On Tue, Aug 5, 2025 at 10:28 PM Arun Menon <arme...@redhat.com> 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 qemu_loadvm_state() must report an error
> in errp, in case of failure.
>
> When postcopy live migration runs, the device states are loaded by
> both the qemu coroutine process_incoming_migration_co() and the
> postcopy_ram_listen_thread(). Therefore, it is important that the
> coroutine also reports the error in case of failure, with
> error_report_err(). Otherwise, the source qemu will not display
> any errors before going into the postcopy pause state.
>
> Signed-off-by: Arun Menon <arme...@redhat.com>
>
Reviewed-by: Marc-André Lureau <marcandre.lur...@redhat.com>
> ---
> migration/migration.c | 7 ++++---
> migration/savevm.c | 31 +++++++++++++++++++------------
> migration/savevm.h | 2 +-
> 3 files changed, 24 insertions(+), 16 deletions(-)
>
> diff --git a/migration/migration.c b/migration/migration.c
> index
> 10c216d25dec01f206eacad2edd24d21f00e614c..bb7d5e1dee52692cbea1d2c8fdca541e6a75bedb
> 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -881,7 +881,7 @@ process_incoming_migration_co(void *opaque)
> MIGRATION_STATUS_ACTIVE);
>
> mis->loadvm_co = qemu_coroutine_self();
> - ret = qemu_loadvm_state(mis->from_src_file);
> + ret = qemu_loadvm_state(mis->from_src_file, &local_err);
> mis->loadvm_co = NULL;
>
> trace_vmstate_downtime_checkpoint("dst-precopy-loadvm-completed");
> @@ -908,7 +908,8 @@ process_incoming_migration_co(void *opaque)
> }
>
> if (ret < 0) {
> - error_setg(&local_err, "load of migration failed: %s",
> strerror(-ret));
> + error_prepend(&local_err, "load of migration failed: %s: ",
> + strerror(-ret));
> goto fail;
> }
>
> @@ -924,7 +925,7 @@ fail:
> migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
> MIGRATION_STATUS_FAILED);
> migrate_set_error(s, local_err);
> - error_free(local_err);
> + error_report_err(local_err);
>
> migration_incoming_state_destroy();
>
> diff --git a/migration/savevm.c b/migration/savevm.c
> index
> 1bd27efe437d4d911728d776e995490d0a45dcf5..ca166ebd397ad80836ed2f9cb20a92f704fd4ed5
> 100644
> --- a/migration/savevm.c
> +++ b/migration/savevm.c
> @@ -3149,28 +3149,24 @@ out:
> return ret;
> }
>
> -int qemu_loadvm_state(QEMUFile *f)
> +int qemu_loadvm_state(QEMUFile *f, Error **errp)
> {
> MigrationState *s = migrate_get_current();
> MigrationIncomingState *mis = migration_incoming_get_current();
> - Error *local_err = NULL;
> int ret;
>
> - if (qemu_savevm_state_blocked(&local_err)) {
> - error_report_err(local_err);
> + if (qemu_savevm_state_blocked(errp)) {
> return -EINVAL;
> }
>
> qemu_loadvm_thread_pool_create(mis);
>
> - ret = qemu_loadvm_state_header(f, &local_err);
> + ret = qemu_loadvm_state_header(f, errp);
> if (ret) {
> - error_report_err(local_err);
> return ret;
> }
>
> - if (qemu_loadvm_state_setup(f, &local_err) != 0) {
> - error_report_err(local_err);
> + if (qemu_loadvm_state_setup(f, errp) != 0) {
> return -EINVAL;
> }
>
> @@ -3181,6 +3177,9 @@ int qemu_loadvm_state(QEMUFile *f)
> cpu_synchronize_all_pre_loadvm();
>
> ret = qemu_loadvm_state_main(f, mis);
> + if (ret < 0) {
> + error_setg(errp, "Load VM state failed: %d", ret);
> + }
> qemu_event_set(&mis->main_thread_load_event);
>
> trace_qemu_loadvm_state_post_main(ret);
> @@ -3198,8 +3197,14 @@ int qemu_loadvm_state(QEMUFile *f)
> if (migrate_has_error(migrate_get_current()) ||
> !qemu_loadvm_thread_pool_wait(s, mis)) {
> ret = -EINVAL;
> + error_setg(errp,
> + "Error while loading VM state: "
> + "Migration stream has error");
> } else {
> ret = qemu_file_get_error(f);
> + if (ret < 0) {
> + error_setg(errp, "Error while loading vmstate : %d", ret);
> + }
> }
> }
> /*
> @@ -3464,6 +3469,7 @@ void qmp_xen_save_devices_state(const char
> *filename, bool has_live, bool live,
>
> void qmp_xen_load_devices_state(const char *filename, Error **errp)
> {
> + ERRP_GUARD();
> QEMUFile *f;
> QIOChannelFile *ioc;
> int ret;
> @@ -3485,10 +3491,10 @@ void qmp_xen_load_devices_state(const char
> *filename, Error **errp)
> f = qemu_file_new_input(QIO_CHANNEL(ioc));
> object_unref(OBJECT(ioc));
>
> - ret = qemu_loadvm_state(f);
> + ret = qemu_loadvm_state(f, errp);
> qemu_fclose(f);
> if (ret < 0) {
> - error_setg(errp, "loading Xen device state failed");
> + error_prepend(errp, "loading Xen device state failed: ");
> }
> migration_incoming_state_destroy();
> }
> @@ -3496,6 +3502,7 @@ void qmp_xen_load_devices_state(const char
> *filename, Error **errp)
> bool load_snapshot(const char *name, const char *vmstate,
> bool has_devices, strList *devices, Error **errp)
> {
> + ERRP_GUARD();
> BlockDriverState *bs_vm_state;
> QEMUSnapshotInfo sn;
> QEMUFile *f;
> @@ -3559,13 +3566,13 @@ bool load_snapshot(const char *name, const char
> *vmstate,
> ret = -EINVAL;
> goto err_drain;
> }
> - ret = qemu_loadvm_state(f);
> + ret = qemu_loadvm_state(f, errp);
> migration_incoming_state_destroy();
>
> bdrv_drain_all_end();
>
> if (ret < 0) {
> - error_setg(errp, "Error %d while loading VM state", ret);
> + error_prepend(errp, "Error %d while loading VM state: ", ret);
> return false;
> }
>
> diff --git a/migration/savevm.h b/migration/savevm.h
> index
> 2d5e9c716686f06720325e82fe90c75335ced1de..b80770b7461a60e2ad6ba5e24a7baeae73d90955
> 100644
> --- a/migration/savevm.h
> +++ b/migration/savevm.h
> @@ -64,7 +64,7 @@ void qemu_savevm_send_colo_enable(QEMUFile *f);
> void qemu_savevm_live_state(QEMUFile *f);
> int qemu_save_device_state(QEMUFile *f);
>
> -int qemu_loadvm_state(QEMUFile *f);
> +int qemu_loadvm_state(QEMUFile *f, Error **errp);
> void qemu_loadvm_state_cleanup(MigrationIncomingState *mis);
> int qemu_loadvm_state_main(QEMUFile *f, MigrationIncomingState *mis);
> int qemu_load_device_state(QEMUFile *f);
>
> --
> 2.50.1
>
>
