Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

# gpg: Signature made Tue 18 Nov 2014 15:04:14 GMT using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/tracing-pull-request:
  Tracing: Fix simpletrace.py error on tcg enabled binary traces
  Tracing docs fix configure option and description
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

docs/tracing.txt

@@ -139,12 +139,12 @@ events are not tightly coupled to a specific trace backend, such as LTTng or
 SystemTap.  Support for trace backends can be added by extending the "tracetool"
 script.
 
-The trace backend is chosen at configure time and only one trace backend can
-be built into the binary:
+The trace backends are chosen at configure time:
 
-    ./configure --trace-backends=simple
+    ./configure --enable-trace-backends=simple
 
 For a list of supported trace backends, try ./configure --help or see below.
+If multiple backends are enabled, the trace is sent to them all.
 
 The following subsections describe the supported trace backends.
 

scripts/tracetool/__init__.py

@@ -253,14 +253,44 @@ class Event(object):
 
 
 def _read_events(fobj):
-    res = []
+    events = []
     for line in fobj:
         if not line.strip():
             continue
         if line.lstrip().startswith('#'):
             continue
-        res.append(Event.build(line))
-    return res
+
+        event = Event.build(line)
+
+        # transform TCG-enabled events
+        if "tcg" not in event.properties:
+            events.append(event)
+        else:
+            event_trans = event.copy()
+            event_trans.name += "_trans"
+            event_trans.properties += ["tcg-trans"]
+            event_trans.fmt = event.fmt[0]
+            args_trans = []
+            for atrans, aorig in zip(
+                    event_trans.transform(tracetool.transform.TCG_2_HOST).args,
+                    event.args):
+                if atrans == aorig:
+                    args_trans.append(atrans)
+            event_trans.args = Arguments(args_trans)
+            event_trans = event_trans.copy()
+
+            event_exec = event.copy()
+            event_exec.name += "_exec"
+            event_exec.properties += ["tcg-exec"]
+            event_exec.fmt = event.fmt[1]
+            event_exec = event_exec.transform(tracetool.transform.TCG_2_HOST)
+
+            new_event = [event_trans, event_exec]
+            event.event_trans, event.event_exec = new_event
+
+            events.extend(new_event)
+
+    return events
 
 
 class TracetoolError (Exception):
@@ -333,35 +363,4 @@ def generate(fevents, format, backends,
 
     events = _read_events(fevents)
 
-    # transform TCG-enabled events
-    new_events = []
-    for event in events:
-        if "tcg" not in event.properties:
-            new_events.append(event)
-        else:
-            event_trans = event.copy()
-            event_trans.name += "_trans"
-            event_trans.properties += ["tcg-trans"]
-            event_trans.fmt = event.fmt[0]
-            args_trans = []
-            for atrans, aorig in zip(
-                    event_trans.transform(tracetool.transform.TCG_2_HOST).args,
-                    event.args):
-                if atrans == aorig:
-                    args_trans.append(atrans)
-            event_trans.args = Arguments(args_trans)
-            event_trans = event_trans.copy()
-
-            event_exec = event.copy()
-            event_exec.name += "_exec"
-            event_exec.properties += ["tcg-exec"]
-            event_exec.fmt = event.fmt[1]
-            event_exec = event_exec.transform(tracetool.transform.TCG_2_HOST)
-
-            new_event = [event_trans, event_exec]
-            event.event_trans, event.event_exec = new_event
-
-            new_events.extend(new_event)
-    events = new_events
-
     tracetool.format.generate(events, format, backend)