QEMU/Devices/Virtio

VirtIO is a platform for IO virtualization, common to several hypervisors (and QEMU).

The guest operating system needs specialized drivers to handle these devices.

Supported devices list

Function	Bus	Type	Device	Usage example
Networking	PCI	10Gb/s	virtio-net-pci	-net nic,model=virtio ...
Storage	PCI	SCSI	virtio-scsi-pci	-device virtio-scsi-pci -drive file=disk.img,if=none,id=hd0 -device scsi-hd,drive=hd0 ...
Storage	PCI	Custom	virtio-blk	-drive file=disk.img,if=virtio ...
Memory	PCI	RAM	virtio-balloon-pci
Serial	PCI	Serial	virtio-serial-pci
Random Number Generator	PCI	RNG	virtio-rng-pci	→ virtio-rng-pci

virtio-rng-pci

Entropy sources

To set up a VirtIO RNG, you first need to provide a source of entropy for it.

For devices exported by the kernel on UNIX-like systems, you can do so like this:
-object rng-random,filename=/dev/random,id=rng0

It is obviously not limited to the kernel RNG, you can choose a hardware RNG too in the very same way.

It also supports EGD, though it is not recommended because of its poor performance.
Example: -chardev socket,host=10.199.13.151,port=9000,id=chr0 -object rng-egd,chardev=chr0,id=rng0

Adding the actual device

Then you can add the actual device, like this: -device virtio-rng-pci,rng=rng0

There's also an option to limit the amount of data the guest received, to avoid starving the host.
Example: max-bytes=512,period=1000 for 512 bytes/s.

Supported Guest Systems

OS	Drivers
Microsoft Windows	http://www.linux-kvm.org/page/WindowsGuestDrivers/Download_Drivers
Linux-based	2.6.x, 3.x, 4.x
FreeBSD	9.x (available), 10.x (in GENERIC kernel) https://www.freebsd.org/cgi/man.cgi?query=virtio&sektion=4
NetBSD	6.0+
OpenBSD	5.9+