feat(vsock): run UdsVsock as a vhost-user backend

alioth-cli/src/vu.rs

@@ -22,6 +22,7 @@ use alioth::mem::mapped::RamBus;
 use alioth::virtio::dev::blk::BlkFileParam;
 use alioth::virtio::dev::fs::shared_dir::SharedDirParam;
 use alioth::virtio::dev::net::tap::NetTapParam;
+use alioth::virtio::dev::vsock::UdsVsockParam;
 use alioth::virtio::dev::{DevParam, Virtio, VirtioDevice};
 use alioth::virtio::vu::backend::{VuBackend, VuEventfd, VuIrqSender};
 use clap::{Args, Subcommand};
@@ -88,6 +89,8 @@ pub enum DevType {
     Blk(DevArgs<BlkFileParam>),
     /// VirtIO filesystem device backed by a shared host directory.
     Fs(DevArgs<SharedDirParam>),
+    /// VirtIO vsock device backed by a Unix domain socket.
+    Vsock(DevArgs<UdsVsockParam>),
 }
 
 #[derive(Args, Debug, Clone)]
@@ -138,6 +141,7 @@ pub fn start(args: VuArgs) -> Result<(), Error> {
             DevType::Net(args) => create_dev(format!("net-{index}"), args, memory.clone()),
             DevType::Blk(args) => create_dev(format!("blk-{index}"), args, memory.clone()),
             DevType::Fs(args) => create_dev(format!("fs-{index}"), args, memory.clone()),
+            DevType::Vsock(args) => create_dev(format!("vsock-{index}"), args, memory.clone()),
         }?;
         let (conn, _) = listener.accept().context(error::Accept)?;
         let backend = VuBackend::new(conn, dev, memory).context(error::CreateVu)?;

alioth/src/virtio/dev/vsock/uds_vsock.rs

@@ -809,6 +809,9 @@ impl VirtioMio for UdsVsock {
                 log::error!("{}: failed to deregister socket: {err}", self.name);
             }
         }
+        if let Err(err) = registry.deregister(&mut SourceFd(&self.listener.as_raw_fd())) {
+            log::error!("{}: failed to deregister listener: {err}", self.name);
+        }
         self.host_ports.clear();
         self.next_port = 1024;
     }

alioth/src/vm/config.rs

@@ -36,7 +36,7 @@ use crate::{
 };
 
 #[cfg(target_os = "linux")]
-#[derive(Debug, PartialEq, Eq, Deserialize, Help)]
+#[derive(Debug, Clone, PartialEq, Eq, Deserialize, Help)]
 pub struct VuSocket {
     pub socket: Box<Path>,
 }
@@ -88,6 +88,10 @@ pub enum VsockParam {
     /// Vsock device mapped to a Unix domain socket.
     #[serde(alias = "uds")]
     Uds(UdsVsockParam),
+    #[cfg(target_os = "linux")]
+    /// Vsock device backed by a vhost-user process.
+    #[serde(alias = "vu")]
+    Vu(VuSocket),
 }
 
 #[derive(Debug, Default, PartialEq, Eq, Deserialize)]

alioth/src/vm/vm.rs

@@ -237,6 +237,14 @@ where
                 #[cfg(target_os = "linux")]
                 VsockParam::Vhost(p) => vm.add_virtio_dev("vhost-vsock", p),
                 VsockParam::Uds(p) => vm.add_virtio_dev("uds-vsock", p),
+                #[cfg(target_os = "linux")]
+                VsockParam::Vu(s) => {
+                    let p = VuFrontendParam {
+                        id: DeviceId::Socket,
+                        socket: s.socket,
+                    };
+                    vm.add_virtio_dev("vu-vsock", p)
+                }
             }?;
         }