configure: fix --meson=/path/to/meson
[qemu.git] / monitor / qmp.c
1 /*
2 * QEMU monitor
3 *
4 * Copyright (c) 2003-2004 Fabrice Bellard
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22 * THE SOFTWARE.
23 */
24
25 #include "qemu/osdep.h"
26
27 #include "chardev/char-io.h"
28 #include "monitor-internal.h"
29 #include "qapi/error.h"
30 #include "qapi/qapi-commands-control.h"
31 #include "qapi/qmp/qdict.h"
32 #include "qapi/qmp/qjson.h"
33 #include "qapi/qmp/qlist.h"
34 #include "qapi/qmp/qstring.h"
35 #include "trace.h"
36
37 struct QMPRequest {
38 /* Owner of the request */
39 MonitorQMP *mon;
40 /*
41 * Request object to be handled or Error to be reported
42 * (exactly one of them is non-null)
43 */
44 QObject *req;
45 Error *err;
46 };
47 typedef struct QMPRequest QMPRequest;
48
49 QmpCommandList qmp_commands, qmp_cap_negotiation_commands;
50
51 static bool qmp_oob_enabled(MonitorQMP *mon)
52 {
53 return mon->capab[QMP_CAPABILITY_OOB];
54 }
55
56 static void monitor_qmp_caps_reset(MonitorQMP *mon)
57 {
58 memset(mon->capab_offered, 0, sizeof(mon->capab_offered));
59 memset(mon->capab, 0, sizeof(mon->capab));
60 mon->capab_offered[QMP_CAPABILITY_OOB] = mon->common.use_io_thread;
61 }
62
63 static void qmp_request_free(QMPRequest *req)
64 {
65 qobject_unref(req->req);
66 error_free(req->err);
67 g_free(req);
68 }
69
70 /* Caller must hold mon->qmp.qmp_queue_lock */
71 static void monitor_qmp_cleanup_req_queue_locked(MonitorQMP *mon)
72 {
73 while (!g_queue_is_empty(mon->qmp_requests)) {
74 qmp_request_free(g_queue_pop_head(mon->qmp_requests));
75 }
76 }
77
78 static void monitor_qmp_cleanup_queue_and_resume(MonitorQMP *mon)
79 {
80 qemu_mutex_lock(&mon->qmp_queue_lock);
81
82 /*
83 * Same condition as in monitor_qmp_bh_dispatcher(), but before
84 * removing an element from the queue (hence no `- 1`).
85 * Also, the queue should not be empty either, otherwise the
86 * monitor hasn't been suspended yet (or was already resumed).
87 */
88 bool need_resume = (!qmp_oob_enabled(mon) ||
89 mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX)
90 && !g_queue_is_empty(mon->qmp_requests);
91
92 monitor_qmp_cleanup_req_queue_locked(mon);
93
94 if (need_resume) {
95 /*
96 * handle_qmp_command() suspended the monitor because the
97 * request queue filled up, to be resumed when the queue has
98 * space again. We just emptied it; resume the monitor.
99 *
100 * Without this, the monitor would remain suspended forever
101 * when we get here while the monitor is suspended. An
102 * unfortunately timed CHR_EVENT_CLOSED can do the trick.
103 */
104 monitor_resume(&mon->common);
105 }
106
107 qemu_mutex_unlock(&mon->qmp_queue_lock);
108 }
109
110 void qmp_send_response(MonitorQMP *mon, const QDict *rsp)
111 {
112 const QObject *data = QOBJECT(rsp);
113 QString *json;
114
115 json = mon->pretty ? qobject_to_json_pretty(data) : qobject_to_json(data);
116 assert(json != NULL);
117
118 qstring_append_chr(json, '\n');
119 monitor_puts(&mon->common, qstring_get_str(json));
120
121 qobject_unref(json);
122 }
123
124 /*
125 * Emit QMP response @rsp to @mon.
126 * Null @rsp can only happen for commands with QCO_NO_SUCCESS_RESP.
127 * Nothing is emitted then.
128 */
129 static void monitor_qmp_respond(MonitorQMP *mon, QDict *rsp)
130 {
131 if (rsp) {
132 qmp_send_response(mon, rsp);
133 }
134 }
135
136 static void monitor_qmp_dispatch(MonitorQMP *mon, QObject *req)
137 {
138 Monitor *old_mon;
139 QDict *rsp;
140 QDict *error;
141
142 old_mon = cur_mon;
143 cur_mon = &mon->common;
144
145 rsp = qmp_dispatch(mon->commands, req, qmp_oob_enabled(mon));
146
147 cur_mon = old_mon;
148
149 if (mon->commands == &qmp_cap_negotiation_commands) {
150 error = qdict_get_qdict(rsp, "error");
151 if (error
152 && !g_strcmp0(qdict_get_try_str(error, "class"),
153 QapiErrorClass_str(ERROR_CLASS_COMMAND_NOT_FOUND))) {
154 /* Provide a more useful error message */
155 qdict_del(error, "desc");
156 qdict_put_str(error, "desc", "Expecting capabilities negotiation"
157 " with 'qmp_capabilities'");
158 }
159 }
160
161 monitor_qmp_respond(mon, rsp);
162 qobject_unref(rsp);
163 }
164
165 /*
166 * Pop a QMP request from a monitor request queue.
167 * Return the request, or NULL all request queues are empty.
168 * We are using round-robin fashion to pop the request, to avoid
169 * processing commands only on a very busy monitor. To achieve that,
170 * when we process one request on a specific monitor, we put that
171 * monitor to the end of mon_list queue.
172 *
173 * Note: if the function returned with non-NULL, then the caller will
174 * be with qmp_mon->qmp_queue_lock held, and the caller is responsible
175 * to release it.
176 */
177 static QMPRequest *monitor_qmp_requests_pop_any_with_lock(void)
178 {
179 QMPRequest *req_obj = NULL;
180 Monitor *mon;
181 MonitorQMP *qmp_mon;
182
183 qemu_mutex_lock(&monitor_lock);
184
185 QTAILQ_FOREACH(mon, &mon_list, entry) {
186 if (!monitor_is_qmp(mon)) {
187 continue;
188 }
189
190 qmp_mon = container_of(mon, MonitorQMP, common);
191 qemu_mutex_lock(&qmp_mon->qmp_queue_lock);
192 req_obj = g_queue_pop_head(qmp_mon->qmp_requests);
193 if (req_obj) {
194 /* With the lock of corresponding queue held */
195 break;
196 }
197 qemu_mutex_unlock(&qmp_mon->qmp_queue_lock);
198 }
199
200 if (req_obj) {
201 /*
202 * We found one request on the monitor. Degrade this monitor's
203 * priority to lowest by re-inserting it to end of queue.
204 */
205 QTAILQ_REMOVE(&mon_list, mon, entry);
206 QTAILQ_INSERT_TAIL(&mon_list, mon, entry);
207 }
208
209 qemu_mutex_unlock(&monitor_lock);
210
211 return req_obj;
212 }
213
214 void monitor_qmp_bh_dispatcher(void *data)
215 {
216 QMPRequest *req_obj = monitor_qmp_requests_pop_any_with_lock();
217 QDict *rsp;
218 bool need_resume;
219 MonitorQMP *mon;
220
221 if (!req_obj) {
222 return;
223 }
224
225 mon = req_obj->mon;
226 /* qmp_oob_enabled() might change after "qmp_capabilities" */
227 need_resume = !qmp_oob_enabled(mon) ||
228 mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1;
229 qemu_mutex_unlock(&mon->qmp_queue_lock);
230 if (req_obj->req) {
231 QDict *qdict = qobject_to(QDict, req_obj->req);
232 QObject *id = qdict ? qdict_get(qdict, "id") : NULL;
233 trace_monitor_qmp_cmd_in_band(qobject_get_try_str(id) ?: "");
234 monitor_qmp_dispatch(mon, req_obj->req);
235 } else {
236 assert(req_obj->err);
237 rsp = qmp_error_response(req_obj->err);
238 req_obj->err = NULL;
239 monitor_qmp_respond(mon, rsp);
240 qobject_unref(rsp);
241 }
242
243 if (need_resume) {
244 /* Pairs with the monitor_suspend() in handle_qmp_command() */
245 monitor_resume(&mon->common);
246 }
247 qmp_request_free(req_obj);
248
249 /* Reschedule instead of looping so the main loop stays responsive */
250 qemu_bh_schedule(qmp_dispatcher_bh);
251 }
252
253 static void handle_qmp_command(void *opaque, QObject *req, Error *err)
254 {
255 MonitorQMP *mon = opaque;
256 QObject *id = NULL;
257 QDict *qdict;
258 QMPRequest *req_obj;
259
260 assert(!req != !err);
261
262 qdict = qobject_to(QDict, req);
263 if (qdict) {
264 id = qdict_get(qdict, "id");
265 } /* else will fail qmp_dispatch() */
266
267 if (req && trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
268 QString *req_json = qobject_to_json(req);
269 trace_handle_qmp_command(mon, qstring_get_str(req_json));
270 qobject_unref(req_json);
271 }
272
273 if (qdict && qmp_is_oob(qdict)) {
274 /* OOB commands are executed immediately */
275 trace_monitor_qmp_cmd_out_of_band(qobject_get_try_str(id) ?: "");
276 monitor_qmp_dispatch(mon, req);
277 qobject_unref(req);
278 return;
279 }
280
281 req_obj = g_new0(QMPRequest, 1);
282 req_obj->mon = mon;
283 req_obj->req = req;
284 req_obj->err = err;
285
286 /* Protect qmp_requests and fetching its length. */
287 qemu_mutex_lock(&mon->qmp_queue_lock);
288
289 /*
290 * Suspend the monitor when we can't queue more requests after
291 * this one. Dequeuing in monitor_qmp_bh_dispatcher() or
292 * monitor_qmp_cleanup_queue_and_resume() will resume it.
293 * Note that when OOB is disabled, we queue at most one command,
294 * for backward compatibility.
295 */
296 if (!qmp_oob_enabled(mon) ||
297 mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1) {
298 monitor_suspend(&mon->common);
299 }
300
301 /*
302 * Put the request to the end of queue so that requests will be
303 * handled in time order. Ownership for req_obj, req,
304 * etc. will be delivered to the handler side.
305 */
306 assert(mon->qmp_requests->length < QMP_REQ_QUEUE_LEN_MAX);
307 g_queue_push_tail(mon->qmp_requests, req_obj);
308 qemu_mutex_unlock(&mon->qmp_queue_lock);
309
310 /* Kick the dispatcher routine */
311 qemu_bh_schedule(qmp_dispatcher_bh);
312 }
313
314 static void monitor_qmp_read(void *opaque, const uint8_t *buf, int size)
315 {
316 MonitorQMP *mon = opaque;
317
318 json_message_parser_feed(&mon->parser, (const char *) buf, size);
319 }
320
321 static QDict *qmp_greeting(MonitorQMP *mon)
322 {
323 QList *cap_list = qlist_new();
324 QObject *ver = NULL;
325 QDict *args;
326 QMPCapability cap;
327
328 args = qdict_new();
329 qmp_marshal_query_version(args, &ver, NULL);
330 qobject_unref(args);
331
332 for (cap = 0; cap < QMP_CAPABILITY__MAX; cap++) {
333 if (mon->capab_offered[cap]) {
334 qlist_append_str(cap_list, QMPCapability_str(cap));
335 }
336 }
337
338 return qdict_from_jsonf_nofail(
339 "{'QMP': {'version': %p, 'capabilities': %p}}",
340 ver, cap_list);
341 }
342
343 static void monitor_qmp_event(void *opaque, QEMUChrEvent event)
344 {
345 QDict *data;
346 MonitorQMP *mon = opaque;
347
348 switch (event) {
349 case CHR_EVENT_OPENED:
350 mon->commands = &qmp_cap_negotiation_commands;
351 monitor_qmp_caps_reset(mon);
352 data = qmp_greeting(mon);
353 qmp_send_response(mon, data);
354 qobject_unref(data);
355 mon_refcount++;
356 break;
357 case CHR_EVENT_CLOSED:
358 /*
359 * Note: this is only useful when the output of the chardev
360 * backend is still open. For example, when the backend is
361 * stdio, it's possible that stdout is still open when stdin
362 * is closed.
363 */
364 monitor_qmp_cleanup_queue_and_resume(mon);
365 json_message_parser_destroy(&mon->parser);
366 json_message_parser_init(&mon->parser, handle_qmp_command,
367 mon, NULL);
368 mon_refcount--;
369 monitor_fdsets_cleanup();
370 break;
371 case CHR_EVENT_BREAK:
372 case CHR_EVENT_MUX_IN:
373 case CHR_EVENT_MUX_OUT:
374 /* Ignore */
375 break;
376 }
377 }
378
379 void monitor_data_destroy_qmp(MonitorQMP *mon)
380 {
381 json_message_parser_destroy(&mon->parser);
382 qemu_mutex_destroy(&mon->qmp_queue_lock);
383 monitor_qmp_cleanup_req_queue_locked(mon);
384 g_queue_free(mon->qmp_requests);
385 }
386
387 static void monitor_qmp_setup_handlers_bh(void *opaque)
388 {
389 MonitorQMP *mon = opaque;
390 GMainContext *context;
391
392 assert(mon->common.use_io_thread);
393 context = iothread_get_g_main_context(mon_iothread);
394 assert(context);
395 qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
396 monitor_qmp_read, monitor_qmp_event,
397 NULL, &mon->common, context, true);
398 monitor_list_append(&mon->common);
399 }
400
401 void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)
402 {
403 MonitorQMP *mon = g_new0(MonitorQMP, 1);
404
405 if (!qemu_chr_fe_init(&mon->common.chr, chr, errp)) {
406 g_free(mon);
407 return;
408 }
409 qemu_chr_fe_set_echo(&mon->common.chr, true);
410
411 /* Note: we run QMP monitor in I/O thread when @chr supports that */
412 monitor_data_init(&mon->common, true, false,
413 qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_GCONTEXT));
414
415 mon->pretty = pretty;
416
417 qemu_mutex_init(&mon->qmp_queue_lock);
418 mon->qmp_requests = g_queue_new();
419
420 json_message_parser_init(&mon->parser, handle_qmp_command, mon, NULL);
421 if (mon->common.use_io_thread) {
422 /*
423 * Make sure the old iowatch is gone. It's possible when
424 * e.g. the chardev is in client mode, with wait=on.
425 */
426 remove_fd_in_watch(chr);
427 /*
428 * We can't call qemu_chr_fe_set_handlers() directly here
429 * since chardev might be running in the monitor I/O
430 * thread. Schedule a bottom half.
431 */
432 aio_bh_schedule_oneshot(iothread_get_aio_context(mon_iothread),
433 monitor_qmp_setup_handlers_bh, mon);
434 /* The bottom half will add @mon to @mon_list */
435 } else {
436 qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
437 monitor_qmp_read, monitor_qmp_event,
438 NULL, &mon->common, NULL, true);
439 monitor_list_append(&mon->common);
440 }
441 }