What protocol is often used to connect to virtual machines hosted by the Kernel-Based Virtual Machine hypervisor?

The protocol commonly used to connect to virtual machines hosted by the Kernel-Based Virtual Machine (KVM) hypervisor is SPICE. This protocol is designed specifically for virtual machine environments to provide enhanced user experience features like audio and video streaming, clipboard sharing, and high-quality graphics.

SPICE (Simple Protocol for Independent Computing Environments) is optimized to work with the virtual desktop infrastructure, enabling remote access to the graphical user interface of virtual machines. It offers performance improvements and a better user experience compared to other protocols, making it the preferred choice for KVM.

While SSH (Secure Shell) is a powerful protocol used to securely access and manage remote servers, it primarily provides command-line access and is less suitable for graphical interfaces. X Forwarding allows graphical applications to run over SSH but does not provide the optimized experience that SPICE does for KVM. NX is also a protocol that facilitates remote desktop solutions but is less common for KVM compared to SPICE.

By understanding these protocols and their specific applications, it's clear why SPICE is the correct answer for connecting to virtual machines in a KVM environment.