The pmap_copy function copies the range specified by src_addr and len from the source physical map src_pmap to the destination physical map dst_pmap at the address dst_addr.
The pmap_copy_page function copies the physical page src to the physical page dst, by mapping the page into kernel virtual address space (KVA), and using bcopy to copy the page.
The pmap_copy routine is only advisory and need not do anything. Actually implementing it may seriously reduce system performance.
The pmap_copy_page routine only operates upon a single page.