To connect VLANs to tap devices the requirement is of vlan that should be available in the host operating system. Any frame that appears on this device can be attached using the QEMU process. This process request is received by another interfaces on VLAN and then frames are received by device. The command that is used to configure the networking mode:

qemu -net nic -net tap,ifname=qtap0 …

QEMU needs tuntap device driver that allow the user-space application to obtain different file discriptors that are connected to a network device. The tap devices can be seen by going to the directory file /dev/net/tun or else calling the function TUNSETIFF ioctl() that is allowed only to the user who are privileged.