Installing Windows 8.1 64 bit in VirtualBox Step By Step Tutorial
Execute these command in terminal
Installing Windows 8.1 64 bit in VirtualBox
"c:\Program Files\Oracle\VirtualBox\VBoxManage.exe" list vms
"c:\Program Files\Oracle\VirtualBox\VBoxManage.exe" setextradata "Windows 8.1" VBoxInternal/CPUM/CMPXCHG16B 1
Change your virtual box path accordingly