UEK provides support for PVHVM guests on Oracle VM. The default is to present only PV drivers when running in an HVM guest. To run kernel-uek fully hardware virtualized, including the drivers, add the parameter xen_emul_unplug=never to the boot parameters in /etc/grub.conf, for example:

kernel /vmlinuz-2.6.32-300.2.1.el6uek ro root=/dev/VolGroup00/LogVol00 xen_emul_unplug=never

Adding this parameter makes the kernel also present the emulated drivers as previously done, such as the 8139cp network driver.