try to using CFU under Linux OS

Hi, All:

I have some questions about how to enable cfu.v in litex.

1. for currently CPU support, it seems VexRisc-V only, not for VexRisc-V SMP.
2. from current project samples, the CFU function enable by using RISC-V custom instruction. the environment is bare metal machine. for linux enable sw/fw, is there
any kernel driver module should be written for CFU operation.
3. for CFU instruction issued, how about the context switch handling?
4. for CFU design, the memory access seems still under develop. how to consider about cpu cache, DMA, DRAM, and CFU.

Many thanks.

BR, Akio