qemu: Add support for --no-shutdown Knob

Add support for --no-shutdown Knob. This allows us to
shutdown the VM without quitting QEMU.

Note: Also fix the comment around --no-reboot to be
more accurate.

Signed-off-by: Manohar Castelino <mcastelino@apple.com>

qemu/qemu.go

@@ -2402,8 +2402,12 @@ type Knobs struct {
 	Realtime bool
 
 	// Exit instead of rebooting
+	// Prevents QEMU from rebooting in the event of a Triple Fault.
 	NoReboot bool
 
+	// Don’t exit QEMU on guest shutdown, but instead only stop the emulation.
+	NoShutdown bool
+
 	// IOMMUPlatform will enable IOMMU for supported devices
 	IOMMUPlatform bool
 }
@@ -2776,6 +2780,10 @@ func (config *Config) appendKnobs() {
 		config.qemuParams = append(config.qemuParams, "--no-reboot")
 	}
 
+	if config.Knobs.NoShutdown {
+		config.qemuParams = append(config.qemuParams, "--no-shutdown")
+	}
+
 	if config.Knobs.Daemonize {
 		config.qemuParams = append(config.qemuParams, "-daemonize")
 	}