The mainly changes are:

1) Update qemuMonitorGetBlockStatsInfo and it's children (Text/JSON)
   functions to return the value of new latency fields.
2) Add new function qemuMonitorGetBlockStatsParamsNumber, which is
   to count how many parameters the underlying QEMU supports.
3) Update virDomainBlockStats in src/qemu/qemu_driver.c to be
   compatible with the changes by 1).

If libvirt daemon gets restarted and there is (at least) one
unresponsive qemu, the startup procedure hangs up. This patch creates
one thread per vm in which we try to reconnect to monitor. Therefore,
blocking in one thread will not affect other APIs.

This patch annotates APIs with low or high priority.
In low set MUST be all APIs which might eventually access monitor
(and thus block indefinitely). Other APIs may be marked as high
priority. However, some must be (e.g. domainDestroy).

For high priority calls (HPC), there are some high priority workers
(HPW) created in the pool. HPW can execute only HPC, although normal
worker can process any call regardless priority. Therefore, only those
APIs which are guaranteed to end in reasonable small amount of time
can be marked as HPC.

The size of this HPC pool is static, because HPC are expected to end
quickly, therefore jobs assigned to this pool will be served quickly.
It can be configured in libvirtd.conf via prio_workers variable.
Default is set to 5.

To mark API with low or high priority, append priority:{low|high} to
it's comment in src/remote/remote_protocol.x. This is similar to
autogen|skipgen. If not marked, the generator assumes low as default.

With this, it is now possible to create external snapshots even
when SELinux is enforcing, and to protect the new file with a
lock manager.

* src/qemu/qemu_driver.c
(qemuDomainSnapshotCreateSingleDiskActive): Create and register
new file with proper permissions and locks.
(qemuDomainSnapshotCreateDiskActive): Update caller.

Lots of earlier patches led up to this point - the qemu snapshot_blkdev
monitor command can now be controlled by libvirt!  Well, insofar as
SELinux doesn't prevent qemu from open(O_CREAT) on the files.  There's
still some followup work before things work with SELinux enforcing,
but this patch is big enough to post now.

There's still room for other improvements, too (for example, taking a
disk snapshot of an inactive domain, by using qemu-img for both internal
and external snapshots; wiring up delete and revert control, including
additional flags from my RFC; supporting active QED disk snapshots;
supporting per-storage-volume snapshots such as LVM or btrfs snapshots;
etc.).  But this patch is the one that proves the new XML works!

* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Wire in
active disk snapshots.
(qemuDomainSnapshotDiskPrepare)
(qemuDomainSnapshotCreateDiskActive)
(qemuDomainSnapshotCreateSingleDiskActive): New functions.

My RFC for snapshot support [1] proposes several rules for when it is
safe to delete or revert to an external snapshot, predicated on
the existence of new API flags.  These will be incrementally added
in future patches, but until then, blindly mishandling a disk
snapshot risks corrupting internal state, so it is better to
outright reject the attempts until the other pieces are in place,
thus incrementally relaxing the restrictions added in this patch.

[1] https://www.redhat.com/archives/libvir-list/2011-August/msg00361.html

* src/qemu/qemu_driver.c (qemuDomainSnapshotCountExternal): New
function.
(qemuDomainUndefineFlags, qemuDomainSnapshotDelete): Use it to add
safety valve.
(qemuDomainRevertToSnapshot, qemuDomainSnapshotCreateXML): Add safety
valve.

Prior to this patch, <domainsnapshot>/<disks> was ignored.  This
changes it to be an error unless an explicit disk snapshot is
requested (a future patch may relax things if it turns out to
be useful to have a <disks> specification alongside a system
checkpoint).

* include/libvirt/libvirt.h.in
(VIR_DOMAIN_SNAPSHOT_CREATE_DISK_ONLY): New flag.
* src/libvirt.c (virDomainSnapshotCreateXML): Document it.
* src/esx/esx_driver.c (esxDomainSnapshotCreateXML): Disk
snapshots not supported yet.
* src/vbox/vbox_tmpl.c (vboxDomainSnapshotCreateXML): Likewise.
* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Likewise.

I got confused when 'virsh domblkinfo dom disk' required the
path to a disk (which can be ambiguous, since a single file
can back multiple disks), rather than the unambiguous target
device name that I was using in disk snapshots.  So, in true
developer fashion, I went for the best of both worlds - all
interfaces that operate on a disk (aka block) now accept
either the target name or the unambiguous path to the backing
file used by the disk.

* src/conf/domain_conf.h (virDomainDiskIndexByName): Add
parameter.
(virDomainDiskPathByName): New prototype.
* src/libvirt_private.syms (domain_conf.h): Export it.
* src/conf/domain_conf.c (virDomainDiskIndexByName): Also allow
searching by path, and decide whether ambiguity is okay.
(virDomainDiskPathByName): New function.
(virDomainDiskRemoveByName, virDomainSnapshotAlignDisks): Update
callers.
* src/qemu/qemu_driver.c (qemudDomainBlockPeek)
(qemuDomainAttachDeviceConfig, qemuDomainUpdateDeviceConfig)
(qemuDomainGetBlockInfo, qemuDiskPathToAlias): Likewise.
* src/qemu/qemu_process.c (qemuProcessFindDomainDiskByPath):
Likewise.
* src/libxl/libxl_driver.c (libxlDomainAttachDeviceDiskLive)
(libxlDomainDetachDeviceDiskLive, libxlDomainAttachDeviceConfig)
(libxlDomainUpdateDeviceConfig): Likewise.
* src/uml/uml_driver.c (umlDomainBlockPeek): Likewise.
* src/xen/xend_internal.c (xenDaemonDomainBlockPeek): Likewise.
* docs/formatsnapshot.html.in: Update documentation.
* tools/virsh.pod (domblkstat, domblkinfo): Likewise.
* docs/schemas/domaincommon.rng (diskTarget): Tighten pattern on
disk targets.
* docs/schemas/domainsnapshot.rng (disksnapshot): Update to match.
* tests/domainsnapshotxml2xmlin/disk_snapshot.xml: Update test.

Since a snapshot is fully recoverable, it is useful to have a
snapshot as a means of hibernating a guest, then reverting to
the snapshot to wake the guest up.  This mode of usage is
similar to 'virsh save/virsh restore', except that virsh
save uses an external file while virsh snapshot keeps the
vm state internal to a qcow2 file.  However, it only works on
persistent domains.

In the usage pattern of snapshot/revert for hibernating a guest,
there is no need to keep the guest running between the two points
in time, especially since that would generate runtime state that
would just be discarded.  Add a flag to make it possible to
stop the domain after the snapshot has completed.

* include/libvirt/libvirt.h.in (VIR_DOMAIN_SNAPSHOT_CREATE_HALT):
New flag.
* src/libvirt.c (virDomainSnapshotCreateXML): Document it.
* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML)
(qemuDomainSnapshotCreateActive): Implement it.

Reverting to a state prior to an external snapshot risks
corrupting any other branches in the snapshot hierarchy that
were using the snapshot as a read-only backing file.  So
disk snapshot code will default to preventing reverting to
a snapshot that has any children, meaning that deleting just
the children of a snapshot becomes a useful operation in
preparing that snapshot for being a future reversion target.
The code for the new flag is simple - it's one less deletion,
plus a tweak to keep the current snapshot correct.

* include/libvirt/libvirt.h.in
(VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN_ONLY): New flag.
* src/libvirt.c (virDomainSnapshotDelete): Document it, and
enforce mutual exclusion.
* src/qemu/qemu_driver.c (qemuDomainSnapshotDelete): Implement
it.

When reverting to a snapshot, the inactive domain configuration
has to be rolled back to what it was at the time of the snapshot.
Additionally, if the VM is active and the snapshot was active,
this now adds a failure if the two configurations are ABI
incompatible, rather than risking qemu confusion.

A future patch will add a VIR_DOMAIN_SNAPSHOT_FORCE flag, which
will be required for two risky code paths - reverting to an
older snapshot that lacked full domain information, and reverting
from running to a live snapshot that requires starting a new qemu
process.  Any reverting that stops a running vm is also a form
of data loss (discarding the current running state to go back in
time), but as that is what reversion usually implies, it is
probably not worth requiring a force flag.

* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Copy out
domain.
(qemuDomainSnapshotCreateXML, qemuDomainRevertToSnapshot): Perform
ABI compatibility checks.

Just like VM saved state images (virsh save), snapshots MUST
track the inactive domain xml to detect any ABI incompatibilities.

The indentation is not perfect, but functionality comes before form.

Later patches will actually supply a full domain; for now, this
wires up the storage to support one, but doesn't ever generate one
in dumpxml output.

Happily, libvirt.c was already rejecting use of VIR_DOMAIN_XML_SECURE
from read-only connections, even though before this patch, there was
no information to be secured by the use of that flag.

And while we're at it, mark the libvirt snapshot metadata files
as internal-use only.

* src/libvirt.c (virDomainSnapshotGetXMLDesc): Document flag.
* src/conf/domain_conf.h (_virDomainSnapshotDef): Add member.
(virDomainSnapshotDefParseString, virDomainSnapshotDefFormat):
Update signature.
* src/conf/domain_conf.c (virDomainSnapshotDefFree): Clean up.
(virDomainSnapshotDefParseString): Optionally parse domain.
(virDomainSnapshotDefFormat): Output full domain.
* src/esx/esx_driver.c (esxDomainSnapshotCreateXML)
(esxDomainSnapshotGetXMLDesc): Update callers.
* src/vbox/vbox_tmpl.c (vboxDomainSnapshotCreateXML)
(vboxDomainSnapshotGetXMLDesc): Likewise.
* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML)
(qemuDomainSnapshotLoad, qemuDomainSnapshotGetXMLDesc)
(qemuDomainSnapshotWriteMetadata): Likewise.
* docs/formatsnapshot.html.in: Rework doc example.
Based on a patch by Philipp Hahn.

A nice benefit of deleting all snapshots at undefine time is that
you don't have to do any reparenting or subtree identification - since
everything goes, this is an O(n) process, whereas using multiple
virDomainSnapshotDelete calls would be O(n^2) or worse.  But it is
only doable for snapshot metadata, where we are in control of the
data being deleted; for the actual snapshots, there's too much
likelihood of something going wrong, and requiring even more API
calls to figure out what failed in the meantime, so callers are
better off deleting the snapshot data themselves one snapshot at
a time where they can deal with failures as they happen.

* src/qemu/qemu_driver.c (qemuDomainUndefineFlags): Honor new flags.

As more clients start to want to know this information, doing
a PATH stat walk and malloc for every client adds up.

We are only caching the location, not the capabilities, so even
if qemu-img is updated in the meantime, it will still probably
live in the same location.  So there is no need to worry about
clearing this particular cache.

* src/qemu/qemu_conf.h (qemud_driver): Add member.
* src/qemu/qemu_driver.c (qemudShutdown): Cleanup.
(qemuFindQemuImgBinary): Add an argument, and cache result.
(qemuDomainSnapshotForEachQcow2, qemuDomainSnapshotDiscard)
(qemuDomainSnapshotCreateInactive, qemuDomainSnapshotRevertInactive)
(qemuDomainSnapshotCreateXML, qemuDomainRevertToSnapshot): Update
callers.

Prepare for code sharing.  No semantic change.

* src/qemu/qemu_driver.c (qemuFindQemuImgBinary)
(qemuDomainSnapshotWriteMetadata)
(qemuDomainSnapshotDiscard)
(qemuDomainSnapshotForEachQcow2): Float up.
(qemuDomainSnapshotDiscardDescendant): Likewise, and rename...
(qemuDomainSnapshotDiscardAll): ...for generic use.
(qemuDomainSnapshotDelete): Update caller.

Just as leaving managed save metadata behind can cause problems
when creating a new domain that happens to collide with the name
of the just-deleted domain, the same is true of leaving any
snapshot metadata behind.  For safety sake, extend the semantic
change of commit b26a9fa9 to also cover snapshot metadata as a
reason to reject undefining an inactive domain.  A future patch
will make sure that shutdown of a transient domain automatically
deletes snapshot metadata (whether by destroy, shutdown, or
guest-initiated action).  Management apps of transient domains
should take care to capture xml of snapshots, if it is necessary
to recreate the snapshot metadata on a later transient domain
with the same name and uuid.

This also documents a new flag that hypervisors can choose to
support as a shortcut for taking care of the metadata as part of
the undefine process; however, nontrivial driver support for these
flags will be deferred to future patches.

Note that ESX and VBox can never be transient; therefore, they
do not have to worry about automatic cleanup after shutdown
(the persistent domain still remains); likewise they never
store snapshot metadata, so the undefine flag is trivial.
The nontrivial work remaining is thus in the qemu driver.

* include/libvirt/libvirt.h.in
(VIR_DOMAIN_UNDEFINE_SNAPSHOTS_METADATA): New flag.
* src/libvirt.c (virDomainUndefine, virDomainUndefineFlags):
Document new limitations and flag.
* src/esx/esx_driver.c (esxDomainUndefineFlags): Trivial
implementation.
* src/vbox/vbox_tmpl.c (vboxDomainUndefineFlags): Likewise.
* src/qemu/qemu_driver.c (qemuDomainUndefineFlags): Enforce
the limitations.

Redefining a qemu snapshot requires a bit of a tweak to the common
snapshot parsing code, but the end result is quite nice.

Be careful that redefinitions do not introduce circular parent
chains.  Also, we don't want to allow conversion between online
and offline existing snapshots.  We could probably do some more
validation for snapshots that don't already exist to make sure
they are even feasible, by parsing qemu-img output, but that
can come later.

* src/conf/domain_conf.h (virDomainSnapshotParseFlags): New
internal flags.
* src/conf/domain_conf.c (virDomainSnapshotDefParseString): Alter
signature to take internal flags.
* src/esx/esx_driver.c (esxDomainSnapshotCreateXML): Update caller.
* src/vbox/vbox_tmpl.c (vboxDomainSnapshotCreateXML): Likewise.
* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Support
new public flags.

Supporting NO_METADATA on snapshot creation is interesting - we must
still return a valid opaque snapshot object, but the user can't get
anything out of it (unless we add a virDomainSnapshotGetName()),
since it is no longer registered with the domain.

Also, virsh now tries to query for secure xml, in anticipation of
when we store <domain> xml inside <domainsnapshot>; for now, we
can trivially support it, since we have nothing secure.

* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Support
new flag.
(qemuDomainSnapshotGetXMLDesc): Trivially support VIR_DOMAIN_XML_SECURE.

Filtering for roots is pretty easy to do.

* src/conf/domain_conf.h (virDomainSnapshotObjListGetNames)
(virDomainSnapshotObjListNum): Update prototype.
* src/conf/domain_conf.c (virDomainSnapshotObjListCopyNames)
(virDomainSnapshotObjListGetNames, virDomainSnapshotObjListCount)
(virDomainSnapshotObjListNum): Support filtering.
* src/qemu/qemu_driver.c (qemuDomainSnapshotNum)
(qemuDomainSnapshotListNames): Update callers.

To make it easier to know when undefine will fail because of existing
snapshot metadata, we need to know how many snapshots have metadata.

Also, it is handy to filter the list of snapshots to just those that
have no parents; document that flag now, but implement it in later patches.

* include/libvirt/libvirt.h.in (VIR_DOMAIN_SNAPSHOT_LIST_ROOTS)
(VIR_DOMAIN_SNAPSHOT_LIST_METADATA): New flags.
* src/libvirt.c (virDomainSnapshotNum)
(virDomainSnapshotListNames): Document them.
* src/esx/esx_driver.c (esxDomainSnapshotNum)
(esxDomainSnapshotListNames): Implement trivial flag.
* src/vbox/vbox_tmpl.c (vboxDomainSnapshotNum)
(vboxDomainSnapshotListNames): Likewise.
* src/qemu/qemu_driver.c (qemuDomainSnapshotNum)
(qemuDomainSnapshotListNames): Likewise.

Adding this was trivial compared to the previous patch for fixing
qemu snapshot deletion in the first place.

* src/qemu/qemu_driver.c (qemuDomainSnapshotDiscard): Add
parameter.
(qemuDomainSnapshotDiscardDescendant, qemuDomainSnapshotDelete):
Update callers.

Similar to the last patch in isolating the filtering from the
client actions, so that clients don't have to reinvent the
filtering.

* src/conf/domain_conf.h (virDomainSnapshotForEachChild): New
prototype.
* src/libvirt_private.syms (domain_conf.h): Export it.
* src/conf/domain_conf.c (virDomainSnapshotActOnChild)
(virDomainSnapshotForEachChild): New functions.
(virDomainSnapshotCountChildren): Delete.
(virDomainSnapshotHasChildren): Simplify.
* src/qemu/qemu_driver.c (qemuDomainSnapshotReparentChildren)
(qemuDomainSnapshotDelete): Likewise.

Deleting a snapshot and all its descendants had problems with
tracking the current snapshot.  The deletion does not necessarily
proceed in depth-first order, so a parent could be deleted
before a child, wreaking havoc on passing the notion of the
current snapshot to the parent.  Furthermore, even if traversal
were depth-first, doing multiple file writes to pass current up
the chain one snapshot at a time is wasteful, comparing to a
single update to the current snapshot at the end of the algorithm.

* src/qemu/qemu_driver.c (snap_remove): Add field.
(qemuDomainSnapshotDiscard): Add parameter.
(qemuDomainSnapshotDiscardDescendant): Adjust accordingly.
(qemuDomainSnapshotDelete): Properly reset current.

This one's nasty.  Ever since we fixed virHashForEach to prevent
nested hash iterations for safety reasons (commit fba550f6),
virDomainSnapshotDelete with VIR_DOMAIN_SNAPSHOT_DELETE_CHILDREN
has been broken for qemu: it deletes children, while leaving
grandchildren intact but pointing to a no-longer-present parent.
But even before then, the code would often appear to succeed to
clean up grandchildren, but risked memory corruption if you have
a large and deep hierarchy of snapshots.

For acting on just children, a single virHashForEach is sufficient.
But for acting on an entire subtree, it requires iteration; and
since we declared recursion as invalid, we have to switch to a
while loop.  Doing this correctly requires quite a bit of overhaul,
so I added a new helper function to isolate the algorithm from the
actions, so that callers do not have to reinvent the iteration.

Note that this _still_ does not handle CHILDREN correctly if one
of the children is the current snapshot; that will be next.

* src/conf/domain_conf.h (_virDomainSnapshotDef): Add mark.
(virDomainSnapshotForEachDescendant): New prototype.
* src/libvirt_private.syms (domain_conf.h): Export it.
* src/conf/domain_conf.c (virDomainSnapshotMarkDescendant)
(virDomainSnapshotActOnDescendant)
(virDomainSnapshotForEachDescendant): New functions.
* src/qemu/qemu_driver.c (qemuDomainSnapshotDiscardChildren):
Replace...
(qemuDomainSnapshotDiscardDescenent): ...with callback that
doesn't nest hash traversal.
(qemuDomainSnapshotDelete): Use new function.

For a system checkpoint of a running or paused domain, it's fairly
easy to honor new flags for altering which state to use after the
revert.  For an inactive snapshot, the revert has to be done while
there is no qemu process, so do back-to-back transitions; this also
lets us revert to inactive snapshots even for transient domains.

* src/qemu/qemu_driver.c (qemuDomainRevertToSnapshot): Support new
flags.

Commit 5e47785b broke reverts to offline system checkpoint snapshots
with older qemu, since there is no longer any code path to use
qemu -loadvm on next boot.  Meanwhile, reverts to offline system
checkpoints have been broken for newer qemu, both before and
after that commit, since -loadvm no longer works to revert to
disk state without accompanying vm state.  Fix both of these by
using qemu-img to revert disk state.

Meanwhile, consolidate the (now 3) clients of a qemu-img iteration
over all disks of a VM into one function, so that any future
algorithmic fixes to the FIXMEs in that function after partial
loop iterations are dealt with at once.  That does mean that this
patch doesn't handle partial reverts very well, but we're not
making the situation any worse in this patch.

* src/qemu/qemu_driver.c (qemuDomainRevertToSnapshot): Use
qemu-img rather than 'qemu -loadvm' to revert to offline snapshot.
(qemuDomainSnapshotRevertInactive): New helper.
(qemuDomainSnapshotCreateInactive): Factor guts...
(qemuDomainSnapshotForEachQcow2): ...into new helper.
(qemuDomainSnapshotDiscard): Use it.

If you take a checkpoint snapshot of a running domain, then pause
qemu, then restore the snapshot, the result should be a running
domain, but the code was leaving things paused.  Furthermore, if
you take a checkpoint of a paused domain, then run, then restore,
there was a brief but non-deterministic window of time where the
domain was running rather than paused.  Fix both of these
discrepancies by always pausing before restoring.

Also, check that the VM is active every time lock is dropped
between two monitor calls.

Finally, straighten out the events that get emitted on each
transition.

* src/qemu/qemu_driver.c (qemuDomainRevertToSnapshot): Always
pause before reversion, and improve events.

Implement the new running/paused overrides for saved state management.

Unfortunately, for virDomainSaveImageDefineXML, the saved state
updates are write-only - I don't know of any way to expose a way
to query the current run/pause setting of an existing save image
file to the user without adding a new API or modifying the domain
xml of virDomainSaveImageGetXMLDesc to include a new element to
reflect the state bit encoded into the save image.  However, I
don't think this is a show-stopper, since the API is designed to
leave the state bit alone unless an explicit flag is used to
change it.

* src/qemu/qemu_driver.c (qemuDomainSaveInternal)
(qemuDomainSaveImageOpen): Adjust signature.
(qemuDomainSaveFlags, qemuDomainManagedSave)
(qemuDomainRestoreFlags, qemuDomainSaveImageGetXMLDesc)
(qemuDomainSaveImageDefineXML, qemuDomainObjRestore): Adjust
callers.

There are two classes of management apps that track events - one
that only cares about on/off (and only needs to track EVENT_STARTED
and EVENT_STOPPED), and one that cares about paused/running (also
tracks EVENT_SUSPENDED/EVENT_RESUMED).  To keep both classes happy,
any transition that can go from inactive to paused must emit two
back-to-back events - one for started and one for suspended (since
later resuming of the domain will only send RESUMED, but the first
class isn't tracking that).

This also fixes a bug where virDomainCreateWithFlags with the
VIR_DOMAIN_START_PAUSED flag failed to start paused when restoring
from a managed save image.

* include/libvirt/libvirt.h.in (VIR_DOMAIN_EVENT_SUSPENDED_RESTORED)
(VIR_DOMAIN_EVENT_SUSPENDED_FROM_SNAPSHOT)
(VIR_DOMAIN_EVENT_RESUMED_FROM_SNAPSHOT): New sub-events.
* src/qemu/qemu_driver.c (qemuDomainRevertToSnapshot): Use them.
(qemuDomainSaveImageStartVM): Likewise, and add parameter.
(qemudDomainCreate, qemuDomainObjStart): Send suspended event when
starting paused.
(qemuDomainObjRestore): Add parameter.
(qemuDomainObjStart, qemuDomainRestoreFlags): Update callers.
* examples/domain-events/events-c/event-test.c
(eventDetailToString): Map new detail strings.

- create a new "redirdev" element for this purpose

Commit 6766ff10 introduced a corner case bug with snapshot creation:
if a snapshot is created, but then we hit OOM while trying to
create the return value of the function, then we have polluted the
internal directory with the snapshot metadata with no way to clean
it up from the running libvirtd.

* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Don't
write metadata file on OOM condition.

Several users have reported problems with 'virsh start' failing because
it was encountering a managed save situation where the managed save file
was incomplete.  Be more robust to this by using two different magic
numbers, so that newer libvirt can gracefully handle an incomplete file
differently than a complete one, while older libvirt will at least fail
up front rather than trying to load only to have qemu fail at the end.

Managed save is a convenience - it exists to preserve as much state
as possible; if the state was not preserved, it is reasonable to just
log that fact, then proceed with a fresh boot.  On the other hand,
user saves are under user control, so we must fail, but by making
the failure message distinct, the user can better decide how to handle
the situation of an incomplete save file.

* src/qemu/qemu_driver.c (QEMUD_SAVE_PARTIAL): New define.
(qemuDomainSaveInternal): Use it to mark incomplete images.
(qemuDomainSaveImageOpen, qemuDomainObjRestore): Add parameter
that controls what to do with partial images.
(qemuDomainRestoreFlags, qemuDomainSaveImageGetXMLDesc)
(qemuDomainSaveImageDefineXML, qemuDomainObjStart): Update callers.
Based on an initial idea by Osier Yang.

In a SELinux or root-squashing NFS environment, libvirt has to go
through some hoops to create a new file that qemu can then open()
by name.  Snapshots are a case where we want to guarantee an empty
file that qemu can open; also, reopening a save file to convert it
from being marked partial to complete requires a reopen to avoid
O_DIRECT headaches.  Refactor some existing code to make it easier
to reuse in later patches.

* src/qemu/qemu_migration.h (qemuMigrationToFile): Drop parameter.
* src/qemu/qemu_migration.c (qemuMigrationToFile): Let cgroup do
the stat, rather than asking caller to do it and pass info down.
* src/qemu/qemu_driver.c (qemuOpenFile): New function, pulled from...
(qemuDomainSaveInternal): ...here.
(doCoreDump, qemuDomainSaveImageOpen): Use it here as well.

The libvirt BlockPull API supports the use of an initial bandwidth limit but the
qemu block_stream API does not.  To get the desired behavior we use the two APIs
strung together: first BlockPull, then BlockJobSetSpeed.  We can do this at the
driver level to avoid duplicated code in each monitor path.
Signed-off-by: NAdam Litke <agl@us.ibm.com>

* src/qemu/qemu_driver.c - qemuDomainSaveInternal: Return directly
will keep the domain object locked, introduced by 173015be.

There is no reason to forbid pausing an autodestroy domain
(not to mention that 'virsh start --paused --autodestroy'
succeeds in creating a paused autodestroy domain).

Meanwhile, qemu was failing to enforce the API documentation that
autodestroy domains cannot be saved.  And while the original
documentation only mentioned save/restore, snapshots are another
form of saving that are close enough in semantics as to make no
sense on one-shot domains.

* src/qemu/qemu_driver.c (qemudDomainSuspend): Drop bogus check.
(qemuDomainSaveInternal, qemuDomainSnapshotCreateXML): Forbid
saves of autodestroy domains.
* src/libvirt.c (virDomainCreateWithFlags, virDomainCreateXML):
Document snapshot interaction.

There have been several instances of people having problems with
a broken managed save file, and not aware that they could use
'virsh managedsave-remove dom' to fix things.  Making it possible
to do this as part of starting a domain makes the same functionality
easier to find, and one less API call.

* include/libvirt/libvirt.h.in (VIR_DOMAIN_START_FORCE_BOOT): New
flag.
* src/libvirt.c (virDomainCreateWithFlags): Document it.
* src/qemu/qemu_driver.c (qemuDomainObjStart): Alter signature.
(qemuAutostartDomain, qemuDomainStartWithFlags): Update callers.
* tools/virsh.c (cmdStart): Expose it in virsh.
* tools/virsh.pod (start): Document it.

The QEMU 'sendkey' command expects keys to be encoded in the same
way as the RFB extended keycode set. Specifically it wants extended
keys to have the high bit of the first byte set, while the Linux
XT KBD driver codeset uses the low bit of the second byte. To deal
with this we introduce a new keymap 'RFB' and use that in the QEMU
driver

* include/libvirt/libvirt.h.in: Add VIR_KEYCODE_SET_RFB
* src/qemu/qemu_driver.c: Use RFB keycode set instead of XT KBD
* src/util/virkeycode-mapgen.py: Auto-generate the RFB keycode
  set from the XT KBD set
* src/util/virkeycode.c: Add RFB keycode entry to table. Add a
  verify check on cardinality of the codeOffset table

Audit all changes to the qemu vm->current_snapshot, and make them
update the saved xml file for both the previous and the new
snapshot, so that there is always at most one snapshot with
<active>1</active> in the xml, and that snapshot is used as the
current snapshot even across libvirtd restarts.

This patch does not fix the case of virDomainSnapshotDelete(,CHILDREN)
where one of the children is the current snapshot; that will be later.

* src/conf/domain_conf.h (_virDomainSnapshotDef): Alter member
type and name.
* src/conf/domain_conf.c (virDomainSnapshotDefParseString)
(virDomainSnapshotDefFormat): Update clients.
* docs/schemas/domainsnapshot.rng: Tighten rng.
* src/qemu/qemu_driver.c (qemuDomainSnapshotLoad): Reload current
snapshot.
(qemuDomainSnapshotCreateXML, qemuDomainRevertToSnapshot)
(qemuDomainSnapshotDiscard): Track current snapshot.