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docs: Clarify configuration steps for PF devices 

Devices that report SR-IOV capabilities cannot be used without special
configuration - namely, the addition of "'device_type': 'type-PF'" or
"'device_type': 'type-VF'" to the '[pci] alias' configuration option.
Spell this out in the docs.

Change-Id: I4abbe30505a5e4ccba16027addd6d5f45066e31b
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>
Closes-Bug: #1852727
(cherry picked from commit 810aafc5ec)
This commit is contained in:
Stephen Finucane 2019-11-15 10:16:28 +00:00 committed by Stephen Finucane
parent 9223613ad3
commit 0c0c5b12cf
2 changed files with 27 additions and 5 deletions
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29
doc/source/admin/pci-passthrough.rst
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@ -100,16 +100,37 @@ If using vendor and product IDs, all PCI devices matching the ``vendor_id`` and
to VMs.
In addition, it is necessary to configure the :oslo.config:option:`pci.alias`
option. As noted previously, PCI devices are requested through flavor extra
specs - specifically via the ``pci_passthrough:alias`` flavor extra spec - so
this config option allows us to map a given type of device to a specific alias.
For example, to map the sample PCI device to the alias ``a1``:
option, which is a JSON-style configuration option that allows you to map a
given device type, identified by the standard PCI ``vendor_id`` and (optional)
``product_id`` fields, to an arbitrary name or *alias*. This alias can then be
used to request a PCI device using the ``pci_passthrough:alias=<alias>`` flavor
extra spec, as discussed previously. For our sample device with a vendor ID of
``0x8086`` and a product ID of ``0x154d``, this would be:
.. code-block:: ini
[pci]
alias = { "vendor_id":"8086", "product_id":"154d", "device_type":"type-PF", "name":"a1" }
It's important to note the addition of the ``device_type`` field. This is
necessary because this PCI device supports SR-IOV. The ``nova-compute`` service
categorizes devices into one of three types, depending on the capabilities the
devices report:
``type-PF``
The device supports SR-IOV and is the parent or root device.
``type-VF``
The device is a child device of a device that supports SR-IOV.
``type-PCI``
The device does not support SR-IOV.
By default, it is only possible to attach ``type-PCI`` devices using PCI
passthrough. If you wish to attach ``type-PF`` or ``type-VF`` devices, you must
specify the ``device_type`` field in the config option. If the device was a
device that did not support SR-IOV, the ``device_type`` field could be omitted.
Refer to :oslo.config:option:`pci.alias` for syntax information.
.. important::

3
nova/conf/pci.py
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@ -60,7 +60,8 @@ Possible Values:
``device_type``
Type of PCI device. Valid values are: ``type-PCI``, ``type-PF`` and
``type-VF``.
``type-VF``. Note that ``"device_type": "type-PF"`` **must** be specified
if you wish to passthrough a device that supports SR-IOV in its entirety.
``numa_policy``
Required NUMA affinity of device. Valid values are: ``legacy``,