[RFC,03/13] migration: Run a post update routine after setting parameters

Commit Message

Fabiano Rosas April 11, 2025, 7:14 p.m. UTC

Some migration parameters are updated immediately once they are set
via migrate-set-parameters. Move that work outside of
migrate_params_apply() and leave that function with the single
responsibility of setting s->parameters and not doing any
side-effects.

Signed-off-by: Fabiano Rosas <[e-mail]>
---
 migration/options.c | 39 +++++++++++++++++++++++++++++----------
 migration/ram.c     |  2 +-
 2 files changed, 30 insertions(+), 11 deletions(-)

Patch

diff --git a/migration/options.c b/migration/options.c
index 7cd465ca94..cac28540dd 100644
--- a/migration/options.c
+++ b/migration/options.c
@@ -1302,7 +1302,7 @@  static void migrate_params_test_apply(MigrateSetParameters *params,
     }
 }
 
-static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
+static void migrate_params_apply(MigrateSetParameters *params)
 {
     MigrationState *s = migrate_get_current();
 
@@ -1344,9 +1344,6 @@  static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
 
     if (params->has_max_bandwidth) {
         s->parameters.max_bandwidth = params->max_bandwidth;
-        if (s->to_dst_file && !migration_in_postcopy()) {
-            migration_rate_set(s->parameters.max_bandwidth);
-        }
     }
 
     if (params->has_avail_switchover_bandwidth) {
@@ -1359,7 +1356,6 @@  static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
 
     if (params->has_x_checkpoint_delay) {
         s->parameters.x_checkpoint_delay = params->x_checkpoint_delay;
-        colo_checkpoint_delay_set();
     }
 
     if (params->has_multifd_channels) {
@@ -1379,13 +1375,9 @@  static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
     }
     if (params->has_xbzrle_cache_size) {
         s->parameters.xbzrle_cache_size = params->xbzrle_cache_size;
-        xbzrle_cache_resize(params->xbzrle_cache_size, errp);
     }
     if (params->has_max_postcopy_bandwidth) {
         s->parameters.max_postcopy_bandwidth = params->max_postcopy_bandwidth;
-        if (s->to_dst_file && migration_in_postcopy()) {
-            migration_rate_set(s->parameters.max_postcopy_bandwidth);
-        }
     }
     if (params->has_max_cpu_throttle) {
         s->parameters.max_cpu_throttle = params->max_cpu_throttle;
@@ -1434,6 +1426,32 @@  static void migrate_params_apply(MigrateSetParameters *params, Error **errp)
     }
 }
 
+static void migrate_post_update_params(MigrateSetParameters *new, Error **errp)
+{
+    MigrationState *s = migrate_get_current();
+
+    if (new->has_max_bandwidth) {
+        if (s->to_dst_file && !migration_in_postcopy()) {
+            migration_rate_set(new->max_bandwidth);
+        }
+    }
+
+    if (new->has_x_checkpoint_delay) {
+        colo_checkpoint_delay_set();
+    }
+
+    if (new->has_xbzrle_cache_size) {
+        xbzrle_cache_resize(new->xbzrle_cache_size, errp);
+    }
+
+    if (new->has_max_postcopy_bandwidth) {
+        if (s->to_dst_file && migration_in_postcopy()) {
+            migration_rate_set(new->max_postcopy_bandwidth);
+        }
+    }
+
+}
+
 void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp)
 {
     MigrationParameters tmp;
@@ -1445,5 +1463,6 @@  void qmp_migrate_set_parameters(MigrateSetParameters *params, Error **errp)
         return;
     }
 
-    migrate_params_apply(params, errp);
+    migrate_params_apply(params);
+    migrate_post_update_params(params, errp);
 }
diff --git a/migration/ram.c b/migration/ram.c
index 424df6d9f1..e0ba8e0d48 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -144,7 +144,7 @@  static void XBZRLE_cache_unlock(void)
 /**
  * xbzrle_cache_resize: resize the xbzrle cache
  *
- * This function is called from migrate_params_apply in main
+ * This function is called from migrate_post_update_config in main
  * thread, possibly while a migration is in progress.  A running
  * migration may be using the cache and might finish during this call,
  * hence changes to the cache are protected by XBZRLE.lock().