There were plenty snapshot XMLs in the tests/domainsnapshotxml2xmlin
directory that actually weren't used in XML testing. The upgraded
domainsnapshotxml2xml test now allows us to use them.
Each <domainsnapshot> can now contain an optional <memory>
element that describes how the VM state was handled, similar
to disk snapshots. The new element will always appear in
output; for back-compat, an input that lacks the element will
assume 'no' or 'internal' according to the domain state.
Along with this change, it is now possible to pass <disks> in
the XML for an offline snapshot; this also needs to be wired up
in a future patch, to make it possible to choose internal vs.
external on a per-disk basis for each disk in an offline domain.
At that point, using the --disk-only flag for an offline domain
will be able to work.
For some examples below, remember that qemu supports the
following snapshot actions:
qemu-img: offline external and internal disk
savevm: online internal VM and disk
migrate: online external VM
transaction: online external disk
=====
<domainsnapshot>
<memory snapshot='no'/>
...
</domainsnapshot>
implies that there is no VM state saved (mandatory for
offline and disk-only snapshots, not possible otherwise);
using qemu-img for offline domains and transaction for online.
=====
<domainsnapshot>
<memory snapshot='internal'/>
...
</domainsnapshot>
state is saved inside one of the disks (as in qemu's 'savevm'
system checkpoint implementation). If needed in the future,
we can also add an attribute pointing out _which_ disk saved
the internal state; maybe disk='vda'.
=====
<domainsnapshot>
<memory snapshot='external' file='/path/to/state'/>
...
</domainsnapshot>
This is not wired up yet, but future patches will allow this to
control a combination of 'virsh save /path/to/state' plus disk
snapshots from the same point in time.
=====
So for 1.0.1 (and later, as needed), I plan to implement this table
of combinations, with '*' designating new code and '+' designating
existing code reached through new combinations of xml and/or the
existing DISK_ONLY flag:
domain memory disk disk-only | result
-----------------------------------------
offline omit omit any | memory=no disk=int, via qemu-img
offline no omit any |+memory=no disk=int, via qemu-img
offline omit/no no any | invalid combination (nothing to snapshot)
offline omit/no int any |+memory=no disk=int, via qemu-img
offline omit/no ext any |*memory=no disk=ext, via qemu-img
offline int/ext any any | invalid combination (no memory to save)
online omit omit off | memory=int disk=int, via savevm
online omit omit on | memory=no disk=default, via transaction
online omit no/ext off | unsupported for now
online omit no on | invalid combination (nothing to snapshot)
online omit ext on | memory=no disk=ext, via transaction
online omit int off |+memory=int disk=int, via savevm
online omit int on | unsupported for now
online no omit any |+memory=no disk=default, via transaction
online no no any | invalid combination (nothing to snapshot)
online no int any | unsupported for now
online no ext any |+memory=no disk=ext, via transaction
online int/ext any on | invalid combination (disk-only vs. memory)
online int omit off |+memory=int disk=int, via savevm
online int no/ext off | unsupported for now
online int int off |+memory=int disk=int, via savevm
online ext omit off |*memory=ext disk=default, via migrate+trans
online ext no off |+memory=ext disk=no, via migrate
online ext int off | unsupported for now
online ext ext off |*memory=ext disk=ext, via migrate+transaction
* docs/schemas/domainsnapshot.rng (memory): New RNG element.
* docs/formatsnapshot.html.in: Document it.
* src/conf/snapshot_conf.h (virDomainSnapshotDef): New fields.
* src/conf/domain_conf.c (virDomainSnapshotDefFree)
(virDomainSnapshotDefParseString, virDomainSnapshotDefFormat):
Manage new fields.
* tests/domainsnapshotxml2xmltest.c: New test.
* tests/domainsnapshotxml2xmlin/*.xml: Update existing tests.
* tests/domainsnapshotxml2xmlout/*.xml: Likewise.
Peter Krempa