vfio/migration: Add Error** argument to .vfio_save_config() handler

Use vmstate_save_state_with_err() to improve error reporting in the
callers and store a reported error under the migration stream. Add
documentation while at it.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Avihai Horon <avihaih@nvidia.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>

1 files changed, 18 insertions, 7 deletions

diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index 43fed0dbdb..5d91364f3b 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -193,21 +193,30 @@ static int vfio_load_buffer(QEMUFile *f, VFIODevice *vbasedev,
     return ret;
 }
 
-static int vfio_save_device_config_state(QEMUFile *f, void *opaque)
+static int vfio_save_device_config_state(QEMUFile *f, void *opaque,
+                                         Error **errp)
 {
     VFIODevice *vbasedev = opaque;
+    int ret;
 
     qemu_put_be64(f, VFIO_MIG_FLAG_DEV_CONFIG_STATE);
 
     if (vbasedev->ops && vbasedev->ops->vfio_save_config) {
-        vbasedev->ops->vfio_save_config(vbasedev, f);
+        ret = vbasedev->ops->vfio_save_config(vbasedev, f, errp);
+        if (ret) {
+            return ret;
+        }
     }
 
     qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
 
     trace_vfio_save_device_config_state(vbasedev->name);
 
-    return qemu_file_get_error(f);
+    ret = qemu_file_get_error(f);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Failed to save state");
+    }
+    return ret;
 }
 
 static int vfio_load_device_config_state(QEMUFile *f, void *opaque)
@@ -592,13 +601,15 @@ static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
 static void vfio_save_state(QEMUFile *f, void *opaque)
 {
     VFIODevice *vbasedev = opaque;
+    Error *local_err = NULL;
     int ret;
 
-    ret = vfio_save_device_config_state(f, opaque);
+    ret = vfio_save_device_config_state(f, opaque, &local_err);
     if (ret) {
-        error_report("%s: Failed to save device config space",
-                     vbasedev->name);
-        qemu_file_set_error(f, ret);
+        error_prepend(&local_err,
+                      "vfio: Failed to save device config space of %s - ",
+                      vbasedev->name);
+        qemu_file_set_error_obj(f, ret, local_err);
     }
 }