to-disk: Add support for --karg

For the same reason we propagate other options.

Note that we had incorrectly included karg in CommonVmOptions
but that can't work without direct kernel boot.

Signed-off-by: Colin Walters <walters@verbum.org>

Author: cgwalters

crates/integration-tests/src/tests/libvirt_verb.rs

@@ -356,6 +356,8 @@ pub fn test_libvirt_run_ssh_full_workflow() {
         LIBVIRT_INTEGRATION_TEST_LABEL,
         "--filesystem",
         "ext4",
+        "--karg",
+        "bcvk.test-install-karg=1",
         &test_image,
     ])
     .expect("Failed to run libvirt run with SSH");
@@ -375,9 +377,9 @@ pub fn test_libvirt_run_ssh_full_workflow() {
     println!("Waiting for VM to boot and SSH to become available...");
     std::thread::sleep(std::time::Duration::from_secs(30));
 
-    // Test SSH connection with simple command
-    println!("Testing SSH connection: echo 'hello world'");
-    let ssh_output = run_bcvk(&["libvirt", "ssh", &domain_name, "--", "echo", "hello world"])
+    // Test SSH connection and read kernel command line
+    println!("Testing SSH connection and validating karg");
+    let ssh_output = run_bcvk(&["libvirt", "ssh", &domain_name, "--", "cat", "/proc/cmdline"])
         .expect("Failed to run libvirt ssh command");
 
     println!("SSH stdout: {}", ssh_output.stdout);
@@ -388,17 +390,19 @@ pub fn test_libvirt_run_ssh_full_workflow() {
 
     // Check SSH results
     if !ssh_output.success() {
-        panic!("SSH connection failed: {}", ssh_output.stderr);
+        panic!(
+            "SSH connection failed: {}\nkernel cmdline: {}",
+            ssh_output.stderr, ssh_output.stdout
+        );
     }
 
-    // Verify we got the expected output
+    // Verify we got the expected karg in /proc/cmdline
     assert!(
-        ssh_output.stdout.contains("hello world"),
-        "Expected 'hello world' in SSH output. Got: {}",
+        ssh_output.stdout.contains("bcvk.test-install-karg=1"),
+        "Expected bcvk.test-install-karg=1 in kernel cmdline.\nActual cmdline: {}",
         ssh_output.stdout
     );
 
-    println!("✓ Successfully executed 'echo hello world' via SSH");
     println!("✓ Full libvirt run + SSH workflow test passed");
 }
 

crates/kit/src/cache_metadata.rs

@@ -153,13 +153,13 @@ impl DiskImageMetadata {
 
 impl DiskImageMetadata {
     /// Create new metadata from InstallOptions and image digest
-    pub fn from(options: &InstallOptions, image: &str, kernel_args: &[String]) -> Self {
+    pub fn from(options: &InstallOptions, image: &str) -> Self {
         Self {
             version: 1,
             digest: image.to_owned(),
             filesystem: options.filesystem.clone(),
             root_size: options.root_size.clone(),
-            kernel_args: kernel_args.to_vec(),
+            kernel_args: options.karg.clone(),
             composefs_native: options.composefs_native,
         }
     }
@@ -180,15 +180,14 @@ pub fn check_cached_disk(
     path: &Path,
     image_digest: &str,
     install_options: &InstallOptions,
-    kernel_args: &[String],
 ) -> Result<Result<(), ValidationError>> {
     if !path.exists() {
         tracing::debug!("Disk image {:?} does not exist", path);
         return Ok(Err(ValidationError::MissingFile));
     }
 
     // Create metadata for the current request to compute expected hash
-    let expected_meta = DiskImageMetadata::from(install_options, image_digest, kernel_args);
+    let expected_meta = DiskImageMetadata::from(install_options, image_digest);
     let expected_hash = expected_meta.compute_cache_hash();
 
     // Read the cache hash from the disk image
@@ -241,26 +240,16 @@ mod tests {
         let install_options1 = InstallOptions {
             filesystem: Some("ext4".to_string()),
             root_size: Some("20G".to_string()),
-            storage_path: None,
-            composefs_native: false,
+            ..Default::default()
         };
-        let metadata1 = DiskImageMetadata::from(
-            &install_options1,
-            "sha256:abc123",
-            &["console=ttyS0".to_string()],
-        );
+        let metadata1 = DiskImageMetadata::from(&install_options1, "sha256:abc123");
 
         let install_options2 = InstallOptions {
             filesystem: Some("ext4".to_string()),
             root_size: Some("20G".to_string()),
-            storage_path: None,
-            composefs_native: false,
+            ..Default::default()
         };
-        let metadata2 = DiskImageMetadata::from(
-            &install_options2,
-            "sha256:abc123",
-            &["console=ttyS0".to_string()],
-        );
+        let metadata2 = DiskImageMetadata::from(&install_options2, "sha256:abc123");
 
         // Same inputs should generate same hash
         assert_eq!(
@@ -272,14 +261,9 @@ mod tests {
         let install_options3 = InstallOptions {
             filesystem: Some("ext4".to_string()),
             root_size: Some("20G".to_string()),
-            storage_path: None,
-            composefs_native: false,
+            ..Default::default()
         };
-        let metadata3 = DiskImageMetadata::from(
-            &install_options3,
-            "sha256:xyz789",
-            &["console=ttyS0".to_string()],
-        );
+        let metadata3 = DiskImageMetadata::from(&install_options3, "sha256:xyz789");
 
         assert_ne!(
             metadata1.compute_cache_hash(),
@@ -290,14 +274,9 @@ mod tests {
         let install_options4 = InstallOptions {
             filesystem: Some("xfs".to_string()),
             root_size: Some("20G".to_string()),
-            storage_path: None,
-            composefs_native: false,
+            ..Default::default()
         };
-        let metadata4 = DiskImageMetadata::from(
-            &install_options4,
-            "sha256:abc123",
-            &["console=ttyS0".to_string()],
-        );
+        let metadata4 = DiskImageMetadata::from(&install_options4, "sha256:abc123");
 
         assert_ne!(
             metadata1.compute_cache_hash(),

crates/kit/src/install_options.rs

@@ -29,6 +29,10 @@ pub struct InstallOptions {
     )]
     pub storage_path: Option<Utf8PathBuf>,
 
+    #[clap(long)]
+    /// Set a kernel argument
+    pub karg: Vec<String>,
+
     /// Default to composefs-native storage
     #[clap(long)]
     pub composefs_native: bool,
@@ -49,6 +53,10 @@ impl InstallOptions {
             args.push(root_size.clone());
         }
 
+        for k in self.karg.iter() {
+            args.push(format!("--karg={k}"));
+        }
+
         if self.composefs_native {
             args.push("--composefs-native".to_owned());
         }

crates/kit/src/libvirt/base_disks.rs

@@ -17,10 +17,9 @@ pub fn find_or_create_base_disk(
     source_image: &str,
     image_digest: &str,
     install_options: &InstallOptions,
-    kernel_args: &[String],
     connect_uri: Option<&str>,
 ) -> Result<Utf8PathBuf> {
-    let metadata = DiskImageMetadata::from(install_options, image_digest, kernel_args);
+    let metadata = DiskImageMetadata::from(install_options, image_digest);
     let cache_hash = metadata.compute_cache_hash();
 
     // Extract short hash for filename (first 16 chars after "sha256:")
@@ -45,7 +44,6 @@ pub fn find_or_create_base_disk(
             base_disk_path.as_std_path(),
             image_digest,
             install_options,
-            kernel_args,
         )?
         .is_ok()
         {
@@ -68,7 +66,6 @@ pub fn find_or_create_base_disk(
         source_image,
         image_digest,
         install_options,
-        kernel_args,
         connect_uri,
     )?;
 
@@ -81,7 +78,6 @@ fn create_base_disk(
     source_image: &str,
     image_digest: &str,
     install_options: &InstallOptions,
-    kernel_args: &[String],
     connect_uri: Option<&str>,
 ) -> Result<()> {
     use crate::run_ephemeral::CommonVmOpts;
@@ -136,7 +132,6 @@ fn create_base_disk(
         temp_disk_path.as_std_path(),
         image_digest,
         install_options,
-        kernel_args,
     )
     .context("Querying cached disk")?;
 

crates/kit/src/libvirt/run.rs

@@ -179,7 +179,6 @@ pub fn run(global_opts: &crate::libvirt::LibvirtOptions, opts: LibvirtRunOpts) -
         &opts.image,
         &image_digest,
         &opts.install,
-        &[], // kernel_args
         connect_uri,
     )
     .with_context(|| "Failed to find or create base disk")?;

crates/kit/src/libvirt/upload.rs

@@ -42,10 +42,6 @@ pub struct LibvirtUploadOpts {
     /// Number of vCPUs for installation VM
     #[clap(long)]
     pub vcpus: Option<u32>,
-
-    /// Additional kernel arguments for installation
-    #[clap(long)]
-    pub karg: Vec<String>,
 }
 
 impl LibvirtUploadOpts {
@@ -219,7 +215,6 @@ pub fn run(global_opts: &crate::libvirt::LibvirtOptions, opts: LibvirtUploadOpts
             common: crate::run_ephemeral::CommonVmOpts {
                 memory: opts.memory.clone(),
                 vcpus: opts.vcpus,
-                kernel_args: opts.karg.clone(),
                 ..Default::default()
             },
             ..Default::default()

crates/kit/src/libvirt_upload_disk.rs

@@ -44,10 +44,6 @@ pub struct LibvirtUploadDiskOpts {
     #[clap(long)]
     pub vcpus: Option<u32>,
 
-    /// Additional kernel arguments for installation
-    #[clap(long)]
-    pub karg: Vec<String>,
-
     /// Skip uploading to libvirt (useful for testing)
     #[clap(long)]
     pub skip_upload: bool,
@@ -290,7 +286,6 @@ pub fn run(opts: LibvirtUploadDiskOpts) -> Result<()> {
             common: crate::run_ephemeral::CommonVmOpts {
                 memory: opts.memory.clone(),
                 vcpus: opts.vcpus,
-                kernel_args: opts.karg.clone(),
                 ..Default::default()
             },
             ..Default::default()

crates/kit/src/run_ephemeral.rs

@@ -165,9 +165,6 @@ pub struct CommonVmOpts {
     #[clap(long, help = "Number of vCPUs")]
     pub vcpus: Option<u32>,
 
-    #[clap(long = "karg", help = "Additional kernel command line arguments")]
-    pub kernel_args: Vec<String>,
-
     #[clap(long, help = "Enable console output to terminal for debugging")]
     pub console: bool,
 
@@ -257,6 +254,9 @@ pub struct RunEphemeralOpts {
         help = "Mount disk file as virtio-blk device at /dev/disk/by-id/virtio-<name>"
     )]
     pub mount_disk_files: Vec<String>,
+
+    #[clap(long = "karg", help = "Additional kernel command line arguments")]
+    pub kernel_args: Vec<String>,
 }
 
 /// Launch privileged container with QEMU+KVM for ephemeral VM, spawning as subprocess.
@@ -982,7 +982,7 @@ StandardOutput=file:/dev/virtio-ports/executestatus
         kernel_cmdline.push("ds=iid-datasource-none".to_string());
     }
 
-    kernel_cmdline.extend(opts.common.kernel_args.clone());
+    kernel_cmdline.extend(opts.kernel_args.clone());
 
     // TODO allocate unlinked unnamed file and pass via fd
     let mut tmp_swapfile = None;

crates/kit/src/to_disk.rs

@@ -310,7 +310,6 @@ pub fn run(opts: ToDiskOpts) -> Result<()> {
             opts.target_disk.as_std_path(),
             &image_digest,
             &opts.install,
-            &opts.additional.common.kernel_args,
         )? {
             Ok(()) => {
                 println!(
@@ -421,6 +420,7 @@ pub fn run(opts: ToDiskOpts) -> Result<()> {
             opts.target_disk,
             opts.additional.format.as_str()
         )], // Attach target disk
+        kernel_args: Default::default(),
     };
 
     // Phase 5: SSH-based VM configuration and execution
@@ -475,7 +475,6 @@ pub fn run(opts: ToDiskOpts) -> Result<()> {
                 &opts.source_image,
                 &opts.target_disk,
                 &opts.install,
-                &opts.additional.common.kernel_args,
                 &opts.additional.format,
             );
             if let Err(e) = write_result {
@@ -496,7 +495,6 @@ fn write_disk_metadata(
     source_image: &str,
     target_disk: &Utf8PathBuf,
     install_options: &InstallOptions,
-    kernel_args: &[String],
     format: &Format,
 ) -> Result<()> {
     // Note: xattrs work on regular files including raw and qcow2 images
@@ -507,7 +505,7 @@ fn write_disk_metadata(
     let digest = inspect.digest.to_string();
 
     // Prepare metadata using the new helper method
-    let metadata = DiskImageMetadata::from(install_options, &digest, kernel_args);
+    let metadata = DiskImageMetadata::from(install_options, &digest);
 
     // Write metadata using rustix fsetxattr
     let file = std::fs::OpenOptions::new()

docs/src/man/bcvk-ephemeral-run-ssh.md

@@ -33,10 +33,6 @@ Run ephemeral VM and SSH into it
 
     Number of vCPUs
 
-**--karg**=*KERNEL_ARGS*
-
-    Additional kernel command line arguments
-
 **--console**
 
     Enable console output to terminal for debugging
@@ -109,6 +105,10 @@ Run ephemeral VM and SSH into it
 
     Mount disk file as virtio-blk device at /dev/disk/by-id/virtio-<name>
 
+**--karg**=*KERNEL_ARGS*
+
+    Additional kernel command line arguments
+
 <!-- END GENERATED OPTIONS -->
 
 # EXAMPLES