From 005ce38ffd9b53aefca411184e4fa38d9548c9c5 Mon Sep 17 00:00:00 2001
From: Leander Kohler <leander.kohler@cyberus-technology.de>
Date: Mon, 9 Mar 2026 16:35:34 +0100
Subject: [PATCH] main: add --no-shutdown

Add a CLI-only --no-shutdown flag that keeps the VMM process alive
after a guest-triggered shutdown.

Management software may still need the Cloud Hypervisor process
after the guest has powered off. Exposing this separately lets
management software, for example libvirt, keep the VMM around in a
way that is closer to QEMU.

The flag only affects the GuestExit path. Fatal exits and other
existing VMM shutdown paths remain unchanged.

On-behalf-of: SAP leander.kohler@sap.com
Signed-off-by: Leander Kohler <leander.kohler@cyberus-technology.de>
---
 cloud-hypervisor/src/main.rs |  8 ++++++++
 vmm/src/lib.rs               | 19 ++++++++++++++++---
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/cloud-hypervisor/src/main.rs b/cloud-hypervisor/src/main.rs
index 06ef1fe30..51b1f38fd 100644
--- a/cloud-hypervisor/src/main.rs
+++ b/cloud-hypervisor/src/main.rs
@@ -373,6 +373,12 @@ fn get_cli_options_sorted(
             .num_args(1..)
             .action(ArgAction::Append)
             .group("vm-config"),
+        Arg::new("no-shutdown")
+            .long("no-shutdown")
+            .help("Do not exit the VMM when the guest shuts down")
+            .num_args(0)
+            .action(ArgAction::SetTrue)
+            .group("vmm-config"),
         Arg::new("numa")
             .long("numa")
             .help(NumaConfig::SYNTAX)
@@ -637,6 +643,7 @@ fn start_vmm(
 
     let exit_evt = EventFd::new(EFD_NONBLOCK).map_err(Error::CreateExitEventFd)?;
     let landlock_enable = cmd_arguments.get_flag("landlock");
+    let no_shutdown = cmd_arguments.get_flag("no-shutdown");
 
     #[allow(unused_mut)]
     let mut event_monitor = cmd_arguments
@@ -733,6 +740,7 @@ fn start_vmm(
         exit_evt.try_clone().unwrap(),
         &seccomp_action,
         hypervisor,
+        no_shutdown,
         landlock_enable,
     )
     .map_err(Error::StartVmmThread)?;
diff --git a/vmm/src/lib.rs b/vmm/src/lib.rs
index eec56c5c1..5dfea07e7 100644
--- a/vmm/src/lib.rs
+++ b/vmm/src/lib.rs
@@ -162,6 +162,10 @@ pub enum Error {
     #[error("Error rebooting VM")]
     VmReboot(#[source] VmError),
 
+    /// Cannot shut the VM down
+    #[error("Error shutting down VM")]
+    VmShutdown(#[source] VmError),
+
     /// Cannot create VMM thread
     #[error("Error spawning VMM thread")]
     VmmThreadSpawn(#[source] io::Error),
@@ -449,6 +453,7 @@ pub fn start_vmm_thread(
     exit_event: EventFd,
     seccomp_action: &SeccompAction,
     hypervisor: Arc<dyn hypervisor::Hypervisor>,
+    no_shutdown: bool,
     landlock_enable: bool,
 ) -> Result<VmmThreadHandle> {
     #[cfg(feature = "guest_debug")]
@@ -488,6 +493,7 @@ pub fn start_vmm_thread(
                     vmm_seccomp_action,
                     hypervisor,
                     exit_event,
+                    no_shutdown,
                 )?;
 
                 vmm.setup_signal_handler(landlock_enable)?;
@@ -627,6 +633,7 @@ pub struct Vmm {
     original_termios_opt: Arc<Mutex<Option<termios>>>,
     console_resize_pipe: Option<Arc<File>>,
     console_info: Option<ConsoleInfo>,
+    no_shutdown: bool,
 }
 
 /// Just a wrapper for the data that goes into
@@ -781,6 +788,7 @@ impl Vmm {
         seccomp_action: SeccompAction,
         hypervisor: Arc<dyn hypervisor::Hypervisor>,
         exit_evt: EventFd,
+        no_shutdown: bool,
     ) -> Result<Self> {
         let mut epoll = EpollContext::new().map_err(Error::Epoll)?;
         let reset_evt = EventFd::new(EFD_NONBLOCK).map_err(Error::EventFdCreate)?;
@@ -833,6 +841,7 @@ impl Vmm {
             original_termios_opt: Arc::new(Mutex::new(None)),
             console_resize_pipe: None,
             console_info: None,
+            no_shutdown,
         })
     }
 
@@ -1688,9 +1697,12 @@ impl Vmm {
                     EpollDispatch::GuestExit => {
                         info!("VM guest exit event");
                         self.guest_exit_evt.read().map_err(Error::EventFdRead)?;
-                        self.vmm_shutdown().map_err(Error::VmmShutdown)?;
-
-                        break 'outer;
+                        if self.no_shutdown {
+                            self.vm_shutdown().map_err(Error::VmShutdown)?;
+                        } else {
+                            self.vmm_shutdown().map_err(Error::VmmShutdown)?;
+                            break 'outer;
+                        }
                     }
                     EpollDispatch::ActivateVirtioDevices => {
                         if let Some(ref vm) = self.vm {
@@ -2630,6 +2642,7 @@ mod unit_tests {
             SeccompAction::Allow,
             hypervisor::new().unwrap(),
             EventFd::new(EFD_NONBLOCK).unwrap(),
+            false,
         )
         .unwrap()
     }