As I understand, you've already enabled the VT-x option in BIOS. That's good. Because you have Linux as your operating system, now you need to install and configure KVM.
KVM Installation
I referred the instructions from Ubuntu community documentation page.
to get KVM installed.To see if your processor supports hardware
virtualization, you can review the output from this command:
$ egrep -c '(vmx|svm)' /proc/cpuinfo
If the output is 0 it means that your CPU doesn't support hardware
virtualization.
Next is to install CPU checker:
$ sudo apt-get install cpu-checker
Now you can check if your cpu supports kvm:
$ sudo kvm-ok
and insert root password
If you see:
"INFO: Your CPU supports KVM extensions KVM acceleration can be used"
It means you can run your virtual machine faster with the KVM
extensions.
If you see:
"INFO: KVM is disabled by your BIOS HINT: Enter your BIOS
setup and enable Virtualization Technology (VT), and then hard
poweroff/poweron your system KVM acceleration can NOT be used"
You need to go to BIOS setup and enable the VT.
Use a 64 bit kernel
Running a 64bit kernel on the host operating system is recommended
since Google no longer offers support for 32bit kernel.. This allows
the serving of more than 2GB of RAM for your VMs. Also, a 64-bit
system can host both 32-bit and 64-bit guests. A 32-bit system can
only host 32-bit guests. To see if your processor is 64-bit, you can
run this command:
$ egrep -c ' lm ' /proc/cpuinfo
If 0 is printed, it means that your CPU is not 64-bit. If 1 or higher,
it is. Note: lm stands for Long Mode which equates to a 64-bit CPU.
Now see if your running kernel is 64-bit, just issue the following
command:
$ uname -m
x86_64 indicates a running 64-bit kernel. If you see i386, i486, i586
or i686, you're running a 32-bit kernel.
Install KVM
For Ubuntu Lucid (12.04 LTS Precise) or later:
$ sudo apt-get install qemu-kvm libvirt-bin ubuntu-vm-builder bridge-utils
If it is displayed, you may ignore the Postfix Configuration below by
selecting "No Configuration"
Next is to add your account to the group kvm and libvirtd
$ sudo adduser your_user_name kvm
$ sudo adduser your_user_name libvirtd
After the installation, you need to relogin so that your user account
becomes an effective member of kvm and libvirtd user groups. The
members of this group can run virtual machines.
Verify Installation You can test if your install has been successful
with the following command:
$ sudo virsh -c qemu:///system list
Hope that helps.