Ticket #4032 (new enhancement)

Opened 5 years ago

Last modified 3 months ago

[feature-request] Nested Virtualization: VT-in-VT

Reported by: Technologov Owned by:
Priority: minor Component: VMM
Version: VirtualBox 2.2.2 Keywords:
Cc: Guest type: Windows
Host type: other

Description (last modified by frank) (diff)

Hi All,

Because more and more virtualization software requires VT (Intel VMX or AMD-V) to run, it makes sense to virtualize it somehow. (at least if host CPU supports hardware VT)

It will allow the following software to run in guests: -Xen (full virtualization mode) -KVM -Hyper-V -Windows Virtual PC -- this is basically a requirement for those who wanna run Windows 7 "XP mode". i.e. It allows for more complete user experience on Win7 guests.

Others can take advantage of it too: -VirtualBox itself :) -VMware Workstation -VMware ESX

-Technologov (yes, I will take advantage of it too :-), yay! )

Change History

comment:1 Changed 5 years ago by Technologov

opened on 17.5.2009.

comment:2 Changed 5 years ago by sandervl73

  • Priority changed from major to minor

A lot of work for questionable usefulness. Definitely very low on our priority list.

comment:3 Changed 4 years ago by Technologov

This is partially related to wish #2988


comment:4 Changed 4 years ago by Technologov

KVM team has developed (untested) patches for both nested VMX and nested SVM. Maybe some ideas can be taken from those patches.

See: (General Info)



comment:5 Changed 3 years ago by Technologov

update: VMware Workstation 8 claims to support this feature !


comment:6 Changed 2 years ago by Technologov

It seems that Linux 3.1 KVM finally achieved nested VMX.

This feature is yet another filler feature that is a "must-have":

Research paper:


comment:7 follow-up: ↓ 8 Changed 2 years ago by frank

What you denote as "must have" needs a lot of implementation time, is very difficult to implement and the benefit of nested virtualization is questionable.

comment:8 in reply to: ↑ 7 Changed 2 years ago by Johan Ryberg

Replying to frank:

What you denote as "must have" needs a lot of implementation time, is very difficult to implement and the benefit of nested virtualization is questionable.

I would very much see this in Virtualbox. I was just about to test a VMware cluster setup and I wanted to use VT-in-VT for this but it was not possible to use hardware virtualization.

Best regards Johan Ryberg

Version 0, edited 2 years ago by Johan Ryberg (next)

comment:9 Changed 2 years ago by vbfun

I would also be very interested to see this in VB too. It'll allow another full fledged hypervisor to run on VB and allow 64bit guests to run in the hypervisor.

comment:10 Changed 2 years ago by DNS

This would be a very useful feature IMHO. In virtualBox, currently I could test almost any software I like, with the exception of other hypervisors. With this capability, the full potential of VirtualBox can be used. Can the devs please reconsider adding this?

Thanks, DNS

comment:11 Changed 22 months ago by Tristan

This feature is essential for development of low-level OS kernel components when your workstation operating system is not suitable - eg, running Linux in a VM, then running your OS component under KVM with gdm attached.

It's also essential for development and testing of VM provisioning systems, or of any software that otherwise interacts with VMMs.

comment:12 Changed 18 months ago by x5560

I know for a fact that VMWare Workstation 9.0 and ESXi 5.0 does infact support this. What it does, is to emulate hardware VT and tricks the guest into thinking it runs on real HW. This is very usefull if you work with hypervisors and need to test certain functionality of a hypervisor but do not actually have thousands of dollars to spend on HW for testing.

I've been using Virtualbox for years, but this is a dealbreaker for me, as i work as a sysadmin and need to be able to test this kind of stuff in my home lab. I am seriously considering to shell out the dough for a VMWare Workstation license and abandon Virualbox.

It's sad, because Virualbox has so much potential. It's the only real open source type 2 hypervisor that is a real competition for VMWare.

comment:13 Changed 18 months ago by frank

  • Description modified (diff)

I know that other virtualization products support nested virtualization. Even with VirtualBox it is possible to execute VirtualBox without VT-x/AMD-V as a guest of VirtualBox with VT-x/AMD-V enabled. But apart from that, implementing full virtualization is too much effort for too little benefit.

comment:14 Changed 18 months ago by Tsso

I also couldn't run Qubes OS in Virtual Box.

comment:15 Changed 16 months ago by itarchitectlev

It seems that this ticket was evaluated a long time ago when the usefulness may have been disputed. In any case, there are real reasons people want to have nested hardware VT.

There is a lot of working happening in the cloud community and evaluating products in this arena often requires hardware VT - which implies two things:

1) You have real hardware available 2) You have nested hardware VT capable virtualization software (e.g. VMware)

Given that we are in a world of cheap memory coupled with multiple core fast CPUs, virtualization is a great boost to doing cloud infrastructure development work. The problem is that the virtualized hardware created under VBox is only one part of the picture - as you're creating virtual hardware to run infrastructure designed to virtualize. Nested Hardware VT is essential here as software emulation in this world is painfully slow.

I have just purchased a VMware product because VirtualBox doesn't support this fundamental feature that I require which will now render my use of VirtualBox redundant.

I have been a big advocate of VirtualBox, but future work now sees this being left behind.

Regards, Kev @itarchitectkev

comment:16 follow-up: ↓ 17 Changed 16 months ago by frank

We didn't discuss against the usefulness of nested virtualization in general. But it remains valid that this is currently too much effort for too few benefit.

comment:17 in reply to: ↑ 16 Changed 15 months ago by denka_b

Replying to frank:

We didn't discuss against the usefulness of nested virtualization in general. But it remains valid that this is currently too much effort for too few benefit.

How is the benefit estimated, and is there anything different in VBox architecture from VMware that makes it feasible there but not here?

I'm in same boat as many, forced to go VMware way because Hyper-V in Windows 8 (guest) is required for Windows Phone 8 emulator to work. I'm not skimping on upgrade, but there is no upgrade path from Windows 7 Pro to Windows 8 :(

Stupid Microsoft - I guess they too have their "too much effort for too little benefit" reasons :)

comment:18 Changed 15 months ago by frank

I don't want to start a discussion here, a public bugtracker is not the right place for doing this. But please be aware that the VirtualBox development is primary driven by paying customer demands. Of course that does not mean that community demands are not being considered. We just have limited resources. Code contribution from the community may speed up the implementation of certain features.

comment:19 Changed 13 months ago by Tristan

How much would this cost? Or what is the right place for doing this - if the community were to save up to buy this feature like they did to buy blender I imagine it would need to be somewhere public.

comment:20 Changed 11 months ago by bluezeak

One of the primary uses of virtualization is for sandbox testing. Nested virtualization allows testing of other hyper visors, as well as ANY application that requires access to processor VT. This type of testing is one of the MAIN reasons people use hypervisors. Virtualbox is my favorite hypervisor, and so I want to see this capability added. If it isn't, I will be required to use other hypervisors that do have it. KVM has it now. And VMware Workstation has it. I will be willing to pay for vmware workstation ... if I have to. I would RATHER get it from VirtualBox.

comment:21 Changed 3 months ago by peterdk

I would love to see this implemented.

My use case: I am a Mobile App developer, and use Ubuntu as my main OS. To be able to develop for Windows Phone I need to run Windows 8 with HyperV enabled (otherwise I can't run WP emulators). Since HyperV requires VT-X, I can't use Virtualbox to run a virtual WP dev environment. Now I need to dualboot.

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