How to auto grab/release mouse pointer in QEMU/KVM?

I tried VMs in virt-manager (or vfio, I don't know the difference), and I found the auto grab and release function a total bargain. Now I switched to QEMU and I don't have this function (at least not by default).

Is there a way to enable it in QEMU?

Thanks for you help ;)

EDIT: I'm on Ubuntu 20.10 and I use the QEMU GTK app