Disabling VT-x/AMD-v in VirtualBox on Ubuntu

VirtualBox on Ubuntu has an issue preventing host waking up from suspend. This issue is marked as resolved, but unfortunately it’s still present in 3.1.2 r56127 running under control of Ubuntu x64. The workaround for this issue is well documented: disable VT-x/AMD-v support. Fine, but… the option is greyed out in the settings:

To change it, you have to go directly to vm configuration file and change enabled attribute in HardwareVirtEx to false. After the change CPU node should look similar to:

      <CPU count="1">

        <HardwareVirtEx enabled="false" exclusive="true"/>

        <HardwareVirtExNestedPaging enabled="false"/>

        <HardwareVirtExVPID enabled="false"/>

        <PAE enabled="true"/>

      </CPU>