Description of problem:
Guest can not boot successfully when use image in nfs shared directory

Version-Release number of selected component (if applicable):
RHEL5.6-Server-x86_64-kvm
kvm-83-199.el5
kvm-qemu-img-83-199.el5
libvirt-0.8.2-6.el5

How reproducible:
Always

Steps to Reproduce:
1.Prepare 2 hosts with same os above
Host A: 10.66.93.197 
Host B: 10.66.92.158
2.On 2 hosts execute:
# iptables -F
# setenforce 0
3.On Host A share an existed image via nfs service 
# cat /etc/exports
/var/lib/libvirt/images 10.66.92.158(rw,no_root_squash,async) 
4.Install a guest on Host B with sharable image 
# mkdir /var/lib/libvirt/migrate
# mount 10.66.93.197:/var/lib/libvirt/images /var/lib/libvirt/migrate
# virt-install -n kvm -r 512 -f /var/lib/libvirt/migrate/kvm.img --import --accelerate
  
Actual results:
step 4: guest can start but hang on boot.
# virsh dumpxml kvm
<domain type='kvm' id='1'>
  <name>kvm</name>
  <uuid>640cfc1a-03c4-be51-4168-4b3dd55120c3</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/migrate/kvm.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='54:52:00:62:a0:58'/>
      <source network='default'/>
      <target dev='vnet0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/2'/>
      <target port='0'/>
    </serial>
    <console type='pty' tty='/dev/pts/2'>
      <source path='/dev/pts/2'/>
      <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:c178,c915</label>
    <imagelabel>system_u:object_r:svirt_image_t:s0:c178,c915</imagelabel>
  </seclabel>
</domain>

#ps -ef|grep qemu-kvm
root      4681     1 43 05:57 ?        00:00:20 /usr/libexec/qemu-kvm -S -M rhel5.4.0 -m 512 -smp 1 -name kvm -uuid 640cfc1a-03c4-be51-4168-4b3dd55120c3 -monitor unix:/var/lib/libvirt/qemu/kvm.monitor,server,nowait -boot c -drive file=/var/lib/libvirt/migrate/kvm.img,if=ide,bus=0,unit=0,boot=on,format=raw,cache=none -net nic,macaddr=54:52:00:62:a0:58,vlan=0 -net tap,fd=16,vlan=0 -serial pty -parallel none -usb -vnc 127.0.0.1:0 -k en-us -vga cirrus -balloon virtio

Expected results:
guest can start successfully.


Additional info:

I have tried other scenario:
install a guest on Host A directly use local existed image
# virt-install -n kvm -r 512 -f /var/lib/libvirt/images/kvm.img --import --accelerate 

the result is: guest can start and boot successfully.