New preconfig runstate will be used in follow up patches
related to introducing --preconfig CLI option and is
intended to replace prelaunch runstate from QEMU start
up to machine_init callback.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Message-Id: <1525423069-61903-4-git-send-email-imammedo@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
[ehabkost: Changed "since 2.13" to "since 3.0"]
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

We're going to make the next release be 3.0, not 2.13; change
the annotations in our json appropriately.

Changes produced with
  sed -i -e 's/2\.13/3.0/g' qapi/*.json
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Message-id: 20180522104000.9044-2-peter.maydell@linaro.org

This adds a minimal query-jobs implementation that shouldn't pose many
design questions. It can later be extended to expose more information,
and especially job-specific information.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

This adds QMP commands that control the transition between states of the
job lifecycle.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

This adds a QMP event that is emitted whenever a job transitions from
one status to another.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

This adds a separate schema file for all job-related definitions that
aren't tied to the block layer.

For a start, move the enums JobType, JobStatus and JobVerb.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

This moves BlockJob.status and the closely related functions
(block_)job_state_transition() and (block_)job_apply_verb to Job. The
two QAPI enums are renamed to JobStatus and JobVerb.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

QAPI types aren't externally visible, so we can rename them without
causing problems. Before we add a job type to Job, rename the enum
so it can be used for more than just block jobs.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>

Clarify that len is just an estimation of the end value of offset, and
that offset increases monotonically while len can change arbitrarily.

While touching the documentation of offset, move it directly after len
to match the order of the declaration below.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>

Commit 0ec4dfb8 changed block-job_pause/resume so that they return an
error if they don't do anything because the job is already
paused/running. It forgot to update the documentation, so do that now.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>

"vlan" will be dropped in 2.13, not in 2.12. And while we're at it,
use the better wording "dropped in" instead of "removed with" (also
for the "dump" removal).
Reported-by: NStefan Hajnoczi <stefanha@redhat.com>
Reported-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

Blank lines and comments as suggested by Eric.
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-Id: <20180427111502.9822-1-dgilbert@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

It pauses an ongoing migration.  Currently it only supports postcopy.
Note that this command will work on either side of the migration.
Basically when we trigger this on one side, it'll interrupt the other
side as well since the other side will get notified on the disconnect
event.

However, it's still possible that the other side is not notified, for
example, when the network is totally broken, or due to some firewall
configuration changes.  In that case, we will also need to run the same
command on the other side so both sides will go into the paused state.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-24-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

---
s/2.12/2.13/

The first allow-oob=true command.  It's used on destination side when
the postcopy migration is paused and ready for a recovery.  After
execution, a new migration channel will be established for postcopy to
continue.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-21-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>
---
s/2.12/2.13/

Introducing new migration state "postcopy-recover". If a migration
procedure is paused and the connection is rebuilt afterward
successfully, we'll switch the source VM state from "postcopy-paused" to
the new state "postcopy-recover", then we'll do the resume logic in the
migration thread (along with the return path thread).

This patch only do the state switch on source side. Another following up
patch will handle the state switching on destination side using the same
status bit.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-10-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

---
s/2.11/2.13/

It will be used when we want to resume one paused migration.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-8-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>
---
s/2.12/2.13/

Introducing a new state "postcopy-paused", which can be used when the
postcopy migration is paused. It is targeted for postcopy network
failure recovery.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-3-peterx@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

This adds a simple copy-on-read filter driver.  It relies on the already
existing COR functionality in the central block layer code, which may be
moved here once we no longer need it there.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-id: 20180421132929.21610-2-mreitz@redhat.com
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

When we've reached the concluded state, we need to expose the error
state if applicable. Add the new field.

This should be sufficient for determining if a job completed
successfully or not after concluding; if we want to discriminate
based on how it failed more mechanically, we can always add an
explicit return code enumeration later.

I didn't bother to make it only show up if we are in the concluded
state; I don't think it's necessary.

Cc: qemu-stable@nongnu.org
Signed-off-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

It's been marked as deprecated since QEMU v2.9.0, so that should have
been enough time for everybody to either just drop unnecessary "vlan=0"
parameters, to switch to the modern -device + -netdev syntax for connecting
guest NICs with host network backends, or to switch to the "hubport" netdev
in case hubs are really wanted instead.

Buglink: https://bugs.launchpad.net/qemu/+bug/658904Signed-off-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NJason Wang <jasowang@redhat.com>

mincore(2) checks whether pages are resident.  Use it to verify that
page cache has been dropped.

You can trigger a verification failure by mmapping the image file from
another process that loads a byte from a page, forcing it to become
resident.  bdrv_co_invalidate_cache() will fail while that process is
alive.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Message-id: 20180427162312.18583-3-stefanha@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

The TARGET_BASE_ARCH values from "configure" don't all map to the
@CpuInfoArch enum constants; in particular "s390x" from the former does
not match @s390 in the latter. Clients are known to rely on the @s390
constant specifically, so we can't change it silently. Instead, deprecate
the @CpuInfoFast.@arch member (in favor of @CpuInfoFast.@target) using the
regular deprecation process.

(No deprecation reminder is added to sysemu_target_to_cpuinfo_arch(): once
@CpuInfoFast.@arch is removed, the assignment expression that calls
sysemu_target_to_cpuinfo_arch() from qmp_query_cpus_fast() will have to
disappear; in turn the static function left without callers will also
break the build, thus it'll have to go.)

Cc: "Daniel P. Berrange" <berrange@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Message-Id: <20180427192852.15013-6-lersek@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

Add a new field @target (of type @SysEmuTarget) to the output of the
@query-cpus-fast command, which provides more information about the
emulation target than the field @arch (of type @CpuInfoArch). Make @target
the new discriminator for the @CpuInfoFast return structure. Keep @arch
for compatibility.

Cc: "Daniel P. Berrange" <berrange@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-Id: <20180427192852.15013-5-lersek@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

Now that we have @SysEmuTarget, it makes sense to restrict
@TargetInfo.@arch to valid sysemu targets at the schema level.

Cc: "Daniel P. Berrange" <berrange@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-Id: <20180427192852.15013-4-lersek@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

We'll soon need an enumeration type that lists all the softmmu targets
that QEMU (the project) supports. Introduce @SysEmuTarget to
"common.json".

The enum constant @x86_64 doesn't match the QAPI convention of preferring
hyphen ("-") over underscore ("_"). This is intentional; the @SysEmuTarget
constants are supposed to produce QEMU executable names when stringified
and appended to the "qemu-system-" prefix. Put differently, the
replacement text of the TARGET_NAME preprocessor macro must be possible to
look up in the list of (stringified) enum constants.

Like other enum types, @SysEmuTarget too can be used for discriminator
fields in unions. For the @i386 constant, a C-language union member called
"i386" would be generated. On mingw build hosts, "i386" is a macro
however. Add "i386" to "polluted_words" at once.

Cc: "Daniel P. Berrange" <berrange@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Message-Id: <20180427192852.15013-3-lersek@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

* Commit ca230ff3 added the @arch field to @CpuInfoFast, but it failed
  to set the new field in qmp_query_cpus_fast(), when TARGET_S390X was not
  defined. The updated @query-cpus-fast example in "qapi-schema.json"
  showed "arch":"x86" only because qmp_query_cpus_fast() calls g_malloc0()
  to allocate @CpuInfoFast, and the CPU_INFO_ARCH_X86 enum constant is
  generated with value 0.

  All @arch values other than @s390 implied the @CpuInfoOther sub-struct
  for @CpuInfoFast -- at the time of writing the patch --, thus no fields
  other than @arch needed to be set when TARGET_S390X was not defined. Set
  @arch now, by copying the corresponding assignments from
  qmp_query_cpus().

* Commit 25fa194b added the @riscv enum constant to @CpuInfoArch (used
  in both @CpuInfo and @CpuInfoFast -- the return types of the @query-cpus
  and @query-cpus-fast commands, respectively), and assigned, in both
  return structures, the @CpuInfoRISCV sub-structure to the new enum
  value.

  However, qmp_query_cpus_fast() would not populate either the @arch field
  or the @CpuInfoRISCV sub-structure, when TARGET_RISCV was defined; only
  qmp_query_cpus() would.

  Assign @CpuInfoOther to the @riscv enum constant in @CpuInfoFast, and
  populate only the @arch field in qmp_query_cpus_fast(). Getting CPU
  state without interrupting KVM is an exceptional thing that only S390X
  does currently. Quoting Cornelia Huck <cohuck@redhat.com>, "s390x is
  exceptional in that it has state in QEMU that is actually interesting
  for upper layers and can be retrieved without performance penalty". See
  also
  <https://www.redhat.com/archives/libvir-list/2018-February/msg00121.html>.

Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>
Cc: Viktor VM Mihajlovski <mihajlov@linux.vnet.ibm.com>
Cc: qemu-stable@nongnu.org
Fixes: ca230ff3
Fixes: 25fa194bSigned-off-by: NLaszlo Ersek <lersek@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Message-Id: <20180427192852.15013-2-lersek@redhat.com>
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

For convenience and clarity, make it possible to call qobject_ref() at
the time when the reference is associated with a variable, or
argument, by making qobject_ref() return the same pointer as given.
Use that to simplify the callers.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-Id: <20180419150145.24795-5-marcandre.lureau@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
[Useless change to qobject_ref_impl() dropped, commit message improved
slightly]
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

Now that we can safely call QOBJECT() on QObject * as well as its
subtypes, we can have macros qobject_ref() / qobject_unref() that work
everywhere instead of having to use QINCREF() / QDECREF() for QObject
and qobject_incref() / qobject_decref() for its subtypes.

The replacement is mechanical, except I broke a long line, and added a
cast in monitor_qmp_cleanup_req_queue_locked().  Unlike
qobject_decref(), qobject_unref() doesn't accept void *.

Note that the new macros evaluate their argument exactly once, thus no
need to shout them.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-Id: <20180419150145.24795-4-marcandre.lureau@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
[Rebased, semantic conflict resolved, commit message improved]
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>

v2: Rebase on top of master
v3: Fix the json format (Eric Blake)
    Fix a comparison issue (Gerd Hoffmann)
Signed-off-by: NElie Tournier <elie.tournier@collabora.com>
Message-id: 20180413135842.21325-2-tournier.elie@gmail.com
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

Postcopy total blocktime is available on destination side only.
But query-migrate was possible only for source. This patch
adds ability to call query-migrate on destination.
To be able to see postcopy blocktime, need to request postcopy-blocktime
capability.

The query-migrate command will show following sample result:
{"return":
    "postcopy-vcpu-blocktime": [115, 100],
    "status": "completed",
    "postcopy-blocktime": 100
}}

postcopy_vcpu_blocktime contains list, where the first item is the first
vCPU in QEMU.

This patch has a drawback, it combines states of incoming and
outgoing migration. Ongoing migration state will overwrite incoming
state. Looks like better to separate query-migrate for incoming and
outgoing migration or add parameter to indicate type of migration.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NAlexey Perevalov <a.perevalov@samsung.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Message-Id: <1521742647-25550-7-git-send-email-a.perevalov@samsung.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

Right now it could be used on destination side to
enable vCPU blocktime calculation for postcopy live migration.
vCPU blocktime - it's time since vCPU thread was put into
interruptible sleep, till memory page was copied and thread awake.
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NAlexey Perevalov <a.perevalov@samsung.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Message-Id: <1521742647-25550-2-git-send-email-a.perevalov@samsung.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

What static=on really does is what we call metadata preallocation for
other block drivers. While we can still change the QMP interface, make
it more consistent by using 'preallocation' for VDI, too.

This doesn't implement any new functionality, so the only supported
preallocation modes are 'off' and 'metadata' for now.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

It may need to treat PC-DIMM and NVDIMM differently, e.g., when
deciding the necessity of non-volatile flag bit in SRAT memory
affinity structures.

A new field 'nvdimm' is added to the union type MemoryDeviceInfo for
such purpose. Its type is currently PCDIMMDeviceInfo and will be
updated when necessary in the future.

It also fixes "info memory-devices"/query-memory-devices which
currently show nvdimm devices as dimm devices since
object_dynamic_cast(obj, TYPE_PC_DIMM) happily cast nvdimm to
TYPE_PC_DIMM which it's been inherited from.
Signed-off-by: NHaozhong Zhang <haozhong.zhang@intel.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NIgor Mammedov <imammedo@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

Set (and clear) histograms through new command
block-latency-histogram-set and show new statistics in
query-blockstats results.

For now, the command is marked experimental with prefix 'x-',
to gain experience with the interface without being stuck
with design decisions.
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20180309165212.97144-3-vsementsov@virtuozzo.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
[eblake: fix typos, mention x- prefix in commit message]
Signed-off-by: NEric Blake <eblake@redhat.com>

This command is only used to test OOB functionality.  It should not be
used for any other purposes.
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180309090006.10018-22-peterx@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
[eblake: grammar tweak]
Signed-off-by: NEric Blake <eblake@redhat.com>

Having "allow-oob":true for a command does not mean that this command
will always be run in out-of-band mode.  The out-of-band quick path will
only be executed if we specify the extra "run-oob" flag when sending the
QMP request:

    { "execute":   "command-that-allows-oob",
      "arguments": { ... },
      "control":   { "run-oob": true } }

The "control" key is introduced to store this extra flag.  "control"
field is used to store arguments that are shared by all the commands,
rather than command specific arguments.  Let "run-oob" be the first.

Note that in the patch I exported qmp_dispatch_check_obj() to be used to
check the request earlier, and at the same time allowed "id" field to be
there since actually we always allow that.
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180309090006.10018-19-peterx@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
[eblake: rebase to qobject_to(), spelling fix]
Signed-off-by: NEric Blake <eblake@redhat.com>

Here "oob" stands for "Out-Of-Band".  When "allow-oob" is set, it means
the command allows out-of-band execution.

The "oob" idea is proposed by Markus Armbruster in following thread:

  https://lists.gnu.org/archive/html/qemu-devel/2017-09/msg02057.html

This new "allow-oob" boolean will be exposed by "query-qmp-schema" as
well for command entries, so that QMP clients can know which commands
can be used in out-of-band calls. For example the command "migrate"
originally looks like:

  {"name": "migrate", "ret-type": "17", "meta-type": "command",
   "arg-type": "86"}

And it'll be changed into:

  {"name": "migrate", "ret-type": "17", "allow-oob": false,
   "meta-type": "command", "arg-type": "86"}

This patch only provides the QMP interface level changes.  It does not
contain the real out-of-band execution implementation yet.
Suggested-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180309090006.10018-18-peterx@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
[eblake: rebase on introspection done by qlit]
Signed-off-by: NEric Blake <eblake@redhat.com>

This event will be emitted if one QMP command is dropped.  Also,
declare an enum for the reasons.
Reviewed-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180309090006.10018-16-peterx@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
[eblake: rebase to master]
Signed-off-by: NEric Blake <eblake@redhat.com>

There were no QMP capabilities defined.  Define the first capability,
"oob", to allow out-of-band messages.

After this patch, we will allow QMP clients to enable QMP capabilities
when sending the first "qmp_capabilities" command.  Originally we are
starting QMP session with no arguments like:

  { "execute": "qmp_capabilities" }

Now we can enable some QMP capabilities using (take OOB as example,
which is the only capability that we support):

  { "execute": "qmp_capabilities",
    "arguments": { "enable": [ "oob" ] } }

When the "arguments" key is not provided, no capability is enabled.

For capability "oob", the monitor needs to be run on a dedicated IO
thread, otherwise the command will fail.  For example, trying to enable
OOB on a MUXed typed QMP monitor will fail.

One thing to mention is that QMP capabilities are per-monitor, and also
when the connection is closed due to some reason, the capabilities will
be reset.

Also, touch up qmp-test.c to test the new bits.
Signed-off-by: NPeter Xu <peterx@redhat.com>
Message-Id: <20180309090006.10018-11-peterx@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
[eblake: touch up commit message]
Signed-off-by: NEric Blake <eblake@redhat.com>

We have a clear replacement, so let's deprecate it.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>
Message-Id: <20180224154033.29559-8-mreitz@redhat.com>
Signed-off-by: NEric Blake <eblake@redhat.com>