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     QMPCapability cap;
 326
 327     qmp_marshal_query_version(NULL, &ver, NULL);
 328
 329     for (cap = 0; cap < QMP_CAPABILITY__MAX; cap++) {
 330         if (mon->capab_offered[cap]) {
 331             qlist_append_str(cap_list, QMPCapability_str(cap));
 332         }
 333     }
 334
 335     return qdict_from_jsonf_nofail(
 336         "{'QMP': {'version': %p, 'capabilities': %p}}",
 337         ver, cap_list);
 338 }
 339
 340 static void monitor_qmp_event(void *opaque, QEMUChrEvent event)
 341 {
 342     QDict *data;
 343     MonitorQMP *mon = opaque;
 344
 345     switch (event) {
 346     case CHR_EVENT_OPENED:
 347         mon->commands = &qmp_cap_negotiation_commands;
 348         monitor_qmp_caps_reset(mon);
 349         data = qmp_greeting(mon);
 350         qmp_send_response(mon, data);
 351         qobject_unref(data);
 352         mon_refcount++;
 353         break;
 354     case CHR_EVENT_CLOSED:
 355         /*
 356          * Note: this is only useful when the output of the chardev
 357          * backend is still open.  For example, when the backend is
 358          * stdio, it's possible that stdout is still open when stdin
 359          * is closed.
 360          */
 361         monitor_qmp_cleanup_queue_and_resume(mon);
 362         json_message_parser_destroy(&mon->parser);
 363         json_message_parser_init(&mon->parser, handle_qmp_command,
 364                                  mon, NULL);
 365         mon_refcount--;
 366         monitor_fdsets_cleanup();
 367         break;
 368     case CHR_EVENT_BREAK:
 369     case CHR_EVENT_MUX_IN:
 370     case CHR_EVENT_MUX_OUT:
 371         /* Ignore */
 372         break;
 373     }
 374 }
 375
 376 void monitor_data_destroy_qmp(MonitorQMP *mon)
 377 {
 378     json_message_parser_destroy(&mon->parser);
 379     qemu_mutex_destroy(&mon->qmp_queue_lock);
 380     monitor_qmp_cleanup_req_queue_locked(mon);
 381     g_queue_free(mon->qmp_requests);
 382 }
 383
 384 static void monitor_qmp_setup_handlers_bh(void *opaque)
 385 {
 386     MonitorQMP *mon = opaque;
 387     GMainContext *context;
 388
 389     assert(mon->common.use_io_thread);
 390     context = iothread_get_g_main_context(mon_iothread);
 391     assert(context);
 392     qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
 393                              monitor_qmp_read, monitor_qmp_event,
 394                              NULL, &mon->common, context, true);
 395     monitor_list_append(&mon->common);
 396 }
 397
 398 void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)
 399 {
 400     MonitorQMP *mon = g_new0(MonitorQMP, 1);
 401
 402     if (!qemu_chr_fe_init(&mon->common.chr, chr, errp)) {
 403         g_free(mon);
 404         return;
 405     }
 406     qemu_chr_fe_set_echo(&mon->common.chr, true);
 407
 408     /* Note: we run QMP monitor in I/O thread when @chr supports that */
 409     monitor_data_init(&mon->common, true, false,
 410                       qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_GCONTEXT));
 411
 412     mon->pretty = pretty;
 413
 414     qemu_mutex_init(&mon->qmp_queue_lock);
 415     mon->qmp_requests = g_queue_new();
 416
 417     json_message_parser_init(&mon->parser, handle_qmp_command, mon, NULL);
 418     if (mon->common.use_io_thread) {
 419         /*
 420          * Make sure the old iowatch is gone.  It's possible when
 421          * e.g. the chardev is in client mode, with wait=on.
 422          */
 423         remove_fd_in_watch(chr);
 424         /*
 425          * We can't call qemu_chr_fe_set_handlers() directly here
 426          * since chardev might be running in the monitor I/O
 427          * thread.  Schedule a bottom half.
 428          */
 429         aio_bh_schedule_oneshot(iothread_get_aio_context(mon_iothread),
 430                                 monitor_qmp_setup_handlers_bh, mon);
 431         /* The bottom half will add @mon to @mon_list */
 432     } else {
 433         qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
 434                                  monitor_qmp_read, monitor_qmp_event,
 435                                  NULL, &mon->common, NULL, true);
 436         monitor_list_append(&mon->common);
 437     }
 438 }