mirror of https://gitee.com/openkylin/libvirt.git
f9db6f3ab6
There are a some scenarios in which we want to prealloc guest memory (e.g. when requested in domain XML, when using hugepages, etc.). With 'regular' <memory/> models (like 'dimm', 'nvdimm' or 'virtio-pmem') or regular guest memory it is corresponding memory-backend-* object that ends up with .prealloc attribute set. And that's desired because neither of those devices can change its size on the fly. However, with virtio-mem model things are a bit different. While one can set .prealloc attribute on corresponding memory-backend-* object it doesn't make much sense, because virtio-mem can inflate/deflate on the fly, i.e. change how big of a portion of the memory-backend-* object is exposed to the guest. For instance, from a say 4GiB module only a half can be exposed to the guest. Therefore, it doesn't make much sense to preallocate whole 4GiB and keep them allocated. But we still want the part exposed to the guest preallocated (when conditions described at the beginning are met). Having said that, with new enough QEMU the virtio-mem-pci device gained new attribute ".prealloc" which instructs the device to talk to the memory backend object and allocate only the requested portion of memory. Now, that our algorithm for setting .prealloc was isolated in a single function, the function can be called when constructing cmd line for virtio-mem-pci device. Signed-off-by: Michal Privoznik <mprivozn@redhat.com> Reviewed-by: Ján Tomko <jtomko@redhat.com> |
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README.rst
.. image:: https://gitlab.com/libvirt/libvirt/badges/master/pipeline.svg
:target: https://gitlab.com/libvirt/libvirt/pipelines
:alt: GitLab CI Build Status
.. image:: https://bestpractices.coreinfrastructure.org/projects/355/badge
:target: https://bestpractices.coreinfrastructure.org/projects/355
:alt: CII Best Practices
.. image:: https://translate.fedoraproject.org/widgets/libvirt/-/libvirt/svg-badge.svg
:target: https://translate.fedoraproject.org/engage/libvirt/
:alt: Translation status
==============================
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:
* libvirt-users@redhat.com (**for user discussions**)
* libvir-list@redhat.com (**for development only**)
Further details on contacting the project are available on the website:
https://libvirt.org/contact.html