Some BSDs include a feature called ‘Machine Check Architecture’, which is intended to report hardware errors to the operating system. This is not suitable for use on a VM, as the machine does not see real hardware – only the virtual abstraction presented to it by the hypervisor – and may cause problems during boot.
We recommend you disable this in your VM’s boot options if you are experiencing problems. For example, you can do this on FreeBSD systems by adding
hw.mca.enabled=0 to the file /boot/loader.conf.local.
If you continue to see problems, some reports also indicate that it may be beneficial to disable TCP Segment Offload (TSO) by adding
hw.bce.tso_enable=0 to the same file.