Why risc-v does not implement dcache flush

[foxriver1025]

I have a dma requirement and need the dcache flush function. When I enable CONFIG_CACHE_MANAGEMENT and CONFIG_ARCH_CACHE, the compiler reports an error.
undefined reference to `arch_dcache_flush_and_invd_range'
I can't find the code for risc-v to implement dcache flush. What should I do?