So THAT'S what it's doing

Rebooting a KVM host at $WORK seems to take a long time -- as in, a long time to actually reboot the host after I type "shutdown -r now". But then the process list shows this:

root     26881  0.0  0.0  64328   824 ?        S    13:30   0:00 /bin/sh /etc/rc6.d/K01libvirt-guests stop
root     26882  0.0  0.0 130220  3504 ?        S    13:30   0:00 virsh managedsave 128b38e0-ce1a-eb4b-5ee5-2746cd0926ce
root     26890  0.0  0.0   8716  1084 ?        S    13:30   0:00 sh -c cat | { dd bs=4096 seek=1 if=/dev/null && dd bs=1048576; } 1<>/var/lib/libvirt/qemu/save//vm-01.example.com.save
root     26891  1.1  0.0   3808   440 ?        S    13:30   0:00 cat
root     26892  0.0  0.0   8716   576 ?        S    13:30   0:00 sh -c cat | { dd bs=4096 seek=1 if=/dev/null && dd bs=1048576; } 1<>/var/lib/libvirt/qemu/save//vm-01.example.com.save

And now I understand.