I have figured it out. The board does support SR-IOV! PCI passthrough must be disabled first for that nic to enable SR-IOV in esxi. I passed through the virtual functions to two different VMs and funny enough, I was able to get over 10Gbps with iperf! There must be some interesting stuff done by the X540. The switching is completely offloaded to the X540 and no CPU usage on the vSwitch in esxi! Awesome!