Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2019-06-14' into staging

Block patches:
- Allow blockdev-backup from nodes that are not in qemu's main AIO
  context to newly added nodes
- Add salvaging mode to qemu-img convert
- Minor fixes to tests, documentation, and for less Valgrind annoyance

# gpg: Signature made Fri 14 Jun 2019 14:38:11 BST
# gpg:                using RSA key 91BEB60A30DB3E8857D11829F407DB0061D5CF40
# gpg:                issuer "mreitz@redhat.com"
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1  1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2019-06-14:
  iotests: Test qemu-img convert -C --salvage
  iotests: Test qemu-img convert --salvage
  blkdebug: Inject errors on .bdrv_co_block_status()
  blkdebug: Add "none" event
  blkdebug: Add @iotype error option
  qemu-img: Add salvaging mode to convert
  qemu-img: Move quiet into ImgConvertState
  blockdev: Overlays are not snapshots
  qapi/block-core: Overlays are not snapshots
  qemu-img: Fix options leakage in img_rebase()
  iotests: restrict 254 to support only qcow2
  hw/block/fdc: floppy command FIFO memory initialization
  iotests: Fix intermittent failure in 219
  iotests: Filter 175's allocation information
  event_match: always match on None value
  iotests: add iotest 256 for testing blockdev-backup across iothread contexts
  iotests.py: rewrite run_job to be pickier
  QEMUMachine: add events_wait method
  iotests.py: do not use infinite waits
  blockdev-backup: don't check aio_context too early

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 50 insertions, 17 deletions

diff --git a/python/qemu/__init__.py b/python/qemu/__init__.py
index 81d9657ec0..dbaf8a5311 100644
--- a/python/qemu/__init__.py
+++ b/python/qemu/__init__.py
@@ -402,42 +402,75 @@ class QEMUMachine(object):
         self._qmp.clear_events()
         return events
 
-    def event_wait(self, name, timeout=60.0, match=None):
+    @staticmethod
+    def event_match(event, match=None):
         """
-        Wait for specified timeout on named event in QMP; optionally filter
-        results by match.
+        Check if an event matches optional match criteria.
+
+        The match criteria takes the form of a matching subdict. The event is
+        checked to be a superset of the subdict, recursively, with matching
+        values whenever the subdict values are not None.
 
-        The 'match' is checked to be a recursive subset of the 'event'; skips
-        branch processing on match's value None
-           {"foo": {"bar": 1}} matches {"foo": None}
-           {"foo": {"bar": 1}} does not matches {"foo": {"baz": None}}
+        This has a limitation that you cannot explicitly check for None values.
+
+        Examples, with the subdict queries on the left:
+         - None matches any object.
+         - {"foo": None} matches {"foo": {"bar": 1}}
+         - {"foo": None} matches {"foo": 5}
+         - {"foo": {"abc": None}} does not match {"foo": {"bar": 1}}
+         - {"foo": {"rab": 2}} matches {"foo": {"bar": 1, "rab": 2}}
         """
-        def event_match(event, match=None):
-            if match is None:
-                return True
+        if match is None:
+            return True
 
+        try:
             for key in match:
                 if key in event:
-                    if isinstance(event[key], dict):
-                        if not event_match(event[key], match[key]):
-                            return False
-                    elif event[key] != match[key]:
+                    if not QEMUMachine.event_match(event[key], match[key]):
                         return False
                 else:
                     return False
-
             return True
+        except TypeError:
+            # either match or event wasn't iterable (not a dict)
+            return match == event
+
+    def event_wait(self, name, timeout=60.0, match=None):
+        """
+        event_wait waits for and returns a named event from QMP with a timeout.
+
+        name: The event to wait for.
+        timeout: QEMUMonitorProtocol.pull_event timeout parameter.
+        match: Optional match criteria. See event_match for details.
+        """
+        return self.events_wait([(name, match)], timeout)
+
+    def events_wait(self, events, timeout=60.0):
+        """
+        events_wait waits for and returns a named event from QMP with a timeout.
+
+        events: a sequence of (name, match_criteria) tuples.
+                The match criteria are optional and may be None.
+                See event_match for details.
+        timeout: QEMUMonitorProtocol.pull_event timeout parameter.
+        """
+        def _match(event):
+            for name, match in events:
+                if (event['event'] == name and
+                    self.event_match(event, match)):
+                    return True
+            return False
 
         # Search cached events
         for event in self._events:
-            if (event['event'] == name) and event_match(event, match):
+            if _match(event):
                 self._events.remove(event)
                 return event
 
         # Poll for new events
         while True:
             event = self._qmp.pull_event(wait=timeout)
-            if (event['event'] == name) and event_match(event, match):
+            if _match(event):
                 return event
             self._events.append(event)