Re: [PATCH 03/14] migration: Propagate errors in migration_completion_precopy()

["Cédric Le Goater" <clg@redhat.com>]

On 5/5/26 10:14, Avihai Horon wrote:
> migration_completion_precopy() doesn't propagate errors to migration
> core which leads to error information loss. Fix that.
> 
> This prepares for a follow-up where migration_switchover_start() can
> fail on switchover-ack and still report a useful error. Errors from
> qemu_savevm_state_complete_precopy() are not propagated yet as it
> requires more plumbing.
> 
> Signed-off-by: Avihai Horon <avihaih@nvidia.com>
> ---
>   migration/migration.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 6fd89995a2..a5c7ca6796 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -2780,23 +2780,28 @@ static bool migration_switchover_start(MigrationState *s, Error **errp)
>   static int migration_completion_precopy(MigrationState *s)
>   {
>       int ret;
> +    Error *local_err = NULL;
>   
>       bql_lock();
>   
>       if (!migrate_mode_is_cpr()) {
>           ret = migration_stop_vm(s, RUN_STATE_FINISH_MIGRATE);
>           if (ret < 0) {
> +            error_setg_errno(&local_err, -ret, "Failed to stop the VM");
>               goto out_unlock;
>           }
>       }
>   
> -    if (!migration_switchover_start(s, NULL)) {
> +    if (!migration_switchover_start(s, &local_err)) {
>           ret = -EFAULT;
>           goto out_unlock;
>       }
>   
>       ret = qemu_savevm_state_complete_precopy(s);
>   out_unlock:
> +    if (local_err) {
> +        migrate_error_propagate(s, local_err);
> +    }
>       bql_unlock();
>       return ret;
>   }

Instead, I would modify migration_completion_precopy() to use the Error
variable in migration_completion() :

   static void migration_completion(MigrationState *s)
   {
       int ret = 0;
       Error *local_err = NULL;

       if (s->state == MIGRATION_STATUS_ACTIVE) {
           ret = migration_completion_precopy(s);

       ...

Thanks,

C.