Reboot Host Machine and Reboot Virtual Machines.

We have a W2008Datacenter with 20 VM.
We have de DC of our company like VM and others types of servers (w2k3 and w2k8)

We need to reboot the Host Machine (upgrade software, upgrade hardware, whatever).
What Happens with the VM?
We dont save the state machines
We dont close the VMs
We dont do nothing when we turn off or turn on the Host Machine.
Hyper-V closes and opens the VM without problem.
Example: We have this host machine (SW2K8LAB01)

We have 9 VM in our lab. The SW2K8LABDC01 is the DC for de LAB domain.

The host machine is a server in this domain.

I reboot SW2K8LAB01 and the Hyper-V left the VMs same before the reboot.