Add --virtiofsd CLI option and VIRTIOFSD_BIN env var support

.gitignore

@@ -1 +1,2 @@
-target/
+target/
+.flox

crates/bcvk-qemu/src/virtiofsd.rs

@@ -21,6 +21,8 @@ pub struct VirtiofsConfig {
     pub readonly: bool,
     /// Optional log file path for virtiofsd output.
     pub log_file: Option<Utf8PathBuf>,
+    /// Optional explicit path to virtiofsd binary (overrides auto-detection).
+    pub virtiofsd_binary: Option<Utf8PathBuf>,
 }
 
 impl Default for VirtiofsConfig {
@@ -32,6 +34,7 @@ impl Default for VirtiofsConfig {
             // We don't need to write to this, there's a transient overlay
             readonly: true,
             log_file: None,
+            virtiofsd_binary: None,
         }
     }
 }
@@ -61,32 +64,42 @@ pub async fn spawn_virtiofsd_async(config: &VirtiofsConfig) -> Result<tokio::pro
     // Validate configuration
     validate_virtiofsd_config(config)?;
 
-    // Try common virtiofsd binary locations
-    let virtiofsd_paths = [
-        "/usr/libexec/virtiofsd",
-        "/usr/bin/virtiofsd",
-        "/usr/local/bin/virtiofsd",
-        "/usr/lib/virtiofsd",
-    ];
-
-    let virtiofsd_binary = virtiofsd_paths
-        .iter()
-        .find(|path| std::path::Path::new(path).exists())
-        .ok_or_else(|| {
-            eyre!(
-                "virtiofsd binary not found. Searched paths: {}. Please install virtiofsd.",
-                virtiofsd_paths.join(", ")
-            )
-        })?;
+    // Resolve virtiofsd binary: explicit override or path search
+    let virtiofsd_binary: String = if let Some(ref path) = config.virtiofsd_binary {
+        if !path.exists() {
+            return Err(eyre!("Explicit virtiofsd binary not found at: {}", path));
+        }
+        camino::absolute_utf8(path)?.to_string()
+    } else {
+        // Try common virtiofsd binary locations
+        let virtiofsd_paths = [
+            "/usr/libexec/virtiofsd",
+            "/usr/bin/virtiofsd",
+            "/usr/local/bin/virtiofsd",
+            "/usr/lib/virtiofsd",
+        ];
+
+        virtiofsd_paths
+            .iter()
+            .find(|path| std::path::Path::new(path).exists())
+            .ok_or_else(|| {
+                eyre!(
+                    "virtiofsd binary not found. Searched paths: {}. \
+                     Set --virtiofsd or VIRTIOFSD_BIN to specify the path explicitly.",
+                    virtiofsd_paths.join(", ")
+                )
+            })?
+            .to_string()
+    };
 
     // Check if virtiofsd supports --readonly flag
-    let supports_readonly = virtiofsd_supports_readonly(virtiofsd_binary).await;
+    let supports_readonly = virtiofsd_supports_readonly(&virtiofsd_binary).await;
     debug!(
         "virtiofsd at {} supports --readonly: {}",
         virtiofsd_binary, supports_readonly
     );
 
-    let mut cmd = tokio::process::Command::new(virtiofsd_binary);
+    let mut cmd = tokio::process::Command::new(&virtiofsd_binary);
     // SAFETY: This API is safe to call in a forked child.
     #[allow(unsafe_code)]
     unsafe {
@@ -148,13 +161,13 @@ pub async fn spawn_virtiofsd_async(config: &VirtiofsConfig) -> Result<tokio::pro
     let child = cmd.spawn().with_context(|| {
         format!(
             "Failed to spawn virtiofsd. Binary: {}, Socket: {}, Shared dir: {}",
-            virtiofsd_binary, config.socket_path, config.shared_dir
+            &virtiofsd_binary, config.socket_path, config.shared_dir
         )
     })?;
 
     debug!(
         "Spawned virtiofsd: binary={}, socket={}, shared_dir={}, debug={}, log_file={:?}",
-        virtiofsd_binary, config.socket_path, config.shared_dir, config.debug, config.log_file
+        &virtiofsd_binary, config.socket_path, config.shared_dir, config.debug, config.log_file
     );
 
     Ok(child)

crates/kit/Cargo.toml

@@ -9,7 +9,7 @@ base64 = "0.22"
 chrono = { version = "0.4", features = ["serde"] }
 const_format = { workspace = true }
 color-eyre = { workspace = true }
-clap = { version = "4.4", features = ["derive"] }
+clap = { version = "4.4", features = ["derive", "env"] }
 clap_mangen = { version = "0.2.20", optional = true }
 data-encoding = { version = "2.9" }
 dirs = "5.0"

crates/kit/src/libvirt/base_disks.rs

@@ -18,6 +18,7 @@ pub fn find_or_create_base_disk(
     image_digest: &str,
     install_options: &InstallOptions,
     connect_uri: Option<&str>,
+    virtiofsd_binary: Option<String>,
 ) -> Result<Utf8PathBuf> {
     let metadata = DiskImageMetadata::from(install_options, image_digest, source_image);
     let cache_hash = metadata.compute_cache_hash();
@@ -67,6 +68,7 @@ pub fn find_or_create_base_disk(
         image_digest,
         install_options,
         connect_uri,
+        virtiofsd_binary,
     )?;
 
     Ok(base_disk_path)
@@ -79,6 +81,7 @@ fn create_base_disk(
     image_digest: &str,
     install_options: &InstallOptions,
     connect_uri: Option<&str>,
+    virtiofsd_binary: Option<String>,
 ) -> Result<()> {
     use crate::run_ephemeral::CommonVmOpts;
     use crate::to_disk::{Format, ToDiskAdditionalOpts, ToDiskOpts};
@@ -116,6 +119,7 @@ fn create_base_disk(
                 memory: crate::common_opts::MemoryOpts {
                     memory: super::LIBVIRT_DEFAULT_MEMORY.to_string(),
                 },
+                virtiofsd_binary,
                 ..Default::default()
             },
             ..Default::default()

crates/kit/src/libvirt/base_disks_cli.rs

@@ -77,6 +77,7 @@ pub fn run_create(
         &image_digest,
         &opts.install_options,
         connect_uri,
+        None,
     )?;
     println!("Created base disk: {path}");
 

crates/kit/src/libvirt/run.rs

@@ -305,6 +305,10 @@ pub struct LibvirtRunOpts {
     #[clap(long = "ignition")]
     pub ignition_config: Option<Utf8PathBuf>,
 
+    /// Path to virtiofsd binary (overrides auto-detection for disk creation)
+    #[clap(long = "virtiofsd", env = "VIRTIOFSD_BIN")]
+    pub virtiofsd_binary: Option<String>,
+
     /// Additional metadata key-value pairs (used internally, not exposed via CLI)
     #[clap(skip)]
     pub metadata: std::collections::HashMap<String, String>,
@@ -488,6 +492,7 @@ pub fn run(global_opts: &crate::libvirt::LibvirtOptions, mut opts: LibvirtRunOpt
         &image_digest,
         &opts.install,
         connect_uri,
+        opts.virtiofsd_binary.take(),
     )
     .with_context(|| "Failed to find or create base disk")?;
 

crates/kit/src/run_ephemeral.rs

@@ -218,6 +218,13 @@ pub struct CommonVmOpts {
         help = "Generate SSH keypair and inject via systemd credentials"
     )]
     pub ssh_keygen: bool,
+
+    #[clap(
+        long = "virtiofsd",
+        env = "VIRTIOFSD_BIN",
+        help = "Path to virtiofsd binary (overrides auto-detection)"
+    )]
+    pub virtiofsd_binary: Option<String>,
 }
 
 impl CommonVmOpts {
@@ -1171,6 +1178,7 @@ pub(crate) async fn run_impl(opts: RunEphemeralOpts) -> Result<()> {
                 debug: false,
                 readonly: is_readonly,
                 log_file: Some(format!("/run/virtiofsd-{}.log", mount_name_str).into()),
+                virtiofsd_binary: opts.common.virtiofsd_binary.as_deref().map(Into::into),
             };
             additional_mounts.push((virtiofsd_config, tag.clone()));
 
@@ -1329,6 +1337,7 @@ StandardOutput=file:/dev/virtio-ports/executestatus
     main_virtiofsd_config.debug = std::env::var("DEBUG_MODE").is_ok();
     // Always log virtiofsd output for debugging
     main_virtiofsd_config.log_file = Some("/run/virtiofsd.log".into());
+    main_virtiofsd_config.virtiofsd_binary = opts.common.virtiofsd_binary.as_deref().map(Into::into);
 
     std::fs::create_dir_all(CONTAINER_STATEDIR)?;