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When migration connection is broken, the QEMU and libvirtd(8) process on the source side receive TCP connection reset notification. QEMU sets the migration status to FAILED and proceeds to migration_cleanup(). Meanwhile, Libvirtd(8) sends a QMP command to migrate_set_capabilities(). The migration_cleanup() and qmp_migrate_set_capabilities() calls race with each other. When the latter is invoked first, since the migration is not running (FAILED), migration capabilities are reset to false, so during migration_cleanup() the QEMU process crashes with assertion failure. Introduce a new migration status FAILING and use it as an interim status when an error occurs. Once migration_cleanup() is done, it sets the migration status to FAILED. This helps to avoid the above race condition and ensuing failure. Interim status FAILING is set wherever the execution moves towards migration_cleanup(): - postcopy_start() - migration_thread() - migration_cleanup() - multifd_send_setup() - bg_migration_thread() - migration_completion() - migration_detect_error() - bg_migration_completion() - multifd_send_error_propagate() - migration_connect_error_propagate() The migration status finally moves to FAILED and reports an appropriate error to the user. Interim status FAILING is _NOT_ set in the following routines because they do not follow the migration_cleanup() path to the FAILED state: - cpr_exec_cb() - qemu_savevm_state() - postcopy_listen_thread() - process_incoming_migration_co() - multifd_recv_terminate_threads() - migration_channel_process_incoming() Reviewed-by: Peter Xu <peterx@redhat.com> Signed-off-by: Prasad Pandit <pjp@fedoraproject.org> Link: https://lore.kernel.org/qemu-devel/20260224102547.226087-1-ppandit@redhat.com Signed-off-by: Fabiano Rosas <farosas@suse.de>