aboutsummaryrefslogtreecommitdiff
path: root/monitor/monitor.c
blob: 0f32892ad4367cd5ba37b1778cea5a9328449264 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
/*
 * QEMU monitor
 *
 * Copyright (c) 2003-2004 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "qemu/osdep.h"
#include "monitor-internal.h"
#include "qapi/error.h"
#include "qapi/opts-visitor.h"
#include "qapi/qapi-emit-events.h"
#include "qapi/qapi-visit-control.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qstring.h"
#include "qemu/error-report.h"
#include "qemu/option.h"
#include "sysemu/qtest.h"
#include "sysemu/sysemu.h"
#include "trace.h"

/*
 * To prevent flooding clients, events can be throttled. The
 * throttling is calculated globally, rather than per-Monitor
 * instance.
 */
typedef struct MonitorQAPIEventState {
    QAPIEvent event;    /* Throttling state for this event type and... */
    QDict *data;        /* ... data, see qapi_event_throttle_equal() */
    QEMUTimer *timer;   /* Timer for handling delayed events */
    QDict *qdict;       /* Delayed event (if any) */
} MonitorQAPIEventState;

typedef struct {
    int64_t rate;       /* Minimum time (in ns) between two events */
} MonitorQAPIEventConf;

/* Shared monitor I/O thread */
IOThread *mon_iothread;

/* Bottom half to dispatch the requests received from I/O thread */
QEMUBH *qmp_dispatcher_bh;

/* Protects mon_list, monitor_qapi_event_state, monitor_destroyed.  */
QemuMutex monitor_lock;
static GHashTable *monitor_qapi_event_state;

MonitorList mon_list;
int mon_refcount;
static bool monitor_destroyed;

__thread Monitor *cur_mon;

/**
 * Is the current monitor, if any, a QMP monitor?
 */
bool monitor_cur_is_qmp(void)
{
    return cur_mon && monitor_is_qmp(cur_mon);
}

/**
 * Is @mon is using readline?
 * Note: not all HMP monitors use readline, e.g., gdbserver has a
 * non-interactive HMP monitor, so readline is not used there.
 */
static inline bool monitor_uses_readline(const MonitorHMP *mon)
{
    return mon->use_readline;
}

static inline bool monitor_is_hmp_non_interactive(const Monitor *mon)
{
    if (monitor_is_qmp(mon)) {
        return false;
    }

    return !monitor_uses_readline(container_of(mon, MonitorHMP, common));
}

static void monitor_flush_locked(Monitor *mon);

static gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond,
                                  void *opaque)
{
    Monitor *mon = opaque;

    qemu_mutex_lock(&mon->mon_lock);
    mon->out_watch = 0;
    monitor_flush_locked(mon);
    qemu_mutex_unlock(&mon->mon_lock);
    return FALSE;
}

/* Caller must hold mon->mon_lock */
static void monitor_flush_locked(Monitor *mon)
{
    int rc;
    size_t len;
    const char *buf;

    if (mon->skip_flush) {
        return;
    }

    buf = qstring_get_str(mon->outbuf);
    len = qstring_get_length(mon->outbuf);

    if (len && !mon->mux_out) {
        rc = qemu_chr_fe_write(&mon->chr, (const uint8_t *) buf, len);
        if ((rc < 0 && errno != EAGAIN) || (rc == len)) {
            /* all flushed or error */
            qobject_unref(mon->outbuf);
            mon->outbuf = qstring_new();
            return;
        }
        if (rc > 0) {
            /* partial write */
            QString *tmp = qstring_from_str(buf + rc);
            qobject_unref(mon->outbuf);
            mon->outbuf = tmp;
        }
        if (mon->out_watch == 0) {
            mon->out_watch =
                qemu_chr_fe_add_watch(&mon->chr, G_IO_OUT | G_IO_HUP,
                                      monitor_unblocked, mon);
        }
    }
}

void monitor_flush(Monitor *mon)
{
    qemu_mutex_lock(&mon->mon_lock);
    monitor_flush_locked(mon);
    qemu_mutex_unlock(&mon->mon_lock);
}

/* flush at every end of line */
int monitor_puts(Monitor *mon, const char *str)
{
    int i;
    char c;

    qemu_mutex_lock(&mon->mon_lock);
    for (i = 0; str[i]; i++) {
        c = str[i];
        if (c == '\n') {
            qstring_append_chr(mon->outbuf, '\r');
        }
        qstring_append_chr(mon->outbuf, c);
        if (c == '\n') {
            monitor_flush_locked(mon);
        }
    }
    qemu_mutex_unlock(&mon->mon_lock);

    return i;
}

int monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
{
    char *buf;
    int n;

    if (!mon) {
        return -1;
    }

    if (monitor_is_qmp(mon)) {
        return -1;
    }

    buf = g_strdup_vprintf(fmt, ap);
    n = monitor_puts(mon, buf);
    g_free(buf);
    return n;
}

int monitor_printf(Monitor *mon, const char *fmt, ...)
{
    int ret;

    va_list ap;
    va_start(ap, fmt);
    ret = monitor_vprintf(mon, fmt, ap);
    va_end(ap);
    return ret;
}

/*
 * Print to current monitor if we have one, else to stderr.
 */
int error_vprintf(const char *fmt, va_list ap)
{
    if (cur_mon && !monitor_cur_is_qmp()) {
        return monitor_vprintf(cur_mon, fmt, ap);
    }
    return vfprintf(stderr, fmt, ap);
}

int error_vprintf_unless_qmp(const char *fmt, va_list ap)
{
    if (!cur_mon) {
        return vfprintf(stderr, fmt, ap);
    }
    if (!monitor_cur_is_qmp()) {
        return monitor_vprintf(cur_mon, fmt, ap);
    }
    return -1;
}


static MonitorQAPIEventConf monitor_qapi_event_conf[QAPI_EVENT__MAX] = {
    /* Limit guest-triggerable events to 1 per second */
    [QAPI_EVENT_RTC_CHANGE]        = { 1000 * SCALE_MS },
    [QAPI_EVENT_WATCHDOG]          = { 1000 * SCALE_MS },
    [QAPI_EVENT_BALLOON_CHANGE]    = { 1000 * SCALE_MS },
    [QAPI_EVENT_QUORUM_REPORT_BAD] = { 1000 * SCALE_MS },
    [QAPI_EVENT_QUORUM_FAILURE]    = { 1000 * SCALE_MS },
    [QAPI_EVENT_VSERPORT_CHANGE]   = { 1000 * SCALE_MS },
    [QAPI_EVENT_MEMORY_DEVICE_SIZE_CHANGE] = { 1000 * SCALE_MS },
};

/*
 * Return the clock to use for recording an event's time.
 * It's QEMU_CLOCK_REALTIME, except for qtests it's
 * QEMU_CLOCK_VIRTUAL, to support testing rate limits.
 * Beware: result is invalid before configure_accelerator().
 */
static inline QEMUClockType monitor_get_event_clock(void)
{
    return qtest_enabled() ? QEMU_CLOCK_VIRTUAL : QEMU_CLOCK_REALTIME;
}

/*
 * Broadcast an event to all monitors.
 * @qdict is the event object.  Its member "event" must match @event.
 * Caller must hold monitor_lock.
 */
static void monitor_qapi_event_emit(QAPIEvent event, QDict *qdict)
{
    Monitor *mon;
    MonitorQMP *qmp_mon;

    trace_monitor_protocol_event_emit(event, qdict);
    QTAILQ_FOREACH(mon, &mon_list, entry) {
        if (!monitor_is_qmp(mon)) {
            continue;
        }

        qmp_mon = container_of(mon, MonitorQMP, common);
        if (qmp_mon->commands != &qmp_cap_negotiation_commands) {
            qmp_send_response(qmp_mon, qdict);
        }
    }
}

static void monitor_qapi_event_handler(void *opaque);

/*
 * Queue a new event for emission to Monitor instances,
 * applying any rate limiting if required.
 */
static void
monitor_qapi_event_queue_no_reenter(QAPIEvent event, QDict *qdict)
{
    MonitorQAPIEventConf *evconf;
    MonitorQAPIEventState *evstate;

    assert(event < QAPI_EVENT__MAX);
    evconf = &monitor_qapi_event_conf[event];
    trace_monitor_protocol_event_queue(event, qdict, evconf->rate);

    qemu_mutex_lock(&monitor_lock);

    if (!evconf->rate) {
        /* Unthrottled event */
        monitor_qapi_event_emit(event, qdict);
    } else {
        QDict *data = qobject_to(QDict, qdict_get(qdict, "data"));
        MonitorQAPIEventState key = { .event = event, .data = data };

        evstate = g_hash_table_lookup(monitor_qapi_event_state, &key);
        assert(!evstate || timer_pending(evstate->timer));

        if (evstate) {
            /*
             * Timer is pending for (at least) evconf->rate ns after
             * last send.  Store event for sending when timer fires,
             * replacing a prior stored event if any.
             */
            qobject_unref(evstate->qdict);
            evstate->qdict = qobject_ref(qdict);
        } else {
            /*
             * Last send was (at least) evconf->rate ns ago.
             * Send immediately, and arm the timer to call
             * monitor_qapi_event_handler() in evconf->rate ns.  Any
             * events arriving before then will be delayed until then.
             */
            int64_t now = qemu_clock_get_ns(monitor_get_event_clock());

            monitor_qapi_event_emit(event, qdict);

            evstate = g_new(MonitorQAPIEventState, 1);
            evstate->event = event;
            evstate->data = qobject_ref(data);
            evstate->qdict = NULL;
            evstate->timer = timer_new_ns(monitor_get_event_clock(),
                                          monitor_qapi_event_handler,
                                          evstate);
            g_hash_table_add(monitor_qapi_event_state, evstate);
            timer_mod_ns(evstate->timer, now + evconf->rate);
        }
    }

    qemu_mutex_unlock(&monitor_lock);
}

void qapi_event_emit(QAPIEvent event, QDict *qdict)
{
    /*
     * monitor_qapi_event_queue_no_reenter() is not reentrant: it
     * would deadlock on monitor_lock.  Work around by queueing
     * events in thread-local storage.
     * TODO: remove this, make it re-enter safe.
     */
    typedef struct MonitorQapiEvent {
        QAPIEvent event;
        QDict *qdict;
        QSIMPLEQ_ENTRY(MonitorQapiEvent) entry;
    } MonitorQapiEvent;
    static __thread QSIMPLEQ_HEAD(, MonitorQapiEvent) event_queue;
    static __thread bool reentered;
    MonitorQapiEvent *ev;

    if (!reentered) {
        QSIMPLEQ_INIT(&event_queue);
    }

    ev = g_new(MonitorQapiEvent, 1);
    ev->qdict = qobject_ref(qdict);
    ev->event = event;
    QSIMPLEQ_INSERT_TAIL(&event_queue, ev, entry);
    if (reentered) {
        return;
    }

    reentered = true;

    while ((ev = QSIMPLEQ_FIRST(&event_queue)) != NULL) {
        QSIMPLEQ_REMOVE_HEAD(&event_queue, entry);
        monitor_qapi_event_queue_no_reenter(ev->event, ev->qdict);
        qobject_unref(ev->qdict);
        g_free(ev);
    }

    reentered = false;
}

/*
 * This function runs evconf->rate ns after sending a throttled
 * event.
 * If another event has since been stored, send it.
 */
static void monitor_qapi_event_handler(void *opaque)
{
    MonitorQAPIEventState *evstate = opaque;
    MonitorQAPIEventConf *evconf = &monitor_qapi_event_conf[evstate->event];

    trace_monitor_protocol_event_handler(evstate->event, evstate->qdict);
    qemu_mutex_lock(&monitor_lock);

    if (evstate->qdict) {
        int64_t now = qemu_clock_get_ns(monitor_get_event_clock());

        monitor_qapi_event_emit(evstate->event, evstate->qdict);
        qobject_unref(evstate->qdict);
        evstate->qdict = NULL;
        timer_mod_ns(evstate->timer, now + evconf->rate);
    } else {
        g_hash_table_remove(monitor_qapi_event_state, evstate);
        qobject_unref(evstate->data);
        timer_free(evstate->timer);
        g_free(evstate);
    }

    qemu_mutex_unlock(&monitor_lock);
}

static unsigned int qapi_event_throttle_hash(const void *key)
{
    const MonitorQAPIEventState *evstate = key;
    unsigned int hash = evstate->event * 255;

    if (evstate->event == QAPI_EVENT_VSERPORT_CHANGE) {
        hash += g_str_hash(qdict_get_str(evstate->data, "id"));
    }

    if (evstate->event == QAPI_EVENT_QUORUM_REPORT_BAD) {
        hash += g_str_hash(qdict_get_str(evstate->data, "node-name"));
    }

    return hash;
}

static gboolean qapi_event_throttle_equal(const void *a, const void *b)
{
    const MonitorQAPIEventState *eva = a;
    const MonitorQAPIEventState *evb = b;

    if (eva->event != evb->event) {
        return FALSE;
    }

    if (eva->event == QAPI_EVENT_VSERPORT_CHANGE) {
        return !strcmp(qdict_get_str(eva->data, "id"),
                       qdict_get_str(evb->data, "id"));
    }

    if (eva->event == QAPI_EVENT_QUORUM_REPORT_BAD) {
        return !strcmp(qdict_get_str(eva->data, "node-name"),
                       qdict_get_str(evb->data, "node-name"));
    }

    return TRUE;
}

int monitor_suspend(Monitor *mon)
{
    if (monitor_is_hmp_non_interactive(mon)) {
        return -ENOTTY;
    }

    qatomic_inc(&mon->suspend_cnt);

    if (mon->use_io_thread) {
        /*
         * Kick I/O thread to make sure this takes effect.  It'll be
         * evaluated again in prepare() of the watch object.
         */
        aio_notify(iothread_get_aio_context(mon_iothread));
    }

    trace_monitor_suspend(mon, 1);
    return 0;
}

static void monitor_accept_input(void *opaque)
{
    Monitor *mon = opaque;

    qemu_chr_fe_accept_input(&mon->chr);
}

void monitor_resume(Monitor *mon)
{
    if (monitor_is_hmp_non_interactive(mon)) {
        return;
    }

    if (qatomic_dec_fetch(&mon->suspend_cnt) == 0) {
        AioContext *ctx;

        if (mon->use_io_thread) {
            ctx = iothread_get_aio_context(mon_iothread);
        } else {
            ctx = qemu_get_aio_context();
        }

        if (!monitor_is_qmp(mon)) {
            MonitorHMP *hmp_mon = container_of(mon, MonitorHMP, common);
            assert(hmp_mon->rs);
            readline_show_prompt(hmp_mon->rs);
        }

        aio_bh_schedule_oneshot(ctx, monitor_accept_input, mon);
    }

    trace_monitor_suspend(mon, -1);
}

int monitor_can_read(void *opaque)
{
    Monitor *mon = opaque;

    return !qatomic_mb_read(&mon->suspend_cnt);
}

void monitor_list_append(Monitor *mon)
{
    qemu_mutex_lock(&monitor_lock);
    /*
     * This prevents inserting new monitors during monitor_cleanup().
     * A cleaner solution would involve the main thread telling other
     * threads to terminate, waiting for their termination.
     */
    if (!monitor_destroyed) {
        QTAILQ_INSERT_HEAD(&mon_list, mon, entry);
        mon = NULL;
    }
    qemu_mutex_unlock(&monitor_lock);

    if (mon) {
        monitor_data_destroy(mon);
        g_free(mon);
    }
}

static void monitor_iothread_init(void)
{
    mon_iothread = iothread_create("mon_iothread", &error_abort);
}

void monitor_data_init(Monitor *mon, bool is_qmp, bool skip_flush,
                       bool use_io_thread)
{
    if (use_io_thread && !mon_iothread) {
        monitor_iothread_init();
    }
    qemu_mutex_init(&mon->mon_lock);
    mon->is_qmp = is_qmp;
    mon->outbuf = qstring_new();
    mon->skip_flush = skip_flush;
    mon->use_io_thread = use_io_thread;
}

void monitor_data_destroy(Monitor *mon)
{
    g_free(mon->mon_cpu_path);
    qemu_chr_fe_deinit(&mon->chr, false);
    if (monitor_is_qmp(mon)) {
        monitor_data_destroy_qmp(container_of(mon, MonitorQMP, common));
    } else {
        readline_free(container_of(mon, MonitorHMP, common)->rs);
    }
    qobject_unref(mon->outbuf);
    qemu_mutex_destroy(&mon->mon_lock);
}

void monitor_cleanup(void)
{
    /*
     * We need to explicitly stop the I/O thread (but not destroy it),
     * clean up the monitor resources, then destroy the I/O thread since
     * we need to unregister from chardev below in
     * monitor_data_destroy(), and chardev is not thread-safe yet
     */
    if (mon_iothread) {
        iothread_stop(mon_iothread);
    }

    /* Flush output buffers and destroy monitors */
    qemu_mutex_lock(&monitor_lock);
    monitor_destroyed = true;
    while (!QTAILQ_EMPTY(&mon_list)) {
        Monitor *mon = QTAILQ_FIRST(&mon_list);
        QTAILQ_REMOVE(&mon_list, mon, entry);
        /* Permit QAPI event emission from character frontend release */
        qemu_mutex_unlock(&monitor_lock);
        monitor_flush(mon);
        monitor_data_destroy(mon);
        qemu_mutex_lock(&monitor_lock);
        g_free(mon);
    }
    qemu_mutex_unlock(&monitor_lock);

    /* QEMUBHs needs to be deleted before destroying the I/O thread */
    qemu_bh_delete(qmp_dispatcher_bh);
    qmp_dispatcher_bh = NULL;
    if (mon_iothread) {
        iothread_destroy(mon_iothread);
        mon_iothread = NULL;
    }
}

static void monitor_qapi_event_init(void)
{
    monitor_qapi_event_state = g_hash_table_new(qapi_event_throttle_hash,
                                                qapi_event_throttle_equal);
}

void monitor_init_globals_core(void)
{
    monitor_qapi_event_init();
    qemu_mutex_init(&monitor_lock);

    /*
     * The dispatcher BH must run in the main loop thread, since we
     * have commands assuming that context.  It would be nice to get
     * rid of those assumptions.
     */
    qmp_dispatcher_bh = aio_bh_new(iohandler_get_aio_context(),
                                   monitor_qmp_bh_dispatcher,
                                   NULL);
}

int monitor_init(MonitorOptions *opts, bool allow_hmp, Error **errp)
{
    Chardev *chr;
    Error *local_err = NULL;

    chr = qemu_chr_find(opts->chardev);
    if (chr == NULL) {
        error_setg(errp, "chardev \"%s\" not found", opts->chardev);
        return -1;
    }

    if (!opts->has_mode) {
        opts->mode = allow_hmp ? MONITOR_MODE_READLINE : MONITOR_MODE_CONTROL;
    }

    switch (opts->mode) {
    case MONITOR_MODE_CONTROL:
        monitor_init_qmp(chr, opts->pretty, &local_err);
        break;
    case MONITOR_MODE_READLINE:
        if (!allow_hmp) {
            error_setg(errp, "Only QMP is supported");
            return -1;
        }
        if (opts->pretty) {
            warn_report("'pretty' is deprecated for HMP monitors, it has no "
                        "effect and will be removed in future versions");
        }
        monitor_init_hmp(chr, true, &local_err);
        break;
    default:
        g_assert_not_reached();
    }

    if (local_err) {
        error_propagate(errp, local_err);
        return -1;
    }
    return 0;
}

int monitor_init_opts(QemuOpts *opts, Error **errp)
{
    Visitor *v;
    MonitorOptions *options;
    int ret;

    v = opts_visitor_new(opts);
    visit_type_MonitorOptions(v, NULL, &options, errp);
    visit_free(v);
    if (!options) {
        return -1;
    }

    ret = monitor_init(options, true, errp);
    qapi_free_MonitorOptions(options);
    return ret;
}

QemuOptsList qemu_mon_opts = {
    .name = "mon",
    .implied_opt_name = "chardev",
    .head = QTAILQ_HEAD_INITIALIZER(qemu_mon_opts.head),
    .desc = {
        {
            .name = "mode",
            .type = QEMU_OPT_STRING,
        },{
            .name = "chardev",
            .type = QEMU_OPT_STRING,
        },{
            .name = "pretty",
            .type = QEMU_OPT_BOOL,
        },
        { /* end of list */ }
    },
};