Introduction

Passthrough of discrete GPUs has been available since XenServer 6.0. With some extensions, we will also be able to support passthrough of integrated GPUs.

• Whether an integrated GPU will be accessible to dom0 or available to passthrough to guests must be configurable via XenAPI.
• Passthrough of an integrated GPU requires an extra flag to be sent to qemu.

Host Configuration

A new host field will be added:

• host.integrated_GPU_passthrough enum(disabled|enable_on_reboot|enabled|disable_on_reboot)

as well as new API calls:

• host.enable_integrated_GPU_passthrough
• host.disable_integrated_GPU_passthrough

Enabling integrated GPU passthrough will modify the xen commandline (using the xen-cmdline tool) such that dom0 will not be able to access the integrated GPU on next boot.

A state diagram for the field host.integrated_GPU_passthrough is shown below:

Note that when a client enables or disables integrated GPU passthrough, the change can be cancelled until the host is rebooted.

Handling vga_arbiter

Normally, xapi will not create a PGPU object for the PCI device with address reported by /dev/vga_arbiter. This is to prevent a GPU in use by dom0 from from being passed through to a guest. This will no longer be the case if:

1. Integrated GPU passthrough is enabled.
2. The vendor ID of the device is contained in a whitelist provided by xapi's config file.

Interfacing with xenopsd

When starting a VM attached to an integrated GPU, the VM config sent to xenopsd will contain a video_card of type IGD_passthrough. This will override the type determined from VM.platform:vga. xapi will consider a GPU to be integrated if both:

1. It resides on bus 0.
2. The vendor ID of the device is contained in a whitelist provided by xapi's config file.

When xenopsd starts qemu for a VM with a video_card of type IGD_passthrough, it will pass the flags "-std-vga" AND "-gfx_passthru".