vringh64_to_cpu
u64 a = vringh64_to_cpu(vrh, desc.addr);
if (!rcheck(vrh, vringh64_to_cpu(vrh, desc.addr), &len, &range,
addr = (void *)(unsigned long)(vringh64_to_cpu(vrh, desc.addr) +
vringh64_to_cpu(vrh, desc.addr) + len);