@puttic. hi!
The general idea is about configuring the IPsec policy with qos pre-classify, then configuring traffic policy under the interface to remark the ipsec traffic.
For the detailed example, please refer to:
http://support.huawei.com/hedex/hdx.do?docid=EDOC1000085855&lang=en&tocURL=resources/dc/dc_ar_cc_ipsec_0019.html.