Xen
From Syslinux Wiki
To load Xen-based kernels you have to use the SYSLINUX multiboot module mboot.c32.
DEFAULT xen LABEL xen KERNEL mboot.c32 APPEND xen-3.0.2-1-i386.gz dom0_mem=262144 --- vmlinuz-2.6.16-2-xen-686 console=tty0 root=/dev/hda1 ro --- initrd.img-2.6.16-2-xen-686 PROMPT 1 TIMEOUT 0