The oVirt developers have stated that the real reasons they want
to have qemu reuse existing volumes when creating a snapshot are:
1. the management framework is set up so that creation has to be
done from a central node for proper resource tracking, and having
libvirt and/or qemu create things violates the framework, and
2. qemu defaults to creating snapshots with an absolute path to
the backing file, but oVirt wants to manage a backing chain that
uses just relative names, to allow for easier migration of a chain
across storage locations.

When 0.9.10 added VIR_DOMAIN_SNAPSHOT_CREATE_REUSE_EXT (commit
4e9953a4), it only addressed point 1, but libvirt was still using
O_TRUNC which violates point 2.  Meanwhile, the new qemu
'transaction' monitor command includes a new optional mode argument
that will force qemu to reuse the metadata of the file it just
opened (with the burden on the caller to have valid metadata there
in the first place).  So, this tweaks the meaning of the flag to
cover both points as intended for use by oVirt.  It is not strictly
backward-compatible to 0.9.10 behavior, but it can be argued that
the O_TRUNC of 0.9.10 was a bug.

Note that this flag is all-or-nothing, and only selects between
'existing' and the default 'absolute-paths'.  A more flexible
approach that would allow per-disk selections, as well as adding
support for the 'no-backing-file' mode, would be possible by
extending the <domainsnapshot> xml to have a per-disk mode, but
until we have a management application expressing a need for that
additional complexity, it is not worth doing.

* src/libvirt.c (virDomainSnapshotCreateXML): Tweak documentation.
* src/qemu/qemu_monitor.h (qemuMonitorDiskSnapshot): Add
parameters.
* src/qemu/qemu_monitor_json.h (qemuMonitorJSONDiskSnapshot):
Likewise.
* src/qemu/qemu_monitor.c (qemuMonitorDiskSnapshot): Pass them
through.
* src/qemu/qemu_monitor_json.c (qemuMonitorJSONDiskSnapshot): Use
new monitor command arguments.
* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateDiskActive)
(qemuDomainSnapshotCreateSingleDiskActive): Adjust callers.
(qemuDomainSnapshotDiskPrepare): Allow qed, modify rules on reuse.

The hardest part about adding transactions is not using the new
monitor command, but undoing the partial changes we made prior
to a failed transaction.

* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateDiskActive): Use
transaction when available.
(qemuDomainSnapshotUndoSingleDiskActive): New function.
(qemuDomainSnapshotCreateSingleDiskActive): Pass through actions.
(qemuDomainSnapshotCreateXML): Adjust caller.

QEmu 1.1 is adding a 'transaction' command to the JSON monitor.
Each element of a transaction corresponds to a top-level command,
with the additional guarantee that the transaction flushes all
pending I/O, then guarantees that all actions will be successful
as a group or that failure will roll back the state to what it
was before the monitor command.  The difference between a
top-level command:

{ "execute": "blockdev-snapshot-sync", "arguments":
  { "device": "virtio0", ... } }

and a transaction:

{ "execute": "transaction", "arguments":
  { "actions": [
    { "type": "blockdev-snapshot-sync", "data":
      { "device": "virtio0", ... } } ] } }

is just a couple of changed key names and nesting the shorter
command inside a JSON array to the longer command.  This patch
just adds the framework; the next patch will actually use a
transaction.

* src/qemu/qemu_monitor_json.c (qemuMonitorJSONMakeCommand): Move
guts...
(qemuMonitorJSONMakeCommandRaw): ...into new helper.  Add support
for array element.
(qemuMonitorJSONTransaction): New command.
(qemuMonitorJSONDiskSnapshot): Support use in a transaction.
* src/qemu/qemu_monitor_json.h (qemuMonitorJSONDiskSnapshot): Add
argument.
(qemuMonitorJSONTransaction): New declaration.
* src/qemu/qemu_monitor.h (qemuMonitorTransaction): Likewise.
(qemuMonitorDiskSnapshot): Add argument.
* src/qemu/qemu_monitor.c (qemuMonitorTransaction): New wrapper.
(qemuMonitorDiskSnapshot): Pass argument on.
* src/qemu/qemu_driver.c
(qemuDomainSnapshotCreateSingleDiskActive): Update caller.

Taking an external snapshot of just one disk is atomic, without having
to pause and resume the VM.  This also paves the way for later patches
to interact with the new qemu 'transaction' monitor command.

The various scenarios when requesting atomic are:
online, 1 disk, old qemu - safe, allowed by this patch
online, more than 1 disk, old qemu - failure, this patch
offline snapshot - safe, once a future patch implements offline disk snapshot
online, 1 or more disks, new qemu - safe, once future patch uses transaction

Taking an online system checkpoint snapshot is atomic, since it is
done via a single 'savevm' monitor command.  Taking an offline system
checkpoint snapshot is atomic, thanks to the previous patch.

* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): Support
new flag for single-disk setups.
(qemuDomainSnapshotDiskPrepare): Check for atomic here.
(qemuDomainSnapshotCreateDiskActive): Skip pausing the VM when
atomic supported.
(qemuDomainSnapshotIsAllowed): Use bool instead of int.

Move error reporting out of the callers, into virURIParse
and virURIFormat, to get consistency.

* include/libvirt/virterror.h, src/util/virterror.c: Add VIR_FROM_URI
* src/util/viruri.c, src/util/viruri.h: Add error reporting
* src/esx/esx_driver.c, src/libvirt.c, src/libxl/libxl_driver.c,
  src/lxc/lxc_driver.c, src/openvz/openvz_driver.c,
  src/qemu/qemu_driver.c, src/qemu/qemu_migration.c,
  src/remote/remote_driver.c, src/uml/uml_driver.c,
  src/vbox/vbox_tmpl.c, src/vmx/vmx.c, src/xen/xen_driver.c,
  src/xen/xend_internal.c, tests/viruritest.c: Remove error
  reporting
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

When a client which started non-p2p migration dies in a bad time, the
source libvirtd never clears the migration job and almost nothing can be
done with the domain without restarting the daemon. This patch makes use
of connection close callbacks and ensures that migration job is properly
discarded when the client disconnects.

Add support for registering arbitrary callback to be called for a domain
when a connection gets closed.

If a guest is paused, we were silently ignoring the quiesce flag,
which results in unclean snapshots, contrary to the intent of the
flag.  Since we can't quiesce without guest agent support, we should
instead fail if the guest is not running.

Meanwhile, if we attempt a quiesce command, but the guest agent
doesn't respond, and we time out, we may have left the command
pending on the guest's queue, and when the guest resumes parsing
commands, it will freeze even though our command is no longer
around to issue a thaw.  To be safe, we must _always_ pair every
quiesce call with a counterpart thaw, even if the quiesce call
failed due to a timeout, so that if a guest wakes up and starts
processing a command backlog, it will not get stuck in a frozen
state.

* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateDiskActive):
Always issue thaw after a quiesce, even if quiesce failed.
(qemuDomainSnapshotFSThaw): Add a parameter.

A common coding pattern for changing blkio parameters is

  1. virDomainGetBlkioParameters

  2. change one or more params

  3. virDomainSetBlkioParameters

For this to work, it must be possible to roundtrip through
the methods without error. Unfortunately virDomainGetBlkioParameters
will return "" for the deviceWeight parameter for guests by default,
which virDomainSetBlkioParameters will then reject as invalid.

This fixes the handling of "" to be a no-op, and also improves the
error message to tell you what was invalid

And don't allow to hotplug a usb disk with "device == lun". This
is the missed pieces in previous virtio-scsi patchset:

http://www.redhat.com/archives/libvir-list/2012-February/msg01052.html

When host-model and host-passthrouh CPU modes were introduced, qemu
driver was properly modify to update guest CPU definition during
migration so that we use the right CPU at the destination. However,
similar treatment is needed for (managed)save and snapshots since they
need to save the exact CPU so that a domain can be properly restored.
To avoid repetition of such situation, all places that need live XML
share the code which generates it.

As a side effect, this patch fixes error reporting from
qemuDomainSnapshotWriteMetadata().

Thanks to cgroups, providing user vs. system time of the overall
guest is easy to add to our existing API.

* include/libvirt/libvirt.h.in (VIR_DOMAIN_CPU_STATS_USERTIME)
(VIR_DOMAIN_CPU_STATS_SYSTEMTIME): New constants.
* src/util/virtypedparam.h (virTypedParameterArrayValidate)
(virTypedParameterAssign): Enforce checking the result.
* src/qemu/qemu_driver.c (qemuDomainGetPercpuStats): Fix offender.
(qemuDomainGetTotalcpuStats): Implement new parameters.
* tools/virsh.c (cmdCPUStats): Tweak output accordingly.

This function was freeing a virDomainNetDef with
VIR_FREE(). virDomainNetDef is a complex structure with many pointers
to other dynamically allocated data; to properly free it
virDomainNetDefFree() must be called instead, otherwise several
strings (and potentially other things) will be leaked.

For some reason, although live hotplug of <hostdev> devices is
supported, persistent hotplug is not. This patch adds the proper
VIR_DOMAIN_DEVICE_HOSTDEV cases to the switches in
qemuDomainAttachDeviceConfig and qemuDomainDetachDeviceConfig.

There are several functions in domain_conf.c that remove a device
object from the domain's list of that object type, but don't free the
object or return it to the caller to free. In many cases this isn't a
problem because the caller already had a pointer to the object and
frees it afterward, but in several cases the removed object was just
left floating around with no references to it.

In particular, the function qemuDomainDetachDeviceConfig() calls
functions to locate and remove net (virDomainNetRemoveByMac), disk
(virDomainDiskRemoveByName()), and lease (virDomainLeaseRemove())
devices, but neither it nor its caller qemuDomainModifyDeviceConfig()
ever obtain a pointer to the device being removed, much less free it.

This patch modifies the following "remove" functions to return a
pointer to the device object being removed from the domain device
arrays, to give the caller the option of freeing the device object
using that pointer if needed. In places where the object was
previously leaked, it is now freed:

  virDomainDiskRemove
  virDomainDiskRemoveByName
  virDomainNetRemove
  virDomainNetRemoveByMac
  virDomainHostdevRemove
  virDomainLeaseRemove
  virDomainLeaseRemoveAt

The functions that had been leaking:

  libxlDomainDetachConfig - leaked a virDomainDiskDef
  qemuDomainDetachDeviceConfig - could leak a virDomainDiskDef,
                            a virDomainNetDef, or a
                            virDomainLeaseDef
  qemuDomainDetachLease   - leaked a virDomainLeaseDef

Some members are generated during XML parse (e.g. MAC address of
an interface); However, with current implementation, if we
are plugging a device both to persistent and live config,
we parse given XML twice: first time for live, second for config.
This is wrong then as the second time we are not guaranteed
to generate same values as we did for the first time.
To prevent that we need to create a copy of DeviceDefPtr;
This is done through format/parse process instead of writing
functions for deep copy as it is easier to maintain:
adding new field to any virDomain*DefPtr doesn't require change
of copying function.

Currently, startupPolicy='requisite' was determining cold boot
by migrateFrom != NULL. That means, if domain was started up
with migrateFrom set we didn't require disk source path and allowed
it to be dropped. However, on snapshot-revert domain wasn't migrated
but according to documentation, requisite should drop disk source
as well.

Using 'unsigned long' for memory values is risky on 32-bit platforms,
as a PAE guest can have more than 4GiB memory.  Our API is
(unfortunately) locked at 'unsigned long' and a scale of 1024, but
the rest of our system should consistently use 64-bit values,
especially since the previous patch centralized overflow checking.

* src/conf/domain_conf.h (_virDomainDef): Always use 64-bit values
for memory.  Change hugepage_backed to a bool.
* src/conf/domain_conf.c (virDomainDefParseXML)
(virDomainDefCheckABIStability, virDomainDefFormatInternal): Fix
clients.
* src/vmx/vmx.c (virVMXFormatConfig): Likewise.
* src/xenxs/xen_sxpr.c (xenParseSxpr, xenFormatSxpr): Likewise.
* src/xenxs/xen_xm.c (xenXMConfigGetULongLong): New function.
(xenXMConfigGetULong, xenXMConfigSetInt): Avoid truncation.
(xenParseXM, xenFormatXM): Fix clients.
* src/phyp/phyp_driver.c (phypBuildLpar): Likewise.
* src/openvz/openvz_driver.c (openvzDomainSetMemoryInternal):
Likewise.
* src/vbox/vbox_tmpl.c (vboxDomainDefineXML): Likewise.
* src/qemu/qemu_command.c (qemuBuildCommandLine): Likewise.
* src/qemu/qemu_process.c (qemuProcessStart): Likewise.
* src/qemu/qemu_monitor.h (qemuMonitorGetBalloonInfo): Likewise.
* src/qemu/qemu_monitor_text.h (qemuMonitorTextGetBalloonInfo):
Likewise.
* src/qemu/qemu_monitor_text.c (qemuMonitorTextGetBalloonInfo):
Likewise.
* src/qemu/qemu_monitor_json.h (qemuMonitorJSONGetBalloonInfo):
Likewise.
* src/qemu/qemu_monitor_json.c (qemuMonitorJSONGetBalloonInfo):
Likewise.
* src/qemu/qemu_driver.c (qemudDomainGetInfo)
(qemuDomainGetXMLDesc): Likewise.
* src/uml/uml_conf.c (umlBuildCommandLine): Likewise.

On 64-bit platforms, unsigned long and unsigned long long are
identical, so we don't have to worry about overflow checks.
On 32-bit platforms, anywhere we narrow unsigned long long back
to unsigned long, we have to worry about overflow; it's easier
to do this in one place by having most of the code use the same
or wider types, and only doing the narrowing at the last minute.
Therefore, the memory set commands remain unsigned long, and
the memory get command now centralizes the overflow check into
libvirt.c, so that drivers don't have to repeat the work.

This also fixes a bug where xen returned the wrong value on
failure (most APIs return -1 on failure, but getMaxMemory
must return 0 on failure).

* src/driver.h (virDrvDomainGetMaxMemory): Use long long.
* src/libvirt.c (virDomainGetMaxMemory): Raise overflow.
* src/test/test_driver.c (testGetMaxMemory): Fix driver.
* src/rpc/gendispatch.pl (name_to_ProcName): Likewise.
* src/xen/xen_hypervisor.c (xenHypervisorGetMaxMemory): Likewise.
* src/xen/xen_driver.c (xenUnifiedDomainGetMaxMemory): Likewise.
* src/xen/xend_internal.c (xenDaemonDomainGetMaxMemory):
Likewise.
* src/xen/xend_internal.h (xenDaemonDomainGetMaxMemory):
Likewise.
* src/xen/xm_internal.c (xenXMDomainGetMaxMemory): Likewise.
* src/xen/xm_internal.h (xenXMDomainGetMaxMemory): Likewise.
* src/xen/xs_internal.c (xenStoreDomainGetMaxMemory): Likewise.
* src/xen/xs_internal.h (xenStoreDomainGetMaxMemory): Likewise.
* src/xenapi/xenapi_driver.c (xenapiDomainGetMaxMemory):
Likewise.
* src/esx/esx_driver.c (esxDomainGetMaxMemory): Likewise.
* src/libxl/libxl_driver.c (libxlDomainGetMaxMemory): Likewise.
* src/qemu/qemu_driver.c (qemudDomainGetMaxMemory): Likewise.
* src/lxc/lxc_driver.c (lxcDomainGetMaxMemory): Likewise.
* src/uml/uml_driver.c (umlDomainGetMaxMemory): Likewise.

Overflow can be user-induced, so it deserves more than being called
an internal error.  Note that in general, 32-bit platforms have
far more places to trigger this error (anywhere the public API
used 'unsigned long' but the other side of the connection is a
64-bit server); but some are possible on 64-bit platforms (where
the public API computes the product of two numbers).

* include/libvirt/virterror.h (VIR_ERR_OVERFLOW): New error.
* src/util/virterror.c (virErrorMsg): Translate it.
* src/libvirt.c (virDomainSetVcpusFlags, virDomainGetVcpuPinInfo)
(virDomainGetVcpus, virDomainGetCPUStats): Use it.
* daemon/remote.c (HYPER_TO_TYPE): Likewise.
* src/qemu/qemu_driver.c (qemuDomainBlockResize): Likewise.

The RPC code assumed that the array returned by the driver would be
fully populated; that is, ncpus on entry resulted in ncpus * return
value on exit.  However, while we don't support holes in the middle
of ncpus, we do want to permit the case of ncpus on entry being
longer than the array returned by the driver (that is, it should be
safe for the caller to pass ncpus=128 on entry, and the driver will
stop populating the array when it hits max_id).

Additionally, a successful return implies that the caller will then
use virTypedParamArrayClear on the entire array; for this to not
free uninitialized memory, the driver must ensure that all skipped
entries are explicitly zeroed (the RPC driver did this, but not
the qemu driver).

There are now three cases:
server 0.9.10 and client 0.9.10 or newer: No impact - there were no
hypervisor drivers that supported cpu stats

server 0.9.11 or newer and client 0.9.10: if the client calls with
ncpus beyond the max, then the rpc call will fail on the client side
and disconnect the client, but the server is no worse for the wear

server 0.9.11 or newer and client 0.9.11: the server can return a
truncated array and the client will do just fine

I reproduced the problem by using a host with 2 CPUs, and doing:
virsh cpu-stats $dom --start 1 --count 2

* daemon/remote.c (remoteDispatchDomainGetCPUStats): Allow driver
to omit tail of array.
* src/remote/remote_driver.c (remoteDomainGetCPUStats):
Accommodate driver that omits tail of array.
* src/libvirt.c (virDomainGetCPUStats): Document this.
* src/qemu/qemu_driver.c (qemuDomainGetPercpuStats): Clear all
unpopulated entries.

* For now, only "cpu_time" is supported.
* cpuacct cgroup is used for providing percpu cputime information.

* src/qemu/qemu.conf     - take care of cpuacct cgroup.
* src/qemu/qemu_conf.c   - take care of cpuacct cgroup.
* src/qemu/qemu_driver.c - added an interface
* src/util/cgroup.c/h    - added interface for getting percpu cputime
Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com>

Qemu supports sizing by bytes; we shouldn't force the user to
round up if they really wanted an unaligned total size.

* include/libvirt/libvirt.h.in (VIR_DOMAIN_BLOCK_RESIZE_BYTES):
New flag.
* src/libvirt.c (virDomainBlockResize): Document it.
* src/qemu/qemu_monitor_json.c (qemuMonitorJSONBlockResize): Take
size in bytes.
* src/qemu/qemu_monitor_text.c (qemuMonitorTextBlockResize):
Likewise.  Pass bytes, not megabytes, to monitor.
* src/qemu/qemu_driver.c (qemuDomainBlockResize): Implement new
flag.

No thanks to 64-bit windows, with 64-bit pid_t, we have to avoid
constructs like 'int pid'.  Our API in libvirt-qemu cannot be
changed without breaking ABI; but then again, libvirt-qemu can
only be used on systems that support UNIX sockets, which rules
out Windows (even if qemu could be compiled there) - so for all
points on the call chain that interact with this API decision,
we require a different variable name to make it clear that we
audited the use for safety.

Adding a syntax-check rule only solves half the battle; anywhere
that uses printf on a pid_t still needs to be converted, but that
will be a separate patch.

* cfg.mk (sc_correct_id_types): New syntax check.
* src/libvirt-qemu.c (virDomainQemuAttach): Document why we didn't
use pid_t for pid, and validate for overflow.
* include/libvirt/libvirt-qemu.h (virDomainQemuAttach): Tweak name
for syntax check.
* src/vmware/vmware_conf.c (vmwareExtractPid): Likewise.
* src/driver.h (virDrvDomainQemuAttach): Likewise.
* tools/virsh.c (cmdQemuAttach): Likewise.
* src/remote/qemu_protocol.x (qemu_domain_attach_args): Likewise.
* src/qemu_protocol-structs (qemu_domain_attach_args): Likewise.
* src/util/cgroup.c (virCgroupPidCode, virCgroupKillInternal):
Likewise.
* src/qemu/qemu_command.c(qemuParseProcFileStrings): Likewise.
(qemuParseCommandLinePid): Use pid_t for pid.
* daemon/libvirtd.c (daemonForkIntoBackground): Likewise.
* src/conf/domain_conf.h (_virDomainObj): Likewise.
* src/probes.d (rpc_socket_new): Likewise.
* src/qemu/qemu_command.h (qemuParseCommandLinePid): Likewise.
* src/qemu/qemu_driver.c (qemudGetProcessInfo, qemuDomainAttach):
Likewise.
* src/qemu/qemu_process.c (qemuProcessAttach): Likewise.
* src/qemu/qemu_process.h (qemuProcessAttach): Likewise.
* src/uml/uml_driver.c (umlGetProcessInfo): Likewise.
* src/util/virnetdev.h (virNetDevSetNamespace): Likewise.
* src/util/virnetdev.c (virNetDevSetNamespace): Likewise.
* tests/testutils.c (virtTestCaptureProgramOutput): Likewise.
* src/conf/storage_conf.h (_virStoragePerms): Use mode_t, uid_t,
and gid_t rather than int.
* src/security/security_dac.c (virSecurityDACSetOwnership): Likewise.
* src/conf/storage_conf.c (virStorageDefParsePerms): Avoid
compiler warning.

This actually wires up the new optional parameter to block_stream:
http://wiki.qemu.org/Features/LiveBlockMigration/ImageStreamingAPI

The error checking is still sparse, since libvirt must not use
qemu-img or header probing on a qcow2 file in use by qemu to
check if the backing file name is valid; so for now, libvirt is
relying on qemu to diagnose an incorrect backing name.  Fixing this
will require libvirt to track the entire backing file chain at the
time qemu is started and keeps it updated with snapshot and pull
operations.

* src/qemu/qemu_monitor_json.c (qemuMonitorJSONBlockJob): Add
parameter, and update callers.
* src/qemu/qemu_monitor_json.h (qemuMonitorJSONBlockJob): Update
signature.
* src/qemu/qemu_monitor.h (qemuMonitorBlockJob): Likewise.
* src/qemu/qemu_driver.c (qemuDomainBlockJobImpl): Update caller.
* src/qemu/qemu_monitor.c (qemuMonitorBlockJob): Likewise.

This patch fixes console corruption, that happens if two concurrent
sessions are opened for a single console on a domain. Result of this
corruption was that each of the console streams recieved just a part
of the data written to the pipe so every console rendered unusable.

New helper function for safe console handling is used to establish the
console stream connection. This function ensures that no other libvirt
client is using the console (with the ability to disconnect consoles of
libvirt clients) and that no UUCP style lockfile is placed on the PTY
device.

* src/qemu/qemu_domain.h
        - add data structure to domain's private data dealing with
          console connections
* src/qemu/qemu_domain.c:
        - allocate/free domain's console data structure
* src/qemu/qemu_driver.c
        - use the new helper function for console handling

using 'system-wakeup' monitor command. It is supported only in JSON,
as we are enabling it if possible. Moreover, this command is available
in qemu-1.1+ which definitely has JSON.

Function xmlParseURI does not remove square brackets around IPv6
address when parsing. One of the solutions is making wrappers around
functions working with xmlURI*. This assures that uri->server will be
always properly assigned and it doesn't have to be changed when used
on some new place in the code.
For this purpose, functions virParseURI and virSaveURI were
added. These function are wrappers around xmlParseURI and xmlSaveUri
respectively.
Also there is one new syntax check function to prohibit these functions
anywhere else.

File changes:
 - src/util/viruri.h        -- declaration
 - src/util/viruri.c        -- definition
 - src/libvirt_private.syms -- symbol export
 - src/Makefile.am          -- added source and header files
 - cfg.mk                   -- added sc_prohibit_xmlURI
 - all others               -- ID name and include fixes

https://bugzilla.redhat.com/show_bug.cgi?id=795656 mentions
that a graceful destroy request can time out, meaning that the
error message is user-visible and should be more appropriate
than just internal error.

* src/qemu/qemu_driver.c (qemuDomainDestroyFlags): Swap error type.

Migrating domains with disks using cache != none is unsafe unless the
disk images are stored on coherent clustered filesystem. Thus we forbid
migrating such domains unless VIR_MIGRATE_UNSAFE flags is used.

This patch is based on an earlier patch by Eric Blake which was never
committed:

https://www.redhat.com/archives/libvir-list/2011-November/msg00243.html

Aside from rebasing, this patch only drops the driver lock once (prior
to the first time the function sleeps), then leaves it dropped until
it returns (Eric's patch would drop and re-acquire the lock around
each call to sleep).

At the time Eric sent his patch, the response (from Dan Berrange) was
that, while it wasn't a good thing to be holding the driver lock while
sleeping, we really need to rethink locking wrt the driver object,
switching to a finer-grained approach that locks individual items
within the driver object separately to allow for greater concurrency.

This is a good plan, and at the time it made sense to not apply the
patch because there was no known bug related to the driver lock being
held in this function.

However, we now know that the length of the wait in qemuProcessKill is
sometimes too short to allow the qemu process to fully flush its disk
cache before SIGKILL is sent, so we need to lengthen the timeout (in
order to improve the situation with management applications until they
can be updated to use the new VIR_DOMAIN_DESTROY_GRACEFUL flag added
in commit 72f8a7f1). But, if we
lengthen the timeout, we also lengthen the amount of time that all
other threads in libvirtd are essentially blocked from doing anything
(since just about everything needs to acquire the driver lock, if only
for long enough to get a pointer to a domain).

The solution is to modify qemuProcessKill to drop the driver lock
while sleeping, as proposed in Eric's patch. Then we can increase the
timeout with a clear conscience, and thus at least lower the chances
that someone running with existing management software will suffer the
consequence's of qemu's disk cache not being flushed.

In the meantime, we still should work on Dan's proposal to make
locking within the driver object more fine grained.

(NB: although I couldn't find any instance where qemuProcessKill() was
called with no jobs active for the domain (or some other guarantee
that the current thread had at least one refcount on the domain
object), this patch still follows Eric's method of temporarily adding
a ref prior to unlocking the domain object, because I couldn't
convince myself 100% that this was the case.)

via user agent. Allow targets mem & hybrid iff system_wakeup
monitor command is available.

When blkdeviotune was first committed in 0.9.8, we had the limitation
that setting one value reset all others.  But bytes and iops should
be relatively independent.  Furthermore, setting tuning values on
a live domain followed by dumpxml did not output the new settings.

* src/qemu/qemu_driver.c (qemuDiskPathToAlias): Add parameter, and
update callers.
(qemuDomainSetBlockIoTune): Don't lose previous unrelated
settings.  Make live changes reflect to dumpxml output.
* tools/virsh.pod (blkdeviotune): Update documentation.

The auto-generated WWN comply with the new addressing schema of WWN:

<quote>
the first nibble is either hex 5 or 6 followed by a 3-byte vendor
identifier and 36 bits for a vendor-specified serial number.
</quote>

We choose hex 5 for the first nibble. And for the 3-bytes vendor ID,
we uses the OUI according to underlying hypervisor type, (invoking
virConnectGetType to get the virt type). e.g. If virConnectGetType
returns "QEMU", we use Qumranet's OUI (00:1A:4A), if returns
ESX|VMWARE, we use VMWARE's OUI (00:05:69). Currently it only
supports qemu|xen|libxl|xenapi|hyperv|esx|vmware drivers. The last
36 bits are auto-generated.

virsh blkiotune dom --device-weights /dev/sda,400 --config

wasn't working correctly.

* src/qemu/qemu_driver.c (qemuDomainSetBlkioParameters): Use
correct definition.

The merge code had too many indirections to easily analyze.

* src/qemu/qemu_driver.c (qemuDomainMergeDeviceWeights): Pick
better variable names.

This is probably not strictly needed as save operation is not live but
we may have other reasons to avoid blocking qemu's main loop.

Qemu uses non-blocking I/O which doesn't play nice with regular file
descriptors. We need to pass a pipe to qemu instead, which can easily be
done using iohelper.