24c32ed374
Fix the misspellings of "overriden" also in code comments. Signed-off-by: Stefan Weil <sw@weilnetz.de> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Message-Id: <20240813125638.395461-1-sw@weilnetz.de> Reviewed-by: Peter Xu <peterx@redhat.com> Reviewed-by: Eric Auger <eric.auger@redhat.com> Signed-off-by: Alex Bennée <alex.bennee@linaro.org> Message-Id: <20240813202329.1237572-20-alex.bennee@linaro.org>
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90 lines
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==================================
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QEMU virtual RAPL MSR helper
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==================================
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Synopsis
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--------
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**qemu-vmsr-helper** [*OPTION*]
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Description
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-----------
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Implements the virtual RAPL MSR helper for QEMU.
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Accessing the RAPL (Running Average Power Limit) MSR enables the RAPL powercap
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driver to advertise and monitor the power consumption or accumulated energy
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consumption of different power domains, such as CPU packages, DRAM, and other
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components when available.
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However those registers are accessible under privileged access (CAP_SYS_RAWIO).
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QEMU can use an external helper to access those privileged registers.
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:program:`qemu-vmsr-helper` is that external helper; it creates a listener
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socket which will accept incoming connections for communication with QEMU.
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If you want to run VMs in a setup like this, this helper should be started as a
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system service, and you should read the QEMU manual section on "RAPL MSR
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support" to find out how to configure QEMU to connect to the socket created by
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:program:`qemu-vmsr-helper`.
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After connecting to the socket, :program:`qemu-vmsr-helper` can
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optionally drop root privileges, except for those capabilities that
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are needed for its operation.
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:program:`qemu-vmsr-helper` can also use the systemd socket activation
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protocol. In this case, the systemd socket unit should specify a
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Unix stream socket, like this::
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[Socket]
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ListenStream=/var/run/qemu-vmsr-helper.sock
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Options
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-------
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.. program:: qemu-vmsr-helper
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.. option:: -d, --daemon
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run in the background (and create a PID file)
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.. option:: -q, --quiet
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decrease verbosity
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.. option:: -v, --verbose
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increase verbosity
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.. option:: -f, --pidfile=PATH
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PID file when running as a daemon. By default the PID file
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is created in the system runtime state directory, for example
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:file:`/var/run/qemu-vmsr-helper.pid`.
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.. option:: -k, --socket=PATH
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path to the socket. By default the socket is created in
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the system runtime state directory, for example
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:file:`/var/run/qemu-vmsr-helper.sock`.
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.. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE]
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.. include:: ../qemu-option-trace.rst.inc
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.. option:: -u, --user=USER
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user to drop privileges to
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.. option:: -g, --group=GROUP
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group to drop privileges to
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.. option:: -h, --help
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Display a help message and exit.
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.. option:: -V, --version
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Display version information and exit.
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