The virtual GPU feature in Nova allows a deployment to provide specific GPU types for instances using physical GPUs that can provide virtual devices.
For example, a single Intel GVT-g or a NVIDIA GRID vGPU physical Graphics Processing Unit (pGPU) can be virtualized as multiple virtual Graphics Processing Units (vGPUs) if the hypervisor supports the hardware driver and has the capability to create guests using those virtual devices.
This feature is highly dependent on the hypervisor, its version and the physical devices present on the host. In addition, the vendor’s vGPU driver software must be installed and configured on the host at the same time.
Important
As of the Queens release, there is no upstream continuous integration testing with a hardware environment that has virtual GPUs and therefore this feature is considered experimental.
Hypervisor-specific caveats are mentioned in the Caveats section.
To enable virtual GPUs, follow the steps below:
Specify which specific GPU type(s) the instances would get.
Edit devices.enabled_vgpu_types
:
[devices]
enabled_vgpu_types = nvidia-35
Note
As of the Queens release, Nova only supports a single type. If more than one vGPU type is specified (as a comma-separated list), only the first one will be used.
To know which specific type(s) to mention, please refer to How to discover a GPU type.
Restart the nova-compute
service.
Warning
Changing the type is possible but since existing physical GPUs can’t address multiple guests having different types, that will make Nova return you a NoValidHost if existing instances with the original type still exist. Accordingly, it’s highly recommended to instead deploy the new type to new compute nodes that don’t already have workloads and rebuild instances on the nodes that need to change types.
Configure a flavor to request one virtual GPU:
$ openstack flavor set vgpu_1 --property "resources:VGPU=1"
Note
As of the Queens release, all hypervisors that support virtual GPUs only accept a single virtual GPU per instance.
The enabled vGPU types on the compute hosts are not exposed to API users. Flavors configured for vGPU support can be tied to host aggregates as a means to properly schedule those flavors onto the compute hosts that support them. See the Host Aggregates for more information.
The nova-scheduler
selects a destination host that has vGPU devices
available by calling the Placement API for a specific VGPU resource class
provided by compute nodes.
$ openstack server create --flavor vgpu_1 --image cirros-0.3.5-x86_64-uec --wait test-vgpu
Note
As of the Queens release, only the FilterScheduler scheduler driver uses the Placement API.
Depending on your hypervisor:
For libvirt, virtual GPUs are seen as mediated devices. Physical PCI devices (the graphic card here) supporting virtual GPUs propose mediated device (mdev) types. Since mediated devices are supported by the Linux kernel through sysfs files after installing the vendor’s virtual GPUs driver software, you can see the required properties as follows:
$ ls /sys/class/mdev_bus/*/mdev_supported_types
/sys/class/mdev_bus/0000:84:00.0/mdev_supported_types:
nvidia-35 nvidia-36 nvidia-37 nvidia-38 nvidia-39 nvidia-40 nvidia-41 nvidia-42 nvidia-43 nvidia-44 nvidia-45
/sys/class/mdev_bus/0000:85:00.0/mdev_supported_types:
nvidia-35 nvidia-36 nvidia-37 nvidia-38 nvidia-39 nvidia-40 nvidia-41 nvidia-42 nvidia-43 nvidia-44 nvidia-45
/sys/class/mdev_bus/0000:86:00.0/mdev_supported_types:
nvidia-35 nvidia-36 nvidia-37 nvidia-38 nvidia-39 nvidia-40 nvidia-41 nvidia-42 nvidia-43 nvidia-44 nvidia-45
/sys/class/mdev_bus/0000:87:00.0/mdev_supported_types:
nvidia-35 nvidia-36 nvidia-37 nvidia-38 nvidia-39 nvidia-40 nvidia-41 nvidia-42 nvidia-43 nvidia-44 nvidia-45
For XenServer, virtual GPU types are created by XenServer at startup
depending on the available hardware and config files present in dom0.
You can run the command of xe vgpu-type-list
from dom0 to get the
available vGPU types. The value for the field of model-name ( RO):
is the vGPU type’s name which can be used to set the nova config option
[devices]/enabled_vgpu_types
. See the following example:
[root@trailblazer-2 ~]# xe vgpu-type-list
uuid ( RO) : 78d2d963-41d6-4130-8842-aedbc559709f
vendor-name ( RO): NVIDIA Corporation
model-name ( RO): GRID M60-8Q
max-heads ( RO): 4
max-resolution ( RO): 4096x2160
uuid ( RO) : a1bb1692-8ce3-4577-a611-6b4b8f35a5c9
vendor-name ( RO): NVIDIA Corporation
model-name ( RO): GRID M60-0Q
max-heads ( RO): 2
max-resolution ( RO): 2560x1600
uuid ( RO) : 69d03200-49eb-4002-b661-824aec4fd26f
vendor-name ( RO): NVIDIA Corporation
model-name ( RO): GRID M60-2A
max-heads ( RO): 1
max-resolution ( RO): 1280x1024
uuid ( RO) : c58b1007-8b47-4336-95aa-981a5634d03d
vendor-name ( RO): NVIDIA Corporation
model-name ( RO): GRID M60-4Q
max-heads ( RO): 4
max-resolution ( RO): 4096x2160
uuid ( RO) : 292a2b20-887f-4a13-b310-98a75c53b61f
vendor-name ( RO): NVIDIA Corporation
model-name ( RO): GRID M60-2Q
max-heads ( RO): 4
max-resolution ( RO): 4096x2160
uuid ( RO) : d377db6b-a068-4a98-92a8-f94bd8d6cc5d
vendor-name ( RO): NVIDIA Corporation
model-name ( RO): GRID M60-0B
max-heads ( RO): 2
max-resolution ( RO): 2560x1600
...
Note
The information below is only valid from the 19.0.0 Stein release and only
for the libvirt driver. Before this release or when using the Xen driver,
inventories and allocations related to a VGPU
resource class are still
on the root resource provider related to the compute node.
If upgrading from Rocky and using the libvirt driver, VGPU
inventory and
allocations are moved to child resource providers that represent actual
physical GPUs.
The examples you will see are using the osc-placement plugin for OpenStackClient. For details on specific commands, see its documentation.
Get the list of resource providers
$ openstack resource provider list
+--------------------------------------+---------------------------------------------------------+------------+
| uuid | name | generation |
+--------------------------------------+---------------------------------------------------------+------------+
| 5958a366-3cad-416a-a2c9-cfbb5a472287 | virtlab606.xxxxxxxxxxxxxxxxxxxxxxxxxxx | 7 |
| fc9b9287-ef5e-4408-aced-d5577560160c | virtlab606.xxxxxxxxxxxxxxxxxxxxxxxxxxx_pci_0000_86_00_0 | 2 |
| e2f8607b-0683-4141-a8af-f5e20682e28c | virtlab606.xxxxxxxxxxxxxxxxxxxxxxxxxxx_pci_0000_85_00_0 | 3 |
| 85dd4837-76f9-41f2-9f19-df386017d8a0 | virtlab606.xxxxxxxxxxxxxxxxxxxxxxxxxxx_pci_0000_87_00_0 | 2 |
| 7033d860-8d8a-4963-8555-0aa902a08653 | virtlab606.xxxxxxxxxxxxxxxxxxxxxxxxxxx_pci_0000_84_00_0 | 2 |
+--------------------------------------+---------------------------------------------------------+------------+
In this example, we see the root resource provider
5958a366-3cad-416a-a2c9-cfbb5a472287
with four other resource providers
that are its children and where each of them corresponds to a single
physical GPU.
Check the inventory of each resource provider to see resource classes
$ openstack resource provider inventory list 5958a366-3cad-416a-a2c9-cfbb5a472287
+----------------+------------------+----------+----------+-----------+----------+-------+
| resource_class | allocation_ratio | max_unit | reserved | step_size | min_unit | total |
+----------------+------------------+----------+----------+-----------+----------+-------+
| VCPU | 16.0 | 48 | 0 | 1 | 1 | 48 |
| MEMORY_MB | 1.5 | 65442 | 512 | 1 | 1 | 65442 |
| DISK_GB | 1.0 | 49 | 0 | 1 | 1 | 49 |
+----------------+------------------+----------+----------+-----------+----------+-------+
$ openstack resource provider inventory list e2f8607b-0683-4141-a8af-f5e20682e28c
+----------------+------------------+----------+----------+-----------+----------+-------+
| resource_class | allocation_ratio | max_unit | reserved | step_size | min_unit | total |
+----------------+------------------+----------+----------+-----------+----------+-------+
| VGPU | 1.0 | 16 | 0 | 1 | 1 | 16 |
+----------------+------------------+----------+----------+-----------+----------+-------+
Here you can see a VGPU
inventory on the child resource provider while
other resource class inventories are still located on the root resource
provider.
Check allocations for each server that is using virtual GPUs
$ openstack server list
+--------------------------------------+-------+--------+---------------------------------------------------------+--------------------------+--------+
| ID | Name | Status | Networks | Image | Flavor |
+--------------------------------------+-------+--------+---------------------------------------------------------+--------------------------+--------+
| 5294f726-33d5-472a-bef1-9e19bb41626d | vgpu2 | ACTIVE | private=10.0.0.14, fd45:cdad:c431:0:f816:3eff:fe78:a748 | cirros-0.4.0-x86_64-disk | vgpu |
| a6811fc2-cec8-4f1d-baea-e2c6339a9697 | vgpu1 | ACTIVE | private=10.0.0.34, fd45:cdad:c431:0:f816:3eff:fe54:cc8f | cirros-0.4.0-x86_64-disk | vgpu |
+--------------------------------------+-------+--------+---------------------------------------------------------+--------------------------+--------+
$ openstack resource provider allocation show 5294f726-33d5-472a-bef1-9e19bb41626d
+--------------------------------------+------------+------------------------------------------------+
| resource_provider | generation | resources |
+--------------------------------------+------------+------------------------------------------------+
| 5958a366-3cad-416a-a2c9-cfbb5a472287 | 8 | {u'VCPU': 1, u'MEMORY_MB': 512, u'DISK_GB': 1} |
| 7033d860-8d8a-4963-8555-0aa902a08653 | 3 | {u'VGPU': 1} |
+--------------------------------------+------------+------------------------------------------------+
$ openstack resource provider allocation show a6811fc2-cec8-4f1d-baea-e2c6339a9697
+--------------------------------------+------------+------------------------------------------------+
| resource_provider | generation | resources |
+--------------------------------------+------------+------------------------------------------------+
| e2f8607b-0683-4141-a8af-f5e20682e28c | 3 | {u'VGPU': 1} |
| 5958a366-3cad-416a-a2c9-cfbb5a472287 | 8 | {u'VCPU': 1, u'MEMORY_MB': 512, u'DISK_GB': 1} |
+--------------------------------------+------------+------------------------------------------------+
In this example, two servers were created using a flavor asking for 1
VGPU
, so when looking at the allocations for each consumer UUID (which
is the server UUID), you can see that VGPU allocation is against the child
resource provider while other allocations are for the root resource
provider. Here, that means that the virtual GPU used by
a6811fc2-cec8-4f1d-baea-e2c6339a9697
is actually provided by the
physical GPU having the PCI ID 0000:85:00.0
.
Note
This information is correct as of the 17.0.0 Queens release. Where improvements have been made or issues fixed, they are noted per item.
For libvirt:
Suspending a guest that has vGPUs doesn’t yet work because of a libvirt
limitation (it can’t hot-unplug mediated devices from a guest). Workarounds
using other instance actions (like snapshotting the instance or shelving it)
are recommended until libvirt gains mdev hot-unplug support. If a user
attempts to suspend the instance, the libvirt driver will raise an exception
that will cause the instance to be set back to ACTIVE. The suspend
action
in the os-instance-actions
API will have an Error state.
Resizing an instance with a new flavor that has vGPU resources doesn’t allocate those vGPUs to the instance (the instance is created without vGPU resources). The proposed workaround is to rebuild the instance after resizing it. The rebuild operation allocates vGPUS to the instance.
Cold migrating an instance to another host will have the same problem as resize. If you want to migrate an instance, make sure to rebuild it after the migration.
Rescue images do not use vGPUs. An instance being rescued does not keep its vGPUs during rescue. During that time, another instance can receive those vGPUs. This is a known issue. The recommended workaround is to rebuild an instance immediately after rescue. However, rebuilding the rescued instance only helps if there are other free vGPUs on the host.
Note
This has been resolved in the Rocky release [1].
For XenServer:
openstack server set --state active <server>
to set it back to ACTIVE.[1] | https://bugs.launchpad.net/nova/+bug/1762688 |
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