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_bh_dispatcher(), 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
 117     g_string_append_c(json, '\n');
 118     monitor_puts(&mon->common, json->str);
 119
 120     g_string_free(json, true);
 121 }
 122
 123 /*
 124  * Emit QMP response @rsp to @mon.
 125  * Null @rsp can only happen for commands with QCO_NO_SUCCESS_RESP.
 126  * Nothing is emitted then.
 127  */
 128 static void monitor_qmp_respond(MonitorQMP *mon, QDict *rsp)
 129 {
 130     if (rsp) {
 131         qmp_send_response(mon, rsp);
 132     }
 133 }
 134
 135 /*
 136  * Runs outside of coroutine context for OOB commands, but in
 137  * coroutine context for everything else.
 138  */
 139 static void monitor_qmp_dispatch(MonitorQMP *mon, QObject *req)
 140 {
 141     QDict *rsp;
 142     QDict *error;
 143
 144     rsp = qmp_dispatch(mon->commands, req, qmp_oob_enabled(mon),
 145                        &mon->common);
 146
 147     if (mon->commands == &qmp_cap_negotiation_commands) {
 148         error = qdict_get_qdict(rsp, "error");
 149         if (error
 150             && !g_strcmp0(qdict_get_try_str(error, "class"),
 151                     QapiErrorClass_str(ERROR_CLASS_COMMAND_NOT_FOUND))) {
 152             /* Provide a more useful error message */
 153             qdict_del(error, "desc");
 154             qdict_put_str(error, "desc", "Expecting capabilities negotiation"
 155                           " with 'qmp_capabilities'");
 156         }
 157     }
 158
 159     monitor_qmp_respond(mon, rsp);
 160     qobject_unref(rsp);
 161 }
 162
 163 /*
 164  * Pop a QMP request from a monitor request queue.
 165  * Return the request, or NULL all request queues are empty.
 166  * We are using round-robin fashion to pop the request, to avoid
 167  * processing commands only on a very busy monitor.  To achieve that,
 168  * when we process one request on a specific monitor, we put that
 169  * monitor to the end of mon_list queue.
 170  *
 171  * Note: if the function returned with non-NULL, then the caller will
 172  * be with qmp_mon->qmp_queue_lock held, and the caller is responsible
 173  * to release it.
 174  */
 175 static QMPRequest *monitor_qmp_requests_pop_any_with_lock(void)
 176 {
 177     QMPRequest *req_obj = NULL;
 178     Monitor *mon;
 179     MonitorQMP *qmp_mon;
 180
 181     qemu_mutex_lock(&monitor_lock);
 182
 183     QTAILQ_FOREACH(mon, &mon_list, entry) {
 184         if (!monitor_is_qmp(mon)) {
 185             continue;
 186         }
 187
 188         qmp_mon = container_of(mon, MonitorQMP, common);
 189         qemu_mutex_lock(&qmp_mon->qmp_queue_lock);
 190         req_obj = g_queue_pop_head(qmp_mon->qmp_requests);
 191         if (req_obj) {
 192             /* With the lock of corresponding queue held */
 193             break;
 194         }
 195         qemu_mutex_unlock(&qmp_mon->qmp_queue_lock);
 196     }
 197
 198     if (req_obj) {
 199         /*
 200          * We found one request on the monitor. Degrade this monitor's
 201          * priority to lowest by re-inserting it to end of queue.
 202          */
 203         QTAILQ_REMOVE(&mon_list, mon, entry);
 204         QTAILQ_INSERT_TAIL(&mon_list, mon, entry);
 205     }
 206
 207     qemu_mutex_unlock(&monitor_lock);
 208
 209     return req_obj;
 210 }
 211
 212 void coroutine_fn monitor_qmp_dispatcher_co(void *data)
 213 {
 214     QMPRequest *req_obj = NULL;
 215     QDict *rsp;
 216     bool need_resume;
 217     MonitorQMP *mon;
 218
 219     while (true) {
 220         assert(qatomic_mb_read(&qmp_dispatcher_co_busy) == true);
 221
 222         /*
 223          * Mark the dispatcher as not busy already here so that we
 224          * don't miss any new requests coming in the middle of our
 225          * processing.
 226          */
 227         qatomic_mb_set(&qmp_dispatcher_co_busy, false);
 228
 229         while (!(req_obj = monitor_qmp_requests_pop_any_with_lock())) {
 230             /*
 231              * No more requests to process.  Wait to be reentered from
 232              * handle_qmp_command() when it pushes more requests, or
 233              * from monitor_cleanup() when it requests shutdown.
 234              */
 235             if (!qmp_dispatcher_co_shutdown) {
 236                 qemu_coroutine_yield();
 237
 238                 /*
 239                  * busy must be set to true again by whoever
 240                  * rescheduled us to avoid double scheduling
 241                  */
 242                 assert(qatomic_xchg(&qmp_dispatcher_co_busy, false) == true);
 243             }
 244
 245             /*
 246              * qmp_dispatcher_co_shutdown may have changed if we
 247              * yielded and were reentered from monitor_cleanup()
 248              */
 249             if (qmp_dispatcher_co_shutdown) {
 250                 return;
 251             }
 252         }
 253
 254         if (qatomic_xchg(&qmp_dispatcher_co_busy, true) == true) {
 255             /*
 256              * Someone rescheduled us (probably because a new requests
 257              * came in), but we didn't actually yield. Do that now,
 258              * only to be immediately reentered and removed from the
 259              * list of scheduled coroutines.
 260              */
 261             qemu_coroutine_yield();
 262         }
 263
 264         /*
 265          * Move the coroutine from iohandler_ctx to qemu_aio_context for
 266          * executing the command handler so that it can make progress if it
 267          * involves an AIO_WAIT_WHILE().
 268          */
 269         aio_co_schedule(qemu_get_aio_context(), qmp_dispatcher_co);
 270         qemu_coroutine_yield();
 271
 272         mon = req_obj->mon;
 273         /* qmp_oob_enabled() might change after "qmp_capabilities" */
 274         need_resume = !qmp_oob_enabled(mon) ||
 275             mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1;
 276         qemu_mutex_unlock(&mon->qmp_queue_lock);
 277         if (req_obj->req) {
 278             if (trace_event_get_state(TRACE_MONITOR_QMP_CMD_IN_BAND)) {
 279                 QDict *qdict = qobject_to(QDict, req_obj->req);
 280                 QObject *id = qdict ? qdict_get(qdict, "id") : NULL;
 281                 GString *id_json;
 282
 283                 id_json = id ? qobject_to_json(id) : g_string_new(NULL);
 284                 trace_monitor_qmp_cmd_in_band(id_json->str);
 285                 g_string_free(id_json, true);
 286             }
 287             monitor_qmp_dispatch(mon, req_obj->req);
 288         } else {
 289             assert(req_obj->err);
 290             rsp = qmp_error_response(req_obj->err);
 291             req_obj->err = NULL;
 292             monitor_qmp_respond(mon, rsp);
 293             qobject_unref(rsp);
 294         }
 295
 296         if (need_resume) {
 297             /* Pairs with the monitor_suspend() in handle_qmp_command() */
 298             monitor_resume(&mon->common);
 299         }
 300         qmp_request_free(req_obj);
 301
 302         /*
 303          * Yield and reschedule so the main loop stays responsive.
 304          *
 305          * Move back to iohandler_ctx so that nested event loops for
 306          * qemu_aio_context don't start new monitor commands.
 307          */
 308         aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co);
 309         qemu_coroutine_yield();
 310     }
 311 }
 312
 313 static void handle_qmp_command(void *opaque, QObject *req, Error *err)
 314 {
 315     MonitorQMP *mon = opaque;
 316     QDict *qdict = qobject_to(QDict, req);
 317     QMPRequest *req_obj;
 318
 319     assert(!req != !err);
 320
 321     if (req && trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
 322         GString *req_json = qobject_to_json(req);
 323         trace_handle_qmp_command(mon, req_json->str);
 324         g_string_free(req_json, true);
 325     }
 326
 327     if (qdict && qmp_is_oob(qdict)) {
 328         /* OOB commands are executed immediately */
 329         if (trace_event_get_state(TRACE_MONITOR_QMP_CMD_OUT_OF_BAND)) {
 330             QObject *id = qdict_get(qdict, "id");
 331             GString *id_json;
 332
 333             id_json = id ? qobject_to_json(id) : g_string_new(NULL);
 334             trace_monitor_qmp_cmd_out_of_band(id_json->str);
 335             g_string_free(id_json, true);
 336         }
 337         monitor_qmp_dispatch(mon, req);
 338         qobject_unref(req);
 339         return;
 340     }
 341
 342     req_obj = g_new0(QMPRequest, 1);
 343     req_obj->mon = mon;
 344     req_obj->req = req;
 345     req_obj->err = err;
 346
 347     /* Protect qmp_requests and fetching its length. */
 348     qemu_mutex_lock(&mon->qmp_queue_lock);
 349
 350     /*
 351      * Suspend the monitor when we can't queue more requests after
 352      * this one.  Dequeuing in monitor_qmp_bh_dispatcher() or
 353      * monitor_qmp_cleanup_queue_and_resume() will resume it.
 354      * Note that when OOB is disabled, we queue at most one command,
 355      * for backward compatibility.
 356      */
 357     if (!qmp_oob_enabled(mon) ||
 358         mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1) {
 359         monitor_suspend(&mon->common);
 360     }
 361
 362     /*
 363      * Put the request to the end of queue so that requests will be
 364      * handled in time order.  Ownership for req_obj, req,
 365      * etc. will be delivered to the handler side.
 366      */
 367     assert(mon->qmp_requests->length < QMP_REQ_QUEUE_LEN_MAX);
 368     g_queue_push_tail(mon->qmp_requests, req_obj);
 369     qemu_mutex_unlock(&mon->qmp_queue_lock);
 370
 371     /* Kick the dispatcher routine */
 372     if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) {
 373         aio_co_wake(qmp_dispatcher_co);
 374     }
 375 }
 376
 377 static void monitor_qmp_read(void *opaque, const uint8_t *buf, int size)
 378 {
 379     MonitorQMP *mon = opaque;
 380
 381     json_message_parser_feed(&mon->parser, (const char *) buf, size);
 382 }
 383
 384 static QDict *qmp_greeting(MonitorQMP *mon)
 385 {
 386     QList *cap_list = qlist_new();
 387     QObject *ver = NULL;
 388     QDict *args;
 389     QMPCapability cap;
 390
 391     args = qdict_new();
 392     qmp_marshal_query_version(args, &ver, NULL);
 393     qobject_unref(args);
 394
 395     for (cap = 0; cap < QMP_CAPABILITY__MAX; cap++) {
 396         if (mon->capab_offered[cap]) {
 397             qlist_append_str(cap_list, QMPCapability_str(cap));
 398         }
 399     }
 400
 401     return qdict_from_jsonf_nofail(
 402         "{'QMP': {'version': %p, 'capabilities': %p}}",
 403         ver, cap_list);
 404 }
 405
 406 static void monitor_qmp_event(void *opaque, QEMUChrEvent event)
 407 {
 408     QDict *data;
 409     MonitorQMP *mon = opaque;
 410
 411     switch (event) {
 412     case CHR_EVENT_OPENED:
 413         mon->commands = &qmp_cap_negotiation_commands;
 414         monitor_qmp_caps_reset(mon);
 415         data = qmp_greeting(mon);
 416         qmp_send_response(mon, data);
 417         qobject_unref(data);
 418         mon_refcount++;
 419         break;
 420     case CHR_EVENT_CLOSED:
 421         /*
 422          * Note: this is only useful when the output of the chardev
 423          * backend is still open.  For example, when the backend is
 424          * stdio, it's possible that stdout is still open when stdin
 425          * is closed.
 426          */
 427         monitor_qmp_cleanup_queue_and_resume(mon);
 428         json_message_parser_destroy(&mon->parser);
 429         json_message_parser_init(&mon->parser, handle_qmp_command,
 430                                  mon, NULL);
 431         mon_refcount--;
 432         monitor_fdsets_cleanup();
 433         break;
 434     case CHR_EVENT_BREAK:
 435     case CHR_EVENT_MUX_IN:
 436     case CHR_EVENT_MUX_OUT:
 437         /* Ignore */
 438         break;
 439     }
 440 }
 441
 442 void monitor_data_destroy_qmp(MonitorQMP *mon)
 443 {
 444     json_message_parser_destroy(&mon->parser);
 445     qemu_mutex_destroy(&mon->qmp_queue_lock);
 446     monitor_qmp_cleanup_req_queue_locked(mon);
 447     g_queue_free(mon->qmp_requests);
 448 }
 449
 450 static void monitor_qmp_setup_handlers_bh(void *opaque)
 451 {
 452     MonitorQMP *mon = opaque;
 453     GMainContext *context;
 454
 455     assert(mon->common.use_io_thread);
 456     context = iothread_get_g_main_context(mon_iothread);
 457     assert(context);
 458     qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
 459                              monitor_qmp_read, monitor_qmp_event,
 460                              NULL, &mon->common, context, true);
 461     monitor_list_append(&mon->common);
 462 }
 463
 464 void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)
 465 {
 466     MonitorQMP *mon = g_new0(MonitorQMP, 1);
 467
 468     if (!qemu_chr_fe_init(&mon->common.chr, chr, errp)) {
 469         g_free(mon);
 470         return;
 471     }
 472     qemu_chr_fe_set_echo(&mon->common.chr, true);
 473
 474     /* Note: we run QMP monitor in I/O thread when @chr supports that */
 475     monitor_data_init(&mon->common, true, false,
 476                       qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_GCONTEXT));
 477
 478     mon->pretty = pretty;
 479
 480     qemu_mutex_init(&mon->qmp_queue_lock);
 481     mon->qmp_requests = g_queue_new();
 482
 483     json_message_parser_init(&mon->parser, handle_qmp_command, mon, NULL);
 484     if (mon->common.use_io_thread) {
 485         /*
 486          * Make sure the old iowatch is gone.  It's possible when
 487          * e.g. the chardev is in client mode, with wait=on.
 488          */
 489         remove_fd_in_watch(chr);
 490         /*
 491          * We can't call qemu_chr_fe_set_handlers() directly here
 492          * since chardev might be running in the monitor I/O
 493          * thread.  Schedule a bottom half.
 494          */
 495         aio_bh_schedule_oneshot(iothread_get_aio_context(mon_iothread),
 496                                 monitor_qmp_setup_handlers_bh, mon);
 497         /* The bottom half will add @mon to @mon_list */
 498     } else {
 499         qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
 500                                  monitor_qmp_read, monitor_qmp_event,
 501                                  NULL, &mon->common, NULL, true);
 502         monitor_list_append(&mon->common);
 503     }
 504 }