Re: [Qemu-devel] [PATCH v2] runstate: add more valid transitions

[Luiz Capitulino <lcapitulino@redhat.com>]

On Fri, 14 Oct 2011 15:37:29 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 10/14/2011 03:23 PM, Luiz Capitulino wrote:
> > I'm not, because I'm assuming that allowing a transition from 'paused' to
> > 'postmigrate' plus this fix:
> >
> >   http://lists.gnu.org/archive/html/qemu-devel/2011-10/msg01430.html
> 
> I think POST_MIGRATE -> FINISH_MIGRATE should be still allowed in case 
> you migrate twice.  Management would probably disallow that, but from 
> the monitor you can do funny things: stop the machine, create two images 
> based on the running machine's image, and migrate to both images.

Yes, you're right. But there's another problem there: the VM is stopped
when the migration process finishes. So, if you migrate again, there
won't be a POST_MIGRATE -> FINISH_MIGRATE transition, as vm_stop() will
just return.

I don't like the idea of changing current vm_stop() to always change the
state, so I'm adding a new function to do that:

diff --git a/cpus.c b/cpus.c
index 8978779..5f5b763 100644
--- a/cpus.c
+++ b/cpus.c
@@ -887,6 +887,17 @@ void vm_stop(RunState state)
     do_vm_stop(state);
 }
 
+/* does a state transition even if the VM is already stopped,
+   current state is forgotten forever */
+void vm_stop_force_state(RunState state)
+{
+    if (runstate_is_running()) {
+        vm_stop(state);
+    } else {
+        runstate_set(state);
+    }
+}
+
 static int tcg_cpu_exec(CPUState *env)
 {
     int ret;
diff --git a/migration.c b/migration.c
index 77a51ad..62b74a6 100644
--- a/migration.c
+++ b/migration.c
@@ -375,7 +375,7 @@ void migrate_fd_put_ready(void *opaque)
         int old_vm_running = runstate_is_running();
 
         DPRINTF("done iterating\n");
-        vm_stop(RUN_STATE_FINISH_MIGRATE);
+        vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
 
         if ((qemu_savevm_state_complete(s->mon, s->file)) < 0) {
             if (old_vm_running) {
diff --git a/sysemu.h b/sysemu.h
index a889d90..7d288f8 100644
--- a/sysemu.h
+++ b/sysemu.h
@@ -35,6 +35,7 @@ void vm_state_notify(int running, RunState state);
 
 void vm_start(void);
 void vm_stop(RunState state);
+void vm_stop_force_state(RunState state);
 
 void qemu_system_reset_request(void);
 void qemu_system_shutdown_request(void);
diff --git a/vl.c b/vl.c
index 2e991fc..613204b 100644
--- a/vl.c
+++ b/vl.c
@@ -346,6 +346,7 @@ static const RunStateTransition runstate_transitions_def[] = {
     { RUN_STATE_PAUSED, RUN_STATE_POSTMIGRATE },
 
     { RUN_STATE_POSTMIGRATE, RUN_STATE_RUNNING },
+    { RUN_STATE_POSTMIGRATE, RUN_STATE_FINISH_MIGRATE },
 
     { RUN_STATE_PRELAUNCH, RUN_STATE_RUNNING },
     { RUN_STATE_PRELAUNCH, RUN_STATE_INMIGRATE },
-- 
1.7.7.rc3