vhost-user-rng.rst

QEMU vhost-user-rng - RNG emulation backend

Synopsis

vhost-user-rng [OPTIONS]

Description

This program is a vhost-user backend that emulates a VirtIO random number generator (RNG). It uses the host's random number generator pool, /dev/urandom by default but configurable at will, to satisfy requests from guests.

This program is designed to work with QEMU's -device vhost-user-rng-pci but should work with any virtual machine monitor (VMM) that supports vhost-user. See the Examples section below.

Options

vhost-user-rng

-h, --help

Print help.

-v, --verbose

Increase verbosity of output

-s, --socket-path=PATH

Listen on vhost-user UNIX domain socket at PATH. Incompatible with --fd.

-f, --fd=FDNUM

Accept connections from vhost-user UNIX domain socket file descriptor FDNUM. The file descriptor must already be listening for connections. Incompatible with --socket-path.

-p, --period

Rate, in milliseconds, at which the RNG hardware can generate random data. Used in conjunction with the --max-bytes option.

-m, --max-bytes

In conjuction with the --period parameter, provides the maximum number of byte per milliseconds a RNG device can generate.

Examples

The daemon should be started first:

host# vhost-user-rng --socket-path=rng.sock --period=1000 --max-bytes=4096

The QEMU invocation needs to create a chardev socket the device can use to communicate as well as share the guests memory over a memfd.

host# qemu-system                             \
    -chardev socket,path=$(PATH)/rng.sock,id=rng0             \
    -device vhost-user-rng-pci,chardev=rng0                   \
    -m 4096                                   \
    -object memory-backend-file,id=mem,size=4G,mem-path=/dev/shm,share=on \
    -numa node,memdev=mem                         \
    ...