openstack/nova
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Merge "[doc] Adding vGPUs max_instances caveat fix for virtual-gpu"

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Zuul 2025-05-15 07:40:47 +00:00 committed by Gerrit Code Review
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doc/source/admin/virtual-gpu.rst
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@ -365,6 +365,38 @@ Caveats
Please refer to the `PCI passthrough documentation`_ for proper
configuration.
* When using recent nVidia GPU architectures like Ampere or newer GPUs which
have SR-IOV feature, Nova can't know how many vGPUs can be used by a specific
type. You then need to create virtual functions and then provide the list
of the virtual functions per GPUs that can be used by setting
``device_addresses``.
.. versionchanged:: 29.0.0
By the 2024.2 Caracal release, if you use those hardware, you need to
provide a new configuration option named
``max_instances`` in the related mdev type group (eg. ``mdev_nvidia-35``)
where the value of that option would be the number of vGPUs that the type
can create.
As an example for the `A40-2Q nVidia GPU type`__ which can create up to 24
vGPUs, please provide the below configuration :
.. __: https://docs.nvidia.com/vgpu/16.0/grid-vgpu-user-guide/index.html#vgpu-types-nvidia-a40
.. code-block:: ini
[devices]
enabled_mdev_types = nvidia-558
[mdev_nvidia-558]
max_instances = 24
As a side note, you can see that we don't use ``device_addresses`` in the
``mdev_nvidia-558`` section, as we don't need to tell which exact virtual
functions we want to use for that type.
* When live-migrating an instance using vGPUs, the libvirt guest domain XML
isn't updated with the new mediated device UUID to use for the target.