A UCS blade's most popular daughter card is a VIC which can provide both Fibre and Ethernet connectivity. Support for this hardware is in a vanilla RHEL6 Linux kernel and a screen cap of running lsmod and modinfo on a machine with this hardware is below. This hardware allows you to present virtual Ethernet or HBAs directly to a virtual machine on RHEV. Cisco's name for this is VM-FEX and RedHat has benchmarks on VM-FEX and KVM performance.
Update: Cisco has documentation on Configuring VM-FEX for KVM.