Hi mruepp,
vSphere supports several virtualization technologies listed below, you may use option #a.
a. vmnic/vmhba Para Virtulization: for networking/storage services, this is supported today using OFED 1.8.1 (or later) for ESX 5.x, Mellanox currently support IPoIB protocol for networking virtulization where you can have vmnic over InfiniBand network (with involves the vSwitch and VMXNET -or other- emulators), as well as SRP protocol for storage virtulization where you can have vmhba over InfiniBand. for more information, check the user manual under "related documents" section under: http://www.mellanox.com/page/products_dyn?&product_family=36&mtag=vmware_drivers
b. Full-function DirectPath I/O: where you can give direct access for SINGLE virtual machine to a single HCA adapter:
see option #1 under: http://cto.vmware.com/wp-content/uploads/2012/09/RDMAonvSphere.pdf. This is supported today.
c. SRIOV DirectPath I/O: where you can give direct access for MULTIPLE virtual machines to a single HCA adapter, will be supported in next OFED release (post OFED 1.8.1) see option #2 under: http://cto.vmware.com/wp-content/uploads/2012/09/RDMAonvSphere.pdf
d. vRDMA (RDMA Para Virtulization): this is an experimental project (not available for customers), see option #3 under: http://cto.vmware.com/wp-content/uploads/2012/09/RDMAonvSphere.pdf