RHEL-5.6 does not support LXC. I wonder how did you get a running LXC guest to test this on.

Hi 'JD'

Steps to Reproduce:
#cat rhel5.xml
<domain type='qemu' id='1'>
  <name>rhel5</name>
  <uuid>87a7652e-dfdb-a618-1b43-3517f9850f4b</uuid>
  <memory>524288</memory>
  <currentMemory>524288</currentMemory>
  <vcpu>1</vcpu>
  <os>
    <type arch='x86_64' machine='rhel5.4.0'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/libexec/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='none'/>
      <source file='/var/lib/libvirt/images/rhel55.img'/>
      <target dev='hda' bus='ide'/>
      <alias name='ide0-hd0'/>
      <address type='drive' controller='0' bus='0' unit='0'/>
    </disk>
    <controller type='ide' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
    </controller>
    <interface type='network'>
      <mac address='54:52:00:6c:8d:ae'/>
      <source network='default'/>
      <target dev='vnet0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/0'/>
      <target port='0'/>
    </serial>
    <console type='pty' tty='/dev/pts/0'>
      <source path='/dev/pts/0'/>
      <target port='0'/>
    </console>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='5900' autoport='yes' keymap='en-us'/>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </video>
  </devices>
  <seclabel type='dynamic' model='selinux'>
    <label>system_u:system_r:svirt_t:s0:c464,c770</label>
    <imagelabel>system_u:object_r:svirt_image_t:s0:c464,c770</imagelabel>
  </seclabel>
</domain>

1.Define and start two RHEL5 guest. 
 # virsh define rhel5.xml
 # virsh start rhel5

Domain rhel5 started

4.# virsh list --all
 Id Name                 State
----------------------------------
  6 rhel5                running

5.# virsh dominfo rhel5
Id:             1
Name:           rhel5
UUID:           87a7652e-dfdb-a618-1b43-3517f9850f4b
OS Type:        hvm
State:          running
CPU(s):         1
CPU time:       2.2s
Max memory:     524288 kB
Used memory:    524288 kB
Persistent:     yes
Autostart:      disable
Security model: selinux
Security DOI:   0
Security label: system_u:system_r:svirt_t:s0:c464,c770 (enforcing)

Reboot host the guest will start automatically

5. # virsh autostart rhel5
Domain rhel5 marked as autostarted

6. # virsh dominfo rhel5
Id:             6
Name:           rhel5
UUID:           87a7652e-dfdb-a618-1b43-3517f9850f4b
OS Type:        hvm
State:          running
CPU(s):         1
CPU time:       82.9s
Max memory:     524288 kB
Used memory:    524288 kB
Persistent:     yes
Autostart:      enable
Security model: selinux
Security DOI:   0
Security label: system_u:system_r:svirt_t:s0:c235,c481 (permissive)

Reboot host the guest will start automatically

Enable 'autostart' or not doesn't take effect actually, guest will auto start by self

The guest was still running when you rebooted the host after step 4. Thus the libvirt-guests init script will automatically save the guest, and restore it on  boot. This is independant of autostart. If you want to test autostart, then you need to make sure the guest is *shutoff*, before rebooting.

Could you retest using correct steps?

Hi 'JD'

 Follow the comment 4,"shutoff" guest with "autostart" will be autostart after host backup.I will closed this bug as not a bug.

 Thanks!