The virDomainDefParse* and virDomainDefFormat* methods both
accept the VIR_DOMAIN_XML_* flags defined in the public API,
along with a set of other VIR_DOMAIN_XML_INTERNAL_* flags
defined in domain_conf.c.
This is seriously confusing & error prone for a number of
reasons:
- VIR_DOMAIN_XML_SECURE, VIR_DOMAIN_XML_MIGRATABLE and
VIR_DOMAIN_XML_UPDATE_CPU are only relevant for the
formatting operation
- Some of the VIR_DOMAIN_XML_INTERNAL_* flags only apply
to parse or to format, but not both.
This patch cleanly separates out the flags. There are two
distint VIR_DOMAIN_DEF_PARSE_* and VIR_DOMAIN_DEF_FORMAT_*
flags that are used by the corresponding methods. The
VIR_DOMAIN_XML_* flags received via public API calls must
be converted to the VIR_DOMAIN_DEF_FORMAT_* flags where
needed.
The various calls to virDomainDefParse which hardcoded the
use of the VIR_DOMAIN_XML_INACTIVE flag change to use the
VIR_DOMAIN_DEF_PARSE_INACTIVE flag.
There is one problem that causes various errors in the daemon. When
domain is waiting for a job, it is unlocked while waiting on the
condition. However, if that domain is for example transient and being
removed in another API (e.g. cancelling incoming migration), it get's
unref'd. If the first call, that was waiting, fails to get the job, it
unref's the domain object, and because it was the last reference, it
causes clearing of the whole domain object. However, when finishing the
call, the domain must be unlocked, but there is no way for the API to
know whether it was cleaned or not (unless there is some ugly temporary
variable, but let's scratch that).
The root cause is that our APIs don't ref the objects they are using and
all use the implicit reference that the object has when it is in the
domain list. That reference can be removed when the API is waiting for
a job. And because each domain doesn't do its ref'ing, it results in
the ugly checking of the return value of virObjectUnref() that we have
everywhere.
This patch changes qemuDomObjFromDomain() to ref the domain (using
virDomainObjListFindByUUIDRef()) and adds qemuDomObjEndAPI() which
should be the only function in which the return value of
virObjectUnref() is checked. This makes all reference counting
deterministic and makes the code a bit clearer.
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
A future patch will allow recursion into backing chains when
collecting block stats. This patch should not change behavior,
but merely moves out the common code that will be reused once
recursion is enabled, and adds the parameter that will turn on
recursion.
* src/qemu/qemu_monitor.h (qemuMonitorGetAllBlockStatsInfo)
(qemuMonitorBlockStatsUpdateCapacity): Add recursion parameter,
although it is ignored for now.
* src/qemu/qemu_monitor.h (qemuMonitorGetAllBlockStatsInfo)
(qemuMonitorBlockStatsUpdateCapacity): Likewise.
* src/qemu/qemu_monitor_json.h
(qemuMonitorJSONGetAllBlockStatsInfo)
(qemuMonitorJSONBlockStatsUpdateCapacity): Likewise.
* src/qemu/qemu_monitor_json.c
(qemuMonitorJSONGetAllBlockStatsInfo)
(qemuMonitorJSONBlockStatsUpdateCapacity): Add parameter, and
split...
(qemuMonitorJSONGetOneBlockStatsInfo)
(qemuMonitorJSONBlockStatsUpdateCapacityOne): ...into helpers.
(qemuMonitorJSONGetBlockStatsInfo): Update caller.
* src/qemu/qemu_driver.c (qemuDomainGetStatsBlock): Update caller.
* src/qemu/qemu_migration.c (qemuMigrationCookieAddNBD): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
Based on previous commit, we can now precreate missing volumes. While
digging out the functionality from storage driver would be nicer, if
you've seen the code it's nearly impossible. So I'm going from the
other end:
1) For given disk target, disk path is looked up.
2) For the disk path, storage pool is looked up, a volume XML is
constructed and then passed to virStorageVolCreateXML() which has all
the knowledge how to create raw images, (encrypted) qcow(2) images,
etc.
One of the advantages of this approach is, we don't have to care about
image conversion - qemu does that for us. So for instance, users can
transform qcow2 into raw on migration (if the correct XML is passed to
the migration API).
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Up 'til now, users need to precreate non-shared storage on migration
themselves. This is not very friendly requirement and we should do
something about it. In this patch, the migration cookie is extended,
so that <nbd/> section does not only contain NBD port, but info on
disks being migrated. This patch sends a list of pairs of:
<disk target; disk size>
to the destination. The actual storage allocation is left for next
commit.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
If job is failed in qemuMigrationRun, we expect the jobinfo type as
FAILED. But jobinfo type won't be updated until entering
qemuMigrationWaitForCompletion. We should make it updated in all
conditions. Moreover, we can't use qemuMigrationUpdateJobStatus
here because job may fail in libvirt, so we can't query job status
from QEMU.
Signed-off-by: Wang Rui <moon.wangrui@huawei.com>
The migration job status is traced in qemuMigrationUpdateJobStatus
which is called in qemuMigrationRun. But if migration is cancelled
before the trace such as in qemuMigrationDriveMirror, the jobinfo
type won't be updated to CANCELLED. After this patch, we can get
jobinfo type CANCELLED if migration is cancelled during drive
mirror. Moreover, we can't use qemuMigrationUpdateJobStatus
because from qemu's point of view it's just the drive mirror being
cancelled and the migration hasn't even started yet.
Signed-off-by: Wang Rui <moon.wangrui@huawei.com>
virReportSystemError is reserved for reporting system errors, calling it
with VIR_ERR_* error codes produces error messages that do not make any
sense, such as
internal error: guest failed to start: Kernel doesn't support user
namespace: Link has been severed
We should prohibit wrong usage with a syntax-check rule.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Oops, I forgot to squash one more instance of the same check in the
previous commit (v1.2.10-144-g52691f9).
https://bugzilla.redhat.com/show_bug.cgi?id=1147331
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Any attempt to start a tunnelled migration with libvirtd that supports
RDMA migration (specifically commit v1.2.8-226-ged22a47) crashes
libvirtd on the destination host.
The crash is inevitable because qemuMigrationPrepareAny is always called
with NULL protocol in case of tunnelled migration.
https://bugzilla.redhat.com/show_bug.cgi?id=1147331
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
We used to set migration capabilities only when a user asked for them in
flags. This is fine when migration succeeds since the QEMU process is
killed in the end but in case migration fails or if it's cancelled, some
capabilities may remain turned on with no way to turn them off. To fix
that, migration capabilities have to be turned on if requested but
explicitly turned off in case they were not requested but QEMU supports
them.
https://bugzilla.redhat.com/show_bug.cgi?id=1163953
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Commit 6e5c79a1 tried to fix deadlock between nwfilter{Define,Undefine}
and starting of guest, but this same deadlock exists for
updating/attaching network device to domain.
The deadlock was introduced by removing global QEMU driver lock because
nwfilter was counting on this lock and ensure that all driver locks are
locked inside of nwfilter{Define,Undefine}.
This patch extends usage of virNWFilterReadLockFilterUpdates to prevent
the deadlock for all possible paths in QEMU driver. LXC and UML drivers
still have global lock.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1143780
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
==404== 232 bytes in 1 blocks are definitely lost in loss record 669 of 758
==404== at 0x4C2B934: calloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==404== by 0x52A2BF3: virAlloc (viralloc.c:144)
==404== by 0x1D49AD70: qemuMigrationCookieAddStatistics (qemu_migration.c:554)
==404== by 0x1D49AD70: qemuMigrationBakeCookie (qemu_migration.c:1228)
==404== by 0x1D4A43B8: qemuMigrationFinish (qemu_migration.c:5002)
==404== by 0x1D4C9339: qemuDomainMigrateFinish3Params (qemu_driver.c:11526)
Introduced by commit 5d6fb96
In qemuMigrationFinish mig->nbd can not be initialized by
qemuMigrationEatCookie without the QEMU_MIGRATION_COOKIE_NBD flag.
That causes qemuMigrationStopNBDServer to return early without
stopping the NBD server properly.
Signed-off-by: Weiwei Li <nuonuoli@tencent.com>
Signed-off-by: Ján Tomko <jtomko@redhat.com>
commit 3e1e16aa8d4238241a1806cb9bdb3b9ad60db777 (Use a port from the
migration range for NBD as well) changed ndb port allocation from
remotePorts to migrationPorts, but did not change the port releasing
process, which makes an error when migrating several times (above 64):
error: internal error: Unable to find an unused port in range
'migration' (49152-49215)
https://bugzilla.redhat.com/show_bug.cgi?id=1159245
Signed-off-by: Weiwei Li <nuonuoli@tencent.com>
Signed-off-by: Ján Tomko <jtomko@redhat.com>
if specifying migration_host to an Ipv6 address without brackets,
it was resolved to an incorrect address, such as:
tcp:2001:0DB8::1428:4444,
but the correct address should be:
tcp:[2001:0DB8::1428]:4444
so we should add brackets when parsing it.
Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Commit fba6bc4 introduced the non-migratable invtsc feature,
breaking save/migration with host-model and host-passthrough.
On hosts with this feature present it was automatically included
in the CPU definition, regardless of QEMU support.
Commit de0aeaf stopped including it by default for host-model,
but failed to fix host-passthrough.
This commit ignores checking of CPU features with host-passthrough,
since we don't pass them to QEMU (only -cpu host is passed),
allowing domains using host-passthrough that were saved with
the broken version of libvirtd to be restored.
https://bugzilla.redhat.com/show_bug.cgi?id=1147584
RDMA Live migration requires registering memory with the hardware, and
thus QEMU offers a new 'capability' to pre-register / mlock() the guest
memory in advance for higher RDMA performance before the migration
begins. This capability is disabled by default, which means QEMU will
register the memory with the hardware in an on-demand basis.
This patch exposes this capability with the following example usage:
virsh migrate --live --rdma-pin-all --migrateuri rdma://hostname domain qemu+ssh://hostname/system
Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
This patch adds support for RDMA protocol in migration URIs.
USAGE: $ virsh migrate --live --migrateuri rdma://hostname domain qemu+ssh://hostname/system
Since libvirt runs QEMU in a pretty restricted environment, several
files needs to be added to cgroup_device_acl (in qemu.conf) for QEMU to
be able to access the host's infiniband hardware. Full documenation of
the feature can be found on QEMU wiki:
http://wiki.qemu.org/Features/RDMALiveMigration
Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Currently we only support TCP protocol for native QEMU migration but
this is going to be changed. Let's make the code more general and remove
hardcoded TCP protocol from several places.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
For compatibility with old libvirt we need to support both tcp:host and
tcp://host migration URIs. Let's make the code that parses them a bit
cleaner.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
RDMA migration uses the 'setup' state in QEMU to optionally lock
all memory before the migration starts. The total time spent in
this state is exposed as VIR_DOMAIN_JOB_SETUP_TIME.
Additionally, QEMU also exports migration throughput (mbps) for both
memory and disk, so let's add them too: VIR_DOMAIN_JOB_MEMORY_BPS,
VIR_DOMAIN_JOB_DISK_BPS.
Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Upstream qemu 1.4 added some drive-mirror tunables not present
when it was first introduced in 1.3. Management apps may want
to set these in some cases (for example, without tuning
granularity down to sector size, a copy may end up occupying
more bytes than the original because an entire cluster is
copied even when only a sector within the cluster is dirty,
although tuning it down results in more CPU time to do the
copy). I haven't personally needed to use the parameters, but
since they exist, and since the new API supports virTypedParams,
we might as well expose them.
Since the tuning parameters aren't often used, and omitted from
the QMP command when unspecified, I think it is safe to rely on
qemu 1.3 to issue an error about them being unsupported, rather
than trying to create a new capability bit in libvirt.
Meanwhile, all versions of qemu from 1.4 to 2.1 have a bug where
a bad granularity (such as non-power-of-2) gives a poor message:
error: internal error: unable to execute QEMU command 'drive-mirror': Invalid parameter 'drive-virtio-disk0'
because of abuse of QERR_INVALID_PARAMETER (which is supposed to
name the parameter that was given a bad value, rather than the
value passed to some other parameter). I don't see that a
capability check will help, so we'll just live with it (and it
has since been improved in upstream qemu).
* src/qemu/qemu_monitor.h (qemuMonitorDriveMirror): Add
parameters.
* src/qemu/qemu_monitor.c (qemuMonitorDriveMirror): Likewise.
* src/qemu/qemu_monitor_json.h (qemuMonitorJSONDriveMirror):
Likewise.
* src/qemu/qemu_monitor_json.c (qemuMonitorJSONDriveMirror):
Likewise.
* src/qemu/qemu_driver.c (qemuDomainBlockCopyCommon): Likewise.
(qemuDomainBlockRebase, qemuDomainBlockCopy): Adjust callers.
* src/qemu/qemu_migration.c (qemuMigrationDriveMirror): Likewise.
* tests/qemumonitorjsontest.c (qemuMonitorJSONDriveMirror): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
If the qemuMigrationEatCookie() fails to set mig, we jump to cleanup:
which will call qemuMigrationCancelDriveMirror() without first checking
if mig == NULL
Signed-off-by: John Ferlan <jferlan@redhat.com>
After the previous commit, migration statistics on the source and
destination hosts are not equal because the destination updated time
statistics. Let's send the result back so that the same data can be
queried on both sides of the migration.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Total time of a migration and total downtime transfered from a source to
a destination host do not count with the transfer time to the
destination host and with the time elapsed before guest CPUs are
resumed. Thus, source libvirtd remembers when migration started and when
guest CPUs were paused. Both timestamps are transferred to destination
libvirtd which uses them to compute total migration time and total
downtime. Obviously, this requires the time to be synchronized between
the two hosts. The reported times are useless otherwise but they would
be equally useless if we didn't do this recomputation so don't lose
anything by doing it.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
When migrating a transient domain or with VIR_MIGRATE_UNDEFINE_SOURCE
flag, the domain may disappear from source host. And so will migration
statistics associated with the domain. We need to transfer the
statistics at the end of a migration so that they can be queried at the
destination host.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
virDomainGetJobStats gains new VIR_DOMAIN_JOB_STATS_COMPLETED flag that
can be used to fetch statistics of a completed job rather than a
currently running job.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Job statistics data were tracked in several structures and variables.
Let's make a new qemuDomainJobInfo structure which can be used as a
single source of statistics data as a preparation for storing data about
completed a job.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
When QEMU fails during incoming migration after we successfully started
it (i.e., during Perform or Finish phase), we report a rather unhelpful
message
Unable to read from monitor: Connection reset by peer
We already have a code that takes error messages from QEMU's error
output but we disable it once QEMU successfully starts. This patch
postpones this until the end of Finish phase during incoming migration
so that we can report a much better error message:
internal error: early end of file from monitor: possible problem:
Unknown savevm section or instance '0000:00:05.0/virtio-balloon' 0
load of migration failed
https://bugzilla.redhat.com/show_bug.cgi?id=1090093
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
While reviewing the new virDomainBlockCopy API, Peter Krempa
pointed out that our existing design of using MiB/s for block
job bandwidth is rather coarse, especially since qemu tracks
it in bytes/s; so virDomainBlockCopy only accepts bytes/s.
But once the new API is implemented for qemu, we will be in
the situation where it is possible to set a value that cannot
be accurately reflected back to the user, because the existing
virDomainGetBlockJobInfo defaults to the coarser units.
Fortunately, we have an escape hatch; and one that has already
served us well in the past: we can use the flags argument to
specify which scale to use (see virDomainBlockResize for prior
art). This patch fixes the query side of the API; made easier
by previous patches that split the query side out from the
modification code. Later patches will address the virsh
interface, as well retrofitting all other blockjob APIs to
also accept a flag for toggling bandwidth units.
* include/libvirt/libvirt.h.in (_virDomainBlockJobInfo)
(VIR_DOMAIN_BLOCK_COPY_BANDWIDTH): Document sizing issues.
(virDomainBlockJobInfoFlags): New enum.
* src/libvirt.c (virDomainGetBlockJobInfo): Document new flag.
* src/qemu/qemu_monitor.h (qemuMonitorBlockJobInfo): Add parameter.
* src/qemu/qemu_monitor.c (qemuMonitorBlockJobInfo): Likewise.
* src/qemu/qemu_monitor_json.h (qemuMonitorJSONBlockJobInfo):
Likewise.
* src/qemu/qemu_monitor_json.c (qemuMonitorJSONBlockJobInfo)
(qemuMonitorJSONGetBlockJobInfoOne): Likewise. Don't scale here.
* src/qemu/qemu_migration.c (qemuMigrationDriveMirror): Update
callers.
* src/qemu/qemu_driver.c (qemuDomainBlockPivot)
(qemuDomainBlockJobImpl): Likewise.
(qemuDomainGetBlockJobInfo): Likewise, and support new flag.
Signed-off-by: Eric Blake <eblake@redhat.com>
Another layer of overly-multiplexed code that deserves to be
split into obviously separate paths for query vs. modify.
This continues the cleanup started in commit cefe0ba.
In the process, make some tweaks to simplify the logic when
parsing the JSON reply. There should be no user-visible
semantic changes.
* src/qemu/qemu_monitor.h (qemuMonitorBlockJob): Drop parameter.
(qemuMonitorBlockJobInfo): New prototype.
(BLOCK_JOB_INFO): Drop enum.
* src/qemu/qemu_monitor_json.h (qemuMonitorJSONBlockJob)
(qemuMonitorJSONBlockJobInfo): Likewise.
* src/qemu/qemu_monitor.c (qemuMonitorBlockJob): Split...
(qemuMonitorBlockJobInfo): ...into second function.
* src/qemu/qemu_monitor_json.c (qemuMonitorJSONBlockJob): Move
block info portions...
(qemuMonitorJSONGetBlockJobInfo): ...here, and rename...
(qemuMonitorJSONBlockJobInfo): ...and export.
(qemuMonitorJSONGetBlockJobInfoOne): Alter return semantics.
* src/qemu/qemu_driver.c (qemuDomainBlockPivot)
(qemuDomainBlockJobImpl, qemuDomainGetBlockJobInfo): Adjust
callers.
* src/qemu/qemu_migration.c (qemuMigrationDriveMirror)
(qemuMigrationCancelDriveMirror): Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
During a QEMU live migration several warning messages about job
handling could be written to syslog on the destination host:
"entering monitor without asking for a nested job is dangerous"
The messages are written because the job handling during migration
uses hard coded asyncJob values in several places that are incorrect.
This patch passes the required asyncJob value around and prevents
the warnings as well as any issues that the warnings may be referring
to.
https://bugzilla.redhat.com/show_bug.cgi?id=1130089
Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Signed-off-by: Ján Tomko <jtomko@redhat.com>
In qemuMigrationToFile we enter the monitor multiple times and don't
check if the VM is still alive after returning form the monitor. Add the
checks to skip pieces of code in case the VM crashes while saving it's
state.
In the future we might need to track state of individual images. Move
the readonly and shared flags to the virStorageSource struct so that we
can keep them in a per-image basis.
To allow changing the name that is recorded in the top of the current
image chain used in a block pull/rebase operation, we need to specify
the backing name to qemu. This is done via the "backing-file" attribute
to the block-stream commad.
Replace:
if (virBufferError(&buf)) {
virBufferFreeAndReset(&buf);
virReportOOMError();
...
}
with:
if (virBufferCheckError(&buf) < 0)
...
This should not be a functional change (unless some callers
misused the virBuffer APIs - a different error would be reported
then)
As we are doing with the enum structures, a cleanup in "src/qemu/"
directory was done now. All the enums that were defined in the
header files were converted to typedefs in this directory. This
patch includes all the adjustments to remove conflicts when you do
this kind of change. "Enum-to-typedef"'s conversions were made in
"src/qemu/qemu_{capabilities, domain, migration, hotplug}.h".
Signed-off-by: Julio Faracco <jcfaracco@gmail.com>
As part of the work on backing chains, I'm finding that it would
be easier to directly manipulate chains of pointers (adding a
snapshot merely adjusts pointers to form the correct list) rather
than copy data from one struct to another. This patch converts
domain disk source to be a pointer.
In this patch, the pointer is ALWAYS allocated (thanks in part to
the previous patch forwarding all disk def allocation through a
common point), and all other changse are just mechanical fallout of
the new type; there should be no functional change. It is possible
that we may want to leave the pointer NULL for a cdrom with no
medium in a later patch, but as that requires a closer audit of the
source to ensure we don't fault on a null dereference, I didn't do
it here.
* src/conf/domain_conf.h (_virDomainDiskDef): Change type of src.
* src/conf/domain_conf.c: Adjust all clients.
* src/security/security_selinux.c: Likewise.
* src/qemu/qemu_domain.c: Likewise.
* src/qemu/qemu_command.c: Likewise.
* src/qemu/qemu_conf.c: Likewise.
* src/qemu/qemu_process.c: Likewise.
* src/qemu/qemu_migration.c: Likewise.
* src/qemu/qemu_driver.c: Likewise.
* src/lxc/lxc_driver.c: Likewise.
* src/lxc/lxc_controller.c: Likewise.
* tests/securityselinuxlabeltest.c: Likewise.
Signed-off-by: Eric Blake <eblake@redhat.com>
This is similar to the previous commit in that we need to explicitly
send migrate_cancel when libvirt detects an error other than those
reported by query-migrate. However, the possibility to hit such error is
pretty small.
When QEMU reports failed or cancelled migration, we don't need to send
it migrate_cancel QMP command. But in all other error paths, such as if
we detect broken connection to a destination daemon or something else
happens inside libvirt, we need to explicitly send migrate_cancel
command instead of relying on the migration to be implicitly cancelled
when destination QEMU is killed.
Because we were not doing so, one could end up with a paused domain
after failed migration.
https://bugzilla.redhat.com/show_bug.cgi?id=1098833
For now, we set the migration URI via command line '--migrate_uri' or
construct the URI by looking up the dest host's hostname which could be
solved by DNS automatically.
But in cases the dest host have two or more NICs to reach, we may need to
send the migration data over a specific NIC which is different from the
automatically resolved one for some reason like performance, security, etc.
Thus we must explicitly specify the migrateuri in command line everytime,
but it is too troublesome if there are many such hosts (and don't forget
virt-manager).
This patch adds a configuration file option on dest host to save the
default value set which can be specified to a migration hostname or
one of this host's addresses used for transferring data, thus user doesn't
have to specify it in command line everytime.
Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
When qemu driver is polling for migration to finish (in
qemuMigrationWaitForCompletion), it may happen that another job allowed
during migration is running and if it does not finish within 30 seconds,
migration would be cancelled because of that. However, we can just
ignore the timeout and let the waiting loop try again later.
If an event fired at the end of migration is ever implemented in QEMU,
we can just wait for the event instead of polling for migration status
and libvirt will behave consistently, i.e., migration won't be cancelled
in case another job started during migration takes long time to finish.
For bug https://bugzilla.redhat.com/show_bug.cgi?id=1083238
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
