migration: qemu_savevm_complete*() helpers

Since we use the same save_complete() hook for both precopy and postcopy,
add a set of helpers to invoke the hook() to dedup the code.

Reviewed-by: Juraj Marcin <jmarcin@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20250613140801.474264-8-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>

1 files changed, 44 insertions, 34 deletions

diff --git a/migration/savevm.c b/migration/savevm.c
index 454e914..c4fd5f5 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1484,6 +1484,38 @@ bool should_send_vmdesc(void)
     return !machine->suppress_vmdesc;
 }
 
+static bool qemu_savevm_complete_exists(SaveStateEntry *se)
+{
+    return se->ops && se->ops->save_complete;
+}
+
+/*
+ * Invoke the ->save_complete() if necessary.
+ * Returns: 0 if skip the current SE or succeeded, <0 if error happened.
+ */
+static int qemu_savevm_complete(SaveStateEntry *se, QEMUFile *f)
+{
+    int ret;
+
+    if (se->ops->is_active) {
+        if (!se->ops->is_active(se->opaque)) {
+            return 0;
+        }
+    }
+
+    trace_savevm_section_start(se->idstr, se->section_id);
+    save_section_header(f, se, QEMU_VM_SECTION_END);
+    ret = se->ops->save_complete(f, se->opaque);
+    trace_savevm_section_end(se->idstr, se->section_id, ret);
+    save_section_footer(f, se);
+
+    if (ret < 0) {
+        qemu_file_set_error(f, ret);
+    }
+
+    return ret;
+}
+
 /*
  * Complete saving any postcopy-able devices.
  *
@@ -1493,27 +1525,13 @@ bool should_send_vmdesc(void)
 void qemu_savevm_state_complete_postcopy(QEMUFile *f)
 {
     SaveStateEntry *se;
-    int ret;
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
-        if (!se->ops || !se->ops->save_complete) {
+        if (!qemu_savevm_complete_exists(se)) {
             continue;
         }
-        if (se->ops->is_active) {
-            if (!se->ops->is_active(se->opaque)) {
-                continue;
-            }
-        }
-        trace_savevm_section_start(se->idstr, se->section_id);
-        /* Section type */
-        qemu_put_byte(f, QEMU_VM_SECTION_END);
-        qemu_put_be32(f, se->section_id);
 
-        ret = se->ops->save_complete(f, se->opaque);
-        trace_savevm_section_end(se->idstr, se->section_id, ret);
-        save_section_footer(f, se);
-        if (ret < 0) {
-            qemu_file_set_error(f, ret);
+        if (qemu_savevm_complete(se, f) < 0) {
             return;
         }
     }
@@ -1559,7 +1577,6 @@ int qemu_savevm_state_complete_precopy_iterable(QEMUFile *f, bool in_postcopy)
 {
     int64_t start_ts_each, end_ts_each;
     SaveStateEntry *se;
-    int ret;
     bool multifd_device_state = multifd_device_state_supported();
 
     if (multifd_device_state) {
@@ -1580,32 +1597,25 @@ int qemu_savevm_state_complete_precopy_iterable(QEMUFile *f, bool in_postcopy)
     }
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
-        if (!se->ops ||
-            (in_postcopy && se->ops->has_postcopy &&
-             se->ops->has_postcopy(se->opaque)) ||
-            !se->ops->save_complete) {
+        if (!qemu_savevm_complete_exists(se)) {
             continue;
         }
 
-        if (se->ops->is_active) {
-            if (!se->ops->is_active(se->opaque)) {
-                continue;
-            }
+        if (in_postcopy && se->ops->has_postcopy &&
+            se->ops->has_postcopy(se->opaque)) {
+            /*
+             * If postcopy will start soon, and if the SE supports
+             * postcopy, then we can skip the SE for the postcopy phase.
+             */
+            continue;
         }
 
         start_ts_each = qemu_clock_get_us(QEMU_CLOCK_REALTIME);
-        trace_savevm_section_start(se->idstr, se->section_id);
-
-        save_section_header(f, se, QEMU_VM_SECTION_END);
-
-        ret = se->ops->save_complete(f, se->opaque);
-        trace_savevm_section_end(se->idstr, se->section_id, ret);
-        save_section_footer(f, se);
-        if (ret < 0) {
-            qemu_file_set_error(f, ret);
+        if (qemu_savevm_complete(se, f) < 0) {
             goto ret_fail_abort_threads;
         }
         end_ts_each = qemu_clock_get_us(QEMU_CLOCK_REALTIME);
+
         trace_vmstate_downtime_save("iterable", se->idstr, se->instance_id,
                                     end_ts_each - start_ts_each);
     }