USB 3 (xHCI) USB host adapter emulation is supported in Red Hat Enterprise Linux 7.2 and above. All USB speeds are available, meaning any generation of USB device can be plugged into a xHCI bus. Additionally, no companion controllers (for USB 1 devices) are required. Note, however, that USB 3 bulk streams are not supported.
Advantages of xHCI:
Virtualization-compatible hardware design, meaning xHCI emulation requires less CPU resources than previous versions due to reduced polling overhead.
USB passthrough of USB 3 devices is available.
Limitations of xHCI: