vmm: add info! message on graceful shutdown

This message makes it easier to confirm a successful shutdown when
scanning logs during development and in production. If the message is
missing and the last log entry is not an error, the most likely cause
is a livelock (e.g. contention on a lock) introduced while developing
new Cloud Hypervisor features.

Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com

src/main.rs

@@ -15,7 +15,7 @@ use std::{env, io};
 use clap::{Arg, ArgAction, ArgGroup, ArgMatches, Command};
 use event_monitor::event;
 use libc::EFD_NONBLOCK;
-use log::{LevelFilter, error, warn};
+use log::{LevelFilter, error, info, warn};
 use option_parser::OptionParser;
 use seccompiler::SeccompAction;
 use signal_hook::consts::SIGSYS;
@@ -891,6 +891,7 @@ fn main() {
     let exit_code = match start_vmm(cmd_arguments) {
         Ok(path) => {
             path.map(|s| std::fs::remove_file(s).ok());
+            info!("Cloud Hypervisor exited successfully");
             0
         }
         Err(top_error) => {