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12.2. Setup

Follow these steps to enable, configure, and start using nested virtualization:
  1. Enable: The feature is disabled by default. To enable it, use the following procedure on the L0 host physical machine.
    For Intel:
    1. Check whether nested virtualization is available on your host system. 
      $ cat /sys/module/kvm_intel/parameters/nested
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      If this command returns Y or 1, the feature is enabled.
      If the command returns 0 or N, use steps ii and iii.
    2. Unload the kvm_intel module: 
      # modprobe -r kvm_intel
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    3. Activate the nesting feature: 
      # modprobe kvm_intel nested=1
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    4. The nesting feature is now enabled only until the next reboot of the L0 host. To enable it permanently, add the following line to the /etc/modprobe.d/kvm.conf file: 
      options kvm_intel nested=1
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    For AMD:
    1. Check whether nested virtualization is available on your system: 
      $ cat /sys/module/kvm_amd/parameters/nested
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      If this command returns Y or 1, the feature is enabled.
      If the command returns 0 or N, use steps ii and iii.
    2. Unload the kvm_amd module 
      # modprobe -r kvm_amd
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    3. Activate the nesting feature 
      # modprobe kvm_amd nested=1
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    4. The nesting feature is now enabled only until the next reboot of the L0 host. To enable it permanently, add the following line to the /etc/modprobe.d/kvm.conf file: 
      options kvm_amd nested=1
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  2. Configure your L1 virtual machine for nested virtualization using one of the following methods:
    virt-manager
    1. Open the GUI of the intended guest and click the Show Virtual Hardware Details icon.
    2. Select the Processor menu, and in the Configuration section, type host-passthrough in the Model field (do not use the drop-down selection), and click Apply.
    Domain XML
    Add the following line to the domain XML file of the guest: 
    <cpu mode='host-passthrough'/>
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    If the guest's XML configuration file already contains a <cpu> element, rewrite it.
  3. To start using nested virtualization, install an L2 guest within the L1 guest. To do this, follow the same procedure as when installing the L1 guest - see Chapter 3, Creating a Virtual Machine for more information.
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