blitzclone

This is super nice, because I heard the normal VirtualBox has pretty buggy nested virtualization.

Yes, this is indeed nice. I have a Chromebook as well and the integration with Linux apps is super seamless. The major usecase for VBox is mostly Windows, though.

We're offering commercial support. We can also help with graphics virtualization and other topics (e.g. performance tuning and automated testing in real world scenarios).

Not yet. Nesting support is on our list. But the performance will not be great.

Yes!

Haha. I understand the sentiment. That's a pretty large effort though and needs some funding as well.

We have used this with recent Intel GPUs that support SR-IOV. This is what you see in the video on the cyberus website. Intel hasn't managed to upstream the drivers for this yet and you have to piece together things, which is very unpleasant. But we are there to help, if someone wants to use this in a professional setting.

We used to have support for Intel GVT-g GPU virtualization as well, which was more of a software solution. This doesn't work with modern Intel GPUs anymore.

That's already b0rken in the Oracle sources.

Ok. We'll try to clarify the situation in the README. Thanks for the feedback!

Thank you!

>How does this work in licensing terms? If VB foss enough?

It's as FOSS as the VirtualBox open source edition.

> Do you expect Oracle to merge this?

That would be nice, but I wouldn't hold my breath. Oracle gonna Oracle.

> If oracle doesn’t merge this, will you keep on maintaining it, potentially forking VirtualBox?

We don't intend to fork VirtualBox. VBox has a somewhat modular architecture where you can plug-in different hypervisor backends. That's what we did. It's not as modular, but our changes to core VirtualBox code is very small.

As far as our plans go, we are pretty open at this point. We are very interested to get to know people that find this useful!

Ooops. Will fix. :) Thanks!

You can also setup VFIO in VirtualBox/KVM. We haven't polished it yet though. You can check the video here to see GPU virtualization in action:

https://www.cyberus-technology.de/products/hypervisor (Don't mind the English, we are not native speakers. :)

It depends on your setup and workload. On a recent Intel CPU, our performance dashboard shows +10% for some benchmarks. It's hard to make a general statement though.

The KVM backend in vanilla VBox cannot be activated without changing the code. If you tried it, you tried the vanilla VBox hypervisor (vboxdrv) instead of KVM.

Well, KVM is used by Google and AWS and others for their clouds. As such, there are a lot of eyes on KVM code. The vboxdrv kernel module that provides the same functionality in vanilla VBox definitely has fewer people looking at it. It also has anti-features, such as code upload from the userspace VirtualBox process to the kernel. This is also the largest security issue with vanilla VBox, because a lot of emulation code runs directly in the kernel.

From a performance perspective, it's a bit more complicated. KVM has support for modern virtualization features (Intel APICv, AMD AVIC, etc) that vanilla VBox lacks. You get these in the VirtualBox/KVM version. On the other hand, vanilla VBox emulates most devices in the kernel (see above). So SATA emulation in vanilla VBox is very fast compared to KVM/Qemu or KVM/VirtualBox for a bit unfair reasons. Modern devices, such as virtio or NVMe, are not as impacted by that.

tl;dr So the performance you get depends on your workload. If it's very interrupt heavy, VirtualBox/KVM will win. If it uses antiquated virtual devices (SATA), vanilla VirtualBox (with vboxdrv) will have an edge.

The KVM backend doesn't have nesting enabled just yet. We're on it.

The name KVM is a bit confusing. It doesn't do anything fundamental different than VirtualBox. The difference is that KVM comes by default with any Linux. VirtualBox ships it's own Linux kernel module for that. That has drawbacks. You typically can't use the newest Linux or the newest features.

KVM also always has the hottest new (performance-relevant) features, because Intel and AMD will always build their hot stuff into KVM first.

Yes.

There is no real connection to UML here. Hardware virtualization (Intel VT, AMD-V) are much faster in practice and also don't require the guest operating system to be heavily modified. So besides as curiosity or test vehicle, approaches like UML are pretty dead.

Yes, we are switching between vanilla VBox and KVM VBox during development quite often and the VMs are fine with it.

Great! What guests do you typically run where you see better performance with libvirt/kvm?

Oracle already had an unfinished and broken KVM backend in the code that was not exposed. Whether they incorporate this polished KVM backend is anyone's guess at this point.

The intention is to have this under the same license as the VBox open source release. If there is a way to clarify this more on the Github page, please advise. :)

The out-of-the-box performance of Windows in VirtualBox is very good and usually better than virt-manager (Qemu). You can tune Qemu to great performance as well, but it takes some fiddling. VirtualBox is in general very user friendly.

Guest integration (drag'n'drop, clipboard), USB passhthrough and audio support is also top-notch in VBox.