The following diagram demonstrates the involvement of the kernel in the Device Assignment and SR-IOV architectures.
Figure 5.2. Device assignment and SR-IOV
Device assignment presents the entire device to the guest. SR-IOV needs support in drivers and hardware, including the NIC and the system board and allows multiple virtual devices to be created and passed into different guests. A vendor-specific driver is required in the guest, however, SR-IOV offers the lowest latency of any network option.