Paravirtualisaation

Paravirtualization is a technique in virtualization that involves modifying the guest operating system's kernel to make it aware it is running in a virtualized environment. Instead of trapping privileged instructions, the paravirtualized guest makes direct calls to the hypervisor through a specialized interface known as a "hypercall." This cooperative approach significantly reduces the overhead associated with traditional full virtualization, where the hypervisor must intercept and emulate every privileged operation.

By avoiding hardware emulation and direct instruction trapping, paravirtualization can achieve near-native performance for many operations. This is particularly beneficial for I/O-intensive workloads. However, it requires specific modifications to the guest operating system, meaning that a paravirtualized guest must be designed or adapted to work with the hypervisor. This contrasts with full virtualization, which can run unmodified guest operating systems.

While full virtualization has gained popularity due to its compatibility with any operating system, paravirtualization remains a valuable technique for maximizing performance in specific scenarios, especially when control over the guest operating system is possible. Many modern hypervisors support paravirtualized drivers for common devices, even for operating systems that are not inherently paravirtualized, offering a hybrid approach.