aboutsummaryrefslogtreecommitdiff
path: root/monitor/qmp.c
blob: 092c527b6fc9c6363f4bf81d85736144b656d038 (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
/*
 * 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 "chardev/char-io.h"
#include "monitor-internal.h"
#include "qapi/error.h"
#include "qapi/qapi-commands-control.h"
#include "qapi/qmp/qdict.h"
#include "qapi/qmp/qjson.h"
#include "qapi/qmp/qlist.h"
#include "trace.h"

struct QMPRequest {
    /* Owner of the request */
    MonitorQMP *mon;
    /*
     * Request object to be handled or Error to be reported
     * (exactly one of them is non-null)
     */
    QObject *req;
    Error *err;
};
typedef struct QMPRequest QMPRequest;

QmpCommandList qmp_commands, qmp_cap_negotiation_commands;

static bool qmp_oob_enabled(MonitorQMP *mon)
{
    return mon->capab[QMP_CAPABILITY_OOB];
}

static void monitor_qmp_caps_reset(MonitorQMP *mon)
{
    memset(mon->capab_offered, 0, sizeof(mon->capab_offered));
    memset(mon->capab, 0, sizeof(mon->capab));
    mon->capab_offered[QMP_CAPABILITY_OOB] = mon->common.use_io_thread;
}

static void qmp_request_free(QMPRequest *req)
{
    qobject_unref(req->req);
    error_free(req->err);
    g_free(req);
}

/* Caller must hold mon->qmp.qmp_queue_lock */
static void monitor_qmp_cleanup_req_queue_locked(MonitorQMP *mon)
{
    while (!g_queue_is_empty(mon->qmp_requests)) {
        qmp_request_free(g_queue_pop_head(mon->qmp_requests));
    }
}

static void monitor_qmp_cleanup_queue_and_resume(MonitorQMP *mon)
{
    QEMU_LOCK_GUARD(&mon->qmp_queue_lock);

    /*
     * Same condition as in monitor_qmp_dispatcher_co(), but before
     * removing an element from the queue (hence no `- 1`).
     * Also, the queue should not be empty either, otherwise the
     * monitor hasn't been suspended yet (or was already resumed).
     */
    bool need_resume = (!qmp_oob_enabled(mon) ||
        mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX)
        && !g_queue_is_empty(mon->qmp_requests);

    monitor_qmp_cleanup_req_queue_locked(mon);

    if (need_resume) {
        /*
         * handle_qmp_command() suspended the monitor because the
         * request queue filled up, to be resumed when the queue has
         * space again.  We just emptied it; resume the monitor.
         *
         * Without this, the monitor would remain suspended forever
         * when we get here while the monitor is suspended.  An
         * unfortunately timed CHR_EVENT_CLOSED can do the trick.
         */
        monitor_resume(&mon->common);
    }

}

void qmp_send_response(MonitorQMP *mon, const QDict *rsp)
{
    const QObject *data = QOBJECT(rsp);
    GString *json;

    json = qobject_to_json_pretty(data, mon->pretty);
    assert(json != NULL);
    trace_monitor_qmp_respond(mon, json->str);

    g_string_append_c(json, '\n');
    monitor_puts(&mon->common, json->str);

    g_string_free(json, true);
}

/*
 * Emit QMP response @rsp to @mon.
 * Null @rsp can only happen for commands with QCO_NO_SUCCESS_RESP.
 * Nothing is emitted then.
 */
static void monitor_qmp_respond(MonitorQMP *mon, QDict *rsp)
{
    if (rsp) {
        qmp_send_response(mon, rsp);
    }
}

/*
 * Runs outside of coroutine context for OOB commands, but in
 * coroutine context for everything else.
 */
static void monitor_qmp_dispatch(MonitorQMP *mon, QObject *req)
{
    QDict *rsp;
    QDict *error;

    rsp = qmp_dispatch(mon->commands, req, qmp_oob_enabled(mon),
                       &mon->common);

    if (mon->commands == &qmp_cap_negotiation_commands) {
        error = qdict_get_qdict(rsp, "error");
        if (error
            && !g_strcmp0(qdict_get_try_str(error, "class"),
                    QapiErrorClass_str(ERROR_CLASS_COMMAND_NOT_FOUND))) {
            /* Provide a more useful error message */
            qdict_del(error, "desc");
            qdict_put_str(error, "desc", "Expecting capabilities negotiation"
                          " with 'qmp_capabilities'");
        }
    }

    monitor_qmp_respond(mon, rsp);
    qobject_unref(rsp);
}

/*
 * Pop a QMP request from a monitor request queue.
 * Return the request, or NULL all request queues are empty.
 * We are using round-robin fashion to pop the request, to avoid
 * processing commands only on a very busy monitor.  To achieve that,
 * when we process one request on a specific monitor, we put that
 * monitor to the end of mon_list queue.
 *
 * Note: if the function returned with non-NULL, then the caller will
 * be with qmp_mon->qmp_queue_lock held, and the caller is responsible
 * to release it.
 */
static QMPRequest *monitor_qmp_requests_pop_any_with_lock(void)
{
    QMPRequest *req_obj = NULL;
    Monitor *mon;
    MonitorQMP *qmp_mon;

    QEMU_LOCK_GUARD(&monitor_lock);

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

        qmp_mon = container_of(mon, MonitorQMP, common);
        qemu_mutex_lock(&qmp_mon->qmp_queue_lock);
        req_obj = g_queue_pop_head(qmp_mon->qmp_requests);
        if (req_obj) {
            /* With the lock of corresponding queue held */
            break;
        }
        qemu_mutex_unlock(&qmp_mon->qmp_queue_lock);
    }

    if (req_obj) {
        /*
         * We found one request on the monitor. Degrade this monitor's
         * priority to lowest by re-inserting it to end of queue.
         */
        QTAILQ_REMOVE(&mon_list, mon, entry);
        QTAILQ_INSERT_TAIL(&mon_list, mon, entry);
    }

    return req_obj;
}

void coroutine_fn monitor_qmp_dispatcher_co(void *data)
{
    QMPRequest *req_obj = NULL;
    QDict *rsp;
    bool oob_enabled;
    MonitorQMP *mon;

    while (true) {
        assert(qatomic_mb_read(&qmp_dispatcher_co_busy) == true);

        /*
         * Mark the dispatcher as not busy already here so that we
         * don't miss any new requests coming in the middle of our
         * processing.
         */
        qatomic_mb_set(&qmp_dispatcher_co_busy, false);

        /* On shutdown, don't take any more requests from the queue */
        if (qmp_dispatcher_co_shutdown) {
            return;
        }

        while (!(req_obj = monitor_qmp_requests_pop_any_with_lock())) {
            /*
             * No more requests to process.  Wait to be reentered from
             * handle_qmp_command() when it pushes more requests, or
             * from monitor_cleanup() when it requests shutdown.
             */
            if (!qmp_dispatcher_co_shutdown) {
                qemu_coroutine_yield();

                /*
                 * busy must be set to true again by whoever
                 * rescheduled us to avoid double scheduling
                 */
                assert(qatomic_xchg(&qmp_dispatcher_co_busy, false) == true);
            }

            /*
             * qmp_dispatcher_co_shutdown may have changed if we
             * yielded and were reentered from monitor_cleanup()
             */
            if (qmp_dispatcher_co_shutdown) {
                return;
            }
        }

        trace_monitor_qmp_in_band_dequeue(req_obj,
                                          req_obj->mon->qmp_requests->length);

        /*
         * @req_obj has a request, we hold req_obj->mon->qmp_queue_lock
         */

        mon = req_obj->mon;

        /*
         * We need to resume the monitor if handle_qmp_command()
         * suspended it.  Two cases:
         * 1. OOB enabled: mon->qmp_requests has no more space
         *    Resume right away, so that OOB commands can get executed while
         *    this request is being processed.
         * 2. OOB disabled: always
         *    Resume only after we're done processing the request,
         * We need to save qmp_oob_enabled() for later, because
         * qmp_qmp_capabilities() can change it.
         */
        oob_enabled = qmp_oob_enabled(mon);
        if (oob_enabled
            && mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1) {
            monitor_resume(&mon->common);
        }

        /*
         * Drop the queue mutex now, before yielding, otherwise we might
         * deadlock if the main thread tries to lock it.
         */
        qemu_mutex_unlock(&mon->qmp_queue_lock);

        if (qatomic_xchg(&qmp_dispatcher_co_busy, true) == true) {
            /*
             * Someone rescheduled us (probably because a new requests
             * came in), but we didn't actually yield. Do that now,
             * only to be immediately reentered and removed from the
             * list of scheduled coroutines.
             */
            qemu_coroutine_yield();
        }

        /*
         * Move the coroutine from iohandler_ctx to qemu_aio_context for
         * executing the command handler so that it can make progress if it
         * involves an AIO_WAIT_WHILE().
         */
        aio_co_schedule(qemu_get_aio_context(), qmp_dispatcher_co);
        qemu_coroutine_yield();

        /* Process request */
        if (req_obj->req) {
            if (trace_event_get_state(TRACE_MONITOR_QMP_CMD_IN_BAND)) {
                QDict *qdict = qobject_to(QDict, req_obj->req);
                QObject *id = qdict ? qdict_get(qdict, "id") : NULL;
                GString *id_json;

                id_json = id ? qobject_to_json(id) : g_string_new(NULL);
                trace_monitor_qmp_cmd_in_band(id_json->str);
                g_string_free(id_json, true);
            }
            monitor_qmp_dispatch(mon, req_obj->req);
        } else {
            assert(req_obj->err);
            trace_monitor_qmp_err_in_band(error_get_pretty(req_obj->err));
            rsp = qmp_error_response(req_obj->err);
            req_obj->err = NULL;
            monitor_qmp_respond(mon, rsp);
            qobject_unref(rsp);
        }

        if (!oob_enabled) {
            monitor_resume(&mon->common);
        }

        qmp_request_free(req_obj);

        /*
         * Yield and reschedule so the main loop stays responsive.
         *
         * Move back to iohandler_ctx so that nested event loops for
         * qemu_aio_context don't start new monitor commands.
         */
        aio_co_schedule(iohandler_get_aio_context(), qmp_dispatcher_co);
        qemu_coroutine_yield();
    }
}

static void handle_qmp_command(void *opaque, QObject *req, Error *err)
{
    MonitorQMP *mon = opaque;
    QDict *qdict = qobject_to(QDict, req);
    QMPRequest *req_obj;

    assert(!req != !err);

    if (req && trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
        GString *req_json = qobject_to_json(req);
        trace_handle_qmp_command(mon, req_json->str);
        g_string_free(req_json, true);
    }

    if (qdict && qmp_is_oob(qdict)) {
        /* OOB commands are executed immediately */
        if (trace_event_get_state(TRACE_MONITOR_QMP_CMD_OUT_OF_BAND)) {
            QObject *id = qdict_get(qdict, "id");
            GString *id_json;

            id_json = id ? qobject_to_json(id) : g_string_new(NULL);
            trace_monitor_qmp_cmd_out_of_band(id_json->str);
            g_string_free(id_json, true);
        }
        monitor_qmp_dispatch(mon, req);
        qobject_unref(req);
        return;
    }

    req_obj = g_new0(QMPRequest, 1);
    req_obj->mon = mon;
    req_obj->req = req;
    req_obj->err = err;

    /* Protect qmp_requests and fetching its length. */
    WITH_QEMU_LOCK_GUARD(&mon->qmp_queue_lock) {

        /*
         * Suspend the monitor when we can't queue more requests after
         * this one.  Dequeuing in monitor_qmp_dispatcher_co() or
         * monitor_qmp_cleanup_queue_and_resume() will resume it.
         * Note that when OOB is disabled, we queue at most one command,
         * for backward compatibility.
         */
        if (!qmp_oob_enabled(mon) ||
            mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1) {
            monitor_suspend(&mon->common);
        }

        /*
         * Put the request to the end of queue so that requests will be
         * handled in time order.  Ownership for req_obj, req,
         * etc. will be delivered to the handler side.
         */
        trace_monitor_qmp_in_band_enqueue(req_obj, mon,
                                          mon->qmp_requests->length);
        assert(mon->qmp_requests->length < QMP_REQ_QUEUE_LEN_MAX);
        g_queue_push_tail(mon->qmp_requests, req_obj);
    }

    /* Kick the dispatcher routine */
    if (!qatomic_xchg(&qmp_dispatcher_co_busy, true)) {
        aio_co_wake(qmp_dispatcher_co);
    }
}

static void monitor_qmp_read(void *opaque, const uint8_t *buf, int size)
{
    MonitorQMP *mon = opaque;

    json_message_parser_feed(&mon->parser, (const char *) buf, size);
}

static QDict *qmp_greeting(MonitorQMP *mon)
{
    QList *cap_list = qlist_new();
    QObject *ver = NULL;
    QDict *args;
    QMPCapability cap;

    args = qdict_new();
    qmp_marshal_query_version(args, &ver, NULL);
    qobject_unref(args);

    for (cap = 0; cap < QMP_CAPABILITY__MAX; cap++) {
        if (mon->capab_offered[cap]) {
            qlist_append_str(cap_list, QMPCapability_str(cap));
        }
    }

    return qdict_from_jsonf_nofail(
        "{'QMP': {'version': %p, 'capabilities': %p}}",
        ver, cap_list);
}

static void monitor_qmp_event(void *opaque, QEMUChrEvent event)
{
    QDict *data;
    MonitorQMP *mon = opaque;

    switch (event) {
    case CHR_EVENT_OPENED:
        mon->commands = &qmp_cap_negotiation_commands;
        monitor_qmp_caps_reset(mon);
        data = qmp_greeting(mon);
        qmp_send_response(mon, data);
        qobject_unref(data);
        mon_refcount++;
        break;
    case CHR_EVENT_CLOSED:
        /*
         * Note: this is only useful when the output of the chardev
         * backend is still open.  For example, when the backend is
         * stdio, it's possible that stdout is still open when stdin
         * is closed.
         */
        monitor_qmp_cleanup_queue_and_resume(mon);
        json_message_parser_destroy(&mon->parser);
        json_message_parser_init(&mon->parser, handle_qmp_command,
                                 mon, NULL);
        mon_refcount--;
        monitor_fdsets_cleanup();
        break;
    case CHR_EVENT_BREAK:
    case CHR_EVENT_MUX_IN:
    case CHR_EVENT_MUX_OUT:
        /* Ignore */
        break;
    }
}

void monitor_data_destroy_qmp(MonitorQMP *mon)
{
    json_message_parser_destroy(&mon->parser);
    qemu_mutex_destroy(&mon->qmp_queue_lock);
    monitor_qmp_cleanup_req_queue_locked(mon);
    g_queue_free(mon->qmp_requests);
}

static void monitor_qmp_setup_handlers_bh(void *opaque)
{
    MonitorQMP *mon = opaque;
    GMainContext *context;

    assert(mon->common.use_io_thread);
    context = iothread_get_g_main_context(mon_iothread);
    assert(context);
    qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
                             monitor_qmp_read, monitor_qmp_event,
                             NULL, &mon->common, context, true);
    monitor_list_append(&mon->common);
}

void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)
{
    MonitorQMP *mon = g_new0(MonitorQMP, 1);

    if (!qemu_chr_fe_init(&mon->common.chr, chr, errp)) {
        g_free(mon);
        return;
    }
    qemu_chr_fe_set_echo(&mon->common.chr, true);

    /* Note: we run QMP monitor in I/O thread when @chr supports that */
    monitor_data_init(&mon->common, true, false,
                      qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_GCONTEXT));

    mon->pretty = pretty;

    qemu_mutex_init(&mon->qmp_queue_lock);
    mon->qmp_requests = g_queue_new();

    json_message_parser_init(&mon->parser, handle_qmp_command, mon, NULL);
    if (mon->common.use_io_thread) {
        /*
         * Make sure the old iowatch is gone.  It's possible when
         * e.g. the chardev is in client mode, with wait=on.
         */
        remove_fd_in_watch(chr);
        /*
         * We can't call qemu_chr_fe_set_handlers() directly here
         * since chardev might be running in the monitor I/O
         * thread.  Schedule a bottom half.
         */
        aio_bh_schedule_oneshot(iothread_get_aio_context(mon_iothread),
                                monitor_qmp_setup_handlers_bh, mon);
        /* The bottom half will add @mon to @mon_list */
    } else {
        qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read,
                                 monitor_qmp_read, monitor_qmp_event,
                                 NULL, &mon->common, NULL, true);
        monitor_list_append(&mon->common);
    }
}