monitor: Split out monitor/qmp.c

Move QMP infrastructure from monitor/misc.c to monitor/qmp.c. This is
code that can be shared for all targets, so compile it only once.

The amount of function and particularly extern variables in
monitor_int.h is probably a bit larger than it needs to be, but this way
no non-trivial code modifications are needed. The interfaces between QMP
and the monitor core can be cleaned up later.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20190613153405.24769-11-kwolf@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[monitor_is_qmp() tidied up to make checkpatch.pl happy,
superfluous #include dropped]
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 406 insertions, 0 deletions

diff --git a/monitor/qmp.c b/monitor/qmp.c
new file mode 100644
index 0000000..7c3d081
--- /dev/null
+++ b/monitor/qmp.c
@@ -0,0 +1,406 @@
+/*
+ * 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-misc.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qjson.h"
+#include "qapi/qmp/qlist.h"
+#include "qapi/qmp/qstring.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_queues(MonitorQMP *mon)
+{
+    qemu_mutex_lock(&mon->qmp_queue_lock);
+    monitor_qmp_cleanup_req_queue_locked(mon);
+    qemu_mutex_unlock(&mon->qmp_queue_lock);
+}
+
+void qmp_send_response(MonitorQMP *mon, const QDict *rsp)
+{
+    const QObject *data = QOBJECT(rsp);
+    QString *json;
+
+    json = mon->common.flags & MONITOR_USE_PRETTY ?
+           qobject_to_json_pretty(data) : qobject_to_json(data);
+    assert(json != NULL);
+
+    qstring_append_chr(json, '\n');
+    monitor_puts(&mon->common, qstring_get_str(json));
+
+    qobject_unref(json);
+}
+
+/*
+ * Emit QMP response @rsp with ID @id 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);
+    }
+}
+
+static void monitor_qmp_dispatch(MonitorQMP *mon, QObject *req)
+{
+    Monitor *old_mon;
+    QDict *rsp;
+    QDict *error;
+
+    old_mon = cur_mon;
+    cur_mon = &mon->common;
+
+    rsp = qmp_dispatch(mon->commands, req, qmp_oob_enabled(mon));
+
+    cur_mon = old_mon;
+
+    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_mutex_lock(&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);
+    }
+
+    qemu_mutex_unlock(&monitor_lock);
+
+    return req_obj;
+}
+
+void monitor_qmp_bh_dispatcher(void *data)
+{
+    QMPRequest *req_obj = monitor_qmp_requests_pop_any_with_lock();
+    QDict *rsp;
+    bool need_resume;
+    MonitorQMP *mon;
+
+    if (!req_obj) {
+        return;
+    }
+
+    mon = req_obj->mon;
+    /*  qmp_oob_enabled() might change after "qmp_capabilities" */
+    need_resume = !qmp_oob_enabled(mon) ||
+        mon->qmp_requests->length == QMP_REQ_QUEUE_LEN_MAX - 1;
+    qemu_mutex_unlock(&mon->qmp_queue_lock);
+    if (req_obj->req) {
+        QDict *qdict = qobject_to(QDict, req_obj->req);
+        QObject *id = qdict ? qdict_get(qdict, "id") : NULL;
+        trace_monitor_qmp_cmd_in_band(qobject_get_try_str(id) ?: "");
+        monitor_qmp_dispatch(mon, req_obj->req);
+    } else {
+        assert(req_obj->err);
+        rsp = qmp_error_response(req_obj->err);
+        req_obj->err = NULL;
+        monitor_qmp_respond(mon, rsp);
+        qobject_unref(rsp);
+    }
+
+    if (need_resume) {
+        /* Pairs with the monitor_suspend() in handle_qmp_command() */
+        monitor_resume(&mon->common);
+    }
+    qmp_request_free(req_obj);
+
+    /* Reschedule instead of looping so the main loop stays responsive */
+    qemu_bh_schedule(qmp_dispatcher_bh);
+}
+
+static void handle_qmp_command(void *opaque, QObject *req, Error *err)
+{
+    MonitorQMP *mon = opaque;
+    QObject *id = NULL;
+    QDict *qdict;
+    QMPRequest *req_obj;
+
+    assert(!req != !err);
+
+    qdict = qobject_to(QDict, req);
+    if (qdict) {
+        id = qdict_get(qdict, "id");
+    } /* else will fail qmp_dispatch() */
+
+    if (req && trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
+        QString *req_json = qobject_to_json(req);
+        trace_handle_qmp_command(mon, qstring_get_str(req_json));
+        qobject_unref(req_json);
+    }
+
+    if (qdict && qmp_is_oob(qdict)) {
+        /* OOB commands are executed immediately */
+        trace_monitor_qmp_cmd_out_of_band(qobject_get_try_str(id) ?: "");
+        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. */
+    qemu_mutex_lock(&mon->qmp_queue_lock);
+
+    /*
+     * Suspend the monitor when we can't queue more requests after
+     * this one.  Dequeuing in monitor_qmp_bh_dispatcher() 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.
+     */
+    assert(mon->qmp_requests->length < QMP_REQ_QUEUE_LEN_MAX);
+    g_queue_push_tail(mon->qmp_requests, req_obj);
+    qemu_mutex_unlock(&mon->qmp_queue_lock);
+
+    /* Kick the dispatcher routine */
+    qemu_bh_schedule(qmp_dispatcher_bh);
+}
+
+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;
+    QMPCapability cap;
+
+    qmp_marshal_query_version(NULL, &ver, NULL);
+
+    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, int 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_queues(mon);
+        json_message_parser_destroy(&mon->parser);
+        json_message_parser_init(&mon->parser, handle_qmp_command,
+                                 mon, NULL);
+        mon_refcount--;
+        monitor_fdsets_cleanup();
+        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, int flags)
+{
+    MonitorQMP *mon = g_new0(MonitorQMP, 1);
+
+    /* Only HMP supports readline */
+    assert(!(flags & MONITOR_USE_READLINE));
+
+    /* Note: we run QMP monitor in I/O thread when @chr supports that */
+    monitor_data_init(&mon->common, flags, false,
+                      qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_GCONTEXT));
+
+    qemu_mutex_init(&mon->qmp_queue_lock);
+    mon->qmp_requests = g_queue_new();
+
+    qemu_chr_fe_init(&mon->common.chr, chr, &error_abort);
+    qemu_chr_fe_set_echo(&mon->common.chr, true);
+
+    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);
+    }
+}