@ypu Thanx for your reply. The reason I want to change this order is that I think there should be a conflict between subtests.cfg and guest-xxx.cfg, and we should use the value from subtests.cfg rather than the default value in guest-xxx.cfg. But now I am not sure my assumption here. It seems the parameter we can set in subtests.cfg should be put in base.cfg and the others in guest-xxx.cfg should not be changed. 

Okey, I need to refresh my memory for this patch.