muvm: gracefully disable hidpipe when /dev/input is missing

Treat missing /dev/input as non-fatal, skip hidpipe setup, and avoid starting guest hidpipe when host hidpipe is disabled.

Author: yzewei

crates/muvm/src/bin/muvm.rs

@@ -291,6 +291,7 @@ fn main() -> Result<ExitCode> {
         }
     }
 
+    let mut enable_hidpipe = false;
     if let Ok(run_path) = env::var("XDG_RUNTIME_DIR") {
         let pulse_path = Path::new(&run_path).join("pulse/native");
         if pulse_path.exists() {
@@ -309,19 +310,22 @@ fn main() -> Result<ExitCode> {
         }
 
         let hidpipe_path = Path::new(&run_path).join("hidpipe");
-        spawn_hidpipe_server(hidpipe_path.clone()).context("Failed to spawn hidpipe thread")?;
-        let hidpipe_path = CString::new(
-            hidpipe_path
-                .to_str()
-                .expect("hidpipe_path should not contain invalid UTF-8"),
-        )
-        .context("Failed to process `hidpipe` path as it contains NUL character")?;
+        enable_hidpipe =
+            spawn_hidpipe_server(hidpipe_path.clone()).context("Failed to spawn hidpipe thread")?;
+        if enable_hidpipe {
+            let hidpipe_path = CString::new(
+                hidpipe_path
+                    .to_str()
+                    .expect("hidpipe_path should not contain invalid UTF-8"),
+            )
+            .context("Failed to process `hidpipe` path as it contains NUL character")?;
 
-        // SAFETY: `hidpipe_path` is a pointer to a `CString` with long enough lifetime.
-        let err = unsafe { krun_add_vsock_port(ctx_id, HIDPIPE_SOCKET, hidpipe_path.as_ptr()) };
-        if err < 0 {
-            let err = Errno::from_raw_os_error(-err);
-            return Err(err).context("Failed to configure vsock for hidpipe socket");
+            // SAFETY: `hidpipe_path` is a pointer to a `CString` with long enough lifetime.
+            let err = unsafe { krun_add_vsock_port(ctx_id, HIDPIPE_SOCKET, hidpipe_path.as_ptr()) };
+            if err < 0 {
+                let err = Errno::from_raw_os_error(-err);
+                return Err(err).context("Failed to configure vsock for hidpipe socket");
+            }
         }
 
         let socket_dir = Path::new(&run_path).join("krun/socket");
@@ -413,6 +417,7 @@ fn main() -> Result<ExitCode> {
         cwd,
         init_commands,
         user_init_commands: options.user_init_commands,
+        enable_hidpipe,
     };
     let mut muvm_config_file = NamedTempFile::new()
         .context("Failed to create a temporary file to store the muvm guest config")?;

crates/muvm/src/guest/bin/muvm-guest.rs

@@ -147,12 +147,16 @@ fn main() -> Result<ExitCode> {
         setup_x11_forwarding(run_path, &host_display)?;
     }
 
-    let uid = options.uid;
-    thread::spawn(move || {
-        if catch_unwind(|| start_hidpipe(uid)).is_err() {
-            eprintln!("hidpipe thread crashed, input device passthrough will no longer function");
-        }
-    });
+    if options.enable_hidpipe {
+        let uid = options.uid;
+        thread::spawn(move || {
+            if catch_unwind(|| start_hidpipe(uid)).is_err() {
+                eprintln!(
+                    "hidpipe thread crashed, input device passthrough will no longer function"
+                );
+            }
+        });
+    }
 
     thread::spawn(|| {
         if catch_unwind(start_pwbridge).is_err() {

crates/muvm/src/hidpipe_server.rs

@@ -280,12 +280,18 @@ where
     }
 }
 
-pub fn spawn_hidpipe_server(socket_path: PathBuf) -> anyhow::Result<()> {
+pub fn spawn_hidpipe_server(socket_path: PathBuf) -> anyhow::Result<bool> {
     let mut evdevs = EvdevContainer::new();
     let epoll = Epoll::new(EpollCreateFlags::empty()).context("Failed to create epoll object")?;
-    for dir_ent in
-        fs::read_dir("/dev/input/").context("Failed to read \"/dev/input/\" directory")?
-    {
+    let dir_entries = match fs::read_dir("/dev/input/") {
+        Ok(entries) => entries,
+        Err(err) if err.kind() == ErrorKind::NotFound => {
+            debug!("Skipping hidpipe initialization: /dev/input is not present");
+            return Ok(false);
+        },
+        Err(err) => return Err(err).context("Failed to read \"/dev/input/\" directory"),
+    };
+    for dir_ent in dir_entries {
         let dir_ent = dir_ent.context("Failed to read directory entry")?;
         if dir_ent
             .file_type()
@@ -321,7 +327,7 @@ pub fn spawn_hidpipe_server(socket_path: PathBuf) -> anyhow::Result<()> {
         .unwrap();
 
     thread::spawn(move || run(evdevs, listen_sock, epoll));
-    Ok(())
+    Ok(true)
 }
 
 fn run(mut evdevs: EvdevContainer, listen_sock: UnixListener, epoll: Epoll) {

crates/muvm/src/utils/launch.rs

@@ -46,6 +46,12 @@ pub struct GuestConfiguration {
     pub cwd: PathBuf,
     pub init_commands: Vec<PathBuf>,
     pub user_init_commands: Vec<PathBuf>,
+    #[serde(default = "default_true")]
+    pub enable_hidpipe: bool,
+}
+
+fn default_true() -> bool {
+    true
 }
 
 pub const PULSE_SOCKET: u32 = 3333;