cachepc-qemu

Fork of AMDESE/qemu with changes for cachepc side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-qemu
Log | Files | Refs | Submodules | LICENSE | sfeed.txt

monitor.c (22199B)


      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#include "monitor-internal.h"
     27#include "qapi/error.h"
     28#include "qapi/opts-visitor.h"
     29#include "qapi/qapi-emit-events.h"
     30#include "qapi/qapi-visit-control.h"
     31#include "qapi/qmp/qdict.h"
     32#include "qemu/error-report.h"
     33#include "qemu/option.h"
     34#include "sysemu/qtest.h"
     35#include "trace.h"
     36
     37/*
     38 * To prevent flooding clients, events can be throttled. The
     39 * throttling is calculated globally, rather than per-Monitor
     40 * instance.
     41 */
     42typedef struct MonitorQAPIEventState {
     43    QAPIEvent event;    /* Throttling state for this event type and... */
     44    QDict *data;        /* ... data, see qapi_event_throttle_equal() */
     45    QEMUTimer *timer;   /* Timer for handling delayed events */
     46    QDict *qdict;       /* Delayed event (if any) */
     47} MonitorQAPIEventState;
     48
     49typedef struct {
     50    int64_t rate;       /* Minimum time (in ns) between two events */
     51} MonitorQAPIEventConf;
     52
     53/* Shared monitor I/O thread */
     54IOThread *mon_iothread;
     55
     56/* Coroutine to dispatch the requests received from I/O thread */
     57Coroutine *qmp_dispatcher_co;
     58
     59/* Set to true when the dispatcher coroutine should terminate */
     60bool qmp_dispatcher_co_shutdown;
     61
     62/*
     63 * qmp_dispatcher_co_busy is used for synchronisation between the
     64 * monitor thread and the main thread to ensure that the dispatcher
     65 * coroutine never gets scheduled a second time when it's already
     66 * scheduled (scheduling the same coroutine twice is forbidden).
     67 *
     68 * It is true if the coroutine is active and processing requests.
     69 * Additional requests may then be pushed onto mon->qmp_requests,
     70 * and @qmp_dispatcher_co_shutdown may be set without further ado.
     71 * @qmp_dispatcher_co_busy must not be woken up in this case.
     72 *
     73 * If false, you also have to set @qmp_dispatcher_co_busy to true and
     74 * wake up @qmp_dispatcher_co after pushing the new requests.
     75 *
     76 * The coroutine will automatically change this variable back to false
     77 * before it yields.  Nobody else may set the variable to false.
     78 *
     79 * Access must be atomic for thread safety.
     80 */
     81bool qmp_dispatcher_co_busy;
     82
     83/*
     84 * Protects mon_list, monitor_qapi_event_state, coroutine_mon,
     85 * monitor_destroyed.
     86 */
     87QemuMutex monitor_lock;
     88static GHashTable *monitor_qapi_event_state;
     89static GHashTable *coroutine_mon; /* Maps Coroutine* to Monitor* */
     90
     91MonitorList mon_list;
     92int mon_refcount;
     93static bool monitor_destroyed;
     94
     95Monitor *monitor_cur(void)
     96{
     97    Monitor *mon;
     98
     99    qemu_mutex_lock(&monitor_lock);
    100    mon = g_hash_table_lookup(coroutine_mon, qemu_coroutine_self());
    101    qemu_mutex_unlock(&monitor_lock);
    102
    103    return mon;
    104}
    105
    106/**
    107 * Sets a new current monitor and returns the old one.
    108 *
    109 * If a non-NULL monitor is set for a coroutine, another call
    110 * resetting it to NULL is required before the coroutine terminates,
    111 * otherwise a stale entry would remain in the hash table.
    112 */
    113Monitor *monitor_set_cur(Coroutine *co, Monitor *mon)
    114{
    115    Monitor *old_monitor = monitor_cur();
    116
    117    qemu_mutex_lock(&monitor_lock);
    118    if (mon) {
    119        g_hash_table_replace(coroutine_mon, co, mon);
    120    } else {
    121        g_hash_table_remove(coroutine_mon, co);
    122    }
    123    qemu_mutex_unlock(&monitor_lock);
    124
    125    return old_monitor;
    126}
    127
    128/**
    129 * Is the current monitor, if any, a QMP monitor?
    130 */
    131bool monitor_cur_is_qmp(void)
    132{
    133    Monitor *cur_mon = monitor_cur();
    134
    135    return cur_mon && monitor_is_qmp(cur_mon);
    136}
    137
    138/**
    139 * Is @mon is using readline?
    140 * Note: not all HMP monitors use readline, e.g., gdbserver has a
    141 * non-interactive HMP monitor, so readline is not used there.
    142 */
    143static inline bool monitor_uses_readline(const MonitorHMP *mon)
    144{
    145    return mon->use_readline;
    146}
    147
    148static inline bool monitor_is_hmp_non_interactive(const Monitor *mon)
    149{
    150    if (monitor_is_qmp(mon)) {
    151        return false;
    152    }
    153
    154    return !monitor_uses_readline(container_of(mon, MonitorHMP, common));
    155}
    156
    157static void monitor_flush_locked(Monitor *mon);
    158
    159static gboolean monitor_unblocked(void *do_not_use, GIOCondition cond,
    160                                  void *opaque)
    161{
    162    Monitor *mon = opaque;
    163
    164    qemu_mutex_lock(&mon->mon_lock);
    165    mon->out_watch = 0;
    166    monitor_flush_locked(mon);
    167    qemu_mutex_unlock(&mon->mon_lock);
    168    return FALSE;
    169}
    170
    171/* Caller must hold mon->mon_lock */
    172static void monitor_flush_locked(Monitor *mon)
    173{
    174    int rc;
    175    size_t len;
    176    const char *buf;
    177
    178    if (mon->skip_flush) {
    179        return;
    180    }
    181
    182    buf = mon->outbuf->str;
    183    len = mon->outbuf->len;
    184
    185    if (len && !mon->mux_out) {
    186        rc = qemu_chr_fe_write(&mon->chr, (const uint8_t *) buf, len);
    187        if ((rc < 0 && errno != EAGAIN) || (rc == len)) {
    188            /* all flushed or error */
    189            g_string_truncate(mon->outbuf, 0);
    190            return;
    191        }
    192        if (rc > 0) {
    193            /* partial write */
    194            g_string_erase(mon->outbuf, 0, rc);
    195        }
    196        if (mon->out_watch == 0) {
    197            mon->out_watch =
    198                qemu_chr_fe_add_watch(&mon->chr, G_IO_OUT | G_IO_HUP,
    199                                      monitor_unblocked, mon);
    200        }
    201    }
    202}
    203
    204void monitor_flush(Monitor *mon)
    205{
    206    qemu_mutex_lock(&mon->mon_lock);
    207    monitor_flush_locked(mon);
    208    qemu_mutex_unlock(&mon->mon_lock);
    209}
    210
    211/* flush at every end of line */
    212int monitor_puts(Monitor *mon, const char *str)
    213{
    214    int i;
    215    char c;
    216
    217    qemu_mutex_lock(&mon->mon_lock);
    218    for (i = 0; str[i]; i++) {
    219        c = str[i];
    220        if (c == '\n') {
    221            g_string_append_c(mon->outbuf, '\r');
    222        }
    223        g_string_append_c(mon->outbuf, c);
    224        if (c == '\n') {
    225            monitor_flush_locked(mon);
    226        }
    227    }
    228    qemu_mutex_unlock(&mon->mon_lock);
    229
    230    return i;
    231}
    232
    233int monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
    234{
    235    char *buf;
    236    int n;
    237
    238    if (!mon) {
    239        return -1;
    240    }
    241
    242    if (monitor_is_qmp(mon)) {
    243        return -1;
    244    }
    245
    246    buf = g_strdup_vprintf(fmt, ap);
    247    n = monitor_puts(mon, buf);
    248    g_free(buf);
    249    return n;
    250}
    251
    252int monitor_printf(Monitor *mon, const char *fmt, ...)
    253{
    254    int ret;
    255
    256    va_list ap;
    257    va_start(ap, fmt);
    258    ret = monitor_vprintf(mon, fmt, ap);
    259    va_end(ap);
    260    return ret;
    261}
    262
    263/*
    264 * Print to current monitor if we have one, else to stderr.
    265 */
    266int error_vprintf(const char *fmt, va_list ap)
    267{
    268    Monitor *cur_mon = monitor_cur();
    269
    270    if (cur_mon && !monitor_cur_is_qmp()) {
    271        return monitor_vprintf(cur_mon, fmt, ap);
    272    }
    273    return vfprintf(stderr, fmt, ap);
    274}
    275
    276int error_vprintf_unless_qmp(const char *fmt, va_list ap)
    277{
    278    Monitor *cur_mon = monitor_cur();
    279
    280    if (!cur_mon) {
    281        return vfprintf(stderr, fmt, ap);
    282    }
    283    if (!monitor_cur_is_qmp()) {
    284        return monitor_vprintf(cur_mon, fmt, ap);
    285    }
    286    return -1;
    287}
    288
    289
    290static MonitorQAPIEventConf monitor_qapi_event_conf[QAPI_EVENT__MAX] = {
    291    /* Limit guest-triggerable events to 1 per second */
    292    [QAPI_EVENT_RTC_CHANGE]        = { 1000 * SCALE_MS },
    293    [QAPI_EVENT_WATCHDOG]          = { 1000 * SCALE_MS },
    294    [QAPI_EVENT_BALLOON_CHANGE]    = { 1000 * SCALE_MS },
    295    [QAPI_EVENT_QUORUM_REPORT_BAD] = { 1000 * SCALE_MS },
    296    [QAPI_EVENT_QUORUM_FAILURE]    = { 1000 * SCALE_MS },
    297    [QAPI_EVENT_VSERPORT_CHANGE]   = { 1000 * SCALE_MS },
    298    [QAPI_EVENT_MEMORY_DEVICE_SIZE_CHANGE] = { 1000 * SCALE_MS },
    299};
    300
    301/*
    302 * Return the clock to use for recording an event's time.
    303 * It's QEMU_CLOCK_REALTIME, except for qtests it's
    304 * QEMU_CLOCK_VIRTUAL, to support testing rate limits.
    305 * Beware: result is invalid before configure_accelerator().
    306 */
    307static inline QEMUClockType monitor_get_event_clock(void)
    308{
    309    return qtest_enabled() ? QEMU_CLOCK_VIRTUAL : QEMU_CLOCK_REALTIME;
    310}
    311
    312/*
    313 * Broadcast an event to all monitors.
    314 * @qdict is the event object.  Its member "event" must match @event.
    315 * Caller must hold monitor_lock.
    316 */
    317static void monitor_qapi_event_emit(QAPIEvent event, QDict *qdict)
    318{
    319    Monitor *mon;
    320    MonitorQMP *qmp_mon;
    321
    322    trace_monitor_protocol_event_emit(event, qdict);
    323    QTAILQ_FOREACH(mon, &mon_list, entry) {
    324        if (!monitor_is_qmp(mon)) {
    325            continue;
    326        }
    327
    328        qmp_mon = container_of(mon, MonitorQMP, common);
    329        if (qmp_mon->commands != &qmp_cap_negotiation_commands) {
    330            qmp_send_response(qmp_mon, qdict);
    331        }
    332    }
    333}
    334
    335static void monitor_qapi_event_handler(void *opaque);
    336
    337/*
    338 * Queue a new event for emission to Monitor instances,
    339 * applying any rate limiting if required.
    340 */
    341static void
    342monitor_qapi_event_queue_no_reenter(QAPIEvent event, QDict *qdict)
    343{
    344    MonitorQAPIEventConf *evconf;
    345    MonitorQAPIEventState *evstate;
    346
    347    assert(event < QAPI_EVENT__MAX);
    348    evconf = &monitor_qapi_event_conf[event];
    349    trace_monitor_protocol_event_queue(event, qdict, evconf->rate);
    350
    351    QEMU_LOCK_GUARD(&monitor_lock);
    352
    353    if (!evconf->rate) {
    354        /* Unthrottled event */
    355        monitor_qapi_event_emit(event, qdict);
    356    } else {
    357        QDict *data = qobject_to(QDict, qdict_get(qdict, "data"));
    358        MonitorQAPIEventState key = { .event = event, .data = data };
    359
    360        evstate = g_hash_table_lookup(monitor_qapi_event_state, &key);
    361        assert(!evstate || timer_pending(evstate->timer));
    362
    363        if (evstate) {
    364            /*
    365             * Timer is pending for (at least) evconf->rate ns after
    366             * last send.  Store event for sending when timer fires,
    367             * replacing a prior stored event if any.
    368             */
    369            qobject_unref(evstate->qdict);
    370            evstate->qdict = qobject_ref(qdict);
    371        } else {
    372            /*
    373             * Last send was (at least) evconf->rate ns ago.
    374             * Send immediately, and arm the timer to call
    375             * monitor_qapi_event_handler() in evconf->rate ns.  Any
    376             * events arriving before then will be delayed until then.
    377             */
    378            int64_t now = qemu_clock_get_ns(monitor_get_event_clock());
    379
    380            monitor_qapi_event_emit(event, qdict);
    381
    382            evstate = g_new(MonitorQAPIEventState, 1);
    383            evstate->event = event;
    384            evstate->data = qobject_ref(data);
    385            evstate->qdict = NULL;
    386            evstate->timer = timer_new_ns(monitor_get_event_clock(),
    387                                          monitor_qapi_event_handler,
    388                                          evstate);
    389            g_hash_table_add(monitor_qapi_event_state, evstate);
    390            timer_mod_ns(evstate->timer, now + evconf->rate);
    391        }
    392    }
    393}
    394
    395void qapi_event_emit(QAPIEvent event, QDict *qdict)
    396{
    397    /*
    398     * monitor_qapi_event_queue_no_reenter() is not reentrant: it
    399     * would deadlock on monitor_lock.  Work around by queueing
    400     * events in thread-local storage.
    401     * TODO: remove this, make it re-enter safe.
    402     */
    403    typedef struct MonitorQapiEvent {
    404        QAPIEvent event;
    405        QDict *qdict;
    406        QSIMPLEQ_ENTRY(MonitorQapiEvent) entry;
    407    } MonitorQapiEvent;
    408    static __thread QSIMPLEQ_HEAD(, MonitorQapiEvent) event_queue;
    409    static __thread bool reentered;
    410    MonitorQapiEvent *ev;
    411
    412    if (!reentered) {
    413        QSIMPLEQ_INIT(&event_queue);
    414    }
    415
    416    ev = g_new(MonitorQapiEvent, 1);
    417    ev->qdict = qobject_ref(qdict);
    418    ev->event = event;
    419    QSIMPLEQ_INSERT_TAIL(&event_queue, ev, entry);
    420    if (reentered) {
    421        return;
    422    }
    423
    424    reentered = true;
    425
    426    while ((ev = QSIMPLEQ_FIRST(&event_queue)) != NULL) {
    427        QSIMPLEQ_REMOVE_HEAD(&event_queue, entry);
    428        monitor_qapi_event_queue_no_reenter(ev->event, ev->qdict);
    429        qobject_unref(ev->qdict);
    430        g_free(ev);
    431    }
    432
    433    reentered = false;
    434}
    435
    436/*
    437 * This function runs evconf->rate ns after sending a throttled
    438 * event.
    439 * If another event has since been stored, send it.
    440 */
    441static void monitor_qapi_event_handler(void *opaque)
    442{
    443    MonitorQAPIEventState *evstate = opaque;
    444    MonitorQAPIEventConf *evconf = &monitor_qapi_event_conf[evstate->event];
    445
    446    trace_monitor_protocol_event_handler(evstate->event, evstate->qdict);
    447    QEMU_LOCK_GUARD(&monitor_lock);
    448
    449    if (evstate->qdict) {
    450        int64_t now = qemu_clock_get_ns(monitor_get_event_clock());
    451
    452        monitor_qapi_event_emit(evstate->event, evstate->qdict);
    453        qobject_unref(evstate->qdict);
    454        evstate->qdict = NULL;
    455        timer_mod_ns(evstate->timer, now + evconf->rate);
    456    } else {
    457        g_hash_table_remove(monitor_qapi_event_state, evstate);
    458        qobject_unref(evstate->data);
    459        timer_free(evstate->timer);
    460        g_free(evstate);
    461    }
    462}
    463
    464static unsigned int qapi_event_throttle_hash(const void *key)
    465{
    466    const MonitorQAPIEventState *evstate = key;
    467    unsigned int hash = evstate->event * 255;
    468
    469    if (evstate->event == QAPI_EVENT_VSERPORT_CHANGE) {
    470        hash += g_str_hash(qdict_get_str(evstate->data, "id"));
    471    }
    472
    473    if (evstate->event == QAPI_EVENT_QUORUM_REPORT_BAD) {
    474        hash += g_str_hash(qdict_get_str(evstate->data, "node-name"));
    475    }
    476
    477    if (evstate->event == QAPI_EVENT_MEMORY_DEVICE_SIZE_CHANGE) {
    478        hash += g_str_hash(qdict_get_str(evstate->data, "qom-path"));
    479    }
    480
    481    return hash;
    482}
    483
    484static gboolean qapi_event_throttle_equal(const void *a, const void *b)
    485{
    486    const MonitorQAPIEventState *eva = a;
    487    const MonitorQAPIEventState *evb = b;
    488
    489    if (eva->event != evb->event) {
    490        return FALSE;
    491    }
    492
    493    if (eva->event == QAPI_EVENT_VSERPORT_CHANGE) {
    494        return !strcmp(qdict_get_str(eva->data, "id"),
    495                       qdict_get_str(evb->data, "id"));
    496    }
    497
    498    if (eva->event == QAPI_EVENT_QUORUM_REPORT_BAD) {
    499        return !strcmp(qdict_get_str(eva->data, "node-name"),
    500                       qdict_get_str(evb->data, "node-name"));
    501    }
    502
    503    if (eva->event == QAPI_EVENT_MEMORY_DEVICE_SIZE_CHANGE) {
    504        return !strcmp(qdict_get_str(eva->data, "qom-path"),
    505                       qdict_get_str(evb->data, "qom-path"));
    506    }
    507
    508    return TRUE;
    509}
    510
    511int monitor_suspend(Monitor *mon)
    512{
    513    if (monitor_is_hmp_non_interactive(mon)) {
    514        return -ENOTTY;
    515    }
    516
    517    qatomic_inc(&mon->suspend_cnt);
    518
    519    if (mon->use_io_thread) {
    520        /*
    521         * Kick I/O thread to make sure this takes effect.  It'll be
    522         * evaluated again in prepare() of the watch object.
    523         */
    524        aio_notify(iothread_get_aio_context(mon_iothread));
    525    }
    526
    527    trace_monitor_suspend(mon, 1);
    528    return 0;
    529}
    530
    531static void monitor_accept_input(void *opaque)
    532{
    533    Monitor *mon = opaque;
    534
    535    qemu_chr_fe_accept_input(&mon->chr);
    536}
    537
    538void monitor_resume(Monitor *mon)
    539{
    540    if (monitor_is_hmp_non_interactive(mon)) {
    541        return;
    542    }
    543
    544    if (qatomic_dec_fetch(&mon->suspend_cnt) == 0) {
    545        AioContext *ctx;
    546
    547        if (mon->use_io_thread) {
    548            ctx = iothread_get_aio_context(mon_iothread);
    549        } else {
    550            ctx = qemu_get_aio_context();
    551        }
    552
    553        if (!monitor_is_qmp(mon)) {
    554            MonitorHMP *hmp_mon = container_of(mon, MonitorHMP, common);
    555            assert(hmp_mon->rs);
    556            readline_show_prompt(hmp_mon->rs);
    557        }
    558
    559        aio_bh_schedule_oneshot(ctx, monitor_accept_input, mon);
    560    }
    561
    562    trace_monitor_suspend(mon, -1);
    563}
    564
    565int monitor_can_read(void *opaque)
    566{
    567    Monitor *mon = opaque;
    568
    569    return !qatomic_mb_read(&mon->suspend_cnt);
    570}
    571
    572void monitor_list_append(Monitor *mon)
    573{
    574    qemu_mutex_lock(&monitor_lock);
    575    /*
    576     * This prevents inserting new monitors during monitor_cleanup().
    577     * A cleaner solution would involve the main thread telling other
    578     * threads to terminate, waiting for their termination.
    579     */
    580    if (!monitor_destroyed) {
    581        QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
    582        mon = NULL;
    583    }
    584    qemu_mutex_unlock(&monitor_lock);
    585
    586    if (mon) {
    587        monitor_data_destroy(mon);
    588        g_free(mon);
    589    }
    590}
    591
    592static void monitor_iothread_init(void)
    593{
    594    mon_iothread = iothread_create("mon_iothread", &error_abort);
    595}
    596
    597void monitor_data_init(Monitor *mon, bool is_qmp, bool skip_flush,
    598                       bool use_io_thread)
    599{
    600    if (use_io_thread && !mon_iothread) {
    601        monitor_iothread_init();
    602    }
    603    qemu_mutex_init(&mon->mon_lock);
    604    mon->is_qmp = is_qmp;
    605    mon->outbuf = g_string_new(NULL);
    606    mon->skip_flush = skip_flush;
    607    mon->use_io_thread = use_io_thread;
    608}
    609
    610void monitor_data_destroy(Monitor *mon)
    611{
    612    g_free(mon->mon_cpu_path);
    613    qemu_chr_fe_deinit(&mon->chr, false);
    614    if (monitor_is_qmp(mon)) {
    615        monitor_data_destroy_qmp(container_of(mon, MonitorQMP, common));
    616    } else {
    617        readline_free(container_of(mon, MonitorHMP, common)->rs);
    618    }
    619    g_string_free(mon->outbuf, true);
    620    qemu_mutex_destroy(&mon->mon_lock);
    621}
    622
    623void monitor_cleanup(void)
    624{
    625    /*
    626     * The dispatcher needs to stop before destroying the monitor and
    627     * the I/O thread.
    628     *
    629     * We need to poll both qemu_aio_context and iohandler_ctx to make
    630     * sure that the dispatcher coroutine keeps making progress and
    631     * eventually terminates.  qemu_aio_context is automatically
    632     * polled by calling AIO_WAIT_WHILE on it, but we must poll
    633     * iohandler_ctx manually.
    634     *
    635     * Letting the iothread continue while shutting down the dispatcher
    636     * means that new requests may still be coming in. This is okay,
    637     * we'll just leave them in the queue without sending a response
    638     * and monitor_data_destroy() will free them.
    639     */
    640    qmp_dispatcher_co_shutdown = true;
    641    if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) {
    642        aio_co_wake(qmp_dispatcher_co);
    643    }
    644
    645    AIO_WAIT_WHILE(qemu_get_aio_context(),
    646                   (aio_poll(iohandler_get_aio_context(), false),
    647                    qatomic_mb_read(&qmp_dispatcher_co_busy)));
    648
    649    /*
    650     * We need to explicitly stop the I/O thread (but not destroy it),
    651     * clean up the monitor resources, then destroy the I/O thread since
    652     * we need to unregister from chardev below in
    653     * monitor_data_destroy(), and chardev is not thread-safe yet
    654     */
    655    if (mon_iothread) {
    656        iothread_stop(mon_iothread);
    657    }
    658
    659    /* Flush output buffers and destroy monitors */
    660    qemu_mutex_lock(&monitor_lock);
    661    monitor_destroyed = true;
    662    while (!QTAILQ_EMPTY(&mon_list)) {
    663        Monitor *mon = QTAILQ_FIRST(&mon_list);
    664        QTAILQ_REMOVE(&mon_list, mon, entry);
    665        /* Permit QAPI event emission from character frontend release */
    666        qemu_mutex_unlock(&monitor_lock);
    667        monitor_flush(mon);
    668        monitor_data_destroy(mon);
    669        qemu_mutex_lock(&monitor_lock);
    670        g_free(mon);
    671    }
    672    qemu_mutex_unlock(&monitor_lock);
    673
    674    if (mon_iothread) {
    675        iothread_destroy(mon_iothread);
    676        mon_iothread = NULL;
    677    }
    678}
    679
    680static void monitor_qapi_event_init(void)
    681{
    682    monitor_qapi_event_state = g_hash_table_new(qapi_event_throttle_hash,
    683                                                qapi_event_throttle_equal);
    684}
    685
    686void monitor_init_globals_core(void)
    687{
    688    monitor_qapi_event_init();
    689    qemu_mutex_init(&monitor_lock);
    690    coroutine_mon = g_hash_table_new(NULL, NULL);
    691
    692    /*
    693     * The dispatcher BH must run in the main loop thread, since we
    694     * have commands assuming that context.  It would be nice to get
    695     * rid of those assumptions.
    696     */
    697    qmp_dispatcher_co = qemu_coroutine_create(monitor_qmp_dispatcher_co, NULL);
    698    qatomic_mb_set(&qmp_dispatcher_co_busy, true);
    699    aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co);
    700}
    701
    702int monitor_init(MonitorOptions *opts, bool allow_hmp, Error **errp)
    703{
    704    Chardev *chr;
    705    Error *local_err = NULL;
    706
    707    chr = qemu_chr_find(opts->chardev);
    708    if (chr == NULL) {
    709        error_setg(errp, "chardev \"%s\" not found", opts->chardev);
    710        return -1;
    711    }
    712
    713    if (!opts->has_mode) {
    714        opts->mode = allow_hmp ? MONITOR_MODE_READLINE : MONITOR_MODE_CONTROL;
    715    }
    716
    717    switch (opts->mode) {
    718    case MONITOR_MODE_CONTROL:
    719        monitor_init_qmp(chr, opts->pretty, &local_err);
    720        break;
    721    case MONITOR_MODE_READLINE:
    722        if (!allow_hmp) {
    723            error_setg(errp, "Only QMP is supported");
    724            return -1;
    725        }
    726        if (opts->pretty) {
    727            error_setg(errp, "'pretty' is not compatible with HMP monitors");
    728            return -1;
    729        }
    730        monitor_init_hmp(chr, true, &local_err);
    731        break;
    732    default:
    733        g_assert_not_reached();
    734    }
    735
    736    if (local_err) {
    737        error_propagate(errp, local_err);
    738        return -1;
    739    }
    740    return 0;
    741}
    742
    743int monitor_init_opts(QemuOpts *opts, Error **errp)
    744{
    745    Visitor *v;
    746    MonitorOptions *options;
    747    int ret;
    748
    749    v = opts_visitor_new(opts);
    750    visit_type_MonitorOptions(v, NULL, &options, errp);
    751    visit_free(v);
    752    if (!options) {
    753        return -1;
    754    }
    755
    756    ret = monitor_init(options, true, errp);
    757    qapi_free_MonitorOptions(options);
    758    return ret;
    759}
    760
    761QemuOptsList qemu_mon_opts = {
    762    .name = "mon",
    763    .implied_opt_name = "chardev",
    764    .head = QTAILQ_HEAD_INITIALIZER(qemu_mon_opts.head),
    765    .desc = {
    766        {
    767            .name = "mode",
    768            .type = QEMU_OPT_STRING,
    769        },{
    770            .name = "chardev",
    771            .type = QEMU_OPT_STRING,
    772        },{
    773            .name = "pretty",
    774            .type = QEMU_OPT_BOOL,
    775        },
    776        { /* end of list */ }
    777    },
    778};