Running A VirtualBox in a VirtualBox generates a critical error

[Valerian]

I have a Ubuntu 19.04 system and I run a a Win10 Dev in a VirtualBox
For some tests I needed a Ubuntu on windows so I Run an Ubuntu VirtualBox in the Windows VirtualBox.
Unfortunately this generates a "Guru" telling me : "A critical error has occurred while running the virtual machine and the machine execution has been stopped."

Did anyone run into this before ? Is there a known workaround ?

[mpack]

Please post a VM log file (of the host VM). With the VM fully shut down, right click and "Show Log" in the GUI, save "VBox.log" (no other file) to a zip, and attach the zip here.

[Valerian]

Here is a log that I just generated by:
1. Starting the VirtualBox (running Win10)
2. Starting the VirtualBox in the VirtualBox and running the Ubuntu image
3. Save log

[mpack]

00:00:00.754447 Full Name: "Intel(R) Core(TM) i7-8650U CPU @ 1.90GHz"

Nested virtualization is only supported on AMD CPUs, and then only if you can enable AMD-v passthrough to the VM.

• Enable Nested VT-x/AMD-V: Enables nested virtualization, with passthrough of hardware
virtualization functions to the guest VM.
This feature is available on host systems that use an AMD CPU. For Intel CPUs, the option
is grayed out.

[Valerian]

I see So other than replace my CPU is there a way around this ?

[mpack]

Not at the moment. Prior to v6 a nested VM was unsupported, period. It still isn't something I'd recommend (two layers of simulation will not provide best possible performance).

[Martin]

You could try the VirtualBox 6.1 Beta:

VirtualBox 6.1 will be a new minor release. Here is an incomplete list of changes since version 6.0:

• Virtualization core: support for nested hardware-virtualization on Intel CPUs (starting with 5th generation Core i, codename Broadwell)

[mpack]

Valerian has an 8th gen i7, so he certainly qualifies... though we're a bit early in the beta phase for my taste.

[socratis]

00:00:00.754467   Mnemonic - Description                                  = guest (host)
00:00:00.754482   UnrestrictedGuest - Unrestricted guest                  = 0 (1)
00:00:00.754485   VmcsShadowing - VMCS shadowing                          = 0 (1)

Yes, it does support nested virtualization (in theory).

@Valerian,
If you use 6.1.0b1 or any beta, make sure that you report your issues in the VirtualBox Beta / Release Candidate Feedback area, not in the "usual" area...