[PATCH v12 01/27] migration: push Error **errp into vmstate_subsection_load()

[Arun Menon]

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.

The errors are temporarily reported using warn_report_err().
This is removed in the subsequent patches in this series,
when we are actually able to propagate the error to the calling
function using errp.

Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com>
Signed-off-by: Arun Menon <arme...@redhat.com>
---
 migration/vmstate.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/migration/vmstate.c b/migration/vmstate.c
index 
5feaa3244d259874f03048326b2497e7db32e47c..3d9f284700368e2fd573d5d77b7f7ab88008cc91
 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
@@ -136,6 +136,7 @@ int vmstate_load_state(QEMUFile *f, const 
VMStateDescription *vmsd,
 {
     const VMStateField *field = vmsd->fields;
     int ret = 0;
+    Error *local_err = NULL;
 
     trace_vmstate_load_state(vmsd->name, version_id);
     if (version_id > vmsd->version_id) {
@@ -225,9 +226,10 @@ 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, &local_err);
     if (ret != 0) {
         qemu_file_set_error(f, ret);
+        warn_report_err(local_err);
         return ret;
     }
     if (vmsd->post_load) {
@@ -566,7 +568,7 @@ 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 +600,8 @@ 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",
+                       idstr, vmsd->name);
             return -ENOENT;
         }
         qemu_file_skip(f, 1); /* subsection */
@@ -608,6 +612,9 @@ 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;
         }
     }

-- 
2.50.1