refactor(vmm): Remove code for restoring old major version snapshots

The snapshot versioning follows the semantic versioning (i.e. snapshot
restore is allowed only if the restore major version is same as the
snapshot major version and the restore minor version is greater than or
equal to the snapshot minor version). We already bumped the major
version up multiple times since we added `mmds_version` state. That
means snapshots taken when `mmds_version` didn't exist are not able to
be restored in the current version. The code to restore such snapshots
is no longer needed.

Signed-off-by: Takahiro Itazuri <[email protected]>

Author: zulinx86

src/vmm/src/device_manager/persist.rs

@@ -556,20 +556,11 @@ impl<'a> Persist<'a> for MMIODeviceManager {
             )?;
         }
 
-        // If the snapshot has the mmds version persisted, initialise the data store with it.
+        // Initialize MMDS if MMDS state is included.
         if let Some(mmds_version) = &state.mmds_version {
             constructor_args
                 .vm_resources
                 .set_mmds_version(mmds_version.clone().into(), constructor_args.instance_id)?;
-        } else if state
-            .net_devices
-            .iter()
-            .any(|dev| dev.device_state.mmds_ns.is_some())
-        {
-            // If there's at least one network device having an mmds_ns, it means
-            // that we are restoring from a version that did not persist the `MmdsVersionState`.
-            // Init with the default.
-            constructor_args.vm_resources.mmds_or_default()?;
         }
 
         for net_state in &state.net_devices {