attempt1: ptmx opens ok=217405 fail=0 (maxvnodes=300)
attempt2: holding 1001 ptmx fds; opens ok=0 fail=200000 errno=19 ENODEV (pty unit cap, not getnewvnode)
guest alive both runs

env: DragonFly 6.5-DEVELOPMENT INVARIANTS kernel, QEMU/KVM 6 vCPU, 4GB RAM