Nested Virtualization is not a new idea. In fact, we announced our first preview of Nested Virtualization running on Windows way back in 2015. From that Windows Insider preview to now, Nested...
Updated Jun 13, 2020
Version 2.0
Blog Post
I have seen the same issue as proboszcz when testing Windows 11 22000.100.210719-2150 about 2 months ago. I am not interested in synthetic benchmarks. I just measured a build in Visual Studio 2019 in the VM (level 1 guest). When nesting was not enabled for the VM, a clean build took 2 min, When nesting was enabled for the VM and Hyper-V installed, a clean build (same solution) took 3 minutes. This was reproducible.
My host hardware:
CPU AMD Ryzen Threadripper 2950X
Mainboard MSI MEG x399 Creation
I was really disappointed to see this slow down in the level 1 VM. If level 2 (nested) VMs would be a bit slower, it would be OK. I have not tried again with the release version of Windows 11, I am afraid the issue is still there.