Nested virtualization

[marius_1956]

I use VirtualBox 6.1.18-142142 on a Windows 10 64 bit host with an Intel(R) Core(TM) i7-6700 CPU.
Based on the contents on page https://docs.oracle.com/en/virtualizati ... -virt.html I created a Windows Server 2019 guest VM and selected the "Enable Nested VT-x/AMD-V" check box on the Processor tab.
However, when I try to install the Hyper-v role in the guest VM I get an error saying that "Hyper-v cannot be installed: The processor does not support second level address translation (SLAT)".
Am I missing any relevant point?
By the way, nested virtualization works fine on the same PC if I use VMware Player.
Regards

[scottgus1]

The CPU needs certain capabilities besides VT-x, if I remember correctly.

Start the VM from full normal shutdown, not save-state. Run until you see the problem happen, then shut down the VM from within the VM's OS if possible. If not possible, close the Virtualbox window for the VM with the Power Off option set.

Right-click the VM in the main Virtualbox window's VM list, choose Show Log. Save the far left tab's log and the hardening log next to it, zip them, and post the zip file, using the forum's Upload Attachment tab.

[fth0]

Am I missing any relevant point?

The documentation is open to interpretation, and the documented nested hypervisors may be the only ones supported. Hyper-V requires hardware virtualization (VT-x) and will most probably not run inside a VirtualBox VM. The VMware Player is known to be able to run without VT-x. Does the VMware Player use hardware virtualization (VT-x) in your case?

[marius_1956]

In my tests VMware Player is used as the host hypervisor.

[marius_1956]

I include the requested logs.
Regards
marius

[scottgus1]

00:00:05.268514 VMX - Virtual-Machine Extensions = 1 (1)
00:00:05.268525 Ept - Extended Page Tables = 0 (1)
00:00:05.268528 UnrestrictedGuest - Unrestricted guest = 0 (1)
00:00:05.268530 VmcsShadowing - VMCS shadowing = 0 (1)

If I read this right, and even more importantly if I remember forum guru fth0's posts correctly, it looks like your processor has the right stuff.

Try installing Virtualbox in your VM, see if you can make another VM inside. If that works, then you got nested virtualization.

If your intent with Hyper-V is to run services that need it, you might need to run Hyper-V on the host OS. Virtualbox mightn't work well when Hyper-V is enabled on the host, so it's either or. See https://www.tenforums.com/tutorials/139 ... puter.html

[fth0]

If I read this right, and even more importantly if I remember forum guru fth0's posts correctly, it looks like your processor has the right stuff.

Confirmed!

My expectation is that as a nested hypervisor inside a VirtualBox VM, VirtualBox or KVM will work, but Hyper-V will not. AFAIR, there was a user who saw Hyper-V complaining about the missing EPT.

[BillG]

I am quite confused by this whole discussion. The initial post says I use VirtualBox 6.1.18-142142 on a Windows 10 64 bit host with an Intel(R) Core(TM) i7-6700 CPU.

In reply to some queries, the fourth post says In my tests VMware Player is used as the host hypervisor.

What exactly are you running on the host? VirtualBox or VMware? If VirtualBox is not running on the host, how is it involved at all? You say you are trying to run Hyper-V in the guest. I doubt that you will ever get Hyper-V to run in a guest unless you also run Hyper-V in the host. Nesting is supported in Hyper-V (with limitations).

[marius_1956]

Many thanks to everybody for the answers.
I suspect I made some confusion, so let me explain.
- My physical box is a Windows 10 64 bit host with an Intel(R) Core(TM) i7-6700 CPU.
- Inside the host I installed VirtualBox 6.1.18-142142
- Inside VirtualBox I installed a Windows Server 2019 guest VM
- When I try to enable the Hyper-v role in the guest Windows Server 2019 VM I get the eror "Hyper-v cannot be installed: The processor does not support second level address translation (SLAT)"
- On the same physical box I installed VMware Workstation 15 Player
- Inside VMware Workstation Player I installed a Windows Server 2019 guest VM
- Inside the guest Windows Server 2019 VM I can enable the Hyper-v role and I can create and run guest VMs
That means, in my opinion, that my HW supports nested virtualization while my VirtualBox does not.
I hope it depends on same problem in my VB configuration, in order to fix it and go on using VB for all my VMs...
Many thanks again
marius

[fth0]

- Inside VirtualBox I installed a Windows Server 2019 guest VM
- When I try to enable the Hyper-v role in the guest Windows Server 2019 VM I get the eror "Hyper-v cannot be installed: The processor does not support second level address translation (SLAT)"

AFAIR, there was a user who saw Hyper-V complaining about the missing EPT.

EPT is Intel's term for SLAT, so you just confirmed my corresponding statement. In consequence, you cannot run Hyper-V as a nested hypervisor inside a VirtualBox VM.

[marius_1956]

So, the statement on page https://docs.oracle.com/en/virtualizati ... -virt.html should be corrected or at least specified...
Many thanks
marius

[scottgus1]

EPT is Intel's term for SLAT

Going to note this, thanks!

[Martin]

So, the statement on page https://docs.oracle.com/en/virtualizati ... -virt.html should be corrected or at least specified...

The manual for the current version
https://docs.oracle.com/en/virtualizati ... ested-virt
doesn' mention Hyper-V.

[fth0]

EPT is Intel's term for SLAT

Going to note this, thanks!

In the Wikipedia article about Second Level Address Translation, EPT is mentioned right in the introduction.