descriptor privilege level

      In the IDT(Interrupt description table), every item can be called gate, such as interrupt

gate, trap gate, call gate and task gate. What's gate?, gate means the start point to some place, off course, every gate should have it's own lock,ok, here I want to say is: in the IDT, DPL just like the lock of interrupt gate, trap gate etc. If the operation want to be executed by CPU, it have to open the lock, that's CPL <= DPL.

      CPL stand for the current running process's privilege, DPL stand for the gate's privilege, if the current running process wants to pass the target gate, the condition CPL <= DPL should be true, that is CPL higher than DPL.