pci: support snapshotting VirtIO PCI devices

Support serializing the device-specific and transport state of a VirtIO
device that uses the PCI transport.

Signed-off-by: Babis Chalios <[email protected]>

Author: bchalios

src/vmm/src/builder.rs

@@ -451,6 +451,8 @@ pub fn build_microvm_from_snapshot(
     // Restore the boot source config paths.
     vm_resources.boot_source.config = microvm_state.vm_info.boot_source;
 
+    let vm = Arc::new(vm);
+
     // Restore devices states.
     // Restoring VMGenID injects an interrupt in the guest to notify it about the new generation
     // ID. As a result, we need to restore DeviceManager after restoring the KVM state, otherwise
@@ -473,7 +475,7 @@ pub fn build_microvm_from_snapshot(
         instance_info: instance_info.clone(),
         shutdown_exit_code: None,
         kvm,
-        vm: Arc::new(vm),
+        vm,
         uffd,
         vcpus_handles: Vec::new(),
         vcpus_exit_evt,

src/vmm/src/device_manager/mod.rs

@@ -309,7 +309,7 @@ pub enum DevicePersistError {
 
 pub struct DeviceRestoreArgs<'a> {
     pub mem: &'a GuestMemoryMmap,
-    pub vm: &'a Vm,
+    pub vm: &'a Arc<Vm>,
     pub event_manager: &'a mut EventManager,
     pub vcpus_exit_evt: &'a EventFd,
     pub vm_resources: &'a mut VmResources,
@@ -384,6 +384,11 @@ impl<'a> Persist<'a> for DeviceManager {
         // Restore PCI devices
         let pci_ctor_args = PciDevicesConstructorArgs {
             resource_allocator: &resource_allocator,
+            vm: constructor_args.vm.clone(),
+            mem: constructor_args.mem,
+            vm_resources: constructor_args.vm_resources,
+            instance_id: constructor_args.instance_id,
+            restored_from_file: constructor_args.restored_from_file,
         };
         let pci_devices = PciDevices::restore(pci_ctor_args, &state.pci_state)?;