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Heal PCI allocation during resize

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During resize an instance with existing PCI allocation can be changed to
consume less, more, or different PCI devices. So the heal allocation
logic needs to handle the case when an existing instance is changed to
consume different PCI devices.

This patch adds support to change existing PCI allocations in placement
during resize.

There is one limitation of the healing logic. It assumes that there is
no in-progress migration when nova is upgraded. If there is an in
progress migration, then the PCI usage will not be healed in the
migration allocation. The placement view will be consistent after such
migration is completed or reverted.

blueprint: pci-device-tracking-in-placement
Change-Id: Icc968c567f9967d7449d6c6c1f57783098e63f55
This commit is contained in:
Balazs Gibizer
2022-08-08 12:34:16 +02:00
parent d483a696a5
commit 98e9989cad
3 changed files with 445 additions and 0 deletions
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doc/source/admin/pci-passthrough.rst
+10
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@@ -394,4 +394,14 @@ be added to the resource provider representing the matching PCI devices.
(Zed) the nova-compute service will refuse to start with such configuration.
It is suggested to use the PCI address of the device instead.
The nova-compute service makes sure that already existing instances with PCI
allocations in the nova DB will have a corresponding PCI allocation in
placement. This allocation healing also acts on any new instances regardless of
the status of the scheduling part of this feature to make sure that the nova
DB and placement are in sync. There is one limitation of the healing logic.
It assumes that there is no in-progress migration when the nova-compute service
is upgraded. If there is an in-progress migration, then the PCI allocation on
the source host of the migration will not be healed. The placement view will be
consistent after such migration is completed or reverted.
For deeper technical details please read the `nova specification. <https://specs.openstack.org/openstack/nova-specs/specs/zed/approved/pci-device-tracking-in-placement.html>`_