trace: [simple] disable all trace points by default

Note that this refers to the backend-specific state (whether the output must be
generated), not the event "disabled" property (which always uses the "nop"
backend).

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>

docs/tracing.txt

@@ -12,11 +12,16 @@ for debugging, profiling, and observing execution.
     ./configure --trace-backend=simple
     make
 
-2. Run the virtual machine to produce a trace file:
+2. Create a file with the events you want to trace:
 
-    qemu ... # your normal QEMU invocation
+   echo bdrv_aio_readv   > /tmp/events
+   echo bdrv_aio_writev >> /tmp/events
 
-3. Pretty-print the binary trace file:
+3. Run the virtual machine to produce a trace file:
+
+    qemu -trace events=/tmp/events ... # your normal QEMU invocation
+
+4. Pretty-print the binary trace file:
 
     ./simpletrace.py trace-events trace-*
 

scripts/tracetool

@@ -221,15 +221,10 @@ EOF
 
 linetoc_simple()
 {
-    local name state
+    local name
     name=$(get_name "$1")
-    if has_property "$1" "disable"; then
-        state="0"
-    else
-        state="1"
-    fi
     cat <<EOF
-{.tp_name = "$name", .state=$state},
+{.tp_name = "$name", .state=0},
 EOF
     simple_event_num=$((simple_event_num + 1))
 }

trace-events

@@ -17,9 +17,6 @@
 # Example: qemu_malloc(size_t size) "size %zu"
 #
 # The "disable" keyword will build without the trace event.
-# In case of 'simple' trace backend, it will allow the trace event to be
-# compiled, but this would be turned off by default. It can be toggled on via
-# the monitor.
 #
 # The <name> must be a valid as a C function name.
 #