1================================== 2QEMU virtual RAPL MSR helper 3================================== 4 5Synopsis 6-------- 7 8**qemu-vmsr-helper** [*OPTION*] 9 10Description 11----------- 12 13Implements the virtual RAPL MSR helper for QEMU. 14 15Accessing the RAPL (Running Average Power Limit) MSR enables the RAPL powercap 16driver to advertise and monitor the power consumption or accumulated energy 17consumption of different power domains, such as CPU packages, DRAM, and other 18components when available. 19 20However those registers are accessible under privileged access (CAP_SYS_RAWIO). 21QEMU can use an external helper to access those privileged registers. 22 23:program:`qemu-vmsr-helper` is that external helper; it creates a listener 24socket which will accept incoming connections for communication with QEMU. 25 26If you want to run VMs in a setup like this, this helper should be started as a 27system service, and you should read the QEMU manual section on "RAPL MSR 28support" to find out how to configure QEMU to connect to the socket created by 29:program:`qemu-vmsr-helper`. 30 31After connecting to the socket, :program:`qemu-vmsr-helper` can 32optionally drop root privileges, except for those capabilities that 33are needed for its operation. 34 35:program:`qemu-vmsr-helper` can also use the systemd socket activation 36protocol. In this case, the systemd socket unit should specify a 37Unix stream socket, like this:: 38 39 [Socket] 40 ListenStream=/var/run/qemu-vmsr-helper.sock 41 42Options 43------- 44 45.. program:: qemu-vmsr-helper 46 47.. option:: -d, --daemon 48 49 run in the background (and create a PID file) 50 51.. option:: -q, --quiet 52 53 decrease verbosity 54 55.. option:: -v, --verbose 56 57 increase verbosity 58 59.. option:: -f, --pidfile=PATH 60 61 PID file when running as a daemon. By default the PID file 62 is created in the system runtime state directory, for example 63 :file:`/var/run/qemu-vmsr-helper.pid`. 64 65.. option:: -k, --socket=PATH 66 67 path to the socket. By default the socket is created in 68 the system runtime state directory, for example 69 :file:`/var/run/qemu-vmsr-helper.sock`. 70 71.. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE] 72 73 .. include:: ../qemu-option-trace.rst.inc 74 75.. option:: -u, --user=USER 76 77 user to drop privileges to 78 79.. option:: -g, --group=GROUP 80 81 group to drop privileges to 82 83.. option:: -h, --help 84 85 Display a help message and exit. 86 87.. option:: -V, --version 88 89 Display version information and exit. 90