* To run more programs on debian, we use 256MB memory described in dts.
  But if the hardware still provides 128MB memory, the memory access
  will wrap around when Linux allocate a physical page excceed 128MB,
  which causes wrong memory access.

* after 4 hours, the command will be sent repeatly

* this is because we can not control the mip.mtip bit in NEMU

* This will skip instruction fetching from MMIO, which is hard to
  compare with NEMU.

Otherwise dmemXbar will not behave correctly.

When SPF/LPF was raised, LSU used to wait until its FSM go back to s_idle then commit.
However, CSR will modify mode/status immediately when it gets PF signal.
Here comes the problem: when a PF is raised, redirect may not happen because mode/status i not right.

* coh should have higher priority to acquire the lock, since coh
  request will block normal request in CoherenceInterconnect

* also put mainargs at 0x80001000 to match AM