Fs as u32,
                     queue_sizes: vec![queue_size; num_queues],
@@ -347,17 +340,18 @@ impl Fs {
                     min_queues: DEFAULT_QUEUE_NUMBER as u16,
                     ..Default::default()
                 },
-                vu: None,
+                vu_common: VhostUserCommon {
+                    socket_path: path.to_string(),
+                    vu_num_queues: num_queues,
+                    ..Default::default()
+                },
+                id,
                 config: VirtioFsConfig::default(),
                 cache,
                 slave_req_support,
                 seccomp_action,
                 guest_memory: None,
-                acked_protocol_features: 0,
-                socket_path: path.to_string(),
                 epoll_thread: None,
-                vu_num_queues: num_queues,
-                migration_started: false,
             });
         }
 
@@ -420,18 +414,20 @@ impl Fs {
                 min_queues: DEFAULT_QUEUE_NUMBER as u16,
                 ..Default::default()
             },
+            vu_common: VhostUserCommon {
+                vu: Some(Arc::new(Mutex::new(vu))),
+                acked_protocol_features,
+                socket_path: path.to_string(),
+                vu_num_queues: num_queues,
+                ..Default::default()
+            },
             id,
-            vu: Some(Arc::new(Mutex::new(vu))),
             config,
             cache,
             slave_req_support,
             seccomp_action,
             guest_memory: None,
-            acked_protocol_features,
-            socket_path: path.to_string(),
             epoll_thread: None,
-            vu_num_queues: num_queues,
-            migration_started: false,
         })
     }
 
@@ -440,8 +436,8 @@ impl Fs {
             avail_features: self.common.avail_features,
             acked_features: self.common.acked_features,
             config: self.config,
-            acked_protocol_features: self.acked_protocol_features,
+            acked_protocol_features: self.vu_common.acked_protocol_features,
-            vu_num_queues: self.vu_num_queues,
+            vu_num_queues: self.vu_common.vu_num_queues,
             slave_req_support: self.slave_req_support,
         }
     }
@@ -450,32 +446,19 @@ impl Fs {
         self.common.avail_features = state.avail_features;
         self.common.acked_features = state.acked_features;
         self.config = state.config;
-        self.acked_protocol_features = state.acked_protocol_features;
+        self.vu_common.acked_protocol_features = state.acked_protocol_features;
-        self.vu_num_queues = state.vu_num_queues;
+        self.vu_common.vu_num_queues = state.vu_num_queues;
         self.slave_req_support = state.slave_req_support;
 
-        let mut vu = match VhostUserHandle::connect_vhost_user(
+        if let Err(e) = self
-            false,
+            .vu_common
-            &self.socket_path,
+            .restore_backend_connection(self.common.acked_features)
-            self.vu_num_queues as u64,
+        {
-            false,
+            error!(
-        ) {
+                "Failed restoring connection with vhost-user backend: {:?}",
-            Ok(r) => r,
+                e
-            Err(e) => {
+            );
-                error!("Failed connecting vhost-user backend: {:?}", e);
-                return;
-            }
-        };
-
-        if let Err(e) = vu.set_protocol_features_vhost_user(
-            self.common.acked_features,
-            self.acked_protocol_features,
-        ) {
-            error!("Failed setting up vhost-user backend: {:?}", e);
-            return;
         }
-
-        self.vu = Some(Arc::new(Mutex::new(vu)));
     }
 }
 
@@ -548,50 +531,20 @@ impl VirtioDevice for Fs {
         let backend_acked_features = self.common.acked_features
             | (self.common.avail_features & VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits());
 
-        let mut inflight: Option<Inflight> =
-            if self.acked_protocol_features & VhostUserProtocolFeatures::INFLIGHT_SHMFD.bits() != 0
-            {
-                Some(Inflight::default())
-            } else {
-                None
-            };
-
-        if self.vu.is_none() {
-            error!("Missing vhost-user handle");
-            return Err(ActivateError::BadActivate);
-        }
-        let vu = self.vu.as_ref().unwrap();
-        vu.lock()
-            .unwrap()
-            .setup_vhost_user(
-                &mem.memory(),
-                queues.clone(),
-                queue_evts.iter().map(|q| q.try_clone().unwrap()).collect(),
-                &interrupt_cb,
-                backend_acked_features,
-                &slave_req_handler,
-                inflight.as_mut(),
-            )
-            .map_err(ActivateError::VhostUserFsSetup)?;
-
         // Run a dedicated thread for handling potential reconnections with
-        // the backend as well as requests initiated by the backend.
+        // the backend.
         let (kill_evt, pause_evt) = self.common.dup_eventfds();
-        let mut handler: VhostUserEpollHandler<SlaveReqHandler> = VhostUserEpollHandler {
+
-            vu: vu.clone(),
+        let mut handler = self.vu_common.activate(
             mem,
-            kill_evt,
-            pause_evt,
             queues,
             queue_evts,
-            virtio_interrupt: interrupt_cb,
+            interrupt_cb,
-            acked_features: backend_acked_features,
+            backend_acked_features,
-            acked_protocol_features: self.acked_protocol_features,
-            socket_path: self.socket_path.clone(),
-            server: false,
             slave_req_handler,
-            inflight,
+            kill_evt,
-        };
+            pause_evt,
+        )?;
 
         let paused = self.common.paused.clone();
         let paused_sync = self.common.paused_sync.clone();
@@ -625,7 +578,7 @@ impl VirtioDevice for Fs {
             self.common.resume().ok()?;
         }
 
-        if let Some(vu) = &self.vu {
+        if let Some(vu) = &self.vu_common.vu {
             if let Err(e) = vu
                 .lock()
                 .unwrap()
@@ -648,9 +601,7 @@ impl VirtioDevice for Fs {
     }
 
     fn shutdown(&mut self) {
-        if let Some(vu) = &self.vu {
+        self.vu_common.shutdown()
-            let _ = unsafe { libc::close(vu.lock().unwrap().socket_handle().as_raw_fd()) };
-        }
     }
 
     fn get_shm_regions(&self) -> Option<VirtioSharedMemoryList> {
@@ -673,24 +624,7 @@ impl VirtioDevice for Fs {
         &mut self,
         region: &Arc<GuestRegionMmap>,
     ) -> std::result::Result<(), crate::Error> {
-        if let Some(vu) = &self.vu {
+        self.vu_common.add_memory_region(&self.guest_memory, region)
-            if self.acked_protocol_features & VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS.bits()
-                != 0
-            {
-                return vu
-                    .lock()
-                    .unwrap()
-                    .add_memory_region(region)
-                    .map_err(crate::Error::VhostUserAddMemoryRegion);
-            } else if let Some(guest_memory) = &self.guest_memory {
-                return vu
-                    .lock()
-                    .unwrap()
-                    .update_mem_table(guest_memory.memory().deref())
-                    .map_err(crate::Error::VhostUserUpdateMemory);
-            }
-        }
-        Ok(())
     }
 
     fn userspace_mappings(&self) -> Vec<UserspaceMapping> {
@@ -711,15 +645,7 @@ impl VirtioDevice for Fs {
 
 impl Pausable for Fs {
     fn pause(&mut self) -> result::Result<(), MigratableError> {
-        if let Some(vu) = &self.vu {
+        self.vu_common.pause()?;
-            vu.lock()
-                .unwrap()
-                .pause_vhost_user(self.vu_num_queues)
-                .map_err(|e| {
-                    MigratableError::Pause(anyhow!("Error pausing vhost-user-fs backend: {:?}", e))
-                })?;
-        }
-
         self.common.pause()
     }
 
@@ -730,19 +656,7 @@ impl Pausable for Fs {
             epoll_thread.thread().unpark();
         }
 
-        if let Some(vu) = &self.vu {
+        self.vu_common.resume()
-            vu.lock()
-                .unwrap()
-                .resume_vhost_user(self.vu_num_queues)
-                .map_err(|e| {
-                    MigratableError::Resume(anyhow!(
-                        "Error resuming vhost-user-fs backend: {:?}",
-                        e
-                    ))
-                })
-        } else {
-            Ok(())
-        }
     }
 }
 
@@ -752,13 +666,7 @@ impl Snapshottable for Fs {
     }
 
     fn snapshot(&mut self) -> std::result::Result<Snapshot, MigratableError> {
-        let snapshot = Snapshot::new_from_versioned_state(&self.id(), &self.state())?;
+        self.vu_common.snapshot(&self.id(), &self.state())
-
-        if self.migration_started {
-            self.shutdown();
-        }
-
-        Ok(snapshot)
     }
 
     fn restore(&mut self, snapshot: Snapshot) -> std::result::Result<(), MigratableError> {
@@ -770,77 +678,19 @@ impl Transportable for Fs {}
 
 impl Migratable for Fs {
     fn start_dirty_log(&mut self) -> std::result::Result<(), MigratableError> {
-        self.migration_started = true;
+        self.vu_common.start_dirty_log(&self.guest_memory)
-        if let Some(vu) = &self.vu {
-            if let Some(guest_memory) = &self.guest_memory {
-                let last_ram_addr = guest_memory.memory().last_addr().raw_value();
-                vu.lock()
-                    .unwrap()
-                    .start_dirty_log(last_ram_addr)
-                    .map_err(|e| {
-                        MigratableError::StartDirtyLog(anyhow!(
-                            "Error starting migration for vhost-user-fs backend: {:?}",
-                            e
-                        ))
-                    })
-            } else {
-                Err(MigratableError::StartDirtyLog(anyhow!(
-                    "Missing guest memory"
-                )))
-            }
-        } else {
-            Ok(())
-        }
     }
 
     fn stop_dirty_log(&mut self) -> std::result::Result<(), MigratableError> {
-        self.migration_started = false;
+        self.vu_common.stop_dirty_log()
-        if let Some(vu) = &self.vu {
-            vu.lock().unwrap().stop_dirty_log().map_err(|e| {
-                MigratableError::StopDirtyLog(anyhow!(
-                    "Error stopping migration for vhost-user-fs backend: {:?}",
-                    e
-                ))
-            })
-        } else {
-            Ok(())
-        }
     }
 
     fn dirty_log(&mut self) -> std::result::Result<MemoryRangeTable, MigratableError> {
-        if let Some(vu) = &self.vu {
+        self.vu_common.dirty_log(&self.guest_memory)
-            if let Some(guest_memory) = &self.guest_memory {
-                let last_ram_addr = guest_memory.memory().last_addr().raw_value();
-                vu.lock().unwrap().dirty_log(last_ram_addr).map_err(|e| {
-                    MigratableError::DirtyLog(anyhow!(
-                        "Error retrieving dirty ranges from vhost-user-fs backend: {:?}",
-                        e
-                    ))
-                })
-            } else {
-                Err(MigratableError::DirtyLog(anyhow!("Missing guest memory")))
-            }
-        } else {
-            Ok(MemoryRangeTable::default())
-        }
     }
 
     fn complete_migration(&mut self) -> std::result::Result<(), MigratableError> {
-        // Make sure the device thread is killed in order to prevent from
+        self.vu_common
-        // reconnections to the socket.
+            .complete_migration(self.common.kill_evt.take())
-        if let Some(kill_evt) = self.common.kill_evt.take() {
-            kill_evt.write(1).map_err(|e| {
-                MigratableError::CompleteMigration(anyhow!(
-                    "Error killing vhost-user-fs threads: {:?}",
-                    e
-                ))
-            })?;
-        }
-
-        // Drop the vhost-user handler to avoid further calls to fail because
-        // the connection with the backend has been closed.
-        self.vu = None;
-
-        Ok(())
     }
 }

virtio-devices/src/vhost_user/mod.rs

@@ -2,19 +2,27 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use crate::{
-    EpollHelper, EpollHelperError, EpollHelperHandler, GuestMemoryMmap, Queue, VirtioInterrupt,
+    ActivateError, EpollHelper, EpollHelperError, EpollHelperHandler, GuestMemoryMmap,
-    EPOLL_HELPER_EVENT_LAST, VIRTIO_F_IN_ORDER, VIRTIO_F_NOTIFICATION_DATA,
+    GuestRegionMmap, Queue, VirtioInterrupt, EPOLL_HELPER_EVENT_LAST, VIRTIO_F_IN_ORDER,
-    VIRTIO_F_ORDER_PLATFORM, VIRTIO_F_RING_EVENT_IDX, VIRTIO_F_RING_INDIRECT_DESC,
+    VIRTIO_F_NOTIFICATION_DATA, VIRTIO_F_ORDER_PLATFORM, VIRTIO_F_RING_EVENT_IDX,
-    VIRTIO_F_VERSION_1,
+    VIRTIO_F_RING_INDIRECT_DESC, VIRTIO_F_VERSION_1,
 };
+use anyhow::anyhow;
 use std::io;
 use std::ops::Deref;
 use std::os::unix::io::AsRawFd;
 use std::sync::{atomic::AtomicBool, Arc, Barrier, Mutex};
-use vhost::vhost_user::message::{VhostUserInflight, VhostUserVirtioFeatures};
+use versionize::Versionize;
+use vhost::vhost_user::message::{
+    VhostUserInflight, VhostUserProtocolFeatures, VhostUserVirtioFeatures,
+};
 use vhost::vhost_user::{MasterReqHandler, VhostUserMasterReqHandler};
 use vhost::Error as VhostError;
-use vm_memory::{mmap::MmapRegionError, Error as MmapError, GuestAddressSpace, GuestMemoryAtomic};
+use vm_memory::{
+    mmap::MmapRegionError, Address, Error as MmapError, GuestAddressSpace, GuestMemory,
+    GuestMemoryAtomic,
+};
+use vm_migration::{protocol::MemoryRangeTable, MigratableError, Snapshot, VersionMapped};
 use vm_virtio::Error as VirtioError;
 use vmm_sys_util::eventfd::EventFd;
 use vu_common_ctrl::VhostUserHandle;
@@ -274,3 +282,251 @@ impl<S: VhostUserMasterReqHandler> EpollHelperHandler for VhostUserEpollHandler<
         false
     }
 }
+
+#[derive(Default)]
+pub struct VhostUserCommon {
+    pub vu: Option<Arc<Mutex<VhostUserHandle>>>,
+    pub acked_protocol_features: u64,
+    pub socket_path: String,
+    pub vu_num_queues: usize,
+    pub migration_started: bool,
+    pub server: bool,
+}
+
+impl VhostUserCommon {
+    #[allow(clippy::too_many_arguments)]
+    pub fn activate<T: VhostUserMasterReqHandler>(
+        &mut self,
+        mem: GuestMemoryAtomic<GuestMemoryMmap>,
+        queues: Vec<Queue>,
+        queue_evts: Vec<EventFd>,
+        interrupt_cb: Arc<dyn VirtioInterrupt>,
+        acked_features: u64,
+        slave_req_handler: Option<MasterReqHandler<T>>,
+        kill_evt: EventFd,
+        pause_evt: EventFd,
+    ) -> std::result::Result<VhostUserEpollHandler<T>, ActivateError> {
+        let mut inflight: Option<Inflight> =
+            if self.acked_protocol_features & VhostUserProtocolFeatures::INFLIGHT_SHMFD.bits() != 0
+            {
+                Some(Inflight::default())
+            } else {
+                None
+            };
+
+        if self.vu.is_none() {
+            error!("Missing vhost-user handle");
+            return Err(ActivateError::BadActivate);
+        }
+        let vu = self.vu.as_ref().unwrap();
+        vu.lock()
+            .unwrap()
+            .setup_vhost_user(
+                &mem.memory(),
+                queues.clone(),
+                queue_evts.iter().map(|q| q.try_clone().unwrap()).collect(),
+                &interrupt_cb,
+                acked_features,
+                &slave_req_handler,
+                inflight.as_mut(),
+            )
+            .map_err(ActivateError::VhostUserBlkSetup)?;
+
+        Ok(VhostUserEpollHandler {
+            vu: vu.clone(),
+            mem,
+            kill_evt,
+            pause_evt,
+            queues,
+            queue_evts,
+            virtio_interrupt: interrupt_cb,
+            acked_features,
+            acked_protocol_features: self.acked_protocol_features,
+            socket_path: self.socket_path.clone(),
+            server: self.server,
+            slave_req_handler,
+            inflight,
+        })
+    }
+
+    pub fn restore_backend_connection(&mut self, acked_features: u64) -> Result<()> {
+        let mut vu = VhostUserHandle::connect_vhost_user(
+            self.server,
+            &self.socket_path,
+            self.vu_num_queues as u64,
+            false,
+        )?;
+
+        vu.set_protocol_features_vhost_user(acked_features, self.acked_protocol_features)?;
+
+        self.vu = Some(Arc::new(Mutex::new(vu)));
+
+        Ok(())
+    }
+
+    pub fn shutdown(&mut self) {
+        if let Some(vu) = &self.vu {
+            let _ = unsafe { libc::close(vu.lock().unwrap().socket_handle().as_raw_fd()) };
+        }
+
+        // Remove socket path if needed
+        if self.server {
+            let _ = std::fs::remove_file(&self.socket_path);
+        }
+    }
+
+    pub fn add_memory_region(
+        &mut self,
+        guest_memory: &Option<GuestMemoryAtomic<GuestMemoryMmap>>,
+        region: &Arc<GuestRegionMmap>,
+    ) -> std::result::Result<(), crate::Error> {
+        if let Some(vu) = &self.vu {
+            if self.acked_protocol_features & VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS.bits()
+                != 0
+            {
+                return vu
+                    .lock()
+                    .unwrap()
+                    .add_memory_region(region)
+                    .map_err(crate::Error::VhostUserAddMemoryRegion);
+            } else if let Some(guest_memory) = guest_memory {
+                return vu
+                    .lock()
+                    .unwrap()
+                    .update_mem_table(guest_memory.memory().deref())
+                    .map_err(crate::Error::VhostUserUpdateMemory);
+            }
+        }
+        Ok(())
+    }
+
+    pub fn pause(&mut self) -> std::result::Result<(), MigratableError> {
+        if let Some(vu) = &self.vu {
+            vu.lock()
+                .unwrap()
+                .pause_vhost_user(self.vu_num_queues)
+                .map_err(|e| {
+                    MigratableError::Pause(anyhow!("Error pausing vhost-user-blk backend: {:?}", e))
+                })
+        } else {
+            Ok(())
+        }
+    }
+
+    pub fn resume(&mut self) -> std::result::Result<(), MigratableError> {
+        if let Some(vu) = &self.vu {
+            vu.lock()
+                .unwrap()
+                .resume_vhost_user(self.vu_num_queues)
+                .map_err(|e| {
+                    MigratableError::Resume(anyhow!(
+                        "Error resuming vhost-user-blk backend: {:?}",
+                        e
+                    ))
+                })
+        } else {
+            Ok(())
+        }
+    }
+
+    pub fn snapshot<T>(
+        &mut self,
+        id: &str,
+        state: &T,
+    ) -> std::result::Result<Snapshot, MigratableError>
+    where
+        T: Versionize + VersionMapped,
+    {
+        let snapshot = Snapshot::new_from_versioned_state(id, state)?;
+
+        if self.migration_started {
+            self.shutdown();
+        }
+
+        Ok(snapshot)
+    }
+
+    pub fn start_dirty_log(
+        &mut self,
+        guest_memory: &Option<GuestMemoryAtomic<GuestMemoryMmap>>,
+    ) -> std::result::Result<(), MigratableError> {
+        self.migration_started = true;
+        if let Some(vu) = &self.vu {
+            if let Some(guest_memory) = guest_memory {
+                let last_ram_addr = guest_memory.memory().last_addr().raw_value();
+                vu.lock()
+                    .unwrap()
+                    .start_dirty_log(last_ram_addr)
+                    .map_err(|e| {
+                        MigratableError::StartDirtyLog(anyhow!(
+                            "Error starting migration for vhost-user backend: {:?}",
+                            e
+                        ))
+                    })
+            } else {
+                Err(MigratableError::StartDirtyLog(anyhow!(
+                    "Missing guest memory"
+                )))
+            }
+        } else {
+            Ok(())
+        }
+    }
+
+    pub fn stop_dirty_log(&mut self) -> std::result::Result<(), MigratableError> {
+        self.migration_started = false;
+        if let Some(vu) = &self.vu {
+            vu.lock().unwrap().stop_dirty_log().map_err(|e| {
+                MigratableError::StopDirtyLog(anyhow!(
+                    "Error stopping migration for vhost-user backend: {:?}",
+                    e
+                ))
+            })
+        } else {
+            Ok(())
+        }
+    }
+
+    pub fn dirty_log(
+        &mut self,
+        guest_memory: &Option<GuestMemoryAtomic<GuestMemoryMmap>>,
+    ) -> std::result::Result<MemoryRangeTable, MigratableError> {
+        if let Some(vu) = &self.vu {
+            if let Some(guest_memory) = guest_memory {
+                let last_ram_addr = guest_memory.memory().last_addr().raw_value();
+                vu.lock().unwrap().dirty_log(last_ram_addr).map_err(|e| {
+                    MigratableError::DirtyLog(anyhow!(
+                        "Error retrieving dirty ranges from vhost-user backend: {:?}",
+                        e
+                    ))
+                })
+            } else {
+                Err(MigratableError::DirtyLog(anyhow!("Missing guest memory")))
+            }
+        } else {
+            Ok(MemoryRangeTable::default())
+        }
+    }
+
+    pub fn complete_migration(
+        &mut self,
+        kill_evt: Option<EventFd>,
+    ) -> std::result::Result<(), MigratableError> {
+        // Make sure the device thread is killed in order to prevent from
+        // reconnections to the socket.
+        if let Some(kill_evt) = kill_evt {
+            kill_evt.write(1).map_err(|e| {
+                MigratableError::CompleteMigration(anyhow!(
+                    "Error killing vhost-user thread: {:?}",
+                    e
+                ))
+            })?;
+        }
+
+        // Drop the vhost-user handler to avoid further calls to fail because
+        // the connection with the backend has been closed.
+        self.vu = None;
+
+        Ok(())
+    }
+}

virtio-devices/src/vhost_user/net.rs

@@ -3,17 +3,15 @@
 
 use crate::seccomp_filters::{get_seccomp_filter, Thread};
 use crate::vhost_user::vu_common_ctrl::{VhostUserConfig, VhostUserHandle};
-use crate::vhost_user::{Error, Inflight, Result, VhostUserEpollHandler};
+use crate::vhost_user::{Error, Result, VhostUserCommon};
 use crate::{
     ActivateError, ActivateResult, EpollHelper, EpollHelperError, EpollHelperHandler, Queue,
     VirtioCommon, VirtioDevice, VirtioDeviceType, VirtioInterrupt, EPOLL_HELPER_EVENT_LAST,
     VIRTIO_F_RING_EVENT_IDX, VIRTIO_F_VERSION_1,
 };
 use crate::{GuestMemoryMmap, GuestRegionMmap};
-use anyhow::anyhow;
 use net_util::{build_net_config_space, CtrlQueue, MacAddr, VirtioNetConfig};
 use seccomp::{SeccompAction, SeccompFilter};
-use std::ops::Deref;
 use std::os::unix::io::AsRawFd;
 use std::result;
 use std::sync::atomic::AtomicBool;
@@ -30,7 +28,7 @@ use virtio_bindings::bindings::virtio_net::{
     VIRTIO_NET_F_HOST_ECN, VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_TSO6, VIRTIO_NET_F_HOST_UFO,
     VIRTIO_NET_F_MAC, VIRTIO_NET_F_MRG_RXBUF,
 };
-use vm_memory::{Address, ByteValued, GuestAddressSpace, GuestMemory, GuestMemoryAtomic};
+use vm_memory::{ByteValued, GuestAddressSpace, GuestMemoryAtomic};
 use vm_migration::{
     protocol::MemoryRangeTable, Migratable, MigratableError, Pausable, Snapshot, Snapshottable,
     Transportable, VersionMapped,
@@ -107,18 +105,13 @@ impl EpollHelperHandler for NetCtrlEpollHandler {
 
 pub struct Net {
     common: VirtioCommon,
+    vu_common: VhostUserCommon,
     id: String,
-    vu: Option<Arc<Mutex<VhostUserHandle>>>,
     config: VirtioNetConfig,
     guest_memory: Option<GuestMemoryAtomic<GuestMemoryMmap>>,
-    acked_protocol_features: u64,
-    socket_path: String,
-    server: bool,
     ctrl_queue_epoll_thread: Option<thread::JoinHandle<()>>,
     epoll_thread: Option<thread::JoinHandle<()>>,
     seccomp_action: SeccompAction,
-    vu_num_queues: usize,
-    migration_started: bool,
 }
 
 impl Net {
@@ -139,7 +132,6 @@ impl Net {
             // queue (with +1) will guarantee that. VirtioPciDevice::new() will
             // create the actual queues based on this information.
             return Ok(Net {
-                id,
                 common: VirtioCommon {
                     device_type: VirtioDeviceType::Net as u32,
                     queue_sizes: vec![vu_cfg.queue_size; num_queues + 1],
@@ -147,17 +139,18 @@ impl Net {
                     min_queues: DEFAULT_QUEUE_NUMBER as u16,
                     ..Default::default()
                 },
-                vu: None,
+                vu_common: VhostUserCommon {
+                    socket_path: vu_cfg.socket,
+                    vu_num_queues: num_queues,
+                    server,
+                    ..Default::default()
+                },
+                id,
                 config: VirtioNetConfig::default(),
                 guest_memory: None,
-                acked_protocol_features: 0,
-                socket_path: vu_cfg.socket,
-                server,
                 ctrl_queue_epoll_thread: None,
                 epoll_thread: None,
                 seccomp_action,
-                vu_num_queues: num_queues,
-                migration_started: false,
             });
         }
 
@@ -230,17 +223,19 @@ impl Net {
                 min_queues: DEFAULT_QUEUE_NUMBER as u16,
                 ..Default::default()
             },
-            vu: Some(Arc::new(Mutex::new(vu))),
+            vu_common: VhostUserCommon {
+                vu: Some(Arc::new(Mutex::new(vu))),
+                acked_protocol_features,
+                socket_path: vu_cfg.socket,
+                vu_num_queues,
+                server,
+                ..Default::default()
+            },
             config,
             guest_memory: None,
-            acked_protocol_features,
-            socket_path: vu_cfg.socket,
-            server,
             ctrl_queue_epoll_thread: None,
             epoll_thread: None,
             seccomp_action,
-            vu_num_queues,
-            migration_started: false,
         })
     }
 
@@ -249,8 +244,8 @@ impl Net {
             avail_features: self.common.avail_features,
             acked_features: self.common.acked_features,
             config: self.config,
-            acked_protocol_features: self.acked_protocol_features,
+            acked_protocol_features: self.vu_common.acked_protocol_features,
-            vu_num_queues: self.vu_num_queues,
+            vu_num_queues: self.vu_common.vu_num_queues,
         }
     }
 
@@ -258,31 +253,18 @@ impl Net {
         self.common.avail_features = state.avail_features;
         self.common.acked_features = state.acked_features;
         self.config = state.config;
-        self.acked_protocol_features = state.acked_protocol_features;
+        self.vu_common.acked_protocol_features = state.acked_protocol_features;
-        self.vu_num_queues = state.vu_num_queues;
+        self.vu_common.vu_num_queues = state.vu_num_queues;
 
-        let mut vu = match VhostUserHandle::connect_vhost_user(
+        if let Err(e) = self
-            self.server,
+            .vu_common
-            &self.socket_path,
+            .restore_backend_connection(self.common.acked_features)
-            self.vu_num_queues as u64,
+        {
-            false,
+            error!(
-        ) {
+                "Failed restoring connection with vhost-user backend: {:?}",
-            Ok(r) => r,
+                e
-            Err(e) => {
+            );
-                error!("Failed connecting vhost-user backend: {:?}", e);
-                return;
-            }
-        };
-
-        if let Err(e) = vu.set_protocol_features_vhost_user(
-            self.common.acked_features,
-            self.acked_protocol_features,
-        ) {
-            error!("Failed setting up vhost-user backend: {:?}", e);
-            return;
         }
-
-        self.vu = Some(Arc::new(Mutex::new(vu)));
     }
 }
 
@@ -379,51 +361,20 @@ impl VirtioDevice for Net {
         let backend_acked_features = self.common.acked_features & !(1 << VIRTIO_NET_F_MAC)
             | (self.common.avail_features & VhostUserVirtioFeatures::PROTOCOL_FEATURES.bits());
 
-        let mut inflight: Option<Inflight> =
-            if self.acked_protocol_features & VhostUserProtocolFeatures::INFLIGHT_SHMFD.bits() != 0
-            {
-                Some(Inflight::default())
-            } else {
-                None
-            };
-
-        if self.vu.is_none() {
-            error!("Missing vhost-user handle");
-            return Err(ActivateError::BadActivate);
-        }
-        let vu = self.vu.as_ref().unwrap();
-        vu.lock()
-            .unwrap()
-            .setup_vhost_user(
-                &mem.memory(),
-                queues.clone(),
-                queue_evts.iter().map(|q| q.try_clone().unwrap()).collect(),
-                &interrupt_cb,
-                backend_acked_features,
-                &slave_req_handler,
-                inflight.as_mut(),
-            )
-            .map_err(ActivateError::VhostUserNetSetup)?;
-
         // Run a dedicated thread for handling potential reconnections with
         // the backend.
         let (kill_evt, pause_evt) = self.common.dup_eventfds();
 
-        let mut handler: VhostUserEpollHandler<SlaveReqHandler> = VhostUserEpollHandler {
+        let mut handler = self.vu_common.activate(
-            vu: vu.clone(),
             mem,
-            kill_evt,
-            pause_evt,
             queues,
             queue_evts,
-            virtio_interrupt: interrupt_cb,
+            interrupt_cb,
-            acked_features: backend_acked_features,
+            backend_acked_features,
-            acked_protocol_features: self.acked_protocol_features,
+            slave_req_handler,
-            socket_path: self.socket_path.clone(),
+            kill_evt,
-            server: self.server,
+            pause_evt,
-            slave_req_handler: None,
+        )?;
-            inflight,
-        };
 
         let paused = self.common.paused.clone();
         let paused_sync = self.common.paused_sync.clone();
@@ -450,7 +401,7 @@ impl VirtioDevice for Net {
             self.common.resume().ok()?;
         }
 
-        if let Some(vu) = &self.vu {
+        if let Some(vu) = &self.vu_common.vu {
             if let Err(e) = vu
                 .lock()
                 .unwrap()
@@ -473,52 +424,20 @@ impl VirtioDevice for Net {
     }
 
     fn shutdown(&mut self) {
-        if let Some(vu) = &self.vu {
+        self.vu_common.shutdown();
-            let _ = unsafe { libc::close(vu.lock().unwrap().socket_handle().as_raw_fd()) };
-        }
-
-        // Remove socket path if needed
-        if self.server {
-            let _ = std::fs::remove_file(&self.socket_path);
-        }
     }
 
     fn add_memory_region(
         &mut self,
         region: &Arc<GuestRegionMmap>,
     ) -> std::result::Result<(), crate::Error> {
-        if let Some(vu) = &self.vu {
+        self.vu_common.add_memory_region(&self.guest_memory, region)
-            if self.acked_protocol_features & VhostUserProtocolFeatures::CONFIGURE_MEM_SLOTS.bits()
-                != 0
-            {
-                return vu
-                    .lock()
-                    .unwrap()
-                    .add_memory_region(region)
-                    .map_err(crate::Error::VhostUserAddMemoryRegion);
-            } else if let Some(guest_memory) = &self.guest_memory {
-                return vu
-                    .lock()
-                    .unwrap()
-                    .update_mem_table(guest_memory.memory().deref())
-                    .map_err(crate::Error::VhostUserUpdateMemory);
-            }
-        }
-        Ok(())
     }
 }
 
 impl Pausable for Net {
     fn pause(&mut self) -> result::Result<(), MigratableError> {
-        if let Some(vu) = &self.vu {
+        self.vu_common.pause()?;
-            vu.lock()
-                .unwrap()
-                .pause_vhost_user(self.vu_num_queues)
-                .map_err(|e| {
-                    MigratableError::Pause(anyhow!("Error pausing vhost-user-net backend: {:?}", e))
-                })?;
-        }
-
         self.common.pause()
     }
 
@@ -533,19 +452,7 @@ impl Pausable for Net {
             ctrl_queue_epoll_thread.thread().unpark();
         }
 
-        if let Some(vu) = &self.vu {
+        self.vu_common.resume()
-            vu.lock()
-                .unwrap()
-                .resume_vhost_user(self.vu_num_queues)
-                .map_err(|e| {
-                    MigratableError::Resume(anyhow!(
-                        "Error resuming vhost-user-net backend: {:?}",
-                        e
-                    ))
-                })
-        } else {
-            Ok(())
-        }
     }
 }
 
@@ -555,13 +462,7 @@ impl Snapshottable for Net {
     }
 
     fn snapshot(&mut self) -> std::result::Result<Snapshot, MigratableError> {
-        let snapshot = Snapshot::new_from_versioned_state(&self.id(), &self.state())?;
+        self.vu_common.snapshot(&self.id(), &self.state())
-
-        if self.migration_started {
-            self.shutdown();
-        }
-
-        Ok(snapshot)
     }
 
     fn restore(&mut self, snapshot: Snapshot) -> std::result::Result<(), MigratableError> {
@@ -573,77 +474,19 @@ impl Transportable for Net {}
 
 impl Migratable for Net {
     fn start_dirty_log(&mut self) -> std::result::Result<(), MigratableError> {
-        self.migration_started = true;
+        self.vu_common.start_dirty_log(&self.guest_memory)
-        if let Some(vu) = &self.vu {
-            if let Some(guest_memory) = &self.guest_memory {
-                let last_ram_addr = guest_memory.memory().last_addr().raw_value();
-                vu.lock()
-                    .unwrap()
-                    .start_dirty_log(last_ram_addr)
-                    .map_err(|e| {
-                        MigratableError::StartDirtyLog(anyhow!(
-                            "Error starting migration for vhost-user-net backend: {:?}",
-                            e
-                        ))
-                    })
-            } else {
-                Err(MigratableError::StartDirtyLog(anyhow!(
-                    "Missing guest memory"
-                )))
-            }
-        } else {
-            Ok(())
-        }
     }
 
     fn stop_dirty_log(&mut self) -> std::result::Result<(), MigratableError> {
-        self.migration_started = false;
+        self.vu_common.stop_dirty_log()
-        if let Some(vu) = &self.vu {
-            vu.lock().unwrap().stop_dirty_log().map_err(|e| {
-                MigratableError::StopDirtyLog(anyhow!(
-                    "Error stopping migration for vhost-user-net backend: {:?}",
-                    e
-                ))
-            })
-        } else {
-            Ok(())
-        }
     }
 
     fn dirty_log(&mut self) -> std::result::Result<MemoryRangeTable, MigratableError> {
-        if let Some(vu) = &self.vu {
+        self.vu_common.dirty_log(&self.guest_memory)
-            if let Some(guest_memory) = &self.guest_memory {
-                let last_ram_addr = guest_memory.memory().last_addr().raw_value();
-                vu.lock().unwrap().dirty_log(last_ram_addr).map_err(|e| {
-                    MigratableError::DirtyLog(anyhow!(
-                        "Error retrieving dirty ranges from vhost-user-net backend: {:?}",
-                        e
-                    ))
-                })
-            } else {
-                Err(MigratableError::DirtyLog(anyhow!("Missing guest memory")))
-            }
-        } else {
-            Ok(MemoryRangeTable::default())
-        }
     }
 
     fn complete_migration(&mut self) -> std::result::Result<(), MigratableError> {
-        // Make sure the device thread is killed in order to prevent from
+        self.vu_common
-        // reconnections to the socket.
+            .complete_migration(self.common.kill_evt.take())
-        if let Some(kill_evt) = self.common.kill_evt.take() {
-            kill_evt.write(1).map_err(|e| {
-                MigratableError::CompleteMigration(anyhow!(
-                    "Error killing vhost-user-net threads: {:?}",
-                    e
-                ))
-            })?;
-        }
-
-        // Drop the vhost-user handler to avoid further calls to fail because
-        // the connection with the backend has been closed.
-        self.vu = None;
-
-        Ok(())
     }
 }