migration: Add Error** argument to .save_setup() handler

The purpose is to record a potential error in the migration stream if
qemu_savevm_state_setup() fails. Most of the current .save_setup()
handlers can be modified to use the Error argument instead of managing
their own and calling locally error_report().

Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Harsh Prateek Bora <harshpb@linux.ibm.com>
Cc: Halil Pasic <pasic@linux.ibm.com>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Eric Blake <eblake@redhat.com>
Cc: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Cc: John Snow <jsnow@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20240320064911.545001-8-clg@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>

8 files changed, 29 insertions, 35 deletions

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index e9bc97fee0..823164e81c 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2172,7 +2172,7 @@ static const VMStateDescription vmstate_spapr = {
     }
 };
 
-static int htab_save_setup(QEMUFile *f, void *opaque)
+static int htab_save_setup(QEMUFile *f, void *opaque, Error **errp)
 {
     SpaprMachineState *spapr = opaque;
 
diff --git a/hw/s390x/s390-stattrib.c b/hw/s390x/s390-stattrib.c
index b743e8a2fe..bc04187b2b 100644
--- a/hw/s390x/s390-stattrib.c
+++ b/hw/s390x/s390-stattrib.c
@@ -168,19 +168,17 @@ static int cmma_load(QEMUFile *f, void *opaque, int version_id)
     return ret;
 }
 
-static int cmma_save_setup(QEMUFile *f, void *opaque)
+static int cmma_save_setup(QEMUFile *f, void *opaque, Error **errp)
 {
     S390StAttribState *sas = S390_STATTRIB(opaque);
     S390StAttribClass *sac = S390_STATTRIB_GET_CLASS(sas);
-    Error *local_err = NULL;
     int res;
     /*
      * Signal that we want to start a migration, thus needing PGSTE dirty
      * tracking.
      */
-    res = sac->set_migrationmode(sas, true, &local_err);
+    res = sac->set_migrationmode(sas, true, errp);
     if (res) {
-        error_report_err(local_err);
         return res;
     }
     qemu_put_be64(f, STATTR_FLAG_EOS);
diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
index bf5a29ddc1..5763c0b683 100644
--- a/hw/vfio/migration.c
+++ b/hw/vfio/migration.c
@@ -376,7 +376,7 @@ static int vfio_save_prepare(void *opaque, Error **errp)
     return 0;
 }
 
-static int vfio_save_setup(QEMUFile *f, void *opaque)
+static int vfio_save_setup(QEMUFile *f, void *opaque, Error **errp)
 {
     VFIODevice *vbasedev = opaque;
     VFIOMigration *migration = vbasedev->migration;
@@ -390,8 +390,8 @@ static int vfio_save_setup(QEMUFile *f, void *opaque)
                                       stop_copy_size);
     migration->data_buffer = g_try_malloc0(migration->data_buffer_size);
     if (!migration->data_buffer) {
-        error_report("%s: Failed to allocate migration data buffer",
-                     vbasedev->name);
+        error_setg(errp, "%s: Failed to allocate migration data buffer",
+                   vbasedev->name);
         return -ENOMEM;
     }
 
@@ -401,8 +401,8 @@ static int vfio_save_setup(QEMUFile *f, void *opaque)
             ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_PRE_COPY,
                                            VFIO_DEVICE_STATE_RUNNING);
             if (ret) {
-                error_report("%s: Failed to set new PRE_COPY state",
-                             vbasedev->name);
+                error_setg(errp, "%s: Failed to set new PRE_COPY state",
+                           vbasedev->name);
                 return ret;
             }
 
@@ -413,8 +413,8 @@ static int vfio_save_setup(QEMUFile *f, void *opaque)
             /* vfio_save_complete_precopy() will go to STOP_COPY */
             break;
         default:
-            error_report("%s: Invalid device state %d", vbasedev->name,
-                         migration->device_state);
+            error_setg(errp, "%s: Invalid device state %d", vbasedev->name,
+                       migration->device_state);
             return -EINVAL;
         }
     }
@@ -425,8 +425,7 @@ static int vfio_save_setup(QEMUFile *f, void *opaque)
 
     ret = qemu_file_get_error(f);
     if (ret < 0) {
-        error_report("%s: save setup failed : %s", vbasedev->name,
-                     strerror(-ret));
+        error_setg_errno(errp, -ret, "%s: save setup failed", vbasedev->name);
     }
 
     return ret;
diff --git a/include/migration/register.h b/include/migration/register.h
index d7b70a8be6..64fc7c1103 100644
--- a/include/migration/register.h
+++ b/include/migration/register.h
@@ -60,10 +60,11 @@ typedef struct SaveVMHandlers {
      *
      * @f: QEMUFile where to send the data
      * @opaque: data pointer passed to register_savevm_live()
+     * @errp: pointer to Error*, to store an error if it happens.
      *
      * Returns zero to indicate success and negative for error
      */
-    int (*save_setup)(QEMUFile *f, void *opaque);
+    int (*save_setup)(QEMUFile *f, void *opaque, Error **errp);
 
     /**
      * @save_cleanup
diff --git a/migration/block-dirty-bitmap.c b/migration/block-dirty-bitmap.c
index 2708abf3d7..542a8c297b 100644
--- a/migration/block-dirty-bitmap.c
+++ b/migration/block-dirty-bitmap.c
@@ -1213,12 +1213,14 @@ fail:
     return ret;
 }
 
-static int dirty_bitmap_save_setup(QEMUFile *f, void *opaque)
+static int dirty_bitmap_save_setup(QEMUFile *f, void *opaque, Error **errp)
 {
     DBMSaveState *s = &((DBMState *)opaque)->save;
     SaveBitmapState *dbms = NULL;
 
     if (init_dirty_bitmap_migration(s) < 0) {
+        error_setg(errp,
+                   "Failed to initialize dirty tracking bitmap for blocks");
         return -1;
     }
 
diff --git a/migration/block.c b/migration/block.c
index f8a11beb37..bae6e94891 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -711,10 +711,9 @@ static void block_migration_cleanup(void *opaque)
     blk_mig_unlock();
 }
 
-static int block_save_setup(QEMUFile *f, void *opaque)
+static int block_save_setup(QEMUFile *f, void *opaque, Error **errp)
 {
     int ret;
-    Error *local_err = NULL;
 
     trace_migration_block_save("setup", block_mig_state.submitted,
                                block_mig_state.transferred);
@@ -722,25 +721,21 @@ static int block_save_setup(QEMUFile *f, void *opaque)
     warn_report("block migration is deprecated;"
                 " use blockdev-mirror with NBD instead");
 
-    ret = init_blk_migration(f, &local_err);
+    ret = init_blk_migration(f, errp);
     if (ret < 0) {
-        error_report_err(local_err);
         return ret;
     }
 
     /* start track dirty blocks */
     ret = set_dirty_tracking();
     if (ret) {
-        error_setg_errno(&local_err, -ret,
-                         "Failed to start block dirty tracking");
-        error_report_err(local_err);
+        error_setg_errno(errp, -ret, "Failed to start block dirty tracking");
         return ret;
     }
 
     ret = flush_blks(f);
     if (ret) {
-        error_setg_errno(&local_err, -ret, "Flushing block failed");
-        error_report_err(local_err);
+        error_setg_errno(errp, -ret, "Flushing block failed");
         return ret;
     }
     blk_mig_reset_dirty_cursor();
diff --git a/migration/ram.c b/migration/ram.c
index 44d7073730..6ea5a06e00 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3066,22 +3066,23 @@ static bool mapped_ram_read_header(QEMUFile *file, MappedRamHeader *header,
  *
  * @f: QEMUFile where to send the data
  * @opaque: RAMState pointer
+ * @errp: pointer to Error*, to store an error if it happens.
  */
-static int ram_save_setup(QEMUFile *f, void *opaque)
+static int ram_save_setup(QEMUFile *f, void *opaque, Error **errp)
 {
     RAMState **rsp = opaque;
     RAMBlock *block;
     int ret, max_hg_page_size;
 
     if (compress_threads_save_setup()) {
-        error_report("%s: failed to start compress threads", __func__);
+        error_setg(errp, "%s: failed to start compress threads", __func__);
         return -1;
     }
 
     /* migration has already setup the bitmap, reuse it. */
     if (!migration_in_colo_state()) {
         if (ram_init_all(rsp) != 0) {
-            error_report("%s: failed to setup RAM for migration", __func__);
+            error_setg(errp, "%s: failed to setup RAM for migration", __func__);
             compress_threads_save_cleanup();
             return -1;
         }
@@ -3118,14 +3119,14 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
 
     ret = rdma_registration_start(f, RAM_CONTROL_SETUP);
     if (ret < 0) {
-        error_report("%s: failed to start RDMA registration", __func__);
+        error_setg(errp, "%s: failed to start RDMA registration", __func__);
         qemu_file_set_error(f, ret);
         return ret;
     }
 
     ret = rdma_registration_stop(f, RAM_CONTROL_SETUP);
     if (ret < 0) {
-        error_report("%s: failed to stop RDMA registration", __func__);
+        error_setg(errp, "%s: failed to stop RDMA registration", __func__);
         qemu_file_set_error(f, ret);
         return ret;
     }
@@ -3142,7 +3143,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     ret = multifd_send_sync_main();
     bql_lock();
     if (ret < 0) {
-        error_report("%s: multifd synchronization failed", __func__);
+        error_setg(errp, "%s: multifd synchronization failed", __func__);
         return ret;
     }
 
@@ -3154,7 +3155,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
     qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
     ret = qemu_fflush(f);
     if (ret < 0) {
-        error_report("%s failed : %s", __func__, strerror(-ret));
+        error_setg_errno(errp, -ret, "%s failed", __func__);
     }
     return ret;
 }
diff --git a/migration/savevm.c b/migration/savevm.c
index 327e9b346e..a2679ba0b8 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1342,11 +1342,9 @@ int qemu_savevm_state_setup(QEMUFile *f, Error **errp)
         }
         save_section_header(f, se, QEMU_VM_SECTION_START);
 
-        ret = se->ops->save_setup(f, se->opaque);
+        ret = se->ops->save_setup(f, se->opaque, errp);
         save_section_footer(f, se);
         if (ret < 0) {
-            error_setg(errp, "failed to setup SaveStateEntry with id(name): "
-                       "%d(%s): %d", se->section_id, se->idstr, ret);
             qemu_file_set_error(f, ret);
             break;
         }