> Ideally, a VM should be indistinguishable from real hardware VMs wouldn't achieve the performance they do without paravirtualization. VMs don't meticulously

> Ideally, a VM should be indistinguishable from real hardware VMs wouldn't achieve the performance they do without paravirtualization. VMs don't meticulously emulate all attached virtual devices. Paravirtualized device drivers more or less forward the I/O request to the hypervisor which handles it in a VM-specific way. For example, it's not super useful for a VM to emulate all the bitwise register-twiddling dances needed to talk to a SATA controller, it can simply have some "backdoor" channel into the hypervisor that says "Queue request to write X to LBA Y for this VM". Since paravirtualization requires specific drivers, it will always be detected.