100 lines
5.1 KiB
Markdown
100 lines
5.1 KiB
Markdown
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title = "Pushing Nested Virtualization to the Limits"
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date = 2022-04-27T19:54:00Z
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draft = false
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summary = "Trying to install all versions of Windows inside nested VMs..."
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tags = ["Experiment", "Virtualization", "Linux", "Windows"]
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aliases = ['/nested-virtualization']
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[hero]
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src = "hero.jpg"
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caption = 'Photo by <a href="https://unsplash.com/@didsss">Didssph</a> via <a href="https://unsplash.com">Unsplash</a>'
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I recently watched a video by SomeOrdinaryGamers in which he decided to install the first version of Windows and upgrade it all the way to Windows 10.
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{{< youtube id=KD3tuWy-z_w loading=lazy start=92 >}}
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Despite the video's thumbnail, I decided that it would a good idea to do something similar: Install all versions of Windows inside nested VMs.
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> [!warning] Disclaimer
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> Do not try this at home. Or do, I don't really care. Just be warned that it is a massive waste of time :upside_down_face:.
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{{< contents >}}
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## The Host
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Sadly, I didn't have access to my supercomputer with 1000s of CPU cores and Terabytes of RAM at the time, so my Legion 7 would have to do. Its specs are as follows:
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- AMD Ryzen 7 5800H (8 Cores, 16 Threads, Base 3.2GHz, Turbo 4.4GHz)
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- NVIDIA GeForce RTX 3070 Mobile
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- 32GB DDR4 3200MHz RAM
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- 2TB M.2 NVMe PCIe SSD
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About a month ago I completed a [single-GPU VFIO passthrough]({{% ref "/posts/vfio" %}}), which allowed me to have near-bare-metal performance on a Windows 10 VM running inside Arch Linux. This meant that my host was pretty much ready to go.
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The plan was simple: Install virtualization software on every operating system and create the nested VMs. Easy, right? Well... The execution was a bit tougher.
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## First VM
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My first victim was my Windows 10 Gaming VM. If you want detailed instructions on how I created it, you can check out the post linked above.
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I originally tried going the Hyper-V route for my next VM but performance inside Windows 10 tanked significantly the moment I enabled it, forcing me to install VirtualBox.
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## Second VM
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After installing VirtualBox, I downloaded a [Windows 8.1 ISO](https://www.microsoft.com/en-us/software-download/windows8ISO) from Microsoft and created a new VM.
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I gave this VM around half of the resources of Windows 10, making sure to also enable nested AMD-V. After a painfully nit-picky installation (thanks Microsoft), I was finally able to boot Windows 8.1.
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General performance was OK-ish and the VM was definitely usable. However, networking was unfathomably slow, peaking at around 0.8MB/s.
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Luckily, VirtualBox provides easy folder sharing between hosts and guests, so all I had to do was download any needed files on Windows 10 and pass them through to Windows 8.1.
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After installing VirtualBox once again, it was time for the third VM.
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## Third VM
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This is where things started to get a bit annoying. As you might know, Microsoft has dropped support for Windows 7, so finding an ISO was a bit more difficult. Luckily, with a bit of google-fu, I found a website that hosted a direct download link.
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While configuring the VM, I noticed that I could no longer enable nested AMD-V. Uh-oh.
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Staying optimistic, I pressed forward and started the Windows 7 installation. I quickly realized that this challenge was a lot harder than I originally expected.
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The installation took a total of 4 painfully slow hours, ending with a blue screen of death right after the installer tried to reboot the VM. All hope was not yet lost though.
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I restarted the VM, and after a one-hour-long boot process (I am not joking), I was greeted with the Windows 7 desktop. Even though the VM booted, the user interface felt beyond sluggish, with every click taking several seconds to register, and animations tearing up the whole screen.
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However, this didn't stop me and my hubris. I installed VirtualBox again.
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## Fourth VM
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My next target was Windows XP. I deliberately skipped Vista because I was too scared of the performance impact it would have. After downloading a dodgy Windows XP ISO, I created a new VM inside VirtualBox.
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This is where I started to realize that my ~insanity~ experiment would soon come to an end. Almost all options, including multiple cores and hardware acceleration, were greyed-out.
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Despite that, I still tried to create a VM. After configuring the available options, I started the Windows XP installation. Sadly, after another hour, I was greeted with an error message saying that AMD-V was not available.
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## Conclusion
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In the end, I managed to create a measly 2 nested VMs before being stopped by VirtualBox limitations.
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I'm guessing that by using the more efficient KVM platform I would be able to nest at least 3, possibly 4 VMs. However, that is an experiment for another time.
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What did I learn from this experience? Absolutely nothing, other than that I am really good at finding ways to procrastinate.
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