Nested virtualization BUG: soft lockup - CPU#4 stuck for 22s! [CPU 1/KVM:28838]

[hamerins]

I am running a KVM vm inside virtualbox. if the VM is set with 1 CPU, it works well. But if i increase the CPU to 2 or more, i am getting CPU stuck message inside virtualbox.

HOST OS: MAC OSX Virtualbox Version: 6.1.6 Host have 12 cores and 64gb ram

Guest OS: Ubuntu 18.04 Guest CPU: 4 Guest Ram: 20GB Nested VT-x/AMD-V and PAE/NX is enabled in processor settings

Nested VM Guest OS: debian Nested VM Guest CPU: 2 Nested VM Guest Ram: 4GB

Partial syslog message and vbox.log is attached

[hamerins]

partial syslog

[hamerins]

vbox.log

[pneumann]

I'm seeing the same issue with VirtualBox 6.1.6 using either KVM or VirtualBox in the guest. Using one vCPU for the nested guest works fine, but two or more result in the "CPU stuck" message in the guest.

Host: Windows 10 Professional x64 Version 10.0.18363.836, Intel Core i7 8700K CPU (6 cores/12 threads), 32 GB RAM

Guest: Oracle Linux 7.8 with UEKR6, 4 vCPUs, 6 GB RAM, Nested VT-x/AMD-V and PAE/NX enabled in processor settings

Nested guests I've tried are Oracle Linux 7.7, Oracle Linux 7.8 and Ubuntu 18.04. All have the same issue.

This may be specific to nested virtualization on Intel CPU hosts. I don't have access to an AMD CPU to check.

[pneumann]

This issue appears to be similar to the problem described in ticket #19315.

[ramshankar]

I think the problem should now be fixed (with SMP nested guests).

Feel free to try out the test builds from https://www.virtualbox.org/wiki/Testbuilds (6.1.x 141725 or newer) and provide your feedback here.

[sequoiar]

I just tried 6.1.x 141725 on mac osx. after launch nested vm, the virtaulbox got crash, even with only one vcpu in nested vm.

[ramshankar]

Replying to sequoiar:

I just tried 6.1.x 141725 on mac osx. after launch nested vm, the virtaulbox got crash, even with only one vcpu in nested vm.

Please upload VBox.log for the crashed VM.