VirtualBox: Host OS processor is spiked while guest OS virtual processor is idle?
Solution 1:
Guess I know the answer. Try disabling IO APIC. Whether it be Linux, Windows, I always had a HUGE backfire with this, and a full throtle on my CPU. IO APIC/Multi-core on Virtualbox is for showoff only I guess. If you really want multiple cores, use VMWare Workstation/Player/Parallels desktop. (Player is free.)
Solution 2:
In a lot of cases, use of io-acpi with a 32bit guest will do that. You need to have an 64bit guest, or to unactive IO-ACPI and use only one core in your VM.