Installation guide

Chapter 11.

KVM Para-virtualized Drivers

Para-virtualized drivers are available for virtualized Windows guests running on KVM hosts. These

para-virtualized drivers are included in the virtio package. The virtio package supports block (storage)

devices and network interface controllers.

Para-virtualized drivers enhance the performance of fully virtualized guests. With the para-virtualized

drivers guest I/O latency decreases and throughput increases to near bare-metal levels. It is

recommended to use the para-virtualized drivers for fully virtualized guests running I/O heavy tasks

and applications.

The KVM para-virtualized drivers are automatically loaded and installed on the following:

• Red Hat Enterprise Linux 3.9 and newer

• Red Hat Enterprise Linux 4.8 and newer

• Red Hat Enterprise Linux 5.3 and newer

• Red Hat Enterprise Linux 6 and newer

• Some versions of Linux based on the 2.6.27 kernel or newer kernel versions.

Versions of Red Hat Enterprise Linux in the list above detect and install the drivers, additional

installation steps are not required.

Note

PCI devices are limited by the virtualized system architecture. Out of the 32 available PCI devices

for a guest, 4 are not removable. This means there are up to 28 free PCI slots available for

additional devices per guest. Each PCI device in a guest can have up to 8 functions.

The following Microsoft Windows versions are expected to function normally using KVM para-

virtualized drivers:

• Windows XP (32-bit only)

• Windows Server 2003 (32-bit and 64-bit versions)

• Windows Server 2008 (32-bit and 64-bit versions)

• Windows 7 (32-bit and 64-bit versions)

11.1. Using the para-virtualized drivers with Red Hat

Enterprise Linux 3.9 guests

Para-virtualized drivers for Red Hat Enterprise Linux 3.9 consist of five kernel modules: virtio,

virtio_blk, virtio_net, virtio_pci and virtio_ring. All five modules must be loaded to

use both the para-virtualized block and network devices drivers.