From Fedora Project Wiki

F13 Virtualization Release Notes

For the moment, I have copied the F12 Virtualization Release Notes for use in constructing the F13 notes.



Kernel Acceleration for KVM Networking

The VHost Net feature moves the task of converting virtio descriptors to skbs and back from qemu userspace to the kernel driver. This was shown to reduce latency by a factor of 5, and improve bandwidth from 90% native to 95% of native on some systems.

It is activated by using -netdevice options (instead of -net) and adding vhost=on flag.

KVM Stable PCI Addresses

KVM guests in Fedora now have stable PCI addresses, reducing the chance that Windows guests will require reactivation as guest configuration is modified.

KVM guest virtual machine devices retain their PCI address allocations as other devices are added or removed from the guest configuration.

Virt x2apic

X2apic improves guest performance by reducing the overhead of APIC access, which is used to program timers and for issuing inter-processor interrupts. By exposing x2apic to guests, and by enabling the guest to utilize x2apic, we improve guest performance.

Fedora 13 supports x2apic in both the host and guest roles.


The virtio-console pci device is now equipped to handle multiple console ports as well as generic ports for guests running on top of qemu and KVM. This facilitates simple communication between guest and host.