Using processor hardware virtualization
To determine whether your computer supports processor virtualization hardware extensions, and that they have been enabled in the system BIOS, run the following in a terminal window:
gnome-boxes --checks
To enable Virtualization on your system:
Reboot the system and open the BIOS menu
Select Restore Defaults option and then Save and Exit
Reboot and again open BIOS
Open the Processor submenu in the Chipset, Advanced CPU Configuration or Northbridge
Enable Intel Virtualization Technology (also known as Intel VT) or AMD-V depending on the brand of the processor. The virtualization extensions may be labeled Virtualization Extensions, Vanderpool or various other names depending on the OEM and system BIOS
Save and Exit
Reboot and run: cat /proc/cpuinfo | grep vmx svm
If there is some output then the virtualization extensions are now enabled. If there is no output your system may not have the virtualization extensions or the correct BIOS setting enabled