[PATCH 5/5] trace: add qmp trace event namespace

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Add a possibility to trace some qmp commands by user selection.

User API is simple: it looks like after this patch we have trace-points
for all qmp commands, in format "qmp:<qmp-command>". So user may do

  --trace qmp:drive-backup

or run qmp command trace-event-set-state with arguments

  name="qmp:drive-backup", enable=true

Patterns are supported in the same way as for general trace events, for
example:

  --trace "qmp:query-*"

to cover query-block, query-block-jobs, and a lot of other query-
commands

or

  --trace "qmp:job-*" --trace "qmp:block-job-*"

to cover job manipulation commands.

Trace event qmp covers both qmp command call and its respond.

Implementation details:

In qmp_dispatch() we add two trace points, similar to
trace_handle_qmp_command. We also check for cmd->tracking field being
set, and for handle-qmp-command/monitor-qmp-respond trace points being
disabled, to not print same information twice.

For qmp trace-event-{get,set}-state and for command line
parse additionally new "qmp:" namespace

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 qapi/qmp-dispatch.c | 20 ++++++++++++++++++++
 softmmu/vl.c        | 21 ++++++++++++++++++++-
 trace/qmp.c         | 20 ++++++++++++++++++++
 qapi/trace-events   |  2 ++
 4 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
index 59600210ce..40fd008fa8 100644
--- a/qapi/qmp-dispatch.c
+++ b/qapi/qmp-dispatch.c
@@ -26,6 +26,9 @@
 #include "qemu/coroutine.h"
 #include "qemu/main-loop.h"
 
+#include "trace.h"
+#include "trace/trace-monitor.h"
+
 CompatPolicy compat_policy;
 
 Visitor *qobject_input_visitor_new_qmp(QObject *obj)
@@ -133,6 +136,12 @@ static void do_qmp_dispatch_bh(void *opaque)
     aio_co_wake(data->co);
 }
 
+static void do_trace_qmp(const char *what, QObject *obj)
+{
+    g_autoptr(GString) req_json = qobject_to_json(obj);
+    trace_qmp(what, req_json->str);
+}
+
 /*
  * Runs outside of coroutine context for OOB commands, but in coroutine
  * context for everything else.
@@ -176,6 +185,11 @@ QDict *qmp_dispatch(const QmpCommandList *cmds, QObject *request,
                   "The command %s has not been found", command);
         goto out;
     }
+    if (!trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND) &&
+        trace_event_get_state_backends(TRACE_QMP) && cmd->tracing)
+    {
+        do_trace_qmp(">>", request);
+    }
     if (cmd->options & QCO_DEPRECATED) {
         switch (compat_policy.deprecated_input) {
         case COMPAT_POLICY_INPUT_ACCEPT:
@@ -282,5 +296,11 @@ out:
         qdict_put_obj(rsp, "id", qobject_ref(id));
     }
 
+    if (!trace_event_get_state_backends(TRACE_MONITOR_QMP_RESPOND) &&
+        trace_event_get_state_backends(TRACE_QMP) && cmd->tracing)
+    {
+        do_trace_qmp("<<", QOBJECT(rsp));
+    }
+
     return rsp;
 }
diff --git a/softmmu/vl.c b/softmmu/vl.c
index 55ab70eb97..fd452b7013 100644
--- a/softmmu/vl.c
+++ b/softmmu/vl.c
@@ -2722,6 +2722,25 @@ void qmp_x_exit_preconfig(Error **errp)
     }
 }
 
+static void trace_opt_parse_with_qmp(const char *optarg)
+{
+    const char *pattern;
+    QemuOpts *opts = qemu_opts_parse_noisily(qemu_find_opts("trace"),
+                                             optarg, true);
+    if (!opts) {
+        exit(1);
+    }
+
+    pattern = qemu_opt_get(opts, "enable");
+    if (pattern && !strncmp(pattern, "qmp:", 4)) {
+        monitor_qmp_set_tracing(pattern + 4, true);
+        qemu_opt_del_all(opts, "enable");
+        qemu_opt_set(opts, "enable", "qmp", &error_abort);
+    }
+
+    trace_opt_parse_opts(opts);
+}
+
 void qemu_init(int argc, char **argv, char **envp)
 {
     QemuOpts *opts;
@@ -3480,7 +3499,7 @@ void qemu_init(int argc, char **argv, char **envp)
                 xen_domid_restrict = true;
                 break;
             case QEMU_OPTION_trace:
-                trace_opt_parse(optarg);
+                trace_opt_parse_with_qmp(optarg);
                 break;
             case QEMU_OPTION_plugin:
                 qemu_plugin_opt_parse(optarg, &plugin_list);
diff --git a/trace/qmp.c b/trace/qmp.c
index 3b4f4702b4..87766422d9 100644
--- a/trace/qmp.c
+++ b/trace/qmp.c
@@ -11,6 +11,7 @@
 #include "qapi/error.h"
 #include "qapi/qapi-commands-trace.h"
 #include "control-vcpu.h"
+#include "monitor/monitor.h"
 
 
 static CPUState *get_cpu(bool has_vcpu, int vcpu, Error **errp)
@@ -77,6 +78,14 @@ TraceEventInfoList *qmp_trace_event_get_state(const char *name,
     bool is_pattern = trace_event_is_pattern(name);
     CPUState *cpu;
 
+    if (!strncmp(name, "qmp:", 4)) {
+        if (!monitor_qmp_is_tracing_enabled(name + 4)) {
+            return NULL;
+        }
+
+        return qmp_trace_event_get_state("qmp", has_vcpu, vcpu, errp);
+    }
+
     /* Check provided vcpu */
     cpu = get_cpu(has_vcpu, vcpu, &err);
     if (err) {
@@ -139,6 +148,17 @@ void qmp_trace_event_set_state(const char *name, bool enable,
     bool is_pattern = trace_event_is_pattern(name);
     CPUState *cpu;
 
+    if (!strncmp(name, "qmp:", 4)) {
+        monitor_qmp_set_tracing(name + 4, enable);
+
+        if (enable || !monitor_qmp_is_tracing_enabled(NULL)) {
+            qmp_trace_event_set_state("qmp", enable, has_ignore_unavailable,
+                                      ignore_unavailable, has_vcpu, vcpu, errp);
+        }
+
+        return;
+    }
+
     /* Check provided vcpu */
     cpu = get_cpu(has_vcpu, vcpu, &err);
     if (err) {
diff --git a/qapi/trace-events b/qapi/trace-events
index cccafc07e5..753433856c 100644
--- a/qapi/trace-events
+++ b/qapi/trace-events
@@ -36,3 +36,5 @@ visit_type_str(void *v, const char *name, char **obj) "v=%p name=%s obj=%p"
 visit_type_number(void *v, const char *name, void *obj) "v=%p name=%s obj=%p"
 visit_type_any(void *v, const char *name, void *obj) "v=%p name=%s obj=%p"
 visit_type_null(void *v, const char *name, void *obj) "v=%p name=%s obj=%p"
+
+qmp(const char *what, const char *json) "%s %s"
-- 
2.29.2