Elevator Pitch

• The 2‑VM limit for macOS guests on Apple Silicon is enforced in the kernel, and can be overridden by booting a development kernel and setting the hidden hv_apple_isa_vm_quota boot-arg.

Key Takeaways

• The VM cap isn’t hardcoded in Virtualization.framework userspace; it’s implemented in closed-source XNU hypervisor code via an internal quota variable.
• A development kernel honors boot-args (hypervisor= and hv_apple_isa_vm_quota=) that can raise the active macOS VM limit (e.g., to 255).
• Using a custom kernel collection on Apple Silicon complicates OS updates; you must revert boot policy/kernel collection to update normally.

Most Memorable Quotes

• “Apple Silicon hosts can only have a maximum of 2 macOS guest VMs active at once.”
• “The number of virtual machines exceeds the limit. The maximum supported number of active virtual machines has been reached.”
• “hv_apple_isa_vm_quota= can override the VM limitation in the kernel!”