Installation guide

4.3. Virt ualized hardware devices

Virtualization on Red Hat Enterprise Linux 6 presents three distinct types of system devices to virtual

machines. The three types include:

Virtualized and emulated devices

Para-virtualized devices

Physically shared devices

These hardware devices all appear as being physically attached to the virtual machine but the

device drivers work in different ways.

4 .3.1. Virt ualiz ed and emulat ed devices

KVM implements many core devices for virtual machines in software. These emulated hardware

devices are crucial for virtualizing operating systems.

Emulated devices are virtual devices which exist entirely in software.

Emulated drivers may use either a physical device or a virtual software device. Emulated drivers are a

translation layer between the virtual machine and the Linux kernel (which manages the source

device). The device level instructions are completely translated by the KVM hypervisor. Any device, of

the same type (storage, network, keyboard, and mouse) and recognized by the Linux kernel, may be

used as the backing source device for the emulated drivers.

Virt u al C PUs ( vCPUs)

A host system can have up to 160 virtual CPUs (vCPUs) that can be presented to guests for

their use, regardless of the number of host CPUs.

Emu lat ed g rap h ics d evices

Two emulated graphics devices are provided. These devices can be connected to with the

SPICE (Simple Protocol for Independent Computing Environments) protocol or with VNC:

A Cirrus CLGD 5446 PCI VGA card (using the cirrus device)

A standard VGA graphics card with Bochs VESA extensions (hardware level, including

all non-standard modes)

Emu lat ed syst em co mp o n en t s

The following core system components are emulated to provide basic system functions:

Intel i440FX host PCI bridge

PIIX3 PCI to ISA bridge

PS/2 mouse and keyboard

EvTouch USB Graphics Tablet

PCI UHCI USB controller and a virtualized USB hub

Emulated serial ports

EHCI controller, virtualized USB storage and a USB mouse

Emu lat ed so u n d d evices

⁠Chapt er 4 . Int roduct io n t o Red Hat virt ualizat ion product s