Is there any way to set up a virtual infiniband network within kvm/qemu? If not, is there a viable open source alternative which would allow virtual infiniband networking?
(Note that I'm not looking to give VMs access to a physical IB network, I'm looking to have an entirely virtual IB network with no IB hardware)
One of the following two drivers is probably what you are looking for: softRoCE (rdma_rxe) or softiWARP (http://www.gitorious.org/softiwarp). The softRoCE driver went upstream in Linux kernel version v4.8.
Currently, to the best of my knowledge, QEMU/KVM can only emulate the basic (but enought to run a VM) set of bios/video/usb/disk/net combo. I know you said you don't want physical hardware, but your best chance at giving a VM some IB capabilities is using PCI passthrough.