Hi Gurus:
  Forgive my junior HW knowledge, I just found that in execlist context 
initialization function populate_lr_context(), this line:
  
          reg_state[CTX_CONTEXT_CONTROL+1] =
                          _MASKED_BIT_ENABLE((1<<3) | MI_RESTORE_INHIBIT);
  
It seems the "Inhibit Synchronous Context Switch" bit is not set here, so when 
HW is trying to wait some events, e.g. semaphore, according to Bspec, per my 
basic understanding, it will switch out current context with some reason bit 
set. Here comes my question, I think if this situation happen, should i915 
remember this context and try to re-schedule it in a proper time, e.g. before 
submitting a new context until the context_completed bit in CSB is set? I don't 
find a register that will remember the context switched out by waiting event, 
so I think it should be i915 to handle this situation or just set "Inhibit 
Synchronous Context Switch" bit here?... 

Thanks,
Zhi.
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