shutdown: Preserve shutdown cause through replay

With the recent addition of ShutdownCause, we want to be able to pass
a cause through any shutdown request, and then faithfully replay that
cause when later replaying the same sequence.  The easiest way is to
expand the reply event mechanism to track a series of values for
EVENT_SHUTDOWN, one corresponding to each value of ShutdownCause.

We are free to change the replay stream as needed, since there are
already no guarantees about being able to use a replay stream by
any other version of qemu than the one that generated it.

The cause is not actually fed back until the next patch changes the
signature for requesting a shutdown; a TODO marks that upcoming change.

Yes, this uses the gcc/clang extension of a ranged case label,
but this is not the first time we've used non-C99 constructs.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Message-Id: <20170515214114.15442-4-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

include/sysemu/replay.h

@@ -13,6 +13,7 @@
  */
 
 #include "qapi-types.h"
+#include "sysemu.h"
 
 /* replay clock kinds */
 enum ReplayClockKind {
@@ -98,7 +99,7 @@ int64_t replay_read_clock(ReplayClockKind kind);
 /* Events */
 
 /*! Called when qemu shutdown is requested. */
-void replay_shutdown_request(void);
+void replay_shutdown_request(ShutdownCause cause);
 /*! Should be called at check points in the execution.
     These check points are skipped, if they were not met.
     Saves checkpoint in the SAVE mode and validates in the PLAY mode.

replay/replay-internal.h

@@ -22,8 +22,9 @@ enum ReplayEvents {
     EVENT_EXCEPTION,
     /* for async events */
     EVENT_ASYNC,
-    /* for shutdown request */
+    /* 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 */

replay/replay.c

@@ -49,8 +49,9 @@ bool replay_next_event_is(int event)
             res = true;
         }
         switch (replay_state.data_kind) {
-        case EVENT_SHUTDOWN:
+        case EVENT_SHUTDOWN ... EVENT_SHUTDOWN_LAST:
             replay_finish_event();
+            /* TODO - pass replay_state.data_kind - EVENT_SHUTDOWN as cause */
             qemu_system_shutdown_request();
             break;
         default:
@@ -170,11 +171,11 @@ bool replay_has_interrupt(void)
     return res;
 }
 
-void replay_shutdown_request(void)
+void replay_shutdown_request(ShutdownCause cause)
 {
     if (replay_mode == REPLAY_MODE_RECORD) {
         replay_mutex_lock();
-        replay_put_event(EVENT_SHUTDOWN);
+        replay_put_event(EVENT_SHUTDOWN + cause);
         replay_mutex_unlock();
     }
 }

vl.c

@@ -1821,8 +1821,8 @@ void qemu_system_killed(int signal, pid_t pid)
 void qemu_system_shutdown_request(void)
 {
     trace_qemu_system_shutdown_request();
-    replay_shutdown_request();
     /* TODO - add a parameter to allow callers to specify reason */
+    replay_shutdown_request(SHUTDOWN_CAUSE_HOST_ERROR);
     shutdown_requested = SHUTDOWN_CAUSE_HOST_ERROR;
     qemu_notify_event();
 }