Auto start enables ivm guest start with host operating system. To enable it you have to run a virsh command for each host kvm guest.

enabling auto start for a kvm guest:
my guest machine name is node1.


ubuntu@kvm:~$ virsh autostart node1

disabling auto start
ubuntu@kvm:~$ virsh --disable autostart node1

you can do the same thing by entering into virsh shell
ubuntu@kvm:~$ virsh
Welcome to virsh, the virtualization interactive terminal.

Type:  'help' for help with commands
       'quit' to quit

virsh # list
 Id    Name                           State
----------------------------------------------------
 2     node1                           running
 3     node2                           running
 4     node3                           running

virsh # autostart  node1
Domain node1 marked as autostarted

virsh # autostart --disable node1
Domain node1 unmarked as autostarted

virsh #

if your memory is good you can even use 'id' numbers in place of vm names, like
ubuntu@kvm:~$ virsh
Welcome to virsh, the virtualization interactive terminal.

Type:  'help' for help with commands
       'quit' to quit

virsh # list
 Id    Name                           State
----------------------------------------------------
 2     node1                           running
 3     node2                           running
 4     node3                           running

virsh # autostart  2
Domain node1 marked as autostarted

virsh #

what this feature does is, each kvm guest will have an xml file which can be  edited using 'virus edit'.These files reside under '/etc/libvirt/qemu/autostart/' directory. Once you enable 'autostart' on first kvm guest, a folder named 'autostart' will be created under the above given path '/etc/libvirt/qemu/autostart/' and a softllink to kvm guest's xml file will be added under this 'autostart' folder as below.
ubuntu@kvm:~$ ls -l /etc/libvirt/qemu
-rw------- 1 root root 2302 Apr 28 18:47 node1.xml
-rw------- 1 root root 2302 Apr 28 18:48 node2.xml
drwxr-xr-x 2 root root 4096 May 15 11:44 autostart
drwxr-xr-x 3 root root 4096 Apr 15 08:04 networks

ubuntu@kvm:~$ ls -l /etc/libvirt/qemu/autostart/
total 0
lrwxrwxrwx 1 root root 25 May 15 11:44 node1.xml -> /etc/libvirt/qemu/node1.xml
lrwxrwxrwx 1 root root 25 May 15 11:44 node2.xml -> /etc/libvirt/qemu/node2xml
Hope you understand after looking at above output, so you can also simply create an soft link to enable autostart and also you can check if auto start for a specific guest is enabled or not.