Today, virtualization technology plays an important role in the computer industry. Virtual Machines (VMs) are deployed in a number of different scenarios to meet the requirements of a market that expects service delivery to be fast, dynamic and transparent. An area where VMs have been more cautiously used is High Performance Computing (HPC). In HPC use cases, there are often strict requirements to the performance throughout a system of several compute nodes. Traditionally, communication between VMs have been limited to standard networking mechanism such as TCP/IP. There are approaches for high performance Inter-VM communication (IVMC) between co-located guests, however, to the best of our knowledge, few solutions combine this with high bandwidth and low latency remote communication. In this thesis, we propose a unified IVMC mechanism based on the Software Infrastructure for Shared-Memory Cluster Interconnect (SISCI) API. SISCI enables local and remote applications communicate through shared memory, which for the remote case is exposed through a PCI Express (PCIe) interconnect utilizing Non-Transparent Bridges (NTBs). In our proof of concept implementation developed for the Qemu/KVM hypervisor, we extend the SISCI API functionality to VMs, allowing them to seamlessly communicate through shared memory, regardless of whether they are co-located or reside on different hosts. Binary compatibility with existing SISCI applications is achieved, and no significant modifications have been made to Qemu/KVM or the guest operating system. Our prototype shows that an approach based on SISCI allows for a near native memory bandwidth between co-located VMs. In addition, guest applications can utilize the performance potential of the underlying PCIe interconnect. Depending on the PCIe adapter card used, a remote bandwidth between 2.9 and 6.9 gigabytes per second is achieved, with a memory latency as low as 0.7 microseconds. This corresponds to an overhead of less than 1 percent when compared to the remote performance of native SISCI applications.