vmm: Create vsock backend

This commit relies on the new vsock::unix module to create the backend
that will be used from the virtio-vsock device.

The concept of backend is interesting here as it would allow for a vhost
kernel backend to be plugged if that was needed someday.

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

vm-virtio/src/lib.rs

@@ -27,7 +27,7 @@ pub mod net;
 mod pmem;
 mod queue;
 mod rng;
-mod vsock;
+pub mod vsock;
 
 pub mod transport;
 pub mod vhost_user;
@@ -49,6 +49,7 @@ const DEVICE_FEATURES_OK: u32 = 0x08;
 const DEVICE_FAILED: u32 = 0x80;
 
 const VIRTIO_F_VERSION_1: u32 = 32;
+const VIRTIO_F_IN_ORDER: u32 = 35;
 
 // Types taken from linux/virtio_ids.h
 #[derive(Copy, Clone)]

vm-virtio/src/vsock/device.rs

@@ -36,11 +36,12 @@ use std::result;
 use std::sync::{Arc, RwLock};
 use std::thread;
 
+use super::VsockBackend;
 use crate::Error as DeviceError;
 use crate::VirtioInterrupt;
 use crate::{
     ActivateError, ActivateResult, DeviceEventT, Queue, VirtioDevice, VirtioDeviceType,
-    VIRTIO_F_VERSION_1,
+    VIRTIO_F_IN_ORDER, VIRTIO_F_VERSION_1,
 };
 use byteorder::{ByteOrder, LittleEndian};
 use vm_memory::GuestMemoryMmap;
@@ -167,19 +168,26 @@ impl VsockEpollHandler {
 }
 
 /// Virtio device exposing virtual socket to the guest.
-pub struct Vsock {
+pub struct Vsock<B: VsockBackend> {
     cid: u64,
+    _backend: Option<B>,
     kill_evt: Option<EventFd>,
     avail_features: u64,
     acked_features: u64,
 }
 
-impl Vsock {
-    pub fn new(cid: u64) -> io::Result<Vsock> {
-        let avail_features = 1u64 << VIRTIO_F_VERSION_1;
+impl<B> Vsock<B>
+where
+    B: VsockBackend,
+{
+    /// Create a new virtio-vsock device with the given VM CID and vsock
+    /// backend.
+    pub fn new(cid: u64, backend: B) -> io::Result<Vsock<B>> {
+        let avail_features = 1u64 << VIRTIO_F_VERSION_1 | 1u64 << VIRTIO_F_IN_ORDER;
 
         Ok(Vsock {
             cid,
+            _backend: Some(backend),
             kill_evt: None,
             avail_features,
             acked_features: 0u64,
@@ -187,7 +195,10 @@ impl Vsock {
     }
 }
 
-impl Drop for Vsock {
+impl<B> Drop for Vsock<B>
+where
+    B: VsockBackend,
+{
     fn drop(&mut self) {
         if let Some(kill_evt) = self.kill_evt.take() {
             // Ignore the result because there is nothing we can do about it.
@@ -196,7 +207,10 @@ impl Drop for Vsock {
     }
 }
 
-impl VirtioDevice for Vsock {
+impl<B> VirtioDevice for Vsock<B>
+where
+    B: VsockBackend,
+{
     fn device_type(&self) -> u32 {
         VirtioDeviceType::TYPE_VSOCK as u32
     }

vm-virtio/src/vsock/mod.rs

@@ -14,6 +14,8 @@ mod packet;
 mod unix;
 
 pub use self::device::Vsock;
+pub use self::unix::VsockUnixBackend;
+pub use self::unix::VsockUnixError;
 
 use std::os::unix::io::RawFd;
 

vm-virtio/src/vsock/unix/mod.rs

@@ -13,6 +13,7 @@ mod muxer_killq;
 mod muxer_rxq;
 
 pub use muxer::VsockMuxer as VsockUnixBackend;
+pub use Error as VsockUnixError;
 
 mod defs {
     /// Maximum number of established connections that we can handle.

vmm/src/device_manager.rs

@@ -76,6 +76,12 @@ pub enum DeviceManagerError {
     /// Cannot create virtio-vsock device
     CreateVirtioVsock(io::Error),
 
+    /// Failed converting Path to &str for the virtio-vsock device.
+    CreateVsockConvertPath,
+
+    /// Cannot create virtio-vsock backend
+    CreateVsockBackend(vm_virtio::vsock::VsockUnixError),
+
     /// Failed parsing disk image format
     DetectImageType(qcow::Error),
 
@@ -801,7 +807,15 @@ impl DeviceManager {
         // Add vsock if required
         if let Some(vsock_list_cfg) = &vm_info.vm_cfg.vsock {
             for vsock_cfg in vsock_list_cfg.iter() {
-                let vsock_device = vm_virtio::Vsock::new(vsock_cfg.cid)
+                let socket_path = vsock_cfg
+                    .sock
+                    .to_str()
+                    .ok_or(DeviceManagerError::CreateVsockConvertPath)?;
+                let backend =
+                    vm_virtio::vsock::VsockUnixBackend::new(vsock_cfg.cid, socket_path.to_string())
+                        .map_err(DeviceManagerError::CreateVsockBackend)?;
+
+                let vsock_device = vm_virtio::Vsock::new(vsock_cfg.cid, backend)
                     .map_err(DeviceManagerError::CreateVirtioVsock)?;
 
                 DeviceManager::add_virtio_pci_device(