Xen FAQ Booting
I have problems getting Xen or dom0 kernel to boot, how can I set up a serial console to log and troubleshoot the boot process?
See the XenSerialConsole wiki page.
I am booting my new EFI-based system. I se "Loading ramdisk..." and then it stops
Go into your BIOS and enable Legacy Booting (non-EFI). If it still doesn't work, upgrade the BIOS to its latest version.