[Qemu-devel] [PATCH v9 06/10] replay: fix save/load vm for non-empty queue

[Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>]

From: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>

This patch does not allows saving/loading vmstate when
replay events queue is not empty. There is no reliable
way to save events queue, because it describes internal
coroutine state. Therefore saving and loading operations
should be deferred to another record/replay step.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
---
 include/sysemu/replay.h  |    3 +++
 migration/savevm.c       |   13 +++++++++++++
 replay/replay-snapshot.c |    6 ++++++
 3 files changed, 22 insertions(+)

diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h
index f1c0712795..5c9db2a2ef 100644
--- a/include/sysemu/replay.h
+++ b/include/sysemu/replay.h
@@ -164,5 +164,8 @@ void replay_audio_in(int *recorded, void *samples, int *wpos, int size);
 /*! Called at the start of execution.
     Loads or saves initial vmstate depending on execution mode. */
 void replay_vmstate_init(void);
+/*! Called to ensure that replay state is consistent and VM snapshot
+    can be created */
+bool replay_can_snapshot(void);
 
 #endif
diff --git a/migration/savevm.c b/migration/savevm.c
index 03ae1bdeb4..358d22170d 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -54,6 +54,7 @@
 #include "qemu/cutils.h"
 #include "io/channel-buffer.h"
 #include "io/channel-file.h"
+#include "sysemu/replay.h"
 
 #ifndef ETH_P_RARP
 #define ETH_P_RARP 0x8035
@@ -2083,6 +2084,12 @@ int save_vmstate(Monitor *mon, const char *name)
     Error *local_err = NULL;
     AioContext *aio_context;
 
+    if (!replay_can_snapshot()) {
+        monitor_printf(mon, "Record/replay does not allow making snapshot right now. "
+                        "Try stopping at another step.\n");
+        return ret;
+    }
+
     if (!bdrv_all_can_snapshot(&bs)) {
         monitor_printf(mon, "Device '%s' is writable but does not "
                        "support snapshots.\n", bdrv_get_device_name(bs));
@@ -2244,6 +2251,12 @@ int load_vmstate(const char *name)
     AioContext *aio_context;
     MigrationIncomingState *mis = migration_incoming_get_current();
 
+    if (!replay_can_snapshot()) {
+        error_report("Record/replay does not allow loading snapshot right now. "
+                     "Try stopping at another step.\n");
+        return -EINVAL;
+    }
+
     if (!bdrv_all_can_snapshot(&bs)) {
         error_report("Device '%s' is writable but does not support snapshots.",
                      bdrv_get_device_name(bs));
diff --git a/replay/replay-snapshot.c b/replay/replay-snapshot.c
index 65e2d375c2..438d82ec33 100644
--- a/replay/replay-snapshot.c
+++ b/replay/replay-snapshot.c
@@ -76,3 +76,9 @@ void replay_vmstate_init(void)
         }
     }
 }
+
+bool replay_can_snapshot(void)
+{
+    return replay_mode == REPLAY_MODE_NONE
+        || !replay_has_events();
+}