Step 1
Reboot the computer and open the system's BIOS menu. This can usually be done by pressing the delete key, the F1 key or Alt and F4 keys depending on the system.
Select Restore Defaults or Restore Optimized Defaults, and then select Save & Exit.
Power off the machine and disconnect the power supply.
Step 2
Enabling the virtualization extensions in BIOS
Power on the machine and open the BIOS (as per Step 1).
Open the Processor submenu The processor settings menu may be hidden 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.
Enable Intel VTd or AMD IOMMU, if the options are available.
Save & Exit.
Run
cat /proc/cpuinfo | grep --color 'vmx\|svm'
If you see vmx or svm in red, 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.
Best Answer
It seems that I have already found the reason. Simply I was searching VT-x model in BIOS setup, but there was line called Intel Virtualization Technology and this one was disabled. After enabling all 64-bit options are visible in my VM. Question can be closed...