virtualbox.org

Hey folks,
I have been reading a lot on this topic, but only found info on similar questions, not exactly mine.

My setup is as follows:
I have Windows 10 latest version with HyperV installed, using the latest generation.
Inside HyperV there is another Windows 10 latest version without HyperV installed. I enabled nested virtualization via Power Shell for this VM.
Inside this VM, there is Virtualbox installed, hosting Linux.
Everything is 64bit and the Hardware Resources are not an issue.

I need this setup due to several constraints.

Generally it works, but the Linux VM is extremly slow.

I played around with Virtualbox settings, enabling nested virtualization, changing the Paravirtualization to HyperV, but none of this had an effect. I anyway understand these settings are for nesting inside Virtualbox, which is not the case for me.

I assume that the Linux VM does not see the "Hardware" virtualization of the HyperV VM (which should be handed though)

Any ideas?

Ideas on what? On why it's slow? Of course it's slow: hardware is being simulated using already simulated hardware, every interrupt is going through countless layers of indirection. It's not even as if all levels are from the same vendor - that would be slow too but at least you might expect they might put in a few clever redirections to speed things up a bit.

To my understanding HyperV is a Layer 1 Hypervisor, that hands over the API to the physical hardware directly.
So I assume, that Virtualbox should be able to use the physical hardware (almost) directly. At least in the same manner as if Virtualbox would not be installed nested but directly on the host.
To my understanding thats the intention of nested virtualization.

Yes, I wonder why it is that slow.

@ tola,

I suggest you read the last paragraph of https://docs.microsoft.com/en-us/virtua ... ualization

Until that (Microsoft) guidance changes, there's not much chance of better performance in using 3rd-party virtualisation in a Hyper-V VM.

A type-1 hypervisor, which I assume is what you mean, is a hypervisor which starts before the main OS. Otherwise there is nothing that fundamentally distinguishes it.

True type-1 hypervisors are rare, because they have to have drivers for every piece of physical hardware out there - and who would have the resources to do that? Prior to Hyper-v there was only VMWare's ESX-i, and I'm pretty sure they restricted themselves to a subset of the server PC market.

There is nothing about a type-1 hypervisor that guarantees better performance.