Correct, currently usermode QEMU does not emulate the mmu, but just has a flat mapping of guestaddr = hostaddr + constant_base_addr. There has been some thought of adding mmu emulation to usermode, though, as the simple fixed mapping has problems (eg if the guest wants to map at some address where there's already something in the host address space, or for guest archs where the highbits of guest addresses are important like ia64).