Using userspace networking with TAP and TUN devices

In Chapter 1, Understanding Linux Virtualization, we used the virt-host-validate command to do some pre-flight checks in terms of the host's preparedness for KVM virtualization. As a part of that process, some of the checks include checking if the following devices exist:

• /dev/kvm: The KVM drivers create a /dev/kvm character device on the host to facilitate direct hardware access for virtual machines. Not having this device means that the VMs won't be able to access physical hardware, although it's enabled in the BIOS and this will reduce the VM's performance significantly.
• /dev/vhost-net: The /dev/vhost-net character device will be created on the host. This device serves as the interface for configuring the vhost-net instance. Not having this device significantly reduces the virtual machine's network performance.
• /dev/net/tun: This is another character special device used for creating TUN...