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Peter Krempa
bf34b90bb4
Consider bitmaps for incoming migration regardless of non-shared storage flag. When bitmaps are offered from the source, consult the local image if the bitmap is present and if not accept migration. Migration of bitmaps which exist in the qcow2 metadata is skipped because qemu rejects such setup (although handles it correctly in case of shared storage setup; see below). This allows bitmap propagation for cases when the qcow2 image is not actually shared between destinations but the data is (using the data_file feature). At the same time this preserves existing bitmap handling semantics for other cases. Specifically qemu, in case of shared storage properly propagates the bitmap which was already recorded in the qcow2 metadata on disk even if libvirt doesn't instruct migration, yet tolerates migration instruction if the file is not yet recorded in the on-disk metadata. In both cases the contents are preserved correctly. When storage is not shared (which includes even cases when we migrate it via NBD) it's expected that the bitmaps don't exist on the destination and thus all will be picked for migration. We can also infer that this wasn't ever a problem by the fact that the code skipping migration of existing bitmaps was broken until recently, and qemu would refuse such config. I've tested all the above scenarios including verifying that the resulting bitmaps capture dirtied regions before and after migration. For testing this the following command is useful: virsh qemu-monitor-command --domain DOMNAME --hmp 'qemu-io -d /machine/peripheral/virtio-disk0/virtio-backend "write -P 0xcc 4M 1M"' Which simulates a write from the guest side without the need to interact with the guest OS. Signed-off-by: Peter Krempa <pkrempa@redhat.com> Reviewed-by: Ján Tomko <jtomko@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