vmm: Add a VmRestore command

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

vmm/src/migration.rs

@@ -2,10 +2,13 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 
+use crate::config::VmConfig;
+use crate::vm::{VmSnapshot, VM_SNAPSHOT_ID};
 use anyhow::anyhow;
 use std::fs::File;
 use std::io::BufReader;
 use std::path::PathBuf;
+use std::sync::{Arc, Mutex};
 use url::Url;
 use vm_migration::{MigratableError, Snapshot};
 
@@ -59,3 +62,23 @@ pub fn recv_vm_snapshot(source_url: &str) -> std::result::Result<Snapshot, Migra
         ))),
     }
 }
+
+pub fn vm_config_from_snapshot(
+    snapshot: &Snapshot,
+) -> std::result::Result<Arc<Mutex<VmConfig>>, MigratableError> {
+    if let Some(vm_section) = snapshot
+        .snapshot_data
+        .get(&format!("{}-section", VM_SNAPSHOT_ID))
+    {
+        let vm_snapshot: VmSnapshot =
+            serde_json::from_slice(&vm_section.snapshot).map_err(|e| {
+                MigratableError::Restore(anyhow!("Could not deserialize VM snapshot {}", e))
+            })?;
+
+        return Ok(vm_snapshot.config);
+    }
+
+    Err(MigratableError::Restore(anyhow!(
+        "Could not find VM config snapshot section"
+    )))
+}