migration: make loadvm_postcopy_handle_resume() void

This is an incremental step in converting vmstate loading
code to report error via Error objects instead of directly
printing it to console/monitor.

Use warn_report() instead of error_report(); it ensures that
a resume command received while the migration is not
in postcopy recover state is not fatal. It only informs that
the command received is unusual, and therefore we should not set
errp with the error string.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Arun Menon <armenon@redhat.com>
Tested-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
Link: https://lore.kernel.org/r/20250918-propagate_tpm_error-v14-13-36f11a6fb9d3@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

migration/savevm.c

diff --git a/migration/savevm.c b/migration/savevm.c
index eb2a905..d145e7b 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2334,12 +2334,12 @@
     }
 }
 
-static int loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
+static void loadvm_postcopy_handle_resume(MigrationIncomingState *mis)
 {
     if (mis->state != MIGRATION_STATUS_POSTCOPY_RECOVER) {
-        error_report("%s: illegal resume received", __func__);
+        warn_report("%s: illegal resume received", __func__);
         /* Don't fail the load, only for this. */
-        return 0;
+        return;
     }
 
     /*
@@ -2391,8 +2391,6 @@
         /* Kick the fast ram load thread too */
         qemu_sem_post(&mis->postcopy_pause_sem_fast_load);
     }
-
-    return 0;
 }
 
 /**
@@ -2647,7 +2645,8 @@
         return ret;
 
     case MIG_CMD_POSTCOPY_RESUME:
-        return loadvm_postcopy_handle_resume(mis);
+        loadvm_postcopy_handle_resume(mis);
+        return 0;
 
     case MIG_CMD_RECV_BITMAP:
         ret = loadvm_handle_recv_bitmap(mis, len);