From 9c95109a6bd2bf5fe034c7a96b5d9ab246101e4a Mon Sep 17 00:00:00 2001
From: Sebastien Boeuf <sebastien.boeuf@intel.com>
Date: Thu, 17 Mar 2022 11:16:32 +0100
Subject: [PATCH] vmm: Streamline reboot code path

Separate the destruction and cleanup of original VM and the creation of
the new one. In particular have a clear hand off point for resources
(e.g. reset EventFd) used by the new VM from the original. In the
situation where vm.shutdown() generates an error this also avoids the
Vmm reference to the Vm (self.vm) from being maintained.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
---
 vmm/src/lib.rs | 98 ++++++++++++++++++++++++++------------------------
 1 file changed, 52 insertions(+), 46 deletions(-)

diff --git a/vmm/src/lib.rs b/vmm/src/lib.rs
index 36e5f5748..cbbf9d24d 100644
--- a/vmm/src/lib.rs
+++ b/vmm/src/lib.rs
@@ -581,56 +581,62 @@ impl Vmm {
             }
         }
 
-        // First we stop the current VM and create a new one.
-        if let Some(ref mut vm) = self.vm {
-            let config = vm.get_config();
-            let serial_pty = vm.serial_pty();
-            let console_pty = vm.console_pty();
-            let console_resize_pipe = vm
-                .console_resize_pipe()
-                .as_ref()
-                .map(|pipe| pipe.try_clone().unwrap());
-            self.vm_shutdown()?;
+        // First we stop the current VM
+        let (config, serial_pty, console_pty, console_resize_pipe) =
+            if let Some(mut vm) = self.vm.take() {
+                let config = vm.get_config();
+                let serial_pty = vm.serial_pty();
+                let console_pty = vm.console_pty();
+                let console_resize_pipe = vm
+                    .console_resize_pipe()
+                    .as_ref()
+                    .map(|pipe| pipe.try_clone().unwrap());
+                vm.shutdown()?;
+                (config, serial_pty, console_pty, console_resize_pipe)
+            } else {
+                return Err(VmError::VmNotCreated);
+            };
 
-            let exit_evt = self.exit_evt.try_clone().map_err(VmError::EventFdClone)?;
-            let reset_evt = self.reset_evt.try_clone().map_err(VmError::EventFdClone)?;
+        let exit_evt = self.exit_evt.try_clone().map_err(VmError::EventFdClone)?;
+        let reset_evt = self.reset_evt.try_clone().map_err(VmError::EventFdClone)?;
+        #[cfg(feature = "gdb")]
+        let debug_evt = self
+            .vm_debug_evt
+            .try_clone()
+            .map_err(VmError::EventFdClone)?;
+        let activate_evt = self
+            .activate_evt
+            .try_clone()
+            .map_err(VmError::EventFdClone)?;
+
+        // The Linux kernel fires off an i8042 reset after doing the ACPI reset so there may be
+        // an event sitting in the shared reset_evt. Without doing this we get very early reboots
+        // during the boot process.
+        if self.reset_evt.read().is_ok() {
+            warn!("Spurious second reset event received. Ignoring.");
+        }
+
+        // Then we create the new VM
+        let mut vm = Vm::new(
+            config,
+            exit_evt,
+            reset_evt,
             #[cfg(feature = "gdb")]
-            let debug_evt = self
-                .vm_debug_evt
-                .try_clone()
-                .map_err(VmError::EventFdClone)?;
-            let activate_evt = self
-                .activate_evt
-                .try_clone()
-                .map_err(VmError::EventFdClone)?;
+            debug_evt,
+            &self.seccomp_action,
+            self.hypervisor.clone(),
+            activate_evt,
+            serial_pty,
+            console_pty,
+            console_resize_pipe,
+        )?;
 
-            // The Linux kernel fires off an i8042 reset after doing the ACPI reset so there may be
-            // an event sitting in the shared reset_evt. Without doing this we get very early reboots
-            // during the boot process.
-            if self.reset_evt.read().is_ok() {
-                warn!("Spurious second reset event received. Ignoring.");
-            }
-            self.vm = Some(Vm::new(
-                config,
-                exit_evt,
-                reset_evt,
-                #[cfg(feature = "gdb")]
-                debug_evt,
-                &self.seccomp_action,
-                self.hypervisor.clone(),
-                activate_evt,
-                serial_pty,
-                console_pty,
-                console_resize_pipe,
-            )?);
-        }
+        // And we boot it
+        vm.boot()?;
 
-        // Then we start the new VM.
-        if let Some(ref mut vm) = self.vm {
-            vm.boot()
-        } else {
-            Err(VmError::VmNotCreated)
-        }
+        self.vm = Some(vm);
+
+        Ok(())
     }
 
     fn vm_info(&self) -> result::Result<VmInfo, VmError> {