Do you mean the macvtap mode doesn't support `tapfd` option of qemu at all?
Sorry, I'm not expert in this field, but I find some comments in this `units_net` file:
```
    For single queue, only returns one file descriptor, it's used by
    fd=<fd> legacy parameter of qemu
```
So I think there is still some qemu version uses legacy param, but I'm unsure macvtap has this param as well. Just want to confirm with you.