libvirt: Add Ignition config injection support

Add support for injecting Ignition configuration files into libvirt
VMs via QEMU's fw_cfg mechanism (x86_64/aarch64) and virtio-blk
(s390x/ppc64le). This enables first-boot provisioning for bootc-based
systems that use Ignition, matching the ephemeral implementation.

Signed-off-by: gursewak1997 <gursmangat@gmail.com>

Author: gursewak1997

crates/integration-tests/src/main.rs

@@ -13,6 +13,7 @@ pub(crate) use integration_tests::{
 
 mod tests {
     pub mod libvirt_base_disks;
+    pub mod libvirt_ignition;
     pub mod libvirt_port_forward;
     pub mod libvirt_upload_disk;
     pub mod libvirt_verb;

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

@@ -0,0 +1,172 @@
+//! Integration tests for Ignition config injection in libvirt VMs
+
+use integration_tests::integration_test;
+use itest::TestResult;
+use scopeguard::defer;
+use tempfile::TempDir;
+use xshell::cmd;
+
+use std::fs;
+
+use camino::Utf8Path;
+
+use crate::{get_bck_command, shell, LIBVIRT_INTEGRATION_TEST_LABEL};
+
+/// Generate a random alphanumeric suffix for VM names to avoid collisions
+fn random_suffix() -> String {
+    use rand::{distr::Alphanumeric, Rng};
+    rand::rng()
+        .sample_iter(&Alphanumeric)
+        .take(8)
+        .map(char::from)
+        .collect()
+}
+
+/// Fedora CoreOS image that supports Ignition
+const FCOS_IMAGE: &str = "quay.io/fedora/fedora-coreos:stable";
+
+/// Test that Ignition config injection mechanism works for libvirt
+///
+/// This test verifies that the Ignition config injection mechanism is working
+/// by checking that the VM can be created with --ignition flag and that the
+/// config file is properly stored.
+fn test_libvirt_ignition_works() -> TestResult {
+    let sh = shell()?;
+    let bck = get_bck_command()?;
+    let label = LIBVIRT_INTEGRATION_TEST_LABEL;
+
+    // Pull FCOS image first
+    cmd!(sh, "podman pull -q {FCOS_IMAGE}").run()?;
+
+    // Create a temporary Ignition config
+    let temp_dir = TempDir::new()?;
+    let config_path = Utf8Path::from_path(temp_dir.path())
+        .expect("temp dir is not utf8")
+        .join("config.ign");
+
+    // Minimal valid Ignition config (v3.3.0 for FCOS)
+    let ignition_config = r#"{"ignition": {"version": "3.3.0"}}"#;
+    fs::write(&config_path, ignition_config)?;
+
+    // Generate a unique VM name to avoid conflicts
+    let vm_name = format!("test-ignition-{}", random_suffix());
+
+    // Create VM with Ignition config
+    // We use --ssh-wait to wait for the VM to boot and verify SSH connectivity
+    // FCOS requires --filesystem to be specified
+    let output = cmd!(
+        sh,
+        "{bck} libvirt run --name {vm_name} --label {label} --ignition {config_path} --filesystem xfs --ssh-wait --memory 2G --cpus 2 {FCOS_IMAGE}"
+    )
+    .ignore_status()
+    .output()?;
+
+    // Cleanup: remove the VM
+    defer! {
+        let _ = cmd!(sh, "{bck} libvirt rm {vm_name} --force").run();
+    }
+
+    // Check that the command succeeded
+    if !output.status.success() {
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        panic!(
+            "Failed to create VM with Ignition config.\nStdout: {}\nStderr: {}",
+            stdout, stderr
+        );
+    }
+
+    // Verify the VM was created
+    let vm_list = cmd!(sh, "{bck} libvirt list").read()?;
+    assert!(
+        vm_list.contains(&vm_name),
+        "VM should be listed after creation"
+    );
+
+    println!("Ignition config injection test passed");
+    Ok(())
+}
+integration_test!(test_libvirt_ignition_works);
+
+/// Test that Ignition config validation rejects nonexistent files
+fn test_libvirt_ignition_invalid_path() -> TestResult {
+    let sh = shell()?;
+    let bck = get_bck_command()?;
+    let label = LIBVIRT_INTEGRATION_TEST_LABEL;
+
+    // Pull FCOS image first
+    cmd!(sh, "podman pull -q {FCOS_IMAGE}").run()?;
+
+    let temp = TempDir::new()?;
+    let nonexistent_path = Utf8Path::from_path(temp.path())
+        .expect("temp dir is not utf8")
+        .join("nonexistent-config.ign");
+
+    let vm_name = format!("test-ignition-invalid-{}", random_suffix());
+
+    let output = cmd!(
+        sh,
+        "{bck} libvirt run --name {vm_name} --label {label} --ignition {nonexistent_path} {FCOS_IMAGE}"
+    )
+    .ignore_status()
+    .output()?;
+
+    assert!(
+        !output.status.success(),
+        "Should fail with nonexistent Ignition config file"
+    );
+
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(
+        stderr.contains("not found"),
+        "Error should mention missing file: {}",
+        stderr
+    );
+
+    println!("Ignition invalid path test passed");
+    Ok(())
+}
+integration_test!(test_libvirt_ignition_invalid_path);
+
+/// Test that Ignition is rejected for images that don't support it
+fn test_libvirt_ignition_unsupported_image() -> TestResult {
+    let sh = shell()?;
+    let bck = get_bck_command()?;
+    let label = LIBVIRT_INTEGRATION_TEST_LABEL;
+
+    // Use standard bootc image that doesn't have Ignition support
+    let image = "quay.io/centos-bootc/centos-bootc:stream10";
+
+    let temp_dir = TempDir::new()?;
+    let config_path = Utf8Path::from_path(temp_dir.path())
+        .expect("temp dir is not utf8")
+        .join("config.ign");
+
+    let ignition_config = r#"{"ignition": {"version": "3.3.0"}}"#;
+    fs::write(&config_path, ignition_config)?;
+
+    let vm_name = format!("test-ignition-unsupported-{}", random_suffix());
+
+    let output = cmd!(
+        sh,
+        "{bck} libvirt run --name {vm_name} --label {label} --ignition {config_path} {image}"
+    )
+    .ignore_status()
+    .output()?;
+
+    assert!(
+        !output.status.success(),
+        "Should fail when using --ignition with non-Ignition image"
+    );
+
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(
+        stderr.contains("does not support Ignition"),
+        "Error should mention missing Ignition support: {}",
+        stderr
+    );
+
+    println!("Ignition unsupported image test passed");
+    Ok(())
+}
+integration_test!(test_libvirt_ignition_unsupported_image);

crates/kit/src/libvirt/domain.rs

@@ -55,6 +55,8 @@ pub struct DomainBuilder {
     nvram_template: Option<String>, // Custom NVRAM template with enrolled keys
     nvram_format: Option<String>,   // Format of NVRAM template (raw, qcow2)
     firmware_log: Option<FirmwareLogOutput>, // OVMF debug log output via isa-debugcon
+    fw_cfg_entries: Vec<(String, String)>, // fw_cfg entries (name, file_path)
+    ignition_disk_path: Option<String>, // Path to Ignition config for virtio-blk injection
 }
 
 impl Default for DomainBuilder {
@@ -86,6 +88,8 @@ impl DomainBuilder {
             nvram_template: None,
             nvram_format: None,
             firmware_log: None,
+            fw_cfg_entries: Vec::new(),
+            ignition_disk_path: None,
         }
     }
 
@@ -204,6 +208,21 @@ impl DomainBuilder {
         self
     }
 
+    /// Add a fw_cfg entry for passing config files to the guest
+    ///
+    /// This is used for Ignition config injection on x86_64/aarch64.
+    /// The entry will be converted to a QEMU commandline argument in the domain XML.
+    pub fn add_fw_cfg(mut self, name: String, file_path: String) -> Self {
+        self.fw_cfg_entries.push((name, file_path));
+        self
+    }
+
+    /// Set Ignition config disk path for virtio-blk injection (s390x/ppc64le)
+    pub fn with_ignition_disk(mut self, disk_path: String) -> Self {
+        self.ignition_disk_path = Some(disk_path);
+        self
+    }
+
     /// Build the domain XML
     pub fn build_xml(self) -> Result<String> {
         let name = self.name.ok_or_else(|| eyre!("Domain name is required"))?;
@@ -221,7 +240,7 @@ impl DomainBuilder {
         let mut writer = XmlWriter::new();
 
         // Root domain element
-        let domain_attrs = if self.qemu_args.is_empty() {
+        let domain_attrs = if self.qemu_args.is_empty() && self.fw_cfg_entries.is_empty() {
             vec![("type", "kvm")]
         } else {
             vec![
@@ -379,6 +398,17 @@ impl DomainBuilder {
             writer.end_element("disk")?;
         }
 
+        // Ignition config disk (virtio-blk with serial="ignition" for s390x/ppc64le)
+        if let Some(ref ignition_disk) = self.ignition_disk_path {
+            writer.start_element("disk", &[("type", "file"), ("device", "disk")])?;
+            writer.write_empty_element("driver", &[("name", "qemu"), ("type", "raw")])?;
+            writer.write_empty_element("source", &[("file", ignition_disk)])?;
+            writer.write_empty_element("target", &[("dev", "vdb"), ("bus", "virtio")])?;
+            writer.write_text_element("serial", "ignition")?;
+            writer.write_empty_element("readonly", &[])?;
+            writer.end_element("disk")?;
+        }
+
         // Network
         let network_config = self.network.as_deref().unwrap_or("default");
         match network_config {
@@ -483,9 +513,22 @@ impl DomainBuilder {
 
         writer.end_element("devices")?;
 
-        // QEMU commandline section (if we have QEMU args)
-        if !self.qemu_args.is_empty() {
+        // QEMU commandline section (if we have QEMU args or fw_cfg entries)
+        if !self.qemu_args.is_empty() || !self.fw_cfg_entries.is_empty() {
             writer.start_element("qemu:commandline", &[])?;
+
+            // Add fw_cfg entries first
+            // Format: -fw_cfg name=<name>,file=<path>
+            // Verified working: config accessible at /sys/firmware/qemu_fw_cfg/by_name/<name>/raw
+            for (name, file_path) in &self.fw_cfg_entries {
+                writer.write_empty_element("qemu:arg", &[("value", "-fw_cfg")])?;
+                writer.write_empty_element(
+                    "qemu:arg",
+                    &[("value", &format!("name={},file={}", name, file_path))],
+                )?;
+            }
+
+            // Then add other QEMU args
             for arg in &self.qemu_args {
                 writer.write_empty_element("qemu:arg", &[("value", arg)])?;
             }

crates/kit/src/libvirt/rm.rs

@@ -5,6 +5,7 @@
 
 use clap::Parser;
 use color_eyre::Result;
+use tracing::debug;
 
 /// Check if a domain is persistent (vs transient)
 ///
@@ -108,6 +109,26 @@ fn remove_vm_impl(
         }
     }
 
+    // Remove Ignition config file if it exists (stored in metadata)
+    // Parse domain XML to get the ignition persistent path
+    if let Ok(xml_output) = global_opts
+        .virsh_command()
+        .args(&["dumpxml", vm_name])
+        .output()
+    {
+        if let Ok(xml_str) = String::from_utf8(xml_output.stdout) {
+            if let Ok(dom) = crate::xml_utils::parse_xml_dom(&xml_str) {
+                if let Some(ignition_path_node) = dom.find("bootc:ignition-persistent-path") {
+                    let ignition_path = ignition_path_node.text_content().trim();
+                    if !ignition_path.is_empty() && std::path::Path::new(ignition_path).exists() {
+                        debug!("Removing Ignition config file: {}", ignition_path);
+                        let _ = std::fs::remove_file(ignition_path); // Don't fail if this fails
+                    }
+                }
+            }
+        }
+    }
+
     // Remove libvirt domain with nvram and storage
     let output = global_opts
         .virsh_command()