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 "trace.h"
  35
  36 struct QMPRequest {
  37     /* Owner of the request */
  38     MonitorQMP *mon;
  39     /*
  40      * Request object to be handled or Error to be reported
  41      * (exactly one of them is non-null)
  42      */
  43     QObject *req;
  44     Error *err;
  45 };
  46 typedef struct QMPRequest QMPRequest;
  47
  48 QmpCommandList qmp_commands, qmp_cap_negotiation_commands;
  49
  50 static bool qmp_oob_enabled(MonitorQMP *mon)
  51 {
  52     return mon->capab[QMP_CAPABILITY_OOB];
  53 }
  54
  55 static void monitor_qmp_caps_reset(MonitorQMP *mon)
  56 {
  57     memset(mon->capab_offered, 0, sizeof(mon->capab_offered));
  58     memset(mon->capab, 0, sizeof(mon->capab));
  59     mon->capab_offered[QMP_CAPABILITY_OOB] = mon->common.use_io_thread;
  60 }
  61
  62 static void qmp_request_free(QMPRequest *req)
  63 {
  64     qobject_unref(req->req);
  65     error_free(req->err);
  66     g_free(req);
  67 }
  68
  69 /* Caller must hold mon->qmp.qmp_queue_lock */
  70 static void monitor_qmp_cleanup_req_queue_locked(MonitorQMP *mon)
  71 {
  72     while (!g_queue_is_empty(mon->qmp_requests)) {
  73         qmp_request_free(g_queue_pop_head(mon->qmp_requests));
  74     }
  75 }
  76
  77 static void monitor_qmp_cleanup_queue_and_resume(MonitorQMP *mon)
  78 {
  79     qemu_mutex_lock(&mon->qmp_queue_lock);
  80
  81     /*
  82      * Same condition as in monitor_qmp_dispatcher_co(), but before
  83      * removing an element from the queue (hence no `- 1`).
  84      * Also, the queue should not be empty either, otherwise the
  85      * monitor hasn't been suspended yet (or was already resumed).
  86      */
  87     bool need_resume = (!qmp_oob_enabled(mon) ||
  88         mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX)
  89         && !g_queue_is_empty(mon->qmp_requests);
  90
  91     monitor_qmp_cleanup_req_queue_locked(mon);
  92
  93     if (need_resume) {
  94         /*
  95          * handle_qmp_command() suspended the monitor because the
  96          * request queue filled up, to be resumed when the queue has
  97          * space again.  We just emptied it; resume the monitor.
  98          *
  99          * Without this, the monitor would remain suspended forever
 100          * when we get here while the monitor is suspended.  An
 101          * unfortunately timed CHR_EVENT_CLOSED can do the trick.
 102          */
 103         monitor_resume(&mon->common);
 104     }
 105
 106     qemu_mutex_unlock(&mon->qmp_queue_lock);
 107 }
 108
 109 void qmp_send_response(MonitorQMP *mon, const QDict *rsp)
 110 {
 111     const QObject *data = QOBJECT(rsp);
 112     GString *json;
 113
 114     json = qobject_to_json_pretty(data, mon->pretty);
 115     assert(json != NULL);
 116     trace_monitor_qmp_respond(mon, json->str);
 117
 118     g_string_append_c(json, '\n');
 119     monitor_puts(&mon->common, json->str);
 120
 121     g_string_free(json, true);
 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 /*
 137  * Runs outside of coroutine context for OOB commands, but in
 138  * coroutine context for everything else.
 139  */
 140 static void monitor_qmp_dispatch(MonitorQMP *mon, QObject *req)
 141 {
 142     QDict *rsp;
 143     QDict *error;
 144
 145     rsp = qmp_dispatch(mon->commands, req, qmp_oob_enabled(mon),
 146                        &mon->common);
 147
 148     if (mon->commands == &qmp_cap_negotiation_commands) {
 149         error = qdict_get_qdict(rsp, "error");
 150         if (error
 151             && !g_strcmp0(qdict_get_try_str(error, "class"),
 152                     QapiErrorClass_str(ERROR_CLASS_COMMAND_NOT_FOUND))) {
 153             /* Provide a more useful error message */
 154             qdict_del(error, "desc");
 155             qdict_put_str(error, "desc", "Expecting capabilities negotiation"
 156                           " with 'qmp_capabilities'");
 157         }
 158     }
 159
 160     monitor_qmp_respond(mon, rsp);
 161     qobject_unref(rsp);
 162 }
 163
 164 /*
 165  * Pop a QMP request from a monitor request queue.
 166  * Return the request, or NULL all request queues are empty.
 167  * We are using round-robin fashion to pop the request, to avoid
 168  * processing commands only on a very busy monitor.  To achieve that,
 169  * when we process one request on a specific monitor, we put that
 170  * monitor to the end of mon_list queue.
 171  *
 172  * Note: if the function returned with non-NULL, then the caller will
 173  * be with qmp_mon->qmp_queue_lock held, and the caller is responsible
 174  * to release it.
 175  */
 176 static QMPRequest *monitor_qmp_requests_pop_any_with_lock(void)
 177 {
 178     QMPRequest *req_obj = NULL;
 179     Monitor *mon;
 180     MonitorQMP *qmp_mon;
 181
 182     qemu_mutex_lock(&monitor_lock);
 183
 184     QTAILQ_FOREACH(mon, &mon_list, entry) {
 185         if (!monitor_is_qmp(mon)) {
 186             continue;
 187         }
 188
 189         qmp_mon = container_of(mon, MonitorQMP, common);
 190         qemu_mutex_lock(&qmp_mon->qmp_queue_lock);
 191         req_obj = g_queue_pop_head(qmp_mon->qmp_requests);
 192         if (req_obj) {
 193             /* With the lock of corresponding queue held */
 194             break;
 195         }
 196         qemu_mutex_unlock(&qmp_mon->qmp_queue_lock);
 197     }
 198
 199     if (req_obj) {
 200         /*
 201          * We found one request on the monitor. Degrade this monitor's
 202          * priority to lowest by re-inserting it to end of queue.
 203          */
 204         QTAILQ_REMOVE(&mon_list, mon, entry);
 205         QTAILQ_INSERT_TAIL(&mon_list, mon, entry);
 206     }
 207
 208     qemu_mutex_unlock(&monitor_lock);
 209
 210     return req_obj;
 211 }
 212
 213 void coroutine_fn monitor_qmp_dispatcher_co(void *data)
 214 {
 215     QMPRequest *req_obj = NULL;
 216     QDict *rsp;
 217     bool oob_enabled;
 218     MonitorQMP *mon;
 219
 220     while (true) {
 221         assert(qatomic_mb_read(&qmp_dispatcher_co_busy) == true);
 222
 223         /*
 224          * Mark the dispatcher as not busy already here so that we
 225          * don't miss any new requests coming in the middle of our
 226          * processing.
 227          */
 228         qatomic_mb_set(&qmp_dispatcher_co_busy, false);
 229
 230         /* On shutdown, don't take any more requests from the queue */
 231         if (qmp_dispatcher_co_shutdown) {
 232             return;
 233         }
 234
 235         while (!(req_obj = monitor_qmp_requests_pop_any_with_lock())) {
 236             /*
 237              * No more requests to process.  Wait to be reentered from
 238              * handle_qmp_command() when it pushes more requests, or
 239              * from monitor_cleanup() when it requests shutdown.
 240              */
 241             if (!qmp_dispatcher_co_shutdown) {
 242                 qemu_coroutine_yield();
 243
 244                 /*
 245                  * busy must be set to true again by whoever
 246                  * rescheduled us to avoid double scheduling
 247                  */
 248                 assert(qatomic_xchg(&qmp_dispatcher_co_busy, false) == true);
 249             }
 250
 251             /*
 252              * qmp_dispatcher_co_shutdown may have changed if we
 253              * yielded and were reentered from monitor_cleanup()
 254              */
 255             if (qmp_dispatcher_co_shutdown) {
 256                 return;
 257             }
 258         }
 259
 260         trace_monitor_qmp_in_band_dequeue(req_obj,
 261                                           req_obj->mon->qmp_requests->length);
 262
 263         if (qatomic_xchg(&qmp_dispatcher_co_busy, true) == true) {
 264             /*
 265              * Someone rescheduled us (probably because a new requests
 266              * came in), but we didn't actually yield. Do that now,
 267              * only to be immediately reentered and removed from the
 268              * list of scheduled coroutines.
 269              */
 270             qemu_coroutine_yield();
 271         }
 272
 273         /*
 274          * Move the coroutine from iohandler_ctx to qemu_aio_context for
 275          * executing the command handler so that it can make progress if it
 276          * involves an AIO_WAIT_WHILE().
 277          */
 278         aio_co_schedule(qemu_get_aio_context(), qmp_dispatcher_co);
 279         qemu_coroutine_yield();
 280
 281         /*
 282          * @req_obj has a request, we hold req_obj->mon->qmp_queue_lock
 283          */
 284
 285         mon = req_obj->mon;
 286
 287         /*
 288          * We need to resume the monitor if handle_qmp_command()
 289          * suspended it.  Two cases:
 290          * 1. OOB enabled: mon->qmp_requests has no more space
 291          *    Resume right away, so that OOB commands can get executed while
 292          *    this request is being processed.
 293          * 2. OOB disabled: always
 294          *    Resume only after we're done processing the request,
 295          * We need to save qmp_oob_enabled() for later, because
 296          * qmp_qmp_capabilities() can change it.
 297          */
 298         oob_enabled = qmp_oob_enabled(mon);
 299         if (oob_enabled
 300             && mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1) {
 301             monitor_resume(&mon->common);
 302         }
 303
 304         qemu_mutex_unlock(&mon->qmp_queue_lock);
 305
 306         /* Process request */
 307         if (req_obj->req) {
 308             if (trace_event_get_state(TRACE_MONITOR_QMP_CMD_IN_BAND)) {
 309                 QDict *qdict = qobject_to(QDict, req_obj->req);
 310                 QObject *id = qdict ? qdict_get(qdict, "id") : NULL;
 311                 GString *id_json;
 312
 313                 id_json = id ? qobject_to_json(id) : g_string_new(NULL);
 314                 trace_monitor_qmp_cmd_in_band(id_json->str);
 315                 g_string_free(id_json, true);
 316             }
 317             monitor_qmp_dispatch(mon, req_obj->req);
 318         } else {
 319             assert(req_obj->err);
 320             trace_monitor_qmp_err_in_band(error_get_pretty(req_obj->err));
 321             rsp = qmp_error_response(req_obj->err);
 322             req_obj->err = NULL;
 323             monitor_qmp_respond(mon, rsp);
 324             qobject_unref(rsp);
 325         }
 326
 327         if (!oob_enabled) {
 328             monitor_resume(&mon->common);
 329         }
 330
 331         qmp_request_free(req_obj);
 332
 333         /*
 334          * Yield and reschedule so the main loop stays responsive.
 335          *
 336          * Move back to iohandler_ctx so that nested event loops for
 337          * qemu_aio_context don't start new monitor commands.
 338          */
 339         aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co);
 340         qemu_coroutine_yield();
 341     }
 342 }
 343
 344 static void handle_qmp_command(void *opaque, QObject *req, Error *err)
 345 {
 346     MonitorQMP *mon = opaque;
 347     QDict *qdict = qobject_to(QDict, req);
 348     QMPRequest *req_obj;
 349
 350     assert(!req != !err);
 351
 352     if (req && trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
 353         GString *req_json = qobject_to_json(req);
 354         trace_handle_qmp_command(mon, req_json->str);
 355         g_string_free(req_json, true);
 356     }
 357
 358     if (qdict && qmp_is_oob(qdict)) {
 359         /* OOB commands are executed immediately */
 360         if (trace_event_get_state(TRACE_MONITOR_QMP_CMD_OUT_OF_BAND)) {
 361             QObject *id = qdict_get(qdict, "id");
 362             GString *id_json;
 363
 364             id_json = id ? qobject_to_json(id) : g_string_new(NULL);
 365             trace_monitor_qmp_cmd_out_of_band(id_json->str);
 366             g_string_free(id_json, true);
 367         }
 368         monitor_qmp_dispatch(mon, req);
 369         qobject_unref(req);
 370         return;
 371     }
 372
 373     req_obj = g_new0(QMPRequest, 1);
 374     req_obj->mon = mon;
 375     req_obj->req = req;
 376     req_obj->err = err;
 377
 378     /* Protect qmp_requests and fetching its length. */
 379     qemu_mutex_lock(&mon->qmp_queue_lock);
 380
 381     /*
 382      * Suspend the monitor when we can't queue more requests after
 383      * this one.  Dequeuing in monitor_qmp_dispatcher_co() or
 384      * monitor_qmp_cleanup_queue_and_resume() will resume it.
 385      * Note that when OOB is disabled, we queue at most one command,
 386      * for backward compatibility.
 387      */
 388     if (!qmp_oob_enabled(mon) ||
 389         mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1) {
 390         monitor_suspend(&mon->common);
 391     }
 392
 393     /*
 394      * Put the request to the end of queue so that requests will be
 395      * handled in time order.  Ownership for req_obj, req,
 396      * etc. will be delivered to the handler side.
 397      */
 398     trace_monitor_qmp_in_band_enqueue(req_obj, mon,
 399                                       mon->qmp_requests->length);
 400     assert(mon->qmp_requests->length < QMP_REQ_QUEUE_LEN_MAX);
 401     g_queue_push_tail(mon->qmp_requests, req_obj);
 402     qemu_mutex_unlock(&mon->qmp_queue_lock);
 403
 404     /* Kick the dispatcher routine */
 405     if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) {
 406         aio_co_wake(qmp_dispatcher_co);
 407     }
 408 }
 409
 410 static void monitor_qmp_read(void *opaque, const uint8_t *buf, int size)
 411 {
 412     MonitorQMP *mon = opaque;
 413
 414     json_message_parser_feed(&mon->parser, (const char *) buf, size);
 415 }
 416
 417 static QDict *qmp_greeting(MonitorQMP *mon)
 418 {
 419     QList *cap_list = qlist_new();
 420     QObject *ver = NULL;
 421     QDict *args;
 422     QMPCapability cap;
 423
 424     args = qdict_new();
 425     qmp_marshal_query_version(args, &ver, NULL);
 426     qobject_unref(args);
 427
 428     for (cap = 0; cap < QMP_CAPABILITY__MAX; cap++) {
 429         if (mon->capab_offered[cap]) {
 430             qlist_append_str(cap_list, QMPCapability_str(cap));
 431         }
 432     }
 433
 434     return qdict_from_jsonf_nofail(
 435         "{'QMP': {'version': %p, 'capabilities': %p}}",
 436         ver, cap_list);
 437 }
 438
 439 static void monitor_qmp_event(void *opaque, QEMUChrEvent event)
 440 {
 441     QDict *data;
 442     MonitorQMP *mon = opaque;
 443
 444     switch (event) {
 445     case CHR_EVENT_OPENED:
 446         mon->commands = &qmp_cap_negotiation_commands;
 447         monitor_qmp_caps_reset(mon);
 448         data = qmp_greeting(mon);
 449         qmp_send_response(mon, data);
 450         qobject_unref(data);
 451         mon_refcount++;
 452         break;
 453     case CHR_EVENT_CLOSED:
 454         /*
 455          * Note: this is only useful when the output of the chardev
 456          * backend is still open.  For example, when the backend is
 457          * stdio, it's possible that stdout is still open when stdin
 458          * is closed.
 459          */
 460         monitor_qmp_cleanup_queue_and_resume(mon);
 461         json_message_parser_destroy(&mon->parser);
 462         json_message_parser_init(&mon->parser, handle_qmp_command,
 463                                  mon, NULL);
 464         mon_refcount--;
 465         monitor_fdsets_cleanup();
 466         break;
 467     case CHR_EVENT_BREAK:
 468     case CHR_EVENT_MUX_IN:
 469     case CHR_EVENT_MUX_OUT:
 470         /* Ignore */
 471         break;
 472     }
 473 }
 474
 475 void monitor_data_destroy_qmp(MonitorQMP *mon)
 476 {
 477     json_message_parser_destroy(&mon->parser);
 478     qemu_mutex_destroy(&mon->qmp_queue_lock);
 479     monitor_qmp_cleanup_req_queue_locked(mon);
 480     g_queue_free(mon->qmp_requests);
 481 }
 482
 483 static void monitor_qmp_setup_handlers_bh(void *opaque)
 484 {
 485     MonitorQMP *mon = opaque;
 486     GMainContext *context;
 487
 488     assert(mon->common.use_io_thread);
 489     context = iothread_get_g_main_context(mon_iothread);
 490     assert(context);
 491     qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
 492                              monitor_qmp_read, monitor_qmp_event,
 493                              NULL, &mon->common, context, true);
 494     monitor_list_append(&mon->common);
 495 }
 496
 497 void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)
 498 {
 499     MonitorQMP *mon = g_new0(MonitorQMP, 1);
 500
 501     if (!qemu_chr_fe_init(&mon->common.chr, chr, errp)) {
 502         g_free(mon);
 503         return;
 504     }
 505     qemu_chr_fe_set_echo(&mon->common.chr, true);
 506
 507     /* Note: we run QMP monitor in I/O thread when @chr supports that */
 508     monitor_data_init(&mon->common, true, false,
 509                       qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_GCONTEXT));
 510
 511     mon->pretty = pretty;
 512
 513     qemu_mutex_init(&mon->qmp_queue_lock);
 514     mon->qmp_requests = g_queue_new();
 515
 516     json_message_parser_init(&mon->parser, handle_qmp_command, mon, NULL);
 517     if (mon->common.use_io_thread) {
 518         /*
 519          * Make sure the old iowatch is gone.  It's possible when
 520          * e.g. the chardev is in client mode, with wait=on.
 521          */
 522         remove_fd_in_watch(chr);
 523         /*
 524          * We can't call qemu_chr_fe_set_handlers() directly here
 525          * since chardev might be running in the monitor I/O
 526          * thread.  Schedule a bottom half.
 527          */
 528         aio_bh_schedule_oneshot(iothread_get_aio_context(mon_iothread),
 529                                 monitor_qmp_setup_handlers_bh, mon);
 530         /* The bottom half will add @mon to @mon_list */
 531     } else {
 532         qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
 533                                  monitor_qmp_read, monitor_qmp_event,
 534                                  NULL, &mon->common, NULL, true);
 535         monitor_list_append(&mon->common);
 536     }
 537 }