Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 538 insertions, 0 deletions

diff --git a/monitor/qmp.c b/monitor/qmp.c
new file mode 100644
index 000000000..092c527b6
--- /dev/null
+++ b/monitor/qmp.c
@@ -0,0 +1,538 @@
+/*
+ * 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);
+    }
+}