virtualbox.org

So I have a couple of odd problems with VirtualBox.

First, my setup:

VirtualBox version: 5.0.10 r104061
OS: Windows 8.1 SL 64-bit
RAM: 12 GB
CPU: Intel Core i7 5500U (mobile cpu)

CPU-Z 1.74.0 reports VT-x among the instruction sets supported by my processor.
Intel's own Processor Identification Utility agrees that my processor supports "VT-x with Extended Page Tables".

Now, here are my problems.

1. When I add a new VM (or look under Settings > General for an already existing one), and I select an from the Version drop-down list, it only shows options marked "(32-bit)" even though I'm running a 64-bit system.

(This is regardless of whether I've selected "Microsoft Windows" or "Linux" in the previous Type drop-down list.)

2. When I try to virtualize an image which requires VT-x (like Windows 8.1 and its ilk) it frowns at me and says "VT-x/AMD-V hardware acceleration is not available on your system. Certain guests (e.g. OS/2 and QNX) require this feature and will fail to boot without it."

So, what's up with this? Why can't I virtualize a 64-bit image? And why isn't VirtualBox detecting VT-x on my CPU?

(Note: There's no option in my BIOS settings to turn VT-x on or off, so unless for some dumb reason it's always turned off in my laptop I doubt that's causing it. And I'm not sure exactly how CPU-Z and the Processor Identification Utility detect these extensions, but surely both couldn't have reported it if it was turned off?)

FAQ: I have a 64bit host, but can't install 64bit guests.

Thanks, I can't believe I missed that.

It doesn't solve my problem, however. The Intel Ark website clearly lists the i7 5500U as having support for VT-x, and their own Identification Utility (as well as CPU-Z) already confirm it. As I already pointed out, my BIOS doesn't have an option to turn it on or off.

Looking through the 3rd point, I don't have Hyper-V (it's not available on 8.1 SL). In fact it's a pretty clean machine in general. The only major thing I can think of that's on it is Visual Studio 2015 Community, could that interfere with VT-x detection?

Is there some other reason that could be preventing VirtualBox from detecting VT-x on my system?

Some BIOSes don't have that switch. Quite a lot of them don't call it "VT-x". All the Intel CPU BIOSes I have used call it "Virtualization Technology". Check your motherboard manufacturer website for what they call it. A BIOS update might be needed.

e3on wrote:It doesn't solve my problem, however. The Intel Ark website clearly lists the i7 5500U as having support for VT-x, and their own Identification Utility (as well as CPU-Z) already confirm it.

That isn't in dispute. The question isn't whether VT-x is present, the question is whether it is enabled and not already in use. Unfortunately none of us can answer the last two questions for you.

The FAQ gave you tips on what to look for in your BIOS, and what to do when you find it.

I can't tell you what effect "Visual Studio 2015 Community" might have.

VT-x is not managed by the OS, hence there is no mechanism to share access like there is to the FPU say. There is however a mechanism in the CPU itself to lock out others from using the feature, which (as a debug or VM app say) you'd typically do to prevent other apps from messing you up. That's what you have. The FAQ gave you tips on the type of app which might grab VT-x for itself.

Hi guys, i came here with the same problem. In my case the third point was key "If (1) and (2) are already taken care of, then make sure that no other host apps are already using VT-x/AMD-v."
Unnistalled avast antivirus and virtualbox came to 64bits again.
thx.

I read yesterday that Avast has a "Use Virtualization Technology" switch for their sandbox feature. The fellow using Avast unchecked that switch and Virtualbox was able to get 64-bit running again, and he could keep Avast. Search about, but it seems you can have your Avast and eat your Virtualbox too.