The WARN_ON() is used to check if we break the legal hierarchy, on
which the effective mems should be equal to configured mems.
Reported-by: NMike Qiu <qiudayu@linux.vnet.ibm.com>
Tested-by: NMike Qiu <qiudayu@linux.vnet.ibm.com>
Signed-off-by: NLi Zefan <lizefan@huawei.com>