qemu

qmp.c (17490B)

---

 /*
  * 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);
     }
 }