Spectre Mitigation/lfence not serializing on VM Startup

I am having the same problem with this version on Ubuntu in VirtualBox. I'm running on a new computer and I have SVM enabled in the bios.

Edit: Ubuntu 18.04 lts freezes while in boot, in wndows Virtual box. Solution?

This answer led me to try turning on an additional core in Settings -> System -> Processor which then would show the "Spectre v2..." text but still boot.

I had the same issue on Windows 10 host inside VirtualBox when I installed Docker it automatically enabled Hyper-V and the Ubuntu Guest Os behaved exactly like you describe, nothing helped but disabling Hyper-V in Windows 10 host settings - Win+R ->OptionalFeatures.exe -> uncheck Hyper-V

Edit: had to also uninstall Docker, as it always after each restart re-enabled hyper-v, although it could be maybe possible to setup VirtualBox instead of Hyper-V as docker engine in docker settings, but rather VirtualBox docker utility = "Docker toolbox"