Building guests

When you build guests to run in a QNX virtualized environment, you must build them for the appropriate hardware architecture, and configure the VMs in which they will run.

You need to have the build environment and tools that correspond to the guests you're building (see Supported build environments).

Validating devices and guests

It may be easier to identify and debug some guest OS and device problems in a non-virtualized environment, before you integrate it into in your hypervisor system. In most environments, guests and devices also need further validation in the hypervisor environment.

For example, run the host OS on your target board and validate that devices work as intended with the host, before trying to configure them as pass-through devices. Checking that pass-through devices work with the host OS can also be helpful in figuring out the pass-through parameters that a given device requires (i.e., by running pidin to find which memory regions and hardware interrupt requests it uses).

In some environments, it could be useful to run the guest OS as the host on your target board, to validate that devices work as intended with it directly, before trying to configure them as pass-through devices. However, if you're building a QNX OS system to use as a guest, the startup driver required for the guest may not work directly on the board; you may have to change the buildfile for the guest to (temporarily) use the appropriate driver for starting it up directly on the board.

CAUTION:

Remember that the hardware presented by a qvm system is fundamentally unlike the hardware presented by the host system. (This characteristic is why the startup driver for guests corresponds to the model that qvm presents to the guest, not the board on which the host resides.)

Further validation of a guest in the hypervisor environment is needed in any of the following situations:
  • The guest uses para-virtualized devices, which by definition don't exist as hardware.
  • The guest uses vdevs, meaning the configuration for the VM that hosts the guest must be updated to include these vdevs (see Configuring the VMs below).
  • Some devices aren't passed through to the guest. In this case, you need different drivers when you run the hypervisor system so the hypervisor host can manage these devices.

Supported guest formats in images

The hypervisor can launch guests placed on the system as bootable images in the following formats:
  • ELF (including multiboot)
  • Linux zImage

Configuring the VMs

Each guest in a hypervisor system is hosted in a hypervisor qvm process. When it is started, each qvm process instance reads its specified configuration file and assembles a VM from the components specified in this file. This VM becomes the virtual environment in which the guest runs.

If you change anything in your guest that accesses hardware (physical or virtual), you need to ensure that the qvm configuration file for the VM that will host the guest is properly configured.

When building a guest to run in a QNX virtualized environment, it is important to remember that the guest must be configured to match the VM in which it will run. This means that it must have the drivers it needs to access devices, whether they are physical or virtual. In the VM, the drivers must be configured to be where the guest expects them to be.

In a QNX OS system, board-specific drivers and other components are brought into the build through BSPs. This is true for a QNX OS that will run in a VM, just as it is for a QNX OS that will run directly on hardware.

For both ARM and x86 hardware platforms, you'll need the BSP for your supported platform to build the hypervisor host domain, and a hypervisor guest BSP to build each QNX OS guest. If you add new devices for your guest, you'll probably need to add the appropriate new drivers to the BSPs, and rebuild the guest with them.

What is true for QNX guests is also true for non-QNX guests: the VM must present to the guest the virtual environment the guest OS expects to find (i.e., the hardware components it has been built to use). The only difference is that QNX OSs (including QNX OSs that will run as guests in virtualized environments) use BSPs to bring in the architecture-specific and board-specific components, while other OSs may use other mechanisms to achieve the same end.

For more information, see Assembling and configuring VMs in the Configuration chapter.

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