Hello, the last version of Xen kernel for SL4/64bit: kernel-xenU-2.6.9-89.35.1.EL.x86_64
does not have xenblk.ko module in initrd file: /boot/initrd-2.6.9-89.35.1.ELxenU.img- so paravirtualized xen guests do not boot (they do not find Xen block devices). After adding the module, lines loading the module to init script and rebuilding initrd everything works fine.
I do not know if this was intended, but as it seems weird for a Xen kernel I am reporting it as a potential bug.
Cheers, Tomasz
