[Pacemaker] How to config STONITH on centos using fence_ipmilan

[david.miao]

I install fence_ipmilan with the command: yum install fence-agents

My stonith configuration is as following:
node master
node slave
...
primitive stonith-master stonith:fence_ipmilan \
     params ipaddr=192.168.1.36 login=root passwd=master 
pcmk_host_list=master pcmk_host_check=static-list action=off \
     op monitor interval=30s
primitive stonith-slave stonith:fence_ipmilan \
     params ipaddr=192.168.1.37 login=root passwd=slave 
pcmk_host_list=slave pcmk_host_check=static-list action=off delay=15s \
     op monitor interval=30s

location stonith-master-mutex-master stonith-master -inf: master
location stonith-slave-mutex-slave stonith-slave -inf: slave

This can work, but my question is: Are the "location" above necessary?
Can I use pcmk_host_list="some nodes" to control which nodes the 
fence_ipmilan agent can run on?
If can`t, what is the meaning of the pcmk_host_list. I have referenced 
to the manual but I can`t understand.