Authors:

avatar of Shmuel Leib Melamud

Shmuel Leib Melamud

Feature pages are design documents that developers have created while collaborating on oVirt.

Most of them are outdated, but provide historical design context.

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Bochs-display

Summary

This feature adds a new display type bochs-display and enables it for UEFI VMs.

Owner

  • Name: Shmuel Melamud
  • Email: smelamud@redhat.com

Description

The bochs-display device is a simple display device which is similar to VGA but without legacy emulation. The code size and complexity needed to emulate this device is an order of magnitude smaller, resulting in a reduced attack surface. Another nice feature is that you can place this device in a PCI Express slot.

For UEFI guests it is safe to use the bochs display device instead of the standard VGA device. The firmware will setup a linear framebuffer as graphics output protocol anyway and never use any legacy VGA features.

For BIOS guests this device might be usable as well, depending on whenever they depend on direct VGA hardware access or not.

Changes to Engine

  1. Add new bochs value to DisplayType enum and the corresponding VmDeviceType.BOCHS value. This automatically adds ‘bochs’ to the selection of display types in the UI and enables generation of the correct video device in libvirt XML.
  2. In all places where graphics device type is derived from display type, return VNC for bochs display type.
  3. In AddVm and UpdateVm commands fail validation, if default display type is set to bochs, but firmware type is not UEFI or cluster compatibility version < 4.5.
  4. If effective firmware type of a VM is changed to non-UEFI, and it has default display type bochs, change it to vga.
  5. In UI, do not include ‘bochs’ as a choice for default display type for a VM, if its effective firmware type is not UEFI or cluster compatibility version < 4.5.
  6. In UI and REST API, when ‘Server’ configuration is chosen for a VM and its effective firmware type is UEFI, select bochs display type by default.

Tests

  1. Open VM creation dialog and select a cluster having compatibility version >= 4.5. Open the list of available display types.
    Expected result: bochs appears in the list of display types.
  2. Open VM creation dialog and select a cluster having compatibility version < 4.5. Open the list of available display types.
    Expected result: bochs does not appear in the list of display types.
  3. Open VM creation dialog and select a cluster having compatibility version >= 4.5. Set VM firware type to BIOS. Open the list of available display types.
    Expected result: bochs does not appear in the list of display types.
  4. Open VM creation dialog and select a cluster having compatibility version >= 4.5 and cluster firmware type BIOS. Set VM firware type to “Cluster default”. Open the list of available display types.
    Expected result: bochs does not appear in the list of display types.
  5. Create a VM with “Cluster default” firmware type and bochs display type in a cluster having UEFI firmware type. Change firmware type of the cluster to BIOS.
    Expected result: Display type of the VM is changed to vga.
  6. Use REST API to create a VM with BIOS firmware type and bochs display type.
    Expected result: VM creation fails.
  7. Use REST API to create a VM with “Cluster default” firmware type and bochs display type in a cluster having BIOS firmware type.
    Expected result: VM creation fails.
  8. Use REST API to update a VM with BIOS firmware type and set its display type to bochs.
    Expected result: VM update fails.
  9. Use REST API to update a VM with “Cluster default” firmware type in a cluster having BIOS firmware type and set its display type to bochs.
    Expected result: VM update fails.
  10. Use REST API to create a VM with bochs display type in a cluster having compatibility version < 4.5.
    Expected result: VM creation fails.
  11. Use REST API to update a VM having bochs display type and set its firmware type to BIOS.
    Expected result: VM display type is changed to vga.
  12. Use REST API to update a VM having bochs display type and set its firmware type to “Cluster default” in a cluster having BIOS firmware type.
    Expected result: VM display type is changed to vga.
  13. Open VM creation dialog and select a cluster having compatibility version >= 4.5. Select ‘Server’ configuration.
    Expected result: Display type bochs is selected.
  14. Use REST API to create a VM with ‘Server’ configuration without setting its display type explicitly.
    Expected result: VM display type is set to bochs.
  15. Create a VM having bochs display type. Run it.
    Expected result: VM XML in the Engine log includes bochs display type.