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This is not a good idea in general, but we can (and have to) do it in specific cases when a feature has always been part of a CPU model in hypervisor's definition, but we ignored it and did not include the feature in our definition. Blindly adding the features to the CPU map and not adding them to existing CPU models breaks migration between old and new libvirt in both directions. New libvirt would complain the features got unexpectedly enabled (as they were not mentioned in the incoming domain XML) even though they were also enabled on the source and the old libvirt just didn't know about them. On the other hand, old libvirt would refuse to accept incoming migration of a domain started by new libvirt because the domain XML would contain CPU features unknown to the old libvirt. This is exactly what happened when several vmx-* features were added a few releases back. Migration between libvirt releases before and after the addition is now broken. This patch adds support for added these features to existing CPU models by marking them with added='yes'. The features will not be considered part of the CPU model and will be described explicitly via additional <feature/> elements, but the compatibility check will not complain if they are enabled by the hypervisor even though they were not explicitly mentioned in the CPU definition and incoming migration from old libvirt will succeed. To fix outgoing migration to old libvirt, we also need to drop all those features from domain XML unless they were explicitly requested by the user. This will be handled by a later patch. Signed-off-by: Jiri Denemark <jdenemar@redhat.com> Reviewed-by: Tim Wiederhake <twiederh@redhat.com> Reviewed-by: Peter Krempa <pkrempa@redhat.com>
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==============================
Libvirt API for virtualization
==============================
Libvirt provides a portable, long term stable C API for managing the
virtualization technologies provided by many operating systems. It
includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware
vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER
Hypervisor.
For some of these hypervisors, it provides a stateful management
daemon which runs on the virtualization host allowing access to the
API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other
languages including Python, Perl, PHP, Go, Java, OCaml, as well as
mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the
website:
https://libvirt.org
License
=======
The libvirt C API is distributed under the terms of GNU Lesser General
Public License, version 2.1 (or later). Some parts of the code that are
not part of the C library may have the more restrictive GNU General
Public License, version 2.0 (or later). See the files ``COPYING.LESSER``
and ``COPYING`` for full license terms & conditions.
Installation
============
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
Contributing
============
The libvirt project welcomes contributions in many ways. For most components
the best way to contribute is to send patches to the primary development
mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
=======
The libvirt project has two primary mailing lists:
* users@lists.libvirt.org (**for user discussions**)
* devel@lists.libvirt.org (**for development only**)
Further details on contacting the project are available on the website:
https://libvirt.org/contact.html