[QEMU HCI-7.4 PATCH] migration: set .vm_old_state in migration_stop_vm() #VSTOR-147066

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

Currently, when a postcopy migration starts, the .vm_old_state isn't
being recorded.  Thus it remains to be set to -1.  That might result into
a VM crash in case migration fails:

  migration_iteration_finish(s)
    runstate_set(s->vm_old_state=-1)
      assert(new_state < RUN_STATE__MAX)

To avoid that, let's just move saving the previous state directly into
the migration_stop_vm() helper.  Add 2nd function argument to
migration_stop_vm() to achieve that.

This code is mimicking what's already done in hci-8.0 and master.

Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
---
 migration/migration.c | 21 ++++++++++-----------
 migration/migration.h |  2 +-
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 00924b4a2a7..8f33181e00a 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -157,9 +157,14 @@ static gint page_request_addr_cmp(gconstpointer ap, gconstpointer bp)
     return (a > b) - (a < b);
 }
 
-int migration_stop_vm(RunState state)
+int migration_stop_vm(MigrationState *s, RunState state)
 {
-    int ret = vm_stop_force_state(state);
+    int ret;
+
+    s->vm_old_state = runstate_get();
+    global_state_store();
+
+    ret = vm_stop_force_state(state);
 
     trace_vmstate_downtime_checkpoint("src-vm-stopped");
 
@@ -2460,8 +2465,7 @@ static int postcopy_start(MigrationState *ms, Error **errp)
     migration_downtime_start(ms);
 
     qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL);
-    global_state_store();
-    ret = migration_stop_vm(RUN_STATE_FINISH_MIGRATE);
+    ret = migration_stop_vm(ms, RUN_STATE_FINISH_MIGRATE);
     if (ret < 0) {
         goto fail;
     }
@@ -2660,10 +2664,7 @@ static int migration_completion_precopy(MigrationState *s,
     migration_downtime_start(s);
     qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL);
 
-    s->vm_old_state = runstate_get();
-    global_state_store();
-
-    ret = migration_stop_vm(RUN_STATE_FINISH_MIGRATE);
+    ret = migration_stop_vm(s, RUN_STATE_FINISH_MIGRATE);
     trace_migration_completion_vm_stop(ret);
     if (ret < 0) {
         goto out_unlock;
@@ -3520,11 +3521,9 @@ static void *bg_migration_thread(void *opaque)
      * transition in vm_stop_force_state() we need to wakeup it up.
      */
     qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER, NULL);
-    s->vm_old_state = runstate_get();
 
-    global_state_store();
     /* Forcibly stop VM before saving state of vCPUs and devices */
-    if (migration_stop_vm(RUN_STATE_PAUSED)) {
+    if (migration_stop_vm(s, RUN_STATE_PAUSED)) {
         goto fail;
     }
     /*
diff --git a/migration/migration.h b/migration/migration.h
index f2704a0e3bd..fc33ee465ac 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -549,6 +549,6 @@ int migration_rp_wait(MigrationState *s);
  */
 void migration_rp_kick(MigrationState *s);
 
-int migration_stop_vm(RunState state);
+int migration_stop_vm(MigrationState *s, RunState state);
 
 #endif
-- 
2.47.1