virtualbox.org

Hi,

Today I noticed this error message when I try to start Windows 7 64Bits Guest :

***************************************************************************************************************
VT-x/AMD-V hardware acceleration has been enabled, but is not operational.
Your 64-bit guest will fail to detect a 64-bit CPU and will not be able to boot.
Please ensure that you have enabled VT-x/AMD-V properly in the BIOS of your host computer.
***************************************************************************************************************

I don't know why this appeared, running VBox 4.2.6 on XP SP3 / Intel Dual Core P8600 2.4Ghz / 4GB / VBox 4.2.6

On the Host I update VBox regularly and use it for years.

I never had such error message until 4.2.6, I restarted and also tried to re-install 4.2.6 just in case of installation get corrupted.

Running non 64bits Guest is OK.

Any idea ?

regards.

I assume you now have something else on your host which is using VT-x. Since only one app can use it it will no longer be available to VirtualBox, and hence you can't run VMs which require it. Common culprits include Hyper-v, system debuggers etc. Think of what else you might have updated on your host recently.

Hi,

I also supposed this (I did some search in the forum and read it could be a possible reason).

I also use VirtualPC (the old one) for years and this has never been a problem (I never run them at same time).

Thank you.

I can't add much to what I said earlier. If VT-x is not available, and it was previously available, then something else must be using it. Only you can know what that might be. I have seen no reports of VBox incorrectly reporting VT-x not available.

Hi,

I finally found that for unknown reason the BIOS settings has been changed and VMM /VT-X disabled !

I should have checked that point (and I do on new machine) but how could I guess somebody/something changed BIOS.

Thank you.

Regarding the vt-x/amd-v problem with 64-bit guests, I have a Dell Inspiron 530 where the BIOS does support hardware virtualization and it was confirmed running VMWare 64-bit guest check (more info at http://kb.vmware.com/selfservice/micros ... Id=1003945). What I found out that my BIOS (and I'm sure others as well) have a bug where awakening from hybernation/hybrid sleep/sleep fails to maintain the hardware virtualization setting. More info here: http://communities.vmware.com/docs/DOC-8978. Dell has, as usual, abandoned support of its products, and has chosen to deliberately refuse to fix this BIOS bug (along with other bugs that have been reported - last BIOS update was in 3/09).