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.
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Jiri Denemark 5fbfa5ab8a cpu: x86: Add support for adding features to existing CPU models
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>
2024-03-14 16:15:06 +01:00
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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:

Further details on contacting the project are available on the website:

https://libvirt.org/contact.html