VirtualBox: High Guest CPU Utilization in VirtualBox

Original Setup:

• VirtualBox: 5.2.12r122591
• Latest Virtual Box tools
• Guest Ubuntu 18.04
• Host Windows 10 (8 CPU, 16GB of memory), i7 CPU, Intel GPU.
• Bi-directional drag and drop, copy and paste
• 4GB of Ram
• 4 CPU
• 128Mb Video Memory
• 3D Acceleration (OpenGL support is awful all sorts of bugs)
• Enable VT-X/AMD-V
• Enable Nested Paging
• Everything else Default.

VBoxClient was taking up more than 100% CPU.

The fix is to turn off 'Nested Paging'.


Edit 09/01/2018
VirtualBox 6.0 seems to have sorted out the problem.