A single physical PCI Express bus can be shared in a virtual environment using the SR-IOV specification.
SR-IOV uses physical and virtual functions to control or configure PCIe devices.
The virtual or physical functions available to the hypervisor or guest operating system depend on the PCIe device.
In contrast, MR-IOV allows I/O PCI Express to share resources among different VMs on different physical machines.
A major field of application for SR-IOV is within high-performance computing (HPC).