Some pci-e resources can be useful to just hand over to VM's directly, like GPU's and infiniband networking cards. This article describes the steps necessary to configure pci-passthrough to hand PCI-devices to certain flavors in the openstack cloud.

Enable IOMMU on the compute-node

First vt-d needs to be enabled in the systems BIOS/UEFI menu. This option might be visible, or hidden behind a generic "Enable Virtualization Technologies". Next up is to enable the IOMMU in ubuntu by modifying /etc/default/grub to contain:

GRUB_CMDLINE_LINUX_DEFAULT="intel_iommu=on iommu=pt"
GRUB_CMDLINE_LINUX="intel_iommu=on iommu=pt"

After a reboot you should be able to see that the IOMMU is enabled correctly like so:

Configure Openstack to know about the PCIe-devices.

Configure host-aggregates to aid in the scheduling.

Create a flavor with PCI-e devices attached

Verify that it works