This prepares ground for the changes coming next which add an Error**
argument to the .save_setup() handler. Callers of qemu_savevm_state_setup()
now handle the error and fail earlier. This is a functional change
that should be examined closely.

Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 migration/savevm.h    |  2 +-
 migration/migration.c | 20 ++++++++++++++++++--
 migration/savevm.c    | 14 +++++++-------
 3 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/migration/savevm.h b/migration/savevm.h
index 74669733dd63a080b765866c703234a5c4939223..9ec96a995c93a42aad621595f0ed58596c532328 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -32,7 +32,7 @@
 bool qemu_savevm_state_blocked(Error **errp);
 void qemu_savevm_non_migratable_list(strList **reasons);
 int qemu_savevm_state_prepare(Error **errp);
-void qemu_savevm_state_setup(QEMUFile *f);
+int qemu_savevm_state_setup(QEMUFile *f, Error **errp);
 bool qemu_savevm_state_guest_unplug_pending(void);
 int qemu_savevm_state_resume_prepare(MigrationState *s);
 void qemu_savevm_state_header(QEMUFile *f);
diff --git a/migration/migration.c b/migration/migration.c
index 5316bbe6704742e604ae55dc7b47a4e11e73c2a4..c1a62b696f62c0d5aca0505e58bc4dc0ff561fde 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -3314,6 +3314,8 @@ static void *migration_thread(void *opaque)
     int64_t setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
     MigThrError thr_error;
     bool urgent = false;
+    Error *local_err = NULL;
+    int ret;
 
     thread = migration_threads_add("live_migration", qemu_get_thread_id());
 
@@ -3357,9 +3359,15 @@ static void *migration_thread(void *opaque)
     }
 
     bql_lock();
-    qemu_savevm_state_setup(s->to_dst_file);
+    ret = qemu_savevm_state_setup(s->to_dst_file, &local_err);
     bql_unlock();
 
+    if (ret) {
+        migrate_set_error(s, local_err);
+        error_free(local_err);
+        goto out;
+     }
+
     qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
                                MIGRATION_STATUS_ACTIVE);
 
@@ -3436,6 +3444,8 @@ static void *bg_migration_thread(void *opaque)
     MigThrError thr_error;
     QEMUFile *fb;
     bool early_fail = true;
+    Error *local_err = NULL;
+    int ret;
 
     rcu_register_thread();
     object_ref(OBJECT(s));
@@ -3469,9 +3479,15 @@ static void *bg_migration_thread(void *opaque)
 
     bql_lock();
     qemu_savevm_state_header(s->to_dst_file);
-    qemu_savevm_state_setup(s->to_dst_file);
+    ret = qemu_savevm_state_setup(s->to_dst_file, &local_err);
     bql_unlock();
 
+    if (ret) {
+        migrate_set_error(s, local_err);
+        error_free(local_err);
+        goto fail;
+    }
+
     qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
                                MIGRATION_STATUS_ACTIVE);
 
diff --git a/migration/savevm.c b/migration/savevm.c
index 51876f2ef674bb76c7e7ef96e1119a083883deac..bc168371a31acf85f29f2c284be181250db45df4 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1311,11 +1311,10 @@ int qemu_savevm_state_prepare(Error **errp)
     return 0;
 }
 
-void qemu_savevm_state_setup(QEMUFile *f)
+int qemu_savevm_state_setup(QEMUFile *f, Error **errp)
 {
     MigrationState *ms = migrate_get_current();
     SaveStateEntry *se;
-    Error *local_err = NULL;
     int ret = 0;
 
     json_writer_int64(ms->vmdesc, "page_size", qemu_target_page_size());
@@ -1351,12 +1350,10 @@ void qemu_savevm_state_setup(QEMUFile *f)
     }
 
     if (ret) {
-        return;
+        return ret;
     }
 
-    if (precopy_notify(PRECOPY_NOTIFY_SETUP, &local_err)) {
-        error_report_err(local_err);
-    }
+    return precopy_notify(PRECOPY_NOTIFY_SETUP, errp);
 }
 
 int qemu_savevm_state_resume_prepare(MigrationState *s)
@@ -1725,7 +1722,10 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
     ms->to_dst_file = f;
 
     qemu_savevm_state_header(f);
-    qemu_savevm_state_setup(f);
+    ret = qemu_savevm_state_setup(f, errp);
+    if (ret) {
+        return ret;
+    }
 
     while (qemu_file_get_error(f) == 0) {
         if (qemu_savevm_state_iterate(f, false) > 0) {
-- 
2.43.2

On Tue, Feb 27, 2024 at 07:03:29PM +0100, Cédric Le Goater wrote:
> @@ -3469,9 +3479,15 @@ static void *bg_migration_thread(void *opaque)
>  
>      bql_lock();
>      qemu_savevm_state_header(s->to_dst_file);
> -    qemu_savevm_state_setup(s->to_dst_file);
> +    ret = qemu_savevm_state_setup(s->to_dst_file, &local_err);
>      bql_unlock();
>  
> +    if (ret) {
> +        migrate_set_error(s, local_err);
> +        error_free(local_err);
> +        goto fail;
> +    }

This chunk may need to be moved above bql unlock.

> +
>      qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
>                                 MIGRATION_STATUS_ACTIVE);
>  

-- 
Peter Xu