VirtualBox not identifying itself as hypervisor

[sysdroid]

Following an investigation done by Red Hat, it was discovered that VirtualBox 4.3.6 r91406 running on Windows 7 32-bit is not setting bit 31 in CPUID correctly. Due to that, the guest incorrectly identifies it's running in a physical machine.

[Frank Mehnert]

I'm not sure if this is really a bug. Why do you think it is mandatory for a hypervisor to set this bit, do you have a use case?

[sysdroid]

I do not have a user case (end user here). My understanding is that Red Hat Enterprise Linux uses this to identify if it's running in a hypervisor or not.

[Frank Mehnert]

I see your point but actually sometimes makes sense that the guest does not know if it is really running on a hypervisor or on bare metal.

[sysdroid]

Yes, I agree. Reading Intel's instruction set manual, it's evident bit 31 is reserved and not officially determined to be an indicative of hypervisor presence or not.

This article summarizes the situation: ​http://homepage.ntlworld.com/jonathan.deboynepollard/FGA/detecting-x86-virtual-machines.html

Here are "instructions" from Microsoft and Vmware: ​http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1009458

​http://msdn.microsoft.com/en-us/library/windows/hardware/ff538624(v=vs.85).aspx

I noticed Linux seems to have specific detection routines for many hypervisors. Perhaps they should think about including VirtulBox (if they can find a characteristic that would make Vbox detectable): ​http://lxr.free-electrons.com/source/arch/x86/include/asm/hypervisor.h#L31

[bird]

We normally do not set this bit, this is intentional on our part (partially for historical reasons, though, so it may change in later releases). Only when selecting a mac os x guest type will the bit be set by default (because we cannot run more recent guests without it).

There probably should've been a setting for this flag in 4.3, but it didn't make it in time, so there is only the low level VBoxManage setextradata [vmname|global] VBoxInternal/CPUM/EnableHVP 1 setting available at present.

[aeichner]

Please reopen if still relevant with a recent VirtualBox release.