Host Devices Assignment¶
KubeVirt provides a mechanism for assigning host devices to a virtual machine. This mechanism is generic and allows various types of PCI devices, such as accelerators (including GPUs) or any other devices attached to a PCI bus, to be assigned. It also allows Linux Mediated devices, such as pre-configured virtual GPUs to be assigned using the same mechanism.
Host preparation for PCI Passthrough¶
Host Devices passthrough requires the virtualization extension and the IOMMU extension (Intel VT-d or AMD IOMMU) to be enabled in the BIOS.
To enable IOMMU, depending on the CPU type, a host should be booted with an additional kernel parameter,
intel_iommu=onfor Intel and
Append these parameters to the end of the GRUB_CMDLINE_LINUX line in the grub configuration file.
# vi /etc/default/grub ... GRUB_CMDLINE_LINUX="nofb splash=quiet console=tty0 ... intel_iommu=on ... # grub2-mkconfig -o /boot/grub2/grub.cfg # reboot
- The vfio-pci kernel module should be enabled on the host.
# modprobe vfio-pci
Preparation of PCI devices for passthrough¶
At this time, KubeVirt is only able to assign PCI devices that are using the
vfio-pci driver. To prepare a specific device for device assignment, it should first be unbound from its original driver and bound to the
- Find the PCI address of the desired device:
$ lspci -DD|grep NVIDIA 0000.65:00.0 3D controller : NVIDIA Corporation TU104GL [Tesla T4] [10de:1eb8] (rev a1)
- Bind that device to the
echo 0000:65:00.0 > /sys/bus/pci/drivers/nvidia/unbind echo "vfio-pci" > /sys/bus/pci/devices/0000\:65\:00.0/driver_override echo 0000:65:00.0 > /sys/bus/pci/drivers/vfio-pci/bind
Preparation of mediated devices such as vGPU¶
At this time, configuration of a Mediated device (mdev) should be done according to the vendor directions. Once the mdev is configured, KubeVirt will be able to discover and use it for device assignment.
Listing permitted devices¶
Administrators can control which host devices are exposed and permitted to be used in the
cluster. Permitted host devices in the cluster will need to be allowlisted in KubeVirt CR by its
vendor:product selector for PCI devices or mediated device names.
configuration: permittedHostDevices: pciHostDevices: - pciVendorSelector: "10DE:1EB8" resourceName: "nvidia.com/TU104GL_Tesla_T4" externalResourceProvider: true - pciVendorSelector: "8086:6F54" resourceName: "intel.com/qat" mediatedDevices: - mdevNameSelector: "GRID T4-1Q" resourceName: "nvidia.com/GRID_T4-1Q"
pciVendorSelectoris a PCI vendor ID and product ID tuple in the form
vendor_id:product_id. This tuple can identify specific types of devices on a host. For example, the identifier
10de:1eb8, shown above, can be found using
$ lspci -nnv|grep -i nvidia 65:00.0 3D controller : NVIDIA Corporation TU104GL [Tesla T4] [10de:1eb8] (rev a1)
mdevNameSelectoris a name of a Mediated device type that can identify specific types of Mediated devices on a host.
You can see what mediated types a given PCI device supports by examining the contents of
/sys/bus/pci/devices/SLOT:BUS:DOMAIN.FUNCTION/mdev_supported_types/TYPE/name. For example, if you have an NVIDIA T4 GPU on your system, and you substitute in the
FUNCTIONvalues that are correct for your system into the above path name, you will see that a
nvidia-226contains the selector string
GRID T4-2Ain its
GRID T4-2Aand specifying it as the
mdevNameSelectorallows KubeVirt to find a corresponding mediated device by matching it against
/sys/class/mdev_bus/SLOT:BUS:DOMAIN.FUNCTION/$mdevUUID/mdev_type/namefor some values of
externalResourceProviderfield indicates that this resource is being provided by an external device plugin. In this case, KubeVirt will only permit the usage of this device in the cluster but will leave the allocation and monitoring to an external device plugin.
Starting a Virtual Machine¶
Host devices can be assigned to virtual machines via the
hostDevices fields. The
deviceNames can reference both PCI
and Mediated device resource names.
kind: VirtualMachineInstance spec: domain: devices: gpus: - deviceName: nvidia.com/TU104GL_Tesla_T4 name: gpu1 - deviceName: nvidia.com/GRID_T4-1Q name: gpu2 hostDevices: - deviceName: intel.com/qat name: quickaccess1