Re: [PATCH v6 01/24] migration: push Error **errp into vmstate_subsection_load()

[Akihiko Odaki]

On 2025/07/21 20:29, Arun Menon wrote:

This is an incremental step in converting vmstate loading
code to report error via Error objects instead of directly
printing it to console/monitor.
It is ensured that vmstate_subsection_load() must report an error
in errp, in case of failure.

Signed-off-by: Arun Menon <arme...@redhat.com>
---
  migration/vmstate.c | 10 +++++++---
  1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/migration/vmstate.c b/migration/vmstate.c
index 
5feaa3244d259874f03048326b2497e7db32e47c..129b19d7603a0ddf8ab6e946e41c1c4d773d1fa8
 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -25,7 +25,7 @@ static int vmstate_subsection_save(QEMUFile *f, const 
VMStateDescription *vmsd,
                                     void *opaque, JSONWriter *vmdesc,
                                     Error **errp);
  static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription 
*vmsd,
-                                   void *opaque);
+                                   void *opaque, Error **errp);

/* Whether this field should exist for either save or load the VM? */

  static bool
@@ -225,7 +225,7 @@ int vmstate_load_state(QEMUFile *f, const 
VMStateDescription *vmsd,
          field++;
      }
      assert(field->flags == VMS_END);
-    ret = vmstate_subsection_load(f, vmsd, opaque);
+    ret = vmstate_subsection_load(f, vmsd, opaque, NULL);
      if (ret != 0) {
          qemu_file_set_error(f, ret);
          return ret;
@@ -566,7 +566,7 @@ vmstate_get_subsection(const VMStateDescription * const 
*sub,
  }

static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,

-                                   void *opaque)
+                                   void *opaque, Error **errp)
  {
      trace_vmstate_subsection_load(vmsd->name);

@@ -598,6 +598,8 @@ static int vmstate_subsection_load(QEMUFile *f, const VMStateDescription *vmsd,

          sub_vmsd = vmstate_get_subsection(vmsd->subsections, idstr);
          if (sub_vmsd == NULL) {
              trace_vmstate_subsection_load_bad(vmsd->name, idstr, "(lookup)");
+            error_setg(errp, "VM subsection '%s'  in '%s' does not exist",

There are two whitespaces before "in" but I think we only need one.

+                       idstr, vmsd->name);
              return -ENOENT;
          }
          qemu_file_skip(f, 1); /* subsection */
@@ -608,6 +610,8 @@ static int vmstate_subsection_load(QEMUFile *f, const 
VMStateDescription *vmsd,
          ret = vmstate_load_state(f, sub_vmsd, opaque, version_id);
          if (ret) {
              trace_vmstate_subsection_load_bad(vmsd->name, idstr, "(child)");
+            error_setg(errp, "Loading VM subsection '%s' in '%s' failed : %d",
+                       idstr, vmsd->name, ret);
              return ret;
          }
      }