trace: always compile support for controlling and querying trace even…

…t states

The current interface is generic for this small set of operations, and thus
other backends can easily modify the "trace/control.c" file to add their own
implementation.

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

docs/tracing.txt

@@ -108,6 +108,36 @@ portability macros, ensure they are preceded and followed by double quotes:
    of trace events.  Marking trace events disabled by default saves the user
    from having to manually disable noisy trace events.
 
+== Generic interface and monitor commands ==
+
+You can programmatically query and control the dynamic state of trace events
+through a backend-agnostic interface:
+
+* trace_print_events
+
+* trace_event_set_state
+  Enables or disables trace events at runtime inside QEMU.
+  The function returns "true" if the state of the event has been successfully
+  changed, or "false" otherwise:
+
+    #include "trace/control.h"
+
+    trace_event_set_state("virtio_irq", true); /* enable */
+    [...]
+    trace_event_set_state("virtio_irq", false); /* disable */
+
+Note that some of the backends do not provide an implementation for this
+interface, in which case QEMU will just print a warning.
+
+This functionality is also provided through monitor commands:
+
+* info trace-events
+  View available trace events and their state.  State 1 means enabled, state 0
+  means disabled.
+
+* trace-event NAME on|off
+  Enable/disable a given trace event.
+
 == Trace backends ==
 
 The "tracetool" script automates tedious trace event code generation and also
@@ -157,27 +187,9 @@ unless you have specific needs for more advanced backends.
   flushed and emptied.  This means the 'info trace' will display few or no
   entries if the buffer has just been flushed.
 
-* info trace-events
-  View available trace events and their state.  State 1 means enabled, state 0
-  means disabled.
-
-* trace-event NAME on|off
-  Enable/disable a given trace event.
-
 * trace-file on|off|flush|set <path>
   Enable/disable/flush the trace file or set the trace file name.
 
-==== Enabling/disabling trace events programmatically ====
-
-The st_change_trace_event_state() function can be used to enable or disable trace
-events at runtime inside QEMU:
-
-    #include "trace.h"
-
-    st_change_trace_event_state("virtio_irq", true); /* enable */
-    [...]
-    st_change_trace_event_state("virtio_irq", false); /* disable */
-
 ==== Analyzing trace files ====
 
 The "simple" backend produces binary trace files that can be formatted with the

hmp-commands.hx

@@ -180,7 +180,6 @@ STEXI
 Output logs to @var{filename}.
 ETEXI
 
-#ifdef CONFIG_TRACE_SIMPLE
     {
         .name       = "trace-event",
         .args_type  = "name:s,option:b",
@@ -195,6 +194,7 @@ STEXI
 changes status of a trace event
 ETEXI
 
+#if defined(CONFIG_SIMPLE_TRACE)
     {
         .name       = "trace-file",
         .args_type  = "op:s?,arg:F?",
@@ -1358,10 +1358,13 @@ ETEXI
 STEXI
 @item info trace
 show contents of trace buffer
+ETEXI
+#endif
+
+STEXI
 @item info trace-events
 show available trace events and their state
 ETEXI
-#endif
 
 STEXI
 @end table

monitor.c

@@ -57,8 +57,9 @@
 #include "json-parser.h"
 #include "osdep.h"
 #include "cpu.h"
+#include "trace/control.h"
 #ifdef CONFIG_TRACE_SIMPLE
-#include "trace.h"
+#include "trace/simple.h"
 #endif
 #include "trace/control.h"
 #include "ui/qemu-spice.h"
@@ -593,7 +594,6 @@ static void do_help_cmd(Monitor *mon, const QDict *qdict)
     help_cmd(mon, qdict_get_try_str(qdict, "name"));
 }
 
-#ifdef CONFIG_TRACE_SIMPLE
 static void do_trace_event_set_state(Monitor *mon, const QDict *qdict)
 {
     const char *tp_name = qdict_get_str(qdict, "name");
@@ -605,6 +605,7 @@ static void do_trace_event_set_state(Monitor *mon, const QDict *qdict)
     }
 }
 
+#ifdef CONFIG_SIMPLE_TRACE
 static void do_trace_file(Monitor *mon, const QDict *qdict)
 {
     const char *op = qdict_get_try_str(qdict, "op");
@@ -1002,12 +1003,12 @@ static void do_info_trace(Monitor *mon)
 {
     st_print_trace((FILE *)mon, &monitor_fprintf);
 }
+#endif
 
 static void do_trace_print_events(Monitor *mon)
 {
     trace_print_events((FILE *)mon, &monitor_fprintf);
 }
-#endif
 
 /**
  * do_quit(): Quit QEMU execution
@@ -3144,14 +3145,14 @@ static const mon_cmd_t info_cmds[] = {
         .help       = "show current contents of trace buffer",
         .mhandler.info = do_info_trace,
     },
+#endif
     {
         .name       = "trace-events",
         .args_type  = "",
         .params     = "",
         .help       = "show available trace-events & their state",
         .mhandler.info = do_trace_print_events,
     },
-#endif
     {
         .name       = NULL,
     },