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

14 files changed, 2341 insertions, 0 deletions

diff --git a/replay/meson.build b/replay/meson.build
new file mode 100644
index 000000000..21aefad22
--- /dev/null
+++ b/replay/meson.build
@@ -0,0 +1,13 @@
+softmmu_ss.add(when: 'CONFIG_TCG', if_true: files(
+  'replay.c',
+  'replay-internal.c',
+  'replay-events.c',
+  'replay-time.c',
+  'replay-input.c',
+  'replay-char.c',
+  'replay-snapshot.c',
+  'replay-net.c',
+  'replay-audio.c',
+  'replay-random.c',
+  'replay-debugging.c',
+), if_false: files('stubs-system.c'))
diff --git a/replay/replay-audio.c b/replay/replay-audio.c
new file mode 100644
index 000000000..91854f02e
--- /dev/null
+++ b/replay/replay-audio.c
@@ -0,0 +1,72 @@
+/*
+ * replay-audio.c
+ *
+ * Copyright (c) 2010-2017 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "sysemu/replay.h"
+#include "replay-internal.h"
+#include "audio/audio.h"
+
+void replay_audio_out(size_t *played)
+{
+    if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
+        replay_save_instructions();
+        replay_put_event(EVENT_AUDIO_OUT);
+        replay_put_qword(*played);
+    } else if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
+        replay_account_executed_instructions();
+        if (replay_next_event_is(EVENT_AUDIO_OUT)) {
+            *played = replay_get_qword();
+            replay_finish_event();
+        } else {
+            error_report("Missing audio out event in the replay log");
+            abort();
+        }
+    }
+}
+
+void replay_audio_in(size_t *recorded, void *samples, size_t *wpos, size_t size)
+{
+    int pos;
+    uint64_t left, right;
+    if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
+        replay_save_instructions();
+        replay_put_event(EVENT_AUDIO_IN);
+        replay_put_qword(*recorded);
+        replay_put_qword(*wpos);
+        for (pos = (*wpos - *recorded + size) % size ; pos != *wpos
+             ; pos = (pos + 1) % size) {
+            audio_sample_to_uint64(samples, pos, &left, &right);
+            replay_put_qword(left);
+            replay_put_qword(right);
+        }
+    } else if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
+        replay_account_executed_instructions();
+        if (replay_next_event_is(EVENT_AUDIO_IN)) {
+            *recorded = replay_get_qword();
+            *wpos = replay_get_qword();
+            for (pos = (*wpos - *recorded + size) % size ; pos != *wpos
+                 ; pos = (pos + 1) % size) {
+                left = replay_get_qword();
+                right = replay_get_qword();
+                audio_sample_from_uint64(samples, pos, left, right);
+            }
+            replay_finish_event();
+        } else {
+            error_report("Missing audio in event in the replay log");
+            abort();
+        }
+    }
+}
diff --git a/replay/replay-char.c b/replay/replay-char.c
new file mode 100644
index 000000000..dc0002367
--- /dev/null
+++ b/replay/replay-char.c
@@ -0,0 +1,158 @@
+/*
+ * replay-char.c
+ *
+ * Copyright (c) 2010-2016 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "sysemu/replay.h"
+#include "replay-internal.h"
+#include "chardev/char.h"
+
+/* Char drivers that generate qemu_chr_be_write events
+   that should be saved into the log. */
+static Chardev **char_drivers;
+static int drivers_count;
+
+/* Char event attributes. */
+typedef struct CharEvent {
+    int id;
+    uint8_t *buf;
+    size_t len;
+} CharEvent;
+
+static int find_char_driver(Chardev *chr)
+{
+    int i = 0;
+    for ( ; i < drivers_count ; ++i) {
+        if (char_drivers[i] == chr) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+void replay_register_char_driver(Chardev *chr)
+{
+    if (replay_mode == REPLAY_MODE_NONE) {
+        return;
+    }
+    char_drivers = g_realloc(char_drivers,
+                             sizeof(*char_drivers) * (drivers_count + 1));
+    char_drivers[drivers_count++] = chr;
+}
+
+void replay_chr_be_write(Chardev *s, uint8_t *buf, int len)
+{
+    CharEvent *event = g_malloc0(sizeof(CharEvent));
+
+    event->id = find_char_driver(s);
+    if (event->id < 0) {
+        fprintf(stderr, "Replay: cannot find char driver\n");
+        exit(1);
+    }
+    event->buf = g_malloc(len);
+    memcpy(event->buf, buf, len);
+    event->len = len;
+
+    replay_add_event(REPLAY_ASYNC_EVENT_CHAR_READ, event, NULL, 0);
+}
+
+void replay_event_char_read_run(void *opaque)
+{
+    CharEvent *event = (CharEvent *)opaque;
+
+    qemu_chr_be_write_impl(char_drivers[event->id], event->buf,
+                           (int)event->len);
+
+    g_free(event->buf);
+    g_free(event);
+}
+
+void replay_event_char_read_save(void *opaque)
+{
+    CharEvent *event = (CharEvent *)opaque;
+
+    replay_put_byte(event->id);
+    replay_put_array(event->buf, event->len);
+}
+
+void *replay_event_char_read_load(void)
+{
+    CharEvent *event = g_malloc0(sizeof(CharEvent));
+
+    event->id = replay_get_byte();
+    replay_get_array_alloc(&event->buf, &event->len);
+
+    return event;
+}
+
+void replay_char_write_event_save(int res, int offset)
+{
+    g_assert(replay_mutex_locked());
+
+    replay_save_instructions();
+    replay_put_event(EVENT_CHAR_WRITE);
+    replay_put_dword(res);
+    replay_put_dword(offset);
+}
+
+void replay_char_write_event_load(int *res, int *offset)
+{
+    g_assert(replay_mutex_locked());
+
+    replay_account_executed_instructions();
+    if (replay_next_event_is(EVENT_CHAR_WRITE)) {
+        *res = replay_get_dword();
+        *offset = replay_get_dword();
+        replay_finish_event();
+    } else {
+        error_report("Missing character write event in the replay log");
+        exit(1);
+    }
+}
+
+int replay_char_read_all_load(uint8_t *buf)
+{
+    g_assert(replay_mutex_locked());
+
+    if (replay_next_event_is(EVENT_CHAR_READ_ALL)) {
+        size_t size;
+        int res;
+        replay_get_array(buf, &size);
+        replay_finish_event();
+        res = (int)size;
+        assert(res >= 0);
+        return res;
+    } else if (replay_next_event_is(EVENT_CHAR_READ_ALL_ERROR)) {
+        int res = replay_get_dword();
+        replay_finish_event();
+        return res;
+    } else {
+        error_report("Missing character read all event in the replay log");
+        exit(1);
+    }
+}
+
+void replay_char_read_all_save_error(int res)
+{
+    g_assert(replay_mutex_locked());
+    assert(res < 0);
+    replay_save_instructions();
+    replay_put_event(EVENT_CHAR_READ_ALL_ERROR);
+    replay_put_dword(res);
+}
+
+void replay_char_read_all_save_buf(uint8_t *buf, int offset)
+{
+    g_assert(replay_mutex_locked());
+    replay_save_instructions();
+    replay_put_event(EVENT_CHAR_READ_ALL);
+    replay_put_array(buf, offset);
+}
diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c
new file mode 100644
index 000000000..1cde50e9f
--- /dev/null
+++ b/replay/replay-debugging.c
@@ -0,0 +1,334 @@
+/*
+ * replay-debugging.c
+ *
+ * Copyright (c) 2010-2020 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "sysemu/replay.h"
+#include "sysemu/runstate.h"
+#include "replay-internal.h"
+#include "monitor/hmp.h"
+#include "monitor/monitor.h"
+#include "qapi/qapi-commands-replay.h"
+#include "qapi/qmp/qdict.h"
+#include "qemu/timer.h"
+#include "block/snapshot.h"
+#include "migration/snapshot.h"
+
+static bool replay_is_debugging;
+static int64_t replay_last_breakpoint;
+static int64_t replay_last_snapshot;
+
+bool replay_running_debug(void)
+{
+    return replay_is_debugging;
+}
+
+void hmp_info_replay(Monitor *mon, const QDict *qdict)
+{
+    if (replay_mode == REPLAY_MODE_NONE) {
+        monitor_printf(mon, "Record/replay is not active\n");
+    } else {
+        monitor_printf(mon,
+            "%s execution '%s': instruction count = %"PRId64"\n",
+            replay_mode == REPLAY_MODE_RECORD ? "Recording" : "Replaying",
+            replay_get_filename(), replay_get_current_icount());
+    }
+}
+
+ReplayInfo *qmp_query_replay(Error **errp)
+{
+    ReplayInfo *retval = g_new0(ReplayInfo, 1);
+
+    retval->mode = replay_mode;
+    if (replay_get_filename()) {
+        retval->filename = g_strdup(replay_get_filename());
+        retval->has_filename = true;
+    }
+    retval->icount = replay_get_current_icount();
+    return retval;
+}
+
+static void replay_break(uint64_t icount, QEMUTimerCB callback, void *opaque)
+{
+    assert(replay_mode == REPLAY_MODE_PLAY);
+    assert(replay_mutex_locked());
+    assert(replay_break_icount >= replay_get_current_icount());
+    assert(callback);
+
+    replay_break_icount = icount;
+
+    if (replay_break_timer) {
+        timer_del(replay_break_timer);
+    }
+    replay_break_timer = timer_new_ns(QEMU_CLOCK_REALTIME,
+                                      callback, opaque);
+}
+
+static void replay_delete_break(void)
+{
+    assert(replay_mode == REPLAY_MODE_PLAY);
+    assert(replay_mutex_locked());
+
+    if (replay_break_timer) {
+        timer_free(replay_break_timer);
+        replay_break_timer = NULL;
+    }
+    replay_break_icount = -1ULL;
+}
+
+static void replay_stop_vm(void *opaque)
+{
+    vm_stop(RUN_STATE_PAUSED);
+    replay_delete_break();
+}
+
+void qmp_replay_break(int64_t icount, Error **errp)
+{
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        if (icount >= replay_get_current_icount()) {
+            replay_break(icount, replay_stop_vm, NULL);
+        } else {
+            error_setg(errp,
+                "cannot set breakpoint at the instruction in the past");
+        }
+    } else {
+        error_setg(errp, "setting the breakpoint is allowed only in play mode");
+    }
+}
+
+void hmp_replay_break(Monitor *mon, const QDict *qdict)
+{
+    int64_t icount = qdict_get_try_int(qdict, "icount", -1LL);
+    Error *err = NULL;
+
+    qmp_replay_break(icount, &err);
+    if (err) {
+        error_report_err(err);
+        return;
+    }
+}
+
+void qmp_replay_delete_break(Error **errp)
+{
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        replay_delete_break();
+    } else {
+        error_setg(errp, "replay breakpoints are allowed only in play mode");
+    }
+}
+
+void hmp_replay_delete_break(Monitor *mon, const QDict *qdict)
+{
+    Error *err = NULL;
+
+    qmp_replay_delete_break(&err);
+    if (err) {
+        error_report_err(err);
+        return;
+    }
+}
+
+static char *replay_find_nearest_snapshot(int64_t icount,
+                                          int64_t *snapshot_icount)
+{
+    BlockDriverState *bs;
+    QEMUSnapshotInfo *sn_tab;
+    QEMUSnapshotInfo *nearest = NULL;
+    char *ret = NULL;
+    int rv;
+    int nb_sns, i;
+    AioContext *aio_context;
+
+    *snapshot_icount = -1;
+
+    bs = bdrv_all_find_vmstate_bs(NULL, false, NULL, NULL);
+    if (!bs) {
+        goto fail;
+    }
+    aio_context = bdrv_get_aio_context(bs);
+
+    aio_context_acquire(aio_context);
+    nb_sns = bdrv_snapshot_list(bs, &sn_tab);
+    aio_context_release(aio_context);
+
+    for (i = 0; i < nb_sns; i++) {
+        rv = bdrv_all_has_snapshot(sn_tab[i].name, false, NULL, NULL);
+        if (rv < 0)
+            goto fail;
+        if (rv == 1) {
+            if (sn_tab[i].icount != -1ULL
+                && sn_tab[i].icount <= icount
+                && (!nearest || nearest->icount < sn_tab[i].icount)) {
+                nearest = &sn_tab[i];
+            }
+        }
+    }
+    if (nearest) {
+        ret = g_strdup(nearest->name);
+        *snapshot_icount = nearest->icount;
+    }
+    g_free(sn_tab);
+
+fail:
+    return ret;
+}
+
+static void replay_seek(int64_t icount, QEMUTimerCB callback, Error **errp)
+{
+    char *snapshot = NULL;
+    int64_t snapshot_icount;
+
+    if (replay_mode != REPLAY_MODE_PLAY) {
+        error_setg(errp, "replay must be enabled to seek");
+        return;
+    }
+
+    snapshot = replay_find_nearest_snapshot(icount, &snapshot_icount);
+    if (snapshot) {
+        if (icount < replay_get_current_icount()
+            || replay_get_current_icount() < snapshot_icount) {
+            vm_stop(RUN_STATE_RESTORE_VM);
+            load_snapshot(snapshot, NULL, false, NULL, errp);
+        }
+        g_free(snapshot);
+    }
+    if (replay_get_current_icount() <= icount) {
+        replay_break(icount, callback, NULL);
+        vm_start();
+    } else {
+        error_setg(errp, "cannot seek to the specified instruction count");
+    }
+}
+
+void qmp_replay_seek(int64_t icount, Error **errp)
+{
+    replay_seek(icount, replay_stop_vm, errp);
+}
+
+void hmp_replay_seek(Monitor *mon, const QDict *qdict)
+{
+    int64_t icount = qdict_get_try_int(qdict, "icount", -1LL);
+    Error *err = NULL;
+
+    qmp_replay_seek(icount, &err);
+    if (err) {
+        error_report_err(err);
+        return;
+    }
+}
+
+static void replay_stop_vm_debug(void *opaque)
+{
+    replay_is_debugging = false;
+    vm_stop(RUN_STATE_DEBUG);
+    replay_delete_break();
+}
+
+bool replay_reverse_step(void)
+{
+    Error *err = NULL;
+
+    assert(replay_mode == REPLAY_MODE_PLAY);
+
+    if (replay_get_current_icount() != 0) {
+        replay_seek(replay_get_current_icount() - 1,
+                    replay_stop_vm_debug, &err);
+        if (err) {
+            error_free(err);
+            return false;
+        }
+        replay_is_debugging = true;
+        return true;
+    }
+
+    return false;
+}
+
+static void replay_continue_end(void)
+{
+    replay_is_debugging = false;
+    vm_stop(RUN_STATE_DEBUG);
+    replay_delete_break();
+}
+
+static void replay_continue_stop(void *opaque)
+{
+    Error *err = NULL;
+    if (replay_last_breakpoint != -1LL) {
+        replay_seek(replay_last_breakpoint, replay_stop_vm_debug, &err);
+        if (err) {
+            error_free(err);
+            replay_continue_end();
+        }
+        return;
+    }
+    /*
+     * No breakpoints since the last snapshot.
+     * Find previous snapshot and try again.
+     */
+    if (replay_last_snapshot != 0) {
+        replay_seek(replay_last_snapshot - 1, replay_continue_stop, &err);
+        if (err) {
+            error_free(err);
+            replay_continue_end();
+        }
+        replay_last_snapshot = replay_get_current_icount();
+    } else {
+        /* Seek to the very first step */
+        replay_seek(0, replay_stop_vm_debug, &err);
+        if (err) {
+            error_free(err);
+            replay_continue_end();
+        }
+    }
+}
+
+bool replay_reverse_continue(void)
+{
+    Error *err = NULL;
+
+    assert(replay_mode == REPLAY_MODE_PLAY);
+
+    if (replay_get_current_icount() != 0) {
+        replay_seek(replay_get_current_icount() - 1,
+                    replay_continue_stop, &err);
+        if (err) {
+            error_free(err);
+            return false;
+        }
+        replay_last_breakpoint = -1LL;
+        replay_is_debugging = true;
+        replay_last_snapshot = replay_get_current_icount();
+        return true;
+    }
+
+    return false;
+}
+
+void replay_breakpoint(void)
+{
+    assert(replay_mode == REPLAY_MODE_PLAY);
+    replay_last_breakpoint = replay_get_current_icount();
+}
+
+void replay_gdb_attached(void)
+{
+    /*
+     * Create VM snapshot on temporary overlay to allow reverse
+     * debugging even if snapshots were not enabled.
+     */
+    if (replay_mode == REPLAY_MODE_PLAY
+        && !replay_snapshot) {
+        if (!save_snapshot("start_debugging", true, NULL, false, NULL, NULL)) {
+            /* Can't create the snapshot. Continue conventional debugging. */
+        }
+    }
+}
diff --git a/replay/replay-events.c b/replay/replay-events.c
new file mode 100644
index 000000000..15983dd25
--- /dev/null
+++ b/replay/replay-events.c
@@ -0,0 +1,335 @@
+/*
+ * replay-events.c
+ *
+ * Copyright (c) 2010-2015 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "sysemu/replay.h"
+#include "replay-internal.h"
+#include "block/aio.h"
+#include "ui/input.h"
+#include "hw/core/cpu.h"
+
+typedef struct Event {
+    ReplayAsyncEventKind event_kind;
+    void *opaque;
+    void *opaque2;
+    uint64_t id;
+
+    QTAILQ_ENTRY(Event) events;
+} Event;
+
+static QTAILQ_HEAD(, Event) events_list = QTAILQ_HEAD_INITIALIZER(events_list);
+static bool events_enabled;
+
+/* Functions */
+
+static void replay_run_event(Event *event)
+{
+    switch (event->event_kind) {
+    case REPLAY_ASYNC_EVENT_BH:
+        aio_bh_call(event->opaque);
+        break;
+    case REPLAY_ASYNC_EVENT_BH_ONESHOT:
+        ((QEMUBHFunc *)event->opaque)(event->opaque2);
+        break;
+    case REPLAY_ASYNC_EVENT_INPUT:
+        qemu_input_event_send_impl(NULL, (InputEvent *)event->opaque);
+        qapi_free_InputEvent((InputEvent *)event->opaque);
+        break;
+    case REPLAY_ASYNC_EVENT_INPUT_SYNC:
+        qemu_input_event_sync_impl();
+        break;
+    case REPLAY_ASYNC_EVENT_CHAR_READ:
+        replay_event_char_read_run(event->opaque);
+        break;
+    case REPLAY_ASYNC_EVENT_BLOCK:
+        aio_bh_call(event->opaque);
+        break;
+    case REPLAY_ASYNC_EVENT_NET:
+        replay_event_net_run(event->opaque);
+        break;
+    default:
+        error_report("Replay: invalid async event ID (%d) in the queue",
+                    event->event_kind);
+        exit(1);
+        break;
+    }
+}
+
+void replay_enable_events(void)
+{
+    if (replay_mode != REPLAY_MODE_NONE) {
+        events_enabled = true;
+    }
+}
+
+bool replay_has_events(void)
+{
+    return !QTAILQ_EMPTY(&events_list);
+}
+
+void replay_flush_events(void)
+{
+    if (replay_mode == REPLAY_MODE_NONE) {
+        return;
+    }
+
+    g_assert(replay_mutex_locked());
+
+    while (!QTAILQ_EMPTY(&events_list)) {
+        Event *event = QTAILQ_FIRST(&events_list);
+        replay_run_event(event);
+        QTAILQ_REMOVE(&events_list, event, events);
+        g_free(event);
+    }
+}
+
+void replay_disable_events(void)
+{
+    if (replay_mode != REPLAY_MODE_NONE) {
+        events_enabled = false;
+        /* Flush events queue before waiting of completion */
+        replay_flush_events();
+    }
+}
+
+/*! Adds specified async event to the queue */
+void replay_add_event(ReplayAsyncEventKind event_kind,
+                      void *opaque,
+                      void *opaque2, uint64_t id)
+{
+    assert(event_kind < REPLAY_ASYNC_COUNT);
+
+    if (!replay_file || replay_mode == REPLAY_MODE_NONE
+        || !events_enabled) {
+        Event e;
+        e.event_kind = event_kind;
+        e.opaque = opaque;
+        e.opaque2 = opaque2;
+        e.id = id;
+        replay_run_event(&e);
+        return;
+    }
+
+    Event *event = g_malloc0(sizeof(Event));
+    event->event_kind = event_kind;
+    event->opaque = opaque;
+    event->opaque2 = opaque2;
+    event->id = id;
+
+    g_assert(replay_mutex_locked());
+    QTAILQ_INSERT_TAIL(&events_list, event, events);
+    qemu_cpu_kick(first_cpu);
+}
+
+void replay_bh_schedule_event(QEMUBH *bh)
+{
+    if (events_enabled) {
+        uint64_t id = replay_get_current_icount();
+        replay_add_event(REPLAY_ASYNC_EVENT_BH, bh, NULL, id);
+    } else {
+        qemu_bh_schedule(bh);
+    }
+}
+
+void replay_bh_schedule_oneshot_event(AioContext *ctx,
+    QEMUBHFunc *cb, void *opaque)
+{
+    if (events_enabled) {
+        uint64_t id = replay_get_current_icount();
+        replay_add_event(REPLAY_ASYNC_EVENT_BH_ONESHOT, cb, opaque, id);
+    } else {
+        aio_bh_schedule_oneshot(ctx, cb, opaque);
+    }
+}
+
+void replay_add_input_event(struct InputEvent *event)
+{
+    replay_add_event(REPLAY_ASYNC_EVENT_INPUT, event, NULL, 0);
+}
+
+void replay_add_input_sync_event(void)
+{
+    replay_add_event(REPLAY_ASYNC_EVENT_INPUT_SYNC, NULL, NULL, 0);
+}
+
+void replay_block_event(QEMUBH *bh, uint64_t id)
+{
+    if (events_enabled) {
+        replay_add_event(REPLAY_ASYNC_EVENT_BLOCK, bh, NULL, id);
+    } else {
+        qemu_bh_schedule(bh);
+    }
+}
+
+static void replay_save_event(Event *event, int checkpoint)
+{
+    if (replay_mode != REPLAY_MODE_PLAY) {
+        /* put the event into the file */
+        replay_put_event(EVENT_ASYNC);
+        replay_put_byte(checkpoint);
+        replay_put_byte(event->event_kind);
+
+        /* save event-specific data */
+        switch (event->event_kind) {
+        case REPLAY_ASYNC_EVENT_BH:
+        case REPLAY_ASYNC_EVENT_BH_ONESHOT:
+            replay_put_qword(event->id);
+            break;
+        case REPLAY_ASYNC_EVENT_INPUT:
+            replay_save_input_event(event->opaque);
+            break;
+        case REPLAY_ASYNC_EVENT_INPUT_SYNC:
+            break;
+        case REPLAY_ASYNC_EVENT_CHAR_READ:
+            replay_event_char_read_save(event->opaque);
+            break;
+        case REPLAY_ASYNC_EVENT_BLOCK:
+            replay_put_qword(event->id);
+            break;
+        case REPLAY_ASYNC_EVENT_NET:
+            replay_event_net_save(event->opaque);
+            break;
+        default:
+            error_report("Unknown ID %" PRId64 " of replay event", event->id);
+            exit(1);
+        }
+    }
+}
+
+/* Called with replay mutex locked */
+void replay_save_events(int checkpoint)
+{
+    g_assert(replay_mutex_locked());
+    g_assert(checkpoint != CHECKPOINT_CLOCK_WARP_START);
+    g_assert(checkpoint != CHECKPOINT_CLOCK_VIRTUAL);
+    while (!QTAILQ_EMPTY(&events_list)) {
+        Event *event = QTAILQ_FIRST(&events_list);
+        replay_save_event(event, checkpoint);
+        replay_run_event(event);
+        QTAILQ_REMOVE(&events_list, event, events);
+        g_free(event);
+    }
+}
+
+static Event *replay_read_event(int checkpoint)
+{
+    Event *event;
+    if (replay_state.read_event_kind == -1) {
+        replay_state.read_event_checkpoint = replay_get_byte();
+        replay_state.read_event_kind = replay_get_byte();
+        replay_state.read_event_id = -1;
+        replay_check_error();
+    }
+
+    if (checkpoint != replay_state.read_event_checkpoint) {
+        return NULL;
+    }
+
+    /* Events that has not to be in the queue */
+    switch (replay_state.read_event_kind) {
+    case REPLAY_ASYNC_EVENT_BH:
+    case REPLAY_ASYNC_EVENT_BH_ONESHOT:
+        if (replay_state.read_event_id == -1) {
+            replay_state.read_event_id = replay_get_qword();
+        }
+        break;
+    case REPLAY_ASYNC_EVENT_INPUT:
+        event = g_malloc0(sizeof(Event));
+        event->event_kind = replay_state.read_event_kind;
+        event->opaque = replay_read_input_event();
+        return event;
+    case REPLAY_ASYNC_EVENT_INPUT_SYNC:
+        event = g_malloc0(sizeof(Event));
+        event->event_kind = replay_state.read_event_kind;
+        event->opaque = 0;
+        return event;
+    case REPLAY_ASYNC_EVENT_CHAR_READ:
+        event = g_malloc0(sizeof(Event));
+        event->event_kind = replay_state.read_event_kind;
+        event->opaque = replay_event_char_read_load();
+        return event;
+    case REPLAY_ASYNC_EVENT_BLOCK:
+        if (replay_state.read_event_id == -1) {
+            replay_state.read_event_id = replay_get_qword();
+        }
+        break;
+    case REPLAY_ASYNC_EVENT_NET:
+        event = g_malloc0(sizeof(Event));
+        event->event_kind = replay_state.read_event_kind;
+        event->opaque = replay_event_net_load();
+        return event;
+    default:
+        error_report("Unknown ID %d of replay event",
+            replay_state.read_event_kind);
+        exit(1);
+        break;
+    }
+
+    QTAILQ_FOREACH(event, &events_list, events) {
+        if (event->event_kind == replay_state.read_event_kind
+            && (replay_state.read_event_id == -1
+                || replay_state.read_event_id == event->id)) {
+            break;
+        }
+    }
+
+    if (event) {
+        QTAILQ_REMOVE(&events_list, event, events);
+    } else {
+        return NULL;
+    }
+
+    /* Read event-specific data */
+
+    return event;
+}
+
+/* Called with replay mutex locked */
+void replay_read_events(int checkpoint)
+{
+    g_assert(replay_mutex_locked());
+    while (replay_state.data_kind == EVENT_ASYNC) {
+        Event *event = replay_read_event(checkpoint);
+        if (!event) {
+            break;
+        }
+        replay_finish_event();
+        replay_state.read_event_kind = -1;
+        replay_run_event(event);
+
+        g_free(event);
+    }
+}
+
+void replay_init_events(void)
+{
+    replay_state.read_event_kind = -1;
+}
+
+void replay_finish_events(void)
+{
+    events_enabled = false;
+    replay_flush_events();
+}
+
+bool replay_events_enabled(void)
+{
+    return events_enabled;
+}
+
+uint64_t blkreplay_next_id(void)
+{
+    if (replay_events_enabled()) {
+        return replay_state.block_request_id++;
+    }
+    return 0;
+}
diff --git a/replay/replay-input.c b/replay/replay-input.c
new file mode 100644
index 000000000..1147e3d34
--- /dev/null
+++ b/replay/replay-input.c
@@ -0,0 +1,140 @@
+/*
+ * replay-input.c
+ *
+ * Copyright (c) 2010-2015 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "sysemu/replay.h"
+#include "replay-internal.h"
+#include "qemu/notify.h"
+#include "ui/input.h"
+#include "qapi/clone-visitor.h"
+#include "qapi/qapi-visit-ui.h"
+
+void replay_save_input_event(InputEvent *evt)
+{
+    InputKeyEvent *key;
+    InputBtnEvent *btn;
+    InputMoveEvent *move;
+    replay_put_dword(evt->type);
+
+    switch (evt->type) {
+    case INPUT_EVENT_KIND_KEY:
+        key = evt->u.key.data;
+        replay_put_dword(key->key->type);
+
+        switch (key->key->type) {
+        case KEY_VALUE_KIND_NUMBER:
+            replay_put_qword(key->key->u.number.data);
+            replay_put_byte(key->down);
+            break;
+        case KEY_VALUE_KIND_QCODE:
+            replay_put_dword(key->key->u.qcode.data);
+            replay_put_byte(key->down);
+            break;
+        case KEY_VALUE_KIND__MAX:
+            /* keep gcc happy */
+            break;
+        }
+        break;
+    case INPUT_EVENT_KIND_BTN:
+        btn = evt->u.btn.data;
+        replay_put_dword(btn->button);
+        replay_put_byte(btn->down);
+        break;
+    case INPUT_EVENT_KIND_REL:
+        move = evt->u.rel.data;
+        replay_put_dword(move->axis);
+        replay_put_qword(move->value);
+        break;
+    case INPUT_EVENT_KIND_ABS:
+        move = evt->u.abs.data;
+        replay_put_dword(move->axis);
+        replay_put_qword(move->value);
+        break;
+    case INPUT_EVENT_KIND__MAX:
+        /* keep gcc happy */
+        break;
+    }
+}
+
+InputEvent *replay_read_input_event(void)
+{
+    InputEvent evt;
+    KeyValue keyValue;
+    InputKeyEvent key;
+    key.key = &keyValue;
+    InputBtnEvent btn;
+    InputMoveEvent rel;
+    InputMoveEvent abs;
+
+    evt.type = replay_get_dword();
+    switch (evt.type) {
+    case INPUT_EVENT_KIND_KEY:
+        evt.u.key.data = &key;
+        evt.u.key.data->key->type = replay_get_dword();
+
+        switch (evt.u.key.data->key->type) {
+        case KEY_VALUE_KIND_NUMBER:
+            evt.u.key.data->key->u.number.data = replay_get_qword();
+            evt.u.key.data->down = replay_get_byte();
+            break;
+        case KEY_VALUE_KIND_QCODE:
+            evt.u.key.data->key->u.qcode.data = (QKeyCode)replay_get_dword();
+            evt.u.key.data->down = replay_get_byte();
+            break;
+        case KEY_VALUE_KIND__MAX:
+            /* keep gcc happy */
+            break;
+        }
+        break;
+    case INPUT_EVENT_KIND_BTN:
+        evt.u.btn.data = &btn;
+        evt.u.btn.data->button = (InputButton)replay_get_dword();
+        evt.u.btn.data->down = replay_get_byte();
+        break;
+    case INPUT_EVENT_KIND_REL:
+        evt.u.rel.data = &rel;
+        evt.u.rel.data->axis = (InputAxis)replay_get_dword();
+        evt.u.rel.data->value = replay_get_qword();
+        break;
+    case INPUT_EVENT_KIND_ABS:
+        evt.u.abs.data = &abs;
+        evt.u.abs.data->axis = (InputAxis)replay_get_dword();
+        evt.u.abs.data->value = replay_get_qword();
+        break;
+    case INPUT_EVENT_KIND__MAX:
+        /* keep gcc happy */
+        break;
+    }
+
+    return QAPI_CLONE(InputEvent, &evt);
+}
+
+void replay_input_event(QemuConsole *src, InputEvent *evt)
+{
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        /* Nothing */
+    } else if (replay_mode == REPLAY_MODE_RECORD) {
+        replay_add_input_event(QAPI_CLONE(InputEvent, evt));
+    } else {
+        qemu_input_event_send_impl(src, evt);
+    }
+}
+
+void replay_input_sync_event(void)
+{
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        /* Nothing */
+    } else if (replay_mode == REPLAY_MODE_RECORD) {
+        replay_add_input_sync_event();
+    } else {
+        qemu_input_event_sync_impl();
+    }
+}
diff --git a/replay/replay-internal.c b/replay/replay-internal.c
new file mode 100644
index 000000000..77d0c8232
--- /dev/null
+++ b/replay/replay-internal.c
@@ -0,0 +1,285 @@
+/*
+ * replay-internal.c
+ *
+ * Copyright (c) 2010-2015 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "sysemu/replay.h"
+#include "sysemu/runstate.h"
+#include "replay-internal.h"
+#include "qemu/error-report.h"
+#include "qemu/main-loop.h"
+
+/* Mutex to protect reading and writing events to the log.
+   data_kind and has_unread_data are also protected
+   by this mutex.
+   It also protects replay events queue which stores events to be
+   written or read to the log. */
+static QemuMutex lock;
+/* Condition and queue for fair ordering of mutex lock requests. */
+static QemuCond mutex_cond;
+static unsigned long mutex_head, mutex_tail;
+
+/* File for replay writing */
+static bool write_error;
+FILE *replay_file;
+
+static void replay_write_error(void)
+{
+    if (!write_error) {
+        error_report("replay write error");
+        write_error = true;
+    }
+}
+
+static void replay_read_error(void)
+{
+    error_report("error reading the replay data");
+    exit(1);
+}
+
+void replay_put_byte(uint8_t byte)
+{
+    if (replay_file) {
+        if (putc(byte, replay_file) == EOF) {
+            replay_write_error();
+        }
+    }
+}
+
+void replay_put_event(uint8_t event)
+{
+    assert(event < EVENT_COUNT);
+    replay_put_byte(event);
+}
+
+
+void replay_put_word(uint16_t word)
+{
+    replay_put_byte(word >> 8);
+    replay_put_byte(word);
+}
+
+void replay_put_dword(uint32_t dword)
+{
+    replay_put_word(dword >> 16);
+    replay_put_word(dword);
+}
+
+void replay_put_qword(int64_t qword)
+{
+    replay_put_dword(qword >> 32);
+    replay_put_dword(qword);
+}
+
+void replay_put_array(const uint8_t *buf, size_t size)
+{
+    if (replay_file) {
+        replay_put_dword(size);
+        if (fwrite(buf, 1, size, replay_file) != size) {
+            replay_write_error();
+        }
+    }
+}
+
+uint8_t replay_get_byte(void)
+{
+    uint8_t byte = 0;
+    if (replay_file) {
+        int r = getc(replay_file);
+        if (r == EOF) {
+            replay_read_error();
+        }
+        byte = r;
+    }
+    return byte;
+}
+
+uint16_t replay_get_word(void)
+{
+    uint16_t word = 0;
+    if (replay_file) {
+        word = replay_get_byte();
+        word = (word << 8) + replay_get_byte();
+    }
+
+    return word;
+}
+
+uint32_t replay_get_dword(void)
+{
+    uint32_t dword = 0;
+    if (replay_file) {
+        dword = replay_get_word();
+        dword = (dword << 16) + replay_get_word();
+    }
+
+    return dword;
+}
+
+int64_t replay_get_qword(void)
+{
+    int64_t qword = 0;
+    if (replay_file) {
+        qword = replay_get_dword();
+        qword = (qword << 32) + replay_get_dword();
+    }
+
+    return qword;
+}
+
+void replay_get_array(uint8_t *buf, size_t *size)
+{
+    if (replay_file) {
+        *size = replay_get_dword();
+        if (fread(buf, 1, *size, replay_file) != *size) {
+            replay_read_error();
+        }
+    }
+}
+
+void replay_get_array_alloc(uint8_t **buf, size_t *size)
+{
+    if (replay_file) {
+        *size = replay_get_dword();
+        *buf = g_malloc(*size);
+        if (fread(*buf, 1, *size, replay_file) != *size) {
+            replay_read_error();
+        }
+    }
+}
+
+void replay_check_error(void)
+{
+    if (replay_file) {
+        if (feof(replay_file)) {
+            error_report("replay file is over");
+            qemu_system_vmstop_request_prepare();
+            qemu_system_vmstop_request(RUN_STATE_PAUSED);
+        } else if (ferror(replay_file)) {
+            error_report("replay file is over or something goes wrong");
+            qemu_system_vmstop_request_prepare();
+            qemu_system_vmstop_request(RUN_STATE_INTERNAL_ERROR);
+        }
+    }
+}
+
+void replay_fetch_data_kind(void)
+{
+    if (replay_file) {
+        if (!replay_state.has_unread_data) {
+            replay_state.data_kind = replay_get_byte();
+            if (replay_state.data_kind == EVENT_INSTRUCTION) {
+                replay_state.instruction_count = replay_get_dword();
+            }
+            replay_check_error();
+            replay_state.has_unread_data = 1;
+            if (replay_state.data_kind >= EVENT_COUNT) {
+                error_report("Replay: unknown event kind %d",
+                             replay_state.data_kind);
+                exit(1);
+            }
+        }
+    }
+}
+
+void replay_finish_event(void)
+{
+    replay_state.has_unread_data = 0;
+    replay_fetch_data_kind();
+}
+
+static __thread bool replay_locked;
+
+void replay_mutex_init(void)
+{
+    qemu_mutex_init(&lock);
+    qemu_cond_init(&mutex_cond);
+    /* Hold the mutex while we start-up */
+    replay_locked = true;
+    ++mutex_tail;
+}
+
+bool replay_mutex_locked(void)
+{
+    return replay_locked;
+}
+
+/* Ordering constraints, replay_lock must be taken before BQL */
+void replay_mutex_lock(void)
+{
+    if (replay_mode != REPLAY_MODE_NONE) {
+        unsigned long id;
+        g_assert(!qemu_mutex_iothread_locked());
+        g_assert(!replay_mutex_locked());
+        qemu_mutex_lock(&lock);
+        id = mutex_tail++;
+        while (id != mutex_head) {
+            qemu_cond_wait(&mutex_cond, &lock);
+        }
+        replay_locked = true;
+        qemu_mutex_unlock(&lock);
+    }
+}
+
+void replay_mutex_unlock(void)
+{
+    if (replay_mode != REPLAY_MODE_NONE) {
+        g_assert(replay_mutex_locked());
+        qemu_mutex_lock(&lock);
+        ++mutex_head;
+        replay_locked = false;
+        qemu_cond_broadcast(&mutex_cond);
+        qemu_mutex_unlock(&lock);
+    }
+}
+
+void replay_advance_current_icount(uint64_t current_icount)
+{
+    int diff = (int)(current_icount - replay_state.current_icount);
+
+    /* Time can only go forward */
+    assert(diff >= 0);
+
+    if (replay_mode == REPLAY_MODE_RECORD) {
+        if (diff > 0) {
+            replay_put_event(EVENT_INSTRUCTION);
+            replay_put_dword(diff);
+            replay_state.current_icount += diff;
+        }
+    } else if (replay_mode == REPLAY_MODE_PLAY) {
+        if (diff > 0) {
+            replay_state.instruction_count -= diff;
+            replay_state.current_icount += diff;
+            if (replay_state.instruction_count == 0) {
+                assert(replay_state.data_kind == EVENT_INSTRUCTION);
+                replay_finish_event();
+                /* Wake up iothread. This is required because
+                    timers will not expire until clock counters
+                    will be read from the log. */
+                qemu_notify_event();
+            }
+        }
+        /* Execution reached the break step */
+        if (replay_break_icount == replay_state.current_icount) {
+            /* Cannot make callback directly from the vCPU thread */
+            timer_mod_ns(replay_break_timer,
+                qemu_clock_get_ns(QEMU_CLOCK_REALTIME));
+        }
+    }
+}
+
+/*! Saves cached instructions. */
+void replay_save_instructions(void)
+{
+    if (replay_file && replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
+        replay_advance_current_icount(replay_get_current_icount());
+    }
+}
diff --git a/replay/replay-internal.h b/replay/replay-internal.h
new file mode 100644
index 000000000..97649ed8d
--- /dev/null
+++ b/replay/replay-internal.h
@@ -0,0 +1,198 @@
+#ifndef REPLAY_INTERNAL_H
+#define REPLAY_INTERNAL_H
+
+/*
+ * replay-internal.h
+ *
+ * Copyright (c) 2010-2015 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+/* Any changes to order/number of events will need to bump REPLAY_VERSION */
+enum ReplayEvents {
+    /* for instruction event */
+    EVENT_INSTRUCTION,
+    /* for software interrupt */
+    EVENT_INTERRUPT,
+    /* for emulated exceptions */
+    EVENT_EXCEPTION,
+    /* for async events */
+    EVENT_ASYNC,
+    /* for shutdown requests, range allows recovery of ShutdownCause */
+    EVENT_SHUTDOWN,
+    EVENT_SHUTDOWN_LAST = EVENT_SHUTDOWN + SHUTDOWN_CAUSE__MAX,
+    /* for character device write event */
+    EVENT_CHAR_WRITE,
+    /* for character device read all event */
+    EVENT_CHAR_READ_ALL,
+    EVENT_CHAR_READ_ALL_ERROR,
+    /* for audio out event */
+    EVENT_AUDIO_OUT,
+    /* for audio in event */
+    EVENT_AUDIO_IN,
+    /* for random number generator */
+    EVENT_RANDOM,
+    /* for clock read/writes */
+    /* some of greater codes are reserved for clocks */
+    EVENT_CLOCK,
+    EVENT_CLOCK_LAST = EVENT_CLOCK + REPLAY_CLOCK_COUNT - 1,
+    /* for checkpoint event */
+    /* some of greater codes are reserved for checkpoints */
+    EVENT_CHECKPOINT,
+    EVENT_CHECKPOINT_LAST = EVENT_CHECKPOINT + CHECKPOINT_COUNT - 1,
+    /* end of log event */
+    EVENT_END,
+    EVENT_COUNT
+};
+
+/* Asynchronous events IDs */
+
+enum ReplayAsyncEventKind {
+    REPLAY_ASYNC_EVENT_BH,
+    REPLAY_ASYNC_EVENT_BH_ONESHOT,
+    REPLAY_ASYNC_EVENT_INPUT,
+    REPLAY_ASYNC_EVENT_INPUT_SYNC,
+    REPLAY_ASYNC_EVENT_CHAR_READ,
+    REPLAY_ASYNC_EVENT_BLOCK,
+    REPLAY_ASYNC_EVENT_NET,
+    REPLAY_ASYNC_COUNT
+};
+
+typedef enum ReplayAsyncEventKind ReplayAsyncEventKind;
+
+typedef struct ReplayState {
+    /*! Cached clock values. */
+    int64_t cached_clock[REPLAY_CLOCK_COUNT];
+    /*! Current icount - number of processed instructions. */
+    uint64_t current_icount;
+    /*! Number of instructions to be executed before other events happen. */
+    int instruction_count;
+    /*! Type of the currently executed event. */
+    unsigned int data_kind;
+    /*! Flag which indicates that event is not processed yet. */
+    unsigned int has_unread_data;
+    /*! Temporary variable for saving current log offset. */
+    uint64_t file_offset;
+    /*! Next block operation id.
+        This counter is global, because requests from different
+        block devices should not get overlapping ids. */
+    uint64_t block_request_id;
+    /*! Prior value of the host clock */
+    uint64_t host_clock_last;
+    /*! Asynchronous event type read from the log */
+    int32_t read_event_kind;
+    /*! Asynchronous event id read from the log */
+    uint64_t read_event_id;
+    /*! Asynchronous event checkpoint id read from the log */
+    int32_t read_event_checkpoint;
+} ReplayState;
+extern ReplayState replay_state;
+
+/* File for replay writing */
+extern FILE *replay_file;
+/* Instruction count of the replay breakpoint */
+extern uint64_t replay_break_icount;
+/* Timer for the replay breakpoint callback */
+extern QEMUTimer *replay_break_timer;
+
+void replay_put_byte(uint8_t byte);
+void replay_put_event(uint8_t event);
+void replay_put_word(uint16_t word);
+void replay_put_dword(uint32_t dword);
+void replay_put_qword(int64_t qword);
+void replay_put_array(const uint8_t *buf, size_t size);
+
+uint8_t replay_get_byte(void);
+uint16_t replay_get_word(void);
+uint32_t replay_get_dword(void);
+int64_t replay_get_qword(void);
+void replay_get_array(uint8_t *buf, size_t *size);
+void replay_get_array_alloc(uint8_t **buf, size_t *size);
+
+/* Mutex functions for protecting replay log file and ensuring
+ * synchronisation between vCPU and main-loop threads. */
+
+void replay_mutex_init(void);
+bool replay_mutex_locked(void);
+
+/*! Checks error status of the file. */
+void replay_check_error(void);
+
+/*! Finishes processing of the replayed event and fetches
+    the next event from the log. */
+void replay_finish_event(void);
+/*! Reads data type from the file and stores it in the
+    data_kind variable. */
+void replay_fetch_data_kind(void);
+
+/*! Advance replay_state.current_icount to the specified value. */
+void replay_advance_current_icount(uint64_t current_icount);
+/*! Saves queued events (like instructions and sound). */
+void replay_save_instructions(void);
+
+/*! Skips async events until some sync event will be found.
+    \return true, if event was found */
+bool replay_next_event_is(int event);
+
+/*! Reads next clock value from the file.
+    If clock kind read from the file is different from the parameter,
+    the value is not used. */
+void replay_read_next_clock(unsigned int kind);
+
+/* Asynchronous events queue */
+
+/*! Initializes events' processing internals */
+void replay_init_events(void);
+/*! Clears internal data structures for events handling */
+void replay_finish_events(void);
+/*! Returns true if there are any unsaved events in the queue */
+bool replay_has_events(void);
+/*! Saves events from queue into the file */
+void replay_save_events(int checkpoint);
+/*! Read events from the file into the input queue */
+void replay_read_events(int checkpoint);
+/*! Adds specified async event to the queue */
+void replay_add_event(ReplayAsyncEventKind event_kind, void *opaque,
+                      void *opaque2, uint64_t id);
+
+/* Input events */
+
+/*! Saves input event to the log */
+void replay_save_input_event(InputEvent *evt);
+/*! Reads input event from the log */
+InputEvent *replay_read_input_event(void);
+/*! Adds input event to the queue */
+void replay_add_input_event(struct InputEvent *event);
+/*! Adds input sync event to the queue */
+void replay_add_input_sync_event(void);
+
+/* Character devices */
+
+/*! Called to run char device read event. */
+void replay_event_char_read_run(void *opaque);
+/*! Writes char read event to the file. */
+void replay_event_char_read_save(void *opaque);
+/*! Reads char event read from the file. */
+void *replay_event_char_read_load(void);
+
+/* Network devices */
+
+/*! Called to run network event. */
+void replay_event_net_run(void *opaque);
+/*! Writes network event to the file. */
+void replay_event_net_save(void *opaque);
+/*! Reads network from the file. */
+void *replay_event_net_load(void);
+
+/* VMState-related functions */
+
+/* Registers replay VMState.
+   Should be called before virtual devices initialization
+   to make cached timers available for post_load functions. */
+void replay_vmstate_register(void);
+
+#endif
diff --git a/replay/replay-net.c b/replay/replay-net.c
new file mode 100644
index 000000000..3b70f71cf
--- /dev/null
+++ b/replay/replay-net.c
@@ -0,0 +1,101 @@
+/*
+ * replay-net.c
+ *
+ * Copyright (c) 2010-2016 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "sysemu/replay.h"
+#include "replay-internal.h"
+#include "net/net.h"
+#include "net/filter.h"
+#include "qemu/iov.h"
+
+struct ReplayNetState {
+    NetFilterState *nfs;
+    int id;
+};
+
+typedef struct NetEvent {
+    uint8_t id;
+    uint32_t flags;
+    uint8_t *data;
+    size_t size;
+} NetEvent;
+
+static NetFilterState **network_filters;
+static int network_filters_count;
+
+ReplayNetState *replay_register_net(NetFilterState *nfs)
+{
+    ReplayNetState *rns = g_new0(ReplayNetState, 1);
+    rns->nfs = nfs;
+    rns->id = network_filters_count++;
+    network_filters = g_realloc(network_filters,
+                                network_filters_count
+                                    * sizeof(*network_filters));
+    network_filters[network_filters_count - 1] = nfs;
+    return rns;
+}
+
+void replay_unregister_net(ReplayNetState *rns)
+{
+    network_filters[rns->id] = NULL;
+    g_free(rns);
+}
+
+void replay_net_packet_event(ReplayNetState *rns, unsigned flags,
+                             const struct iovec *iov, int iovcnt)
+{
+    NetEvent *event = g_new(NetEvent, 1);
+    event->flags = flags;
+    event->data = g_malloc(iov_size(iov, iovcnt));
+    event->size = iov_size(iov, iovcnt);
+    event->id = rns->id;
+    iov_to_buf(iov, iovcnt, 0, event->data, event->size);
+
+    replay_add_event(REPLAY_ASYNC_EVENT_NET, event, NULL, 0);
+}
+
+void replay_event_net_run(void *opaque)
+{
+    NetEvent *event = opaque;
+    struct iovec iov = {
+        .iov_base = (void *)event->data,
+        .iov_len = event->size
+    };
+
+    assert(event->id < network_filters_count);
+
+    qemu_netfilter_pass_to_next(network_filters[event->id]->netdev,
+        event->flags, &iov, 1, network_filters[event->id]);
+
+    g_free(event->data);
+    g_free(event);
+}
+
+void replay_event_net_save(void *opaque)
+{
+    NetEvent *event = opaque;
+
+    replay_put_byte(event->id);
+    replay_put_dword(event->flags);
+    replay_put_array(event->data, event->size);
+}
+
+void *replay_event_net_load(void)
+{
+    NetEvent *event = g_new(NetEvent, 1);
+
+    event->id = replay_get_byte();
+    event->flags = replay_get_dword();
+    replay_get_array_alloc(&event->data, &event->size);
+
+    return event;
+}
diff --git a/replay/replay-random.c b/replay/replay-random.c
new file mode 100644
index 000000000..afc7a0fcc
--- /dev/null
+++ b/replay/replay-random.c
@@ -0,0 +1,44 @@
+/*
+ * replay-random.c
+ *
+ * Copyright (c) 2010-2020 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "sysemu/replay.h"
+#include "replay-internal.h"
+
+void replay_save_random(int ret, void *buf, size_t len)
+{
+    g_assert(replay_mutex_locked());
+
+    replay_save_instructions();
+    replay_put_event(EVENT_RANDOM);
+    replay_put_dword(ret);
+    replay_put_array(buf, len);
+}
+
+int replay_read_random(void *buf, size_t len)
+{
+    int ret = 0;
+    g_assert(replay_mutex_locked());
+
+    replay_account_executed_instructions();
+    if (replay_next_event_is(EVENT_RANDOM)) {
+        size_t buf_size = 0;
+        ret = replay_get_dword();
+        replay_get_array(buf, &buf_size);
+        replay_finish_event();
+        g_assert(buf_size == len);
+    } else {
+        error_report("Missing random event in the replay log");
+        exit(1);
+    }
+    return ret;
+}
diff --git a/replay/replay-snapshot.c b/replay/replay-snapshot.c
new file mode 100644
index 000000000..e8767a193
--- /dev/null
+++ b/replay/replay-snapshot.c
@@ -0,0 +1,100 @@
+/*
+ * replay-snapshot.c
+ *
+ * Copyright (c) 2010-2016 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "sysemu/replay.h"
+#include "replay-internal.h"
+#include "monitor/monitor.h"
+#include "qapi/qmp/qstring.h"
+#include "qemu/error-report.h"
+#include "migration/vmstate.h"
+#include "migration/snapshot.h"
+
+static int replay_pre_save(void *opaque)
+{
+    ReplayState *state = opaque;
+    state->file_offset = ftell(replay_file);
+
+    return 0;
+}
+
+static int replay_post_load(void *opaque, int version_id)
+{
+    ReplayState *state = opaque;
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        fseek(replay_file, state->file_offset, SEEK_SET);
+        /* If this was a vmstate, saved in recording mode,
+           we need to initialize replay data fields. */
+        replay_fetch_data_kind();
+    } else if (replay_mode == REPLAY_MODE_RECORD) {
+        /* This is only useful for loading the initial state.
+           Therefore reset all the counters. */
+        state->instruction_count = 0;
+        state->block_request_id = 0;
+    }
+
+    return 0;
+}
+
+static const VMStateDescription vmstate_replay = {
+    .name = "replay",
+    .version_id = 2,
+    .minimum_version_id = 2,
+    .pre_save = replay_pre_save,
+    .post_load = replay_post_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_INT64_ARRAY(cached_clock, ReplayState, REPLAY_CLOCK_COUNT),
+        VMSTATE_UINT64(current_icount, ReplayState),
+        VMSTATE_INT32(instruction_count, ReplayState),
+        VMSTATE_UINT32(data_kind, ReplayState),
+        VMSTATE_UINT32(has_unread_data, ReplayState),
+        VMSTATE_UINT64(file_offset, ReplayState),
+        VMSTATE_UINT64(block_request_id, ReplayState),
+        VMSTATE_INT32(read_event_kind, ReplayState),
+        VMSTATE_UINT64(read_event_id, ReplayState),
+        VMSTATE_INT32(read_event_checkpoint, ReplayState),
+        VMSTATE_END_OF_LIST()
+    },
+};
+
+void replay_vmstate_register(void)
+{
+    vmstate_register(NULL, 0, &vmstate_replay, &replay_state);
+}
+
+void replay_vmstate_init(void)
+{
+    Error *err = NULL;
+
+    if (replay_snapshot) {
+        if (replay_mode == REPLAY_MODE_RECORD) {
+            if (!save_snapshot(replay_snapshot,
+                               true, NULL, false, NULL, &err)) {
+                error_report_err(err);
+                error_report("Could not create snapshot for icount record");
+                exit(1);
+            }
+        } else if (replay_mode == REPLAY_MODE_PLAY) {
+            if (!load_snapshot(replay_snapshot, NULL, false, NULL, &err)) {
+                error_report_err(err);
+                error_report("Could not load snapshot for icount replay");
+                exit(1);
+            }
+        }
+    }
+}
+
+bool replay_can_snapshot(void)
+{
+    return replay_mode == REPLAY_MODE_NONE
+        || !replay_has_events();
+}
diff --git a/replay/replay-time.c b/replay/replay-time.c
new file mode 100644
index 000000000..00ebcb7a4
--- /dev/null
+++ b/replay/replay-time.c
@@ -0,0 +1,62 @@
+/*
+ * replay-time.c
+ *
+ * Copyright (c) 2010-2015 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "sysemu/replay.h"
+#include "replay-internal.h"
+#include "qemu/error-report.h"
+
+int64_t replay_save_clock(ReplayClockKind kind, int64_t clock,
+                          int64_t raw_icount)
+{
+    g_assert(replay_file);
+    g_assert(replay_mutex_locked());
+
+    /*
+     * Due to the caller's locking requirements we get the icount from it
+     * instead of using replay_save_instructions().
+     */
+    replay_advance_current_icount(raw_icount);
+    replay_put_event(EVENT_CLOCK + kind);
+    replay_put_qword(clock);
+
+    return clock;
+}
+
+void replay_read_next_clock(ReplayClockKind kind)
+{
+    unsigned int read_kind = replay_state.data_kind - EVENT_CLOCK;
+
+    assert(read_kind == kind);
+
+    int64_t clock = replay_get_qword();
+
+    replay_check_error();
+    replay_finish_event();
+
+    replay_state.cached_clock[read_kind] = clock;
+}
+
+/*! Reads next clock event from the input. */
+int64_t replay_read_clock(ReplayClockKind kind, int64_t raw_icount)
+{
+    int64_t ret;
+    g_assert(replay_file && replay_mutex_locked());
+
+    replay_advance_current_icount(raw_icount);
+
+    if (replay_next_event_is(EVENT_CLOCK + kind)) {
+        replay_read_next_clock(kind);
+    }
+    ret = replay_state.cached_clock[kind];
+
+    return ret;
+}
diff --git a/replay/replay.c b/replay/replay.c
new file mode 100644
index 000000000..6df2abc18
--- /dev/null
+++ b/replay/replay.c
@@ -0,0 +1,403 @@
+/*
+ * replay.c
+ *
+ * Copyright (c) 2010-2015 Institute for System Programming
+ *                         of the Russian Academy of Sciences.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "sysemu/cpu-timers.h"
+#include "sysemu/replay.h"
+#include "sysemu/runstate.h"
+#include "replay-internal.h"
+#include "qemu/main-loop.h"
+#include "qemu/option.h"
+#include "sysemu/cpus.h"
+#include "qemu/error-report.h"
+
+/* Current version of the replay mechanism.
+   Increase it when file format changes. */
+#define REPLAY_VERSION              0xe0200a
+/* Size of replay log header */
+#define HEADER_SIZE                 (sizeof(uint32_t) + sizeof(uint64_t))
+
+ReplayMode replay_mode = REPLAY_MODE_NONE;
+char *replay_snapshot;
+
+/* Name of replay file  */
+static char *replay_filename;
+ReplayState replay_state;
+static GSList *replay_blockers;
+
+/* Replay breakpoints */
+uint64_t replay_break_icount = -1ULL;
+QEMUTimer *replay_break_timer;
+
+bool replay_next_event_is(int event)
+{
+    bool res = false;
+
+    /* nothing to skip - not all instructions used */
+    if (replay_state.instruction_count != 0) {
+        assert(replay_state.data_kind == EVENT_INSTRUCTION);
+        return event == EVENT_INSTRUCTION;
+    }
+
+    while (true) {
+        unsigned int data_kind = replay_state.data_kind;
+        if (event == data_kind) {
+            res = true;
+        }
+        switch (data_kind) {
+        case EVENT_SHUTDOWN ... EVENT_SHUTDOWN_LAST:
+            replay_finish_event();
+            qemu_system_shutdown_request(data_kind - EVENT_SHUTDOWN);
+            break;
+        default:
+            /* clock, time_t, checkpoint and other events */
+            return res;
+        }
+    }
+    return res;
+}
+
+uint64_t replay_get_current_icount(void)
+{
+    return icount_get_raw();
+}
+
+int replay_get_instructions(void)
+{
+    int res = 0;
+    replay_mutex_lock();
+    if (replay_next_event_is(EVENT_INSTRUCTION)) {
+        res = replay_state.instruction_count;
+        if (replay_break_icount != -1LL) {
+            uint64_t current = replay_get_current_icount();
+            assert(replay_break_icount >= current);
+            if (current + res > replay_break_icount) {
+                res = replay_break_icount - current;
+            }
+        }
+    }
+    replay_mutex_unlock();
+    return res;
+}
+
+void replay_account_executed_instructions(void)
+{
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
+        if (replay_state.instruction_count > 0) {
+            replay_advance_current_icount(replay_get_current_icount());
+        }
+    }
+}
+
+bool replay_exception(void)
+{
+
+    if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
+        replay_save_instructions();
+        replay_put_event(EVENT_EXCEPTION);
+        return true;
+    } else if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
+        bool res = replay_has_exception();
+        if (res) {
+            replay_finish_event();
+        }
+        return res;
+    }
+
+    return true;
+}
+
+bool replay_has_exception(void)
+{
+    bool res = false;
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
+        replay_account_executed_instructions();
+        res = replay_next_event_is(EVENT_EXCEPTION);
+    }
+
+    return res;
+}
+
+bool replay_interrupt(void)
+{
+    if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
+        replay_save_instructions();
+        replay_put_event(EVENT_INTERRUPT);
+        return true;
+    } else if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
+        bool res = replay_has_interrupt();
+        if (res) {
+            replay_finish_event();
+        }
+        return res;
+    }
+
+    return true;
+}
+
+bool replay_has_interrupt(void)
+{
+    bool res = false;
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
+        replay_account_executed_instructions();
+        res = replay_next_event_is(EVENT_INTERRUPT);
+    }
+    return res;
+}
+
+void replay_shutdown_request(ShutdownCause cause)
+{
+    if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
+        replay_put_event(EVENT_SHUTDOWN + cause);
+    }
+}
+
+bool replay_checkpoint(ReplayCheckpoint checkpoint)
+{
+    bool res = false;
+    static bool in_checkpoint;
+    assert(EVENT_CHECKPOINT + checkpoint <= EVENT_CHECKPOINT_LAST);
+
+    if (!replay_file) {
+        return true;
+    }
+
+    if (in_checkpoint) {
+        /*
+           Recursion occurs when HW event modifies timers.
+           Prevent performing icount warp in this case and
+           wait for another invocation of the checkpoint.
+        */
+        g_assert(replay_mode == REPLAY_MODE_PLAY);
+        return false;
+    }
+    in_checkpoint = true;
+
+    replay_save_instructions();
+
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
+        if (replay_next_event_is(EVENT_CHECKPOINT + checkpoint)) {
+            replay_finish_event();
+        } else if (replay_state.data_kind != EVENT_ASYNC) {
+            res = false;
+            goto out;
+        }
+        replay_read_events(checkpoint);
+        /* replay_read_events may leave some unread events.
+           Return false if not all of the events associated with
+           checkpoint were processed */
+        res = replay_state.data_kind != EVENT_ASYNC;
+    } else if (replay_mode == REPLAY_MODE_RECORD) {
+        g_assert(replay_mutex_locked());
+        replay_put_event(EVENT_CHECKPOINT + checkpoint);
+        /* This checkpoint belongs to several threads.
+           Processing events from different threads is
+           non-deterministic */
+        if (checkpoint != CHECKPOINT_CLOCK_WARP_START
+            /* FIXME: this is temporary fix, other checkpoints
+                      may also be invoked from the different threads someday.
+                      Asynchronous event processing should be refactored
+                      to create additional replay event kind which is
+                      nailed to the one of the threads and which processes
+                      the event queue. */
+            && checkpoint != CHECKPOINT_CLOCK_VIRTUAL) {
+            replay_save_events(checkpoint);
+        }
+        res = true;
+    }
+out:
+    in_checkpoint = false;
+    return res;
+}
+
+bool replay_has_checkpoint(void)
+{
+    bool res = false;
+    if (replay_mode == REPLAY_MODE_PLAY) {
+        g_assert(replay_mutex_locked());
+        replay_account_executed_instructions();
+        res = EVENT_CHECKPOINT <= replay_state.data_kind
+              && replay_state.data_kind <= EVENT_CHECKPOINT_LAST;
+    }
+    return res;
+}
+
+static void replay_enable(const char *fname, int mode)
+{
+    const char *fmode = NULL;
+    assert(!replay_file);
+
+    switch (mode) {
+    case REPLAY_MODE_RECORD:
+        fmode = "wb";
+        break;
+    case REPLAY_MODE_PLAY:
+        fmode = "rb";
+        break;
+    default:
+        fprintf(stderr, "Replay: internal error: invalid replay mode\n");
+        exit(1);
+    }
+
+    atexit(replay_finish);
+
+    replay_file = fopen(fname, fmode);
+    if (replay_file == NULL) {
+        fprintf(stderr, "Replay: open %s: %s\n", fname, strerror(errno));
+        exit(1);
+    }
+
+    replay_filename = g_strdup(fname);
+    replay_mode = mode;
+    replay_mutex_init();
+
+    replay_state.data_kind = -1;
+    replay_state.instruction_count = 0;
+    replay_state.current_icount = 0;
+    replay_state.has_unread_data = 0;
+
+    /* skip file header for RECORD and check it for PLAY */
+    if (replay_mode == REPLAY_MODE_RECORD) {
+        fseek(replay_file, HEADER_SIZE, SEEK_SET);
+    } else if (replay_mode == REPLAY_MODE_PLAY) {
+        unsigned int version = replay_get_dword();
+        if (version != REPLAY_VERSION) {
+            fprintf(stderr, "Replay: invalid input log file version\n");
+            exit(1);
+        }
+        /* go to the beginning */
+        fseek(replay_file, HEADER_SIZE, SEEK_SET);
+        replay_fetch_data_kind();
+    }
+
+    replay_init_events();
+}
+
+void replay_configure(QemuOpts *opts)
+{
+    const char *fname;
+    const char *rr;
+    ReplayMode mode = REPLAY_MODE_NONE;
+    Location loc;
+
+    if (!opts) {
+        return;
+    }
+
+    loc_push_none(&loc);
+    qemu_opts_loc_restore(opts);
+
+    rr = qemu_opt_get(opts, "rr");
+    if (!rr) {
+        /* Just enabling icount */
+        goto out;
+    } else if (!strcmp(rr, "record")) {
+        mode = REPLAY_MODE_RECORD;
+    } else if (!strcmp(rr, "replay")) {
+        mode = REPLAY_MODE_PLAY;
+    } else {
+        error_report("Invalid icount rr option: %s", rr);
+        exit(1);
+    }
+
+    fname = qemu_opt_get(opts, "rrfile");
+    if (!fname) {
+        error_report("File name not specified for replay");
+        exit(1);
+    }
+
+    replay_snapshot = g_strdup(qemu_opt_get(opts, "rrsnapshot"));
+    replay_vmstate_register();
+    replay_enable(fname, mode);
+
+out:
+    loc_pop(&loc);
+}
+
+void replay_start(void)
+{
+    if (replay_mode == REPLAY_MODE_NONE) {
+        return;
+    }
+
+    if (replay_blockers) {
+        error_reportf_err(replay_blockers->data, "Record/replay: ");
+        exit(1);
+    }
+    if (!icount_enabled()) {
+        error_report("Please enable icount to use record/replay");
+        exit(1);
+    }
+
+    /* Timer for snapshotting will be set up here. */
+
+    replay_enable_events();
+}
+
+void replay_finish(void)
+{
+    if (replay_mode == REPLAY_MODE_NONE) {
+        return;
+    }
+
+    replay_save_instructions();
+
+    /* finalize the file */
+    if (replay_file) {
+        if (replay_mode == REPLAY_MODE_RECORD) {
+            /*
+             * Can't do it in the signal handler, therefore
+             * add shutdown event here for the case of Ctrl-C.
+             */
+            replay_shutdown_request(SHUTDOWN_CAUSE_HOST_SIGNAL);
+            /* write end event */
+            replay_put_event(EVENT_END);
+
+            /* write header */
+            fseek(replay_file, 0, SEEK_SET);
+            replay_put_dword(REPLAY_VERSION);
+        }
+
+        fclose(replay_file);
+        replay_file = NULL;
+    }
+    if (replay_filename) {
+        g_free(replay_filename);
+        replay_filename = NULL;
+    }
+
+    g_free(replay_snapshot);
+    replay_snapshot = NULL;
+
+    replay_mode = REPLAY_MODE_NONE;
+
+    replay_finish_events();
+}
+
+void replay_add_blocker(Error *reason)
+{
+    replay_blockers = g_slist_prepend(replay_blockers, reason);
+}
+
+const char *replay_get_filename(void)
+{
+    return replay_filename;
+}
diff --git a/replay/stubs-system.c b/replay/stubs-system.c
new file mode 100644
index 000000000..5c262b08f
--- /dev/null
+++ b/replay/stubs-system.c
@@ -0,0 +1,96 @@
+#include "qemu/osdep.h"
+#include "sysemu/replay.h"
+#include "ui/input.h"
+
+void replay_input_event(QemuConsole *src, InputEvent *evt)
+{
+    qemu_input_event_send_impl(src, evt);
+}
+
+void replay_input_sync_event(void)
+{
+    qemu_input_event_sync_impl();
+}
+
+void replay_add_blocker(Error *reason)
+{
+}
+void replay_audio_in(size_t *recorded, void *samples, size_t *wpos, size_t size)
+{
+}
+void replay_audio_out(size_t *played)
+{
+}
+void replay_breakpoint(void)
+{
+}
+bool replay_can_snapshot(void)
+{
+    return true;
+}
+void replay_configure(struct QemuOpts *opts)
+{
+}
+void replay_flush_events(void)
+{
+}
+void replay_gdb_attached(void)
+{
+}
+bool replay_running_debug(void)
+{
+    return false;
+}
+void replay_shutdown_request(ShutdownCause cause)
+{
+}
+void replay_start(void)
+{
+}
+void replay_vmstate_init(void)
+{
+}
+
+#include "monitor/monitor.h"
+#include "monitor/hmp.h"
+#include "qapi/qapi-commands-replay.h"
+#include "qapi/error.h"
+#include "qemu/error-report.h"
+
+void hmp_info_replay(Monitor *mon, const QDict *qdict)
+{
+    error_report("replay support not available");
+}
+void hmp_replay_break(Monitor *mon, const QDict *qdict)
+{
+    error_report("replay support not available");
+}
+void hmp_replay_delete_break(Monitor *mon, const QDict *qdict)
+{
+    error_report("replay support not available");
+}
+void hmp_replay_seek(Monitor *mon, const QDict *qdict)
+{
+    error_report("replay support not available");
+}
+ReplayInfo *qmp_query_replay(Error **errp)
+{
+    error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
+              "replay support not available");
+    return NULL;
+}
+void qmp_replay_break(int64_t icount, Error **errp)
+{
+    error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
+              "replay support not available");
+}
+void qmp_replay_delete_break(Error **errp)
+{
+    error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
+              "replay support not available");
+}
+void qmp_replay_seek(int64_t icount, Error **errp)
+{
+    error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
+              "replay support not available");
+}