Following up on @David Weber and @alchemy's answer:

You want to follow this step-by-step.

NB: Keep in mind the value of your Target path.

After you've added the new virtual hardware, enter the VM and do:

1. Create a directory inside your VM: mkdir /mnt/random

2. Mount: mount -t 9p -o trans=virtio <value_of_target> /mnt/random