separate boot source config from runtime details

Signed-off-by: Diana Popa <dpopa@amazon.com>

Author: dianpopa

src/vmm/src/builder.rs

@@ -78,7 +78,7 @@ pub enum StartMicrovmError {
     KernelLoader(linux_loader::loader::Error),
     /// Cannot load command line string.
     LoadCommandline(linux_loader::loader::Error),
-    /// Cannot start the VM because the kernel was not configured.
+    /// Cannot start the VM because the kernel builder was not configured.
     MissingKernelConfig,
     /// Cannot start the VM because the size of the guest memory  was not specified.
     MissingMemSizeConfig,
@@ -326,7 +326,9 @@ pub fn build_microvm_for_boot(
     // Timestamp for measuring microVM boot duration.
     let request_ts = TimestampUs::default();
 
-    let boot_config = vm_resources.boot_source().ok_or(MissingKernelConfig)?;
+    let boot_config = vm_resources
+        .boot_source_builder()
+        .ok_or(MissingKernelConfig)?;
 
     let track_dirty_pages = vm_resources.track_dirty_pages();
     let guest_memory =

src/vmm/src/resources.rs

@@ -12,7 +12,9 @@ use utils::net::ipv4addr::is_link_local_valid;
 
 use crate::device_manager::persist::SharedDeviceType;
 use crate::vmm_config::balloon::*;
-use crate::vmm_config::boot_source::{BootConfig, BootSourceConfig, BootSourceConfigError};
+use crate::vmm_config::boot_source::{
+    BootConfig, BootSource, BootSourceConfig, BootSourceConfigError,
+};
 use crate::vmm_config::drive::*;
 use crate::vmm_config::instance_info::InstanceInfo;
 use crate::vmm_config::logger::{init_logger, LoggerConfig, LoggerConfigError};
@@ -99,8 +101,8 @@ pub struct VmmConfig {
 pub struct VmResources {
     /// The vCpu and memory configuration for this microVM.
     vm_config: VmConfig,
-    /// The boot configuration for this microVM.
-    boot_config: Option<BootConfig>,
+    /// The boot source spec (contains both config and builder) for this microVM.
+    boot_source: BootSource,
     /// The block devices.
     pub block: BlockBuilder,
     /// The vsock device.
@@ -146,7 +148,7 @@ impl VmResources {
             resources.update_vm_config(&machine_config)?;
         }
 
-        resources.set_boot_source(vmm_config.boot_source)?;
+        resources.build_boot_source(vmm_config.boot_source)?;
 
         for drive_config in vmm_config.block_devices.into_iter() {
             resources.set_block_device(drive_config)?;
@@ -340,8 +342,13 @@ impl VmResources {
     }
 
     /// Gets a reference to the boot source configuration.
-    pub fn boot_source(&self) -> Option<&BootConfig> {
-        self.boot_config.as_ref()
+    pub fn boot_source_config(&self) -> &BootSourceConfig {
+        &self.boot_source.config
+    }
+
+    /// Gets a reference to the boot source builder.
+    pub fn boot_source_builder(&self) -> Option<&BootConfig> {
+        self.boot_source.builder.as_ref()
     }
 
     /// Sets a balloon device to be attached when the VM starts.
@@ -358,15 +365,21 @@ impl VmResources {
         self.balloon.set(config)
     }
 
-    /// Set the guest boot source configuration.
-    pub fn set_boot_source(
+    /// Obtains the boot source hooks (kernel fd, commandline creation and validation).
+    pub fn build_boot_source(
         &mut self,
         boot_source_cfg: BootSourceConfig,
     ) -> Result<BootSourceConfigError> {
-        self.boot_config = Some(BootConfig::new(boot_source_cfg)?);
+        self.set_boot_source_config(boot_source_cfg);
+        self.boot_source.builder = Some(BootConfig::new(&self.boot_source_config())?);
         Ok(())
     }
 
+    /// Set the boot source configuration (contains raw kernel config details).
+    pub fn set_boot_source_config(&mut self, boot_source_cfg: BootSourceConfig) {
+        self.boot_source.config = boot_source_cfg;
+    }
+
     /// Inserts a block to be attached when the VM starts.
     // Only call this function as part of user configuration.
     // If the drive_id does not exist, a new Block Device Config is added to the list.
@@ -465,16 +478,10 @@ impl VmResources {
 
 impl From<&VmResources> for VmmConfig {
     fn from(resources: &VmResources) -> Self {
-        let boot_source = resources
-            .boot_config
-            .as_ref()
-            .map(BootSourceConfig::from)
-            .unwrap_or_default();
-
         VmmConfig {
             balloon_device: resources.balloon.get_config().ok(),
             block_devices: resources.block.configs(),
-            boot_source,
+            boot_source: resources.boot_source_config().clone(),
             logger: None,
             machine_config: Some(resources.vm_config.clone()),
             metrics: None,

src/vmm/src/rpc_interface.rs

@@ -483,7 +483,7 @@ impl<'a> PrebootApiController<'a> {
     fn set_boot_source(&mut self, cfg: BootSourceConfig) -> ActionResult {
         self.boot_path = true;
         self.vm_resources
-            .set_boot_source(cfg)
+            .build_boot_source(cfg)
             .map(|()| VmmData::Empty)
             .map_err(VmmActionError::BootSource)
     }

src/vmm/src/vmm_config/boot_source.rs

@@ -35,12 +35,6 @@ pub struct BootSourceConfig {
     pub boot_args: Option<String>,
 }
 
-impl From<&BootConfig> for BootSourceConfig {
-    fn from(cfg: &BootConfig) -> Self {
-        cfg.description.clone()
-    }
-}
-
 /// Errors associated with actions on `BootSourceConfig`.
 #[derive(Debug)]
 pub enum BootSourceConfigError {
@@ -69,21 +63,29 @@ impl Display for BootSourceConfigError {
     }
 }
 
-/// Holds the kernel configuration.
+/// Holds the kernel specification (both configuration as well as runtime details).
+#[derive(Default)]
+pub struct BootSource {
+    /// The boot source configuration.
+    pub config: BootSourceConfig,
+    /// The boot source builder (a boot source allocated and validated).
+    /// It is an option cause a resumed microVM does not need it.
+    pub builder: Option<BootConfig>,
+}
+
+/// Holds the kernel builder (created and validates based on BootSourceConfig).
 pub struct BootConfig {
     /// The commandline validated against correctness.
     pub cmdline: linux_loader::cmdline::Cmdline,
     /// The descriptor to the kernel file.
-    pub kernel_file: std::fs::File,
+    pub kernel_file: File,
     /// The descriptor to the initrd file, if there is one.
-    pub initrd_file: Option<std::fs::File>,
-    /// The configuration above fields are based on.
-    pub description: BootSourceConfig,
+    pub initrd_file: Option<File>,
 }
 
 impl BootConfig {
     /// Creates the BootConfig based on a given configuration.
-    pub fn new(cfg: BootSourceConfig) -> std::result::Result<Self, BootSourceConfigError> {
+    pub fn new(cfg: &BootSourceConfig) -> std::result::Result<Self, BootSourceConfigError> {
         use self::BootSourceConfigError::{
             InvalidInitrdPath, InvalidKernelCommandLine, InvalidKernelPath,
         };
@@ -107,8 +109,6 @@ impl BootConfig {
             cmdline,
             kernel_file,
             initrd_file,
-            // We can simply store original config since it doesn't support updates.
-            description: cfg,
         })
     }
 }