Does anyone enable FPU successfully in riscv arch?

[ite-ch]

Hi,

I had already set CONFIG_CPU_HAS_FPU, CONFIG_FPU, CONFIG_FPU_SHARING, CONFIG_FLOAT_HARD, but it doesn't seem to work.
I tried to monitor csr mstatus when initializing, and I found that mstatus is set 0x80007800 util switch_to_main_thread(), then swap to main thread, I printed content of mstatus in the begining of bg_thread_main() function, but I saw mstatus is changed to 0x88.
It means FS[1:0] field is set to zero.
I have no idea what happened between switch_to_main_thread() and bg_thread_main().
Any one can help?
Does anyone can share the experience of enabling HW float in riscv arch?

Thanks,
CH