Since 2009 the ancestor project of the illumos-gate learned to do "fastboot" (stop the current kernel instance and pass control to the next one, bypassing hardware motherboard reset and POST checks, which can take minutes on server-grade hardware) and did so by default on most non-virtual hardware. Unfortunately, there is sometimes some hardware (driver?) or other environmental issue which prohibit fastboot from properly working. This is noticeable by the message "Syncing disks... Rebooting..." which stays on your console forever.
As a single-instance solution, you can see if the complete reboot would work (you might want to manually stop your
zones and other important services before issuing this command):
This should go to the "POST" tests of the hardware.
If the complete reboot works, you can set up the SMF
boot-config service to use it instead of