No, i proto jsem napsal, že UEFI, protože vůbec ani nevím, kde bych tam měl informaci o podpoře virtualizace hledat...  

  Otevřeně řečeno, čučel jsem do toho UEFI jak tele na nová vrata.  
 
 
inxi -F:
Kernel: 4.15.0-36-generic x86_64 (64 bit)
           Desktop: Cinnamon 3.6.7  Distro: Linux Mint 18.3 Sylvia
Machine:   Mobo: ASUSTeK model: PRIME H270-PRO v: Rev X.0x
           Bios: American Megatrends v: 0808 date: 07/10/2017
CPU:       Dual core Intel Core i3-7100 (-HT-MCP-) cache: 3072 KB 
           clock speeds: max: 3900 MHz 1: 800 MHz 2: 800 MHz 3: 800 MHz
           4: 800 MHz
Graphics:  Card: NVIDIA GM107 [GeForce GTX 750]
           Display Server: X.Org 1.18.4 drivers: nvidia (unloaded: fbdev,vesa,nouveau)
           Resolution: 1280x1024@60.02hz
           GLX Renderer: GeForce GTX 750/PCIe/SSE2
           GLX Version: 4.5.0 NVIDIA 384.130
Audio:     Card-1 Intel Device a2f0 driver: snd_hda_intel
           Card-2 NVIDIA Device 0fbc driver: snd_hda_intel
           Sound: Advanced Linux Sound Architecture v: k4.15.0-36-generic
Network:   Card: Intel Ethernet Connection (2) I219-V driver: e1000e
           IF: enp0s31f6 state: up speed: 100 Mbps duplex: full
           mac: 18:31:bf:09:22:cb
Drives:    HDD Total Size: 2250.5GB (35.6% used)
           ID-1: /dev/sda model: Samsung_SSD_850 size: 250.1GB
           ID-2: /dev/sdb model: WDC_WD20EFRX size: 2000.4GB
Partition: ID-1: / size: 221G used: 7.8G (4%) fs: ext4 dev: /dev/sda2
           ID-2: swap-1 size: 8.45GB used: 0.00GB (0%) fs: swap dev: /dev/sda3
RAID:      No RAID devices: /proc/mdstat, md_mod kernel module present
Sensors:   System Temperatures: cpu: 29.8C mobo: 27.8C gpu: 36C
           Fan Speeds (in rpm): cpu: 0
Info:      Processes: 193 Uptime: 1:53 Memory: 1066.4/7914.2MB
           Client: Shell (bash) inxi: 2.2.35
Instalační soubor virtualboxu byl ten, co jeho jméno končí ...amd64.deb.