================================== QEMU virtual RAPL MSR helper

Synopsis

qemu-vmsr-helper [OPTION]

Description

Implements the virtual RAPL MSR helper for QEMU.

Accessing the RAPL (Running Average Power Limit) MSR enables the RAPL powercap driver to advertise and monitor the power consumption or accumulated energy consumption of different power domains, such as CPU packages, DRAM, and other components when available.

However those registers are accessible under privileged access (CAP_SYS_RAWIO). QEMU can use an external helper to access those privileged registers.

:program:qemu-vmsr-helper is that external helper; it creates a listener socket which will accept incoming connections for communication with QEMU.

If you want to run VMs in a setup like this, this helper should be started as a system service, and you should read the QEMU manual section on "RAPL MSR support" to find out how to configure QEMU to connect to the socket created by :program:qemu-vmsr-helper.

After connecting to the socket, :program:qemu-vmsr-helper can optionally drop root privileges, except for those capabilities that are needed for its operation.

:program:qemu-vmsr-helper can also use the systemd socket activation protocol. In this case, the systemd socket unit should specify a Unix stream socket, like this::

[Socket]
ListenStream=/var/run/qemu-vmsr-helper.sock

Options

.. program:: qemu-vmsr-helper

.. option:: -d, --daemon

run in the background (and create a PID file)

.. option:: -q, --quiet

decrease verbosity

.. option:: -v, --verbose

increase verbosity

.. option:: -f, --pidfile=PATH

PID file when running as a daemon. By default the PID file is created in the system runtime state directory, for example :file:/var/run/qemu-vmsr-helper.pid.

.. option:: -k, --socket=PATH

path to the socket. By default the socket is created in the system runtime state directory, for example :file:/var/run/qemu-vmsr-helper.sock.

.. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]

.. include:: ../qemu-option-trace.rst.inc

.. option:: -u, --user=USER

user to drop privileges to

.. option:: -g, --group=GROUP

group to drop privileges to

.. option:: -h, --help

Display a help message and exit.

.. option:: -V, --version

Display version information and exit.