[RFC v3 2/2] migration: Update error description whenever migration fails

[Tejus GK]

There are places outside of migration.c which eventually leads to a
migration failure, but the failure reason is never updated. Hence
libvirt doesn't know why the migration failed when it queries for it.

Signed-off-by: Tejus GK <tejus.gk@nutanix.com>
---
 migration/savevm.c  | 13 ++++++++++---
 migration/vmstate.c | 13 ++++++++++---
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index e33788343a..39d4ecdd41 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1068,10 +1068,14 @@ void qemu_savevm_send_open_return_path(QEMUFile *f)
 int qemu_savevm_send_packaged(QEMUFile *f, const uint8_t *buf, size_t len)
 {
     uint32_t tmp;
+    MigrationState *ms = migrate_get_current();
+    Error *local_err = NULL;
 
     if (len > MAX_VM_CMD_PACKAGED_SIZE) {
-        error_report("%s: Unreasonably large packaged state: %zu",
+        error_setg(&local_err, "%s: Unreasonably large packaged state: %zu",
                      __func__, len);
+        migrate_set_error(ms, local_err);
+        error_report_err(local_err);
         return -1;
     }
 
@@ -1456,6 +1460,7 @@ int 
qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
     int vmdesc_len;
     SaveStateEntry *se;
     int ret;
+    Error *local_err = NULL;
 
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
         if (se->vmsd && se->vmsd->early_setup) {
@@ -1475,8 +1480,10 @@ int 
qemu_savevm_state_complete_precopy_non_iterable(QEMUFile *f,
          * bdrv_activate_all() on the other end won't fail. */
         ret = bdrv_inactivate_all();
         if (ret) {
-            error_report("%s: bdrv_inactivate_all() failed (%d)",
-                         __func__, ret);
+            error_setg(&local_err, "%s: bdrv_inactivate_all() failed (%d)",
+                       __func__, ret);
+            migrate_set_error(ms, local_err);
+            error_report_err(local_err);
             qemu_file_set_error(f, ret);
             return ret;
         }
diff --git a/migration/vmstate.c b/migration/vmstate.c
index af01d54b6f..3a5770b925 100644
--- a/migration/vmstate.c
+++ b/migration/vmstate.c
@@ -14,6 +14,7 @@
 #include "migration.h"
 #include "migration/vmstate.h"
 #include "savevm.h"
+#include "qapi/error.h"
 #include "qapi/qmp/json-writer.h"
 #include "qemu-file.h"
 #include "qemu/bitops.h"
@@ -323,6 +324,8 @@ int vmstate_save_state_v(QEMUFile *f, const 
VMStateDescription *vmsd,
 {
     int ret = 0;
     const VMStateField *field = vmsd->fields;
+    MigrationState *ms = migrate_get_current();
+    Error *local_err = NULL;
 
     trace_vmstate_save_state_top(vmsd->name);
 
@@ -330,7 +333,9 @@ int vmstate_save_state_v(QEMUFile *f, const 
VMStateDescription *vmsd,
         ret = vmsd->pre_save(opaque);
         trace_vmstate_save_state_pre_save_res(vmsd->name, ret);
         if (ret) {
-            error_report("pre-save failed: %s", vmsd->name);
+            error_setg(&local_err, "pre-save failed: %s", vmsd->name);
+            migrate_set_error(ms, local_err);
+            error_report_err(local_err);
             return ret;
         }
     }
@@ -383,8 +388,10 @@ int vmstate_save_state_v(QEMUFile *f, const 
VMStateDescription *vmsd,
                                      vmdesc_loop);
                 }
                 if (ret) {
-                    error_report("Save of field %s/%s failed",
-                                 vmsd->name, field->name);
+                    error_setg(&local_err, "Save of field %s/%s failed",
+                                vmsd->name, field->name);
+                    migrate_set_error(ms, local_err);
+                    error_report_err(local_err);
                     if (vmsd->post_save) {
                         vmsd->post_save(opaque);
                     }
-- 
2.22.3