replay: allow replay stopping and restarting

This patch fixes bug with stopping and restarting replay
through monitor.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20160926080815.6992.71818.stgit@PASHA-ISP>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

block/blkreplay.c

@@ -20,11 +20,6 @@ typedef struct Request {
     QEMUBH *bh;
 } Request;
 
-/* Next request id.
-   This counter is global, because requests from different
-   block devices should not get overlapping ids. */
-static uint64_t request_id;
-
 static int blkreplay_open(BlockDriverState *bs, QDict *options, int flags,
                           Error **errp)
 {
@@ -84,7 +79,7 @@ static void block_request_create(uint64_t reqid, BlockDriverState *bs,
 static int coroutine_fn blkreplay_co_preadv(BlockDriverState *bs,
     uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
 {
-    uint64_t reqid = request_id++;
+    uint64_t reqid = blkreplay_next_id();
     int ret = bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
     block_request_create(reqid, bs, qemu_coroutine_self());
     qemu_coroutine_yield();
@@ -95,7 +90,7 @@ static int coroutine_fn blkreplay_co_preadv(BlockDriverState *bs,
 static int coroutine_fn blkreplay_co_pwritev(BlockDriverState *bs,
     uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags)
 {
-    uint64_t reqid = request_id++;
+    uint64_t reqid = blkreplay_next_id();
     int ret = bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
     block_request_create(reqid, bs, qemu_coroutine_self());
     qemu_coroutine_yield();
@@ -106,7 +101,7 @@ static int coroutine_fn blkreplay_co_pwritev(BlockDriverState *bs,
 static int coroutine_fn blkreplay_co_pwrite_zeroes(BlockDriverState *bs,
     int64_t offset, int count, BdrvRequestFlags flags)
 {
-    uint64_t reqid = request_id++;
+    uint64_t reqid = blkreplay_next_id();
     int ret = bdrv_co_pwrite_zeroes(bs->file, offset, count, flags);
     block_request_create(reqid, bs, qemu_coroutine_self());
     qemu_coroutine_yield();
@@ -117,7 +112,7 @@ static int coroutine_fn blkreplay_co_pwrite_zeroes(BlockDriverState *bs,
 static int coroutine_fn blkreplay_co_pdiscard(BlockDriverState *bs,
                                               int64_t offset, int count)
 {
-    uint64_t reqid = request_id++;
+    uint64_t reqid = blkreplay_next_id();
     int ret = bdrv_co_pdiscard(bs->file->bs, offset, count);
     block_request_create(reqid, bs, qemu_coroutine_self());
     qemu_coroutine_yield();
@@ -127,7 +122,7 @@ static int coroutine_fn blkreplay_co_pdiscard(BlockDriverState *bs,
 
 static int coroutine_fn blkreplay_co_flush(BlockDriverState *bs)
 {
-    uint64_t reqid = request_id++;
+    uint64_t reqid = blkreplay_next_id();
     int ret = bdrv_co_flush(bs->file->bs);
     block_request_create(reqid, bs, qemu_coroutine_self());
     qemu_coroutine_yield();

cpus.c

@@ -750,6 +750,7 @@ static int do_vm_stop(RunState state)
     }
 
     bdrv_drain_all();
+    replay_disable_events();
     ret = blk_flush_all();
 
     return ret;

include/sysemu/replay.h

@@ -105,6 +105,8 @@ bool replay_checkpoint(ReplayCheckpoint checkpoint);
 
 /*! Disables storing events in the queue */
 void replay_disable_events(void);
+/*! Enables storing events in the queue */
+void replay_enable_events(void);
 /*! Returns true when saving events is enabled */
 bool replay_events_enabled(void);
 /*! Adds bottom half event to the queue */
@@ -115,6 +117,8 @@ void replay_input_event(QemuConsole *src, InputEvent *evt);
 void replay_input_sync_event(void);
 /*! Adds block layer event to the queue */
 void replay_block_event(QEMUBH *bh, uint64_t id);
+/*! Returns ID for the next block event */
+uint64_t blkreplay_next_id(void);
 
 /* Character device */
 

replay/replay-events.c

@@ -309,3 +309,11 @@ 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;
+}

replay/replay-internal.h

@@ -68,6 +68,10 @@ typedef struct ReplayState {
     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;
 } ReplayState;
 extern ReplayState replay_state;
 
@@ -123,8 +127,6 @@ void replay_read_next_clock(unsigned int kind);
 void replay_init_events(void);
 /*! Clears internal data structures for events handling */
 void replay_finish_events(void);
-/*! Enables storing events in the queue */
-void replay_enable_events(void);
 /*! Flushes events queue */
 void replay_flush_events(void);
 /*! Clears events list before loading new VM state */

replay/replay-snapshot.c

@@ -50,6 +50,7 @@ static const VMStateDescription vmstate_replay = {
         VMSTATE_UINT32(data_kind, ReplayState),
         VMSTATE_UINT32(has_unread_data, ReplayState),
         VMSTATE_UINT64(file_offset, ReplayState),
+        VMSTATE_UINT64(block_request_id, ReplayState),
         VMSTATE_END_OF_LIST()
     },
 };

stubs/replay.c

@@ -67,3 +67,8 @@ void replay_char_read_all_save_buf(uint8_t *buf, int offset)
 void replay_block_event(QEMUBH *bh, uint64_t id)
 {
 }
+
+uint64_t blkreplay_next_id(void)
+{
+    return 0;
+}

vl.c

@@ -784,6 +784,7 @@ void vm_start(void)
     if (runstate_is_running()) {
         qapi_event_send_stop(&error_abort);
     } else {
+        replay_enable_events();
         cpu_enable_ticks();
         runstate_set(RUN_STATE_RUNNING);
         vm_state_notify(1, RUN_STATE_RUNNING);