Error: Couldn't find the end of CPUID sub-leaves

[AbQualcosa]

To day I upgraded VirtualBox from VirtualBox-4.3.6-91406-Win to VirtualBox-4.3.8-92456-Win on my SOny Vaio with windows 8.1 pro.
When I try to start a windows xp VM that yesterday was working well, i get this error:

Apertura di una sessione per la Macchina Virtuale XPsp3 non riuscita.

Couldn't find the end of CPUID sub-leaves. (VERR_CPUM_TOO_MANY_CPUID_SUBLEAVES).

Codice 'uscita: E_FAIL (0x80004005)
Componente: Console
Interfaccia: IConsole {8ab7c520-2442-4b66-8d74-4ff1e195d2b6}

Thanks

[AbQualcosa]

I went back to the VirtualBox-4.3.6-91406-Win and all works .

[Perryg]

We first saw this yesterday and the poster has raised a ticket at bugtracker.

[michaln]

You probably have Hyper-V enabled. It's highly recommended to disable it if you want to use VirtualBox.

[Perryg]

You probably have Hyper-V enabled. It's highly recommended to disable it if you want to use VirtualBox.

Interesting. Is this a new logging feature? Before it just failed with no VT-x available when Hyper-v was being used.

[michaln]

Interesting. Is this a new logging feature?

No... a new feature to more closely mirror the host CPU's MSRs (model-specific registers). Turns out Hyper-V does something funny in their CPUID implementation which confuses our initial implementation (which had only been tested on a multitude of real processors ).

[PT]

Hi,
I got the same problem - CPUID sub-leaves...
To get VirtualBox up and running again you have to uninstall Hyper-V. If that's not possible you have to use an earlier version of VirtualBox.

[Hong]

I use VirtualBox because of Genymotion. The primary reason that I use Genymotion's Android emulators instead of Intel's images with comparable or even better performance is its allowing running Hyper-V for other purposes on the same machine. It looks like that I will have to keep in mind not to upgrade VB to ruin this nice feature.
VB has been working very well. Hats off to the VB team.

[michaln]

It looks like that I will have to keep in mind not to upgrade VB to ruin this nice feature.

This will be fixed in the next maintenance release. Just avoid version 4.3.8.

[Hong]

This will be fixed in the next maintenance release. Just avoid version 4.3.8.

Thank you for the clarification. I am so glad to hear this feature will be restored in the future.