Merge "Use :oslo-config: role in hypervisor-kvm doc"

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Zuul 2019-02-14 04:05:30 +00:00 committed by Gerrit Code Review
commit 37f3a96a74

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@ -233,7 +233,8 @@ image, and any ephemeral storage. Inside the virtual machine, this is normally
presented as two virtual hard disks (for example, ``/dev/vda`` and ``/dev/vdb``
respectively). However, inside OpenStack, this can be derived from one of these
methods: ``lvm``, ``qcow``, ``rbd`` or ``flat``, chosen using the
``images_type`` option in ``nova.conf`` on the compute node.
:oslo.config:option:`libvirt.images_type` option in ``nova.conf`` on the
compute node.
.. note::
@ -241,7 +242,8 @@ methods: ``lvm``, ``qcow``, ``rbd`` or ``flat``, chosen using the
Flat back end uses either raw or QCOW2 storage. It never uses a backing
store, so when using QCOW2 it copies an image rather than creating an
overlay. By default, it creates raw files but will use QCOW2 when creating a
disk from a QCOW2 if ``force_raw_images`` is not set in configuration.
disk from a QCOW2 if :oslo.config:option:`force_raw_images` is not set in
configuration.
QCOW is the default backing store. It uses a copy-on-write philosophy to delay
allocation of storage until it is actually needed. This means that the space
@ -255,8 +257,8 @@ reserved on the physical disk.
Local `LVM volumes
<https://en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux)>`__ can also be
used. Set ``images_volume_group = nova_local`` where ``nova_local`` is the name
of the LVM group you have created.
used. Set the :oslo.config:option:`libvirt.images_volume_group` configuration
option to the name of the LVM group you have created.
Specify the CPU model of KVM guests
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@ -277,12 +279,13 @@ of standard CPU model names. These models are defined in the
``/usr/share/libvirt/cpu_map.xml`` file. Check this file to determine which
models are supported by your local installation.
Two Compute configuration options in the ``[libvirt]`` group of ``nova.conf``
define which type of CPU model is exposed to the hypervisor when using KVM:
``cpu_mode`` and ``cpu_model``.
Two Compute configuration options in the :oslo.config:group:`libvirt` group
of ``nova.conf`` define which type of CPU model is exposed to the hypervisor
when using KVM: :oslo.config:option:`libvirt.cpu_mode` and
:oslo.config:option:`libvirt.cpu_model`.
The ``cpu_mode`` option can take one of the following values: ``none``,
``host-passthrough``, ``host-model``, and ``custom``.
The :oslo.config:option:`libvirt.cpu_mode` option can take one of the following
values: ``none``, ``host-passthrough``, ``host-model``, and ``custom``.
See `Effective Virtual CPU configuration in Nova`_ for a recorded presentation
about this topic.
@ -323,7 +326,7 @@ may even include the running kernel. Use this mode only if
* your compute nodes have a very large degree of homogeneity
(i.e. substantially all of your compute nodes use the exact same CPU
generation and model), and you make sure to only live-migrate
between hosts with exactly matching kernel versions, `or`
between hosts with exactly matching kernel versions, *or*
* you decide, for some reason and against established best practices,
that your compute infrastructure should not support any live
@ -343,10 +346,11 @@ option. For example, to configure the KVM guests to expose Nehalem CPUs, your
cpu_mode = custom
cpu_model = Nehalem
In selecting the ``custom`` mode, along with a ``cpu_model`` that
matches the oldest of your compute node CPUs, you can ensure that live
migration between compute nodes will always be possible. However, you
should ensure that the ``cpu_model`` you select passes the correct CPU
In selecting the ``custom`` mode, along with a
:oslo.config:option:`libvirt.cpu_model` that matches the oldest of your compute
node CPUs, you can ensure that live migration between compute nodes will always
be possible. However, you should ensure that the
:oslo.config:option:`libvirt.cpu_model` you select passes the correct CPU
feature flags to the guest.
If you need to further tweak your CPU feature flags in the ``custom``
@ -362,7 +366,7 @@ a CPU model. Instead, the hypervisor chooses the default model.
Set CPU feature flags
~~~~~~~~~~~~~~~~~~~~~
Regardless of whether your selected ``cpu_mode`` is
Regardless of whether your selected :oslo.config:option:`libvirt.cpu_mode` is
``host-passthrough``, ``host-model``, or ``custom``, it is also
possible to selectively enable additional feature flags. Suppose your
selected ``custom`` CPU model is ``IvyBridge``, which normally does
@ -403,8 +407,9 @@ A reboot may be required for the change to become effective.
Nested guest support in ``nova.conf``
-------------------------------------
To support nested guests, you must set your ``cpu_mode`` configuration
to one of the following options:
To support nested guests, you must set your
:oslo.config:option:`libvirt.cpu_mode` configuration to one of the following
options:
Host pass through
In this mode, nested virtualization is automatically enabled once
@ -424,7 +429,7 @@ Host model
matching CPU model exposes the ``vmx`` feature flag to guests by
default (you can verify this with ``virsh capabilities`` on your
compute node). If your CPU model does not pass in the ``vmx`` flag,
you can force it with ``cpu_model_extra_flags``:
you can force it with :oslo.config:option:`libvirt.cpu_model_extra_flags`:
.. code-block:: ini