Correct TL;DR<p>* High performence overhead and complexity of VM.<p>* Hypervisor vulnerabilities.<p>* Unikernel are small because the responsibilities are shifted to the process.<p>* &quot;Unikernels are entirely undebuggable.&quot;<p>---<p>IMO process isolation (segmentation, paging etc) already gives 100% performence with most security. And since these are old and simpler hardware designs, hardware bugs are less likely to happen.