Firmware and Boot Modes
OpenVMM supports several ways to boot a guest VM, each with different firmware requirements and guest OS compatibility:
| Boot mode | Architecture | Firmware | Use case |
|---|---|---|---|
| UEFI | x86_64, AArch64 | mu_msvm | Windows, modern Linux, full UEFI environment |
| PCAT BIOS | x86_64 | Hyper-V PCAT BIOS | Legacy OS, Gen1-style boot |
| Linux Direct | x86_64, AArch64 | None (VMM is the bootloader) | Fast Linux boot, development, testing |
| IGVM | x86_64, AArch64 | Packaged in IGVM file | OpenHCL paravisor, confidential VMs |
The boot mode is selected by which --kernel, --uefi, --pcat, or
--igvm flag is passed on the command line (or the equivalent ttrpc
configuration).