Kashyap Chamarthy bcd6b42047 libvirt: Allow disabling CPU flags via cpu_model_extra_flags
Parse a comma-separated list of CPU flags from
`[libvirt]/cpu_model_extra_flags`.  If the CPU flag starts with '+',
enable the feature in Nova guest CPU guest XML, or if it starts with
'-', disable the feature.  If neither '+' nor '-' is specified, enable
the flag.  For example, on a compute node that is running hardware (e.g.
an Intel server that supports TSX) and virtualization software that
supports the given CPU flags, if a user provides this config:

    [libvirt]
    cpu_mode = custom
    cpu_models = Cascadelake-Server
    cpu_model_extra_flags = -hle, -rtm, +ssbd, mtrr

Then Nova should generate this CPU for the guest:

     <cpu match='exact'>
       <model fallback='forbid'>Cascadelake-Server</model>
       <vendor>Intel</vendor>
       <feature policy='require' name='ssbd'/>
       <feature policy='require' name='mtrr'/>
       <feature policy='disable' name='hle'/>
       <feature policy='disable' name='rtm'/>
     </cpu>

This ability to selectively disable CPU flags lets you avoid any CPU
flags that need to be disabled for any number of reasons.  E.g. disable
a CPU flag that is a potential security risk, or disable one that causes
a performance penalty.

blueprint: allow-disabling-cpu-flags

Change-Id: I2ef7c5bef87bd64c087f3b136c2faac9a3865f10
Signed-off-by: Patrick Uiterwijk <patrick@puiterwijk.org>
Signed-off-by: Kashyap Chamarthy <kchamart@redhat.com>
2021-03-04 17:40:06 +01:00
2020-05-15 15:59:53 +01:00
2019-04-19 19:45:52 +00:00
2014-05-07 12:14:26 -07:00
2020-01-17 11:30:40 +00:00
2017-11-24 16:51:12 -05:00
2010-05-27 23:05:26 -07:00
2017-09-07 15:42:31 +02:00
2021-02-11 12:22:42 +00:00
2017-03-02 11:50:48 +00:00

==============
OpenStack Nova
==============

.. image:: https://governance.openstack.org/tc/badges/nova.svg
    :target: https://governance.openstack.org/tc/reference/tags/index.html

.. Change things from this point on


OpenStack Nova provides a cloud computing fabric controller, supporting a wide
variety of compute technologies, including: libvirt (KVM, Xen, LXC and more),
Hyper-V, VMware, OpenStack Ironic and PowerVM.

Use the following resources to learn more.

API
---

To learn how to use Nova's API, consult the documentation available online at:

- `Compute API Guide <https://docs.openstack.org/api-guide/compute/>`__
- `Compute API Reference <https://docs.openstack.org/api-ref/compute/>`__

For more information on OpenStack APIs, SDKs and CLIs in general, refer to:

- `OpenStack for App Developers <https://www.openstack.org/appdev/>`__
- `Development resources for OpenStack clouds
  <https://developer.openstack.org/>`__

Operators
---------

To learn how to deploy and configure OpenStack Nova, consult the documentation
available online at:

- `OpenStack Nova <https://docs.openstack.org/nova/>`__

In the unfortunate event that bugs are discovered, they should be reported to
the appropriate bug tracker. If you obtained the software from a 3rd party
operating system vendor, it is often wise to use their own bug tracker for
reporting problems. In all other cases use the master OpenStack bug tracker,
available at:

- `Bug Tracker <https://bugs.launchpad.net/nova>`__

Developers
----------

For information on how to contribute to Nova, please see the contents of the
CONTRIBUTING.rst.

Any new code must follow the development guidelines detailed in the HACKING.rst
file, and pass all unit tests.

Further developer focused documentation is available at:

- `Official Nova Documentation <https://docs.openstack.org/nova/>`__
- `Official Client Documentation
  <https://docs.openstack.org/python-novaclient/>`__

Other Information
-----------------

During each `Summit`_ and `Project Team Gathering`_, we agree on what the whole
community wants to focus on for the upcoming release. The plans for nova can
be found at:

- `Nova Specs <http://specs.openstack.org/openstack/nova-specs/>`__

.. _Summit: https://www.openstack.org/summit/
.. _Project Team Gathering: https://www.openstack.org/ptg/
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