Ubuntu 14.04
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Nested KVM
Configure nested KVM. It's possible to install KVM and create virtual machines as nested KVM on KVM host.
[1] Make sure the current settings for Nested KVM and change it if needed.
# show the current setting ( if the result is "Y", it's OK )

cat /sys/module/kvm_intel/parameters/nested

# if the result is "N", change like follows and reboot the system )

[root@dlp ~]#
echo 'options kvm_intel nested=1' >> /etc/modprobe.d/qemu-system-x86.conf
[2] Make sure the CPU model on your computer.
[root@dlp ~]#
virsh capabilities | egrep "/model|/vendor"

# CPU model

# CPU vendor

[3] Edit the configuration of a virtual machine you'd like to nest like follows. It's OK to configure nested KVM and you can create virtual machines on the virtual machine nested.
[root@dlp ~]#
virsh edit www
# edit a virtual machine "www"
# add following lines

<cpu mode='custom' match='exact'>
# CPU model

  <model fallback='allow'>Westmere</model>
# CPU vendor

  <feature policy='require' name='vmx'/>