Nested virtualization : VM2 extremely slow

[Md-Marouane]

Hello everybody,

I would need assistance please

I am trying to do nested virtualization with Virtualbox but I have a big problem with slowness on my VM2.
- On my VM1 I installed Ubuntu Budgie with 11GB of RAM, 60GB of disk space and with 3 CPUs and I enabled nested virtualization via the CLI with this command : VBoxManage.exe modifyvm "VM1_Name" --nested-hw-virt on => Everything works fine on this one, no problem
- On this VM1 I installed VirtualBox and I created a VM2 with 8 GB of RAM, 20 GB of disk space and with 2 CPUs. 12 hours after launching the VM2 from the Ubuntu ISO, I finally arrived on the desktop to be able to do the installation. It is extremely slow! Even a Windows 95 PC runs 1000 times faster than this VM.

Why is it so slow?
I even tried to install an Ubuntu Server in this VM2 but it's the same thing => extremely slow.

My PC specs :
Windows 10 Home
16 GB RAM
Processor Intel Core i7-4702MQ CPU 2.20 GHz

Thanks

[fth0]

If you needed to use the VBoxManage command because the VirtualBox Manager wouldn't let you enable Nested VT-x/AMD-V, then your CPU is missing the VMCS Shadowing feature that VirtualBox needs to provide efficient nested virtualization. For details, see Nested VT-x and VMCS Shadowing.

[Md-Marouane]

Thanks a lot for your answer. Indeed, I have checked and I don't have the VMCS Shadowing feature on my CPU.
However, I saw a lot of guys on Youtube enable Nested VT-x/AMD-V via the VBoxManage because they couldn't enable it via the VirtualBox Manager and the nested virtualization works fine on their computer.

How can this be explained?

[fth0]

There will be differences between their setup and yours. What are those differences?

From the perspective of the VirtualBox forums, nested virtualization is rarely used. The few users that turn up here, usually have the same problem as you have.