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[sean mooney <1961567@xxxxxxxxxxxxxxxxxx>]

This is not a bug.

we intentionally do not provide any device ordering guarnetees.

this has been requested several times in the past however we cannot provide this enverant since
libvirt does not guretee the addresses it will assign will be stable and the behavior is not portable across different hyperviors.

the device role tagging feature was designed to provide an alternitive.
https://specs.openstack.org/openstack/nova-specs/specs/mitaka/approved/virt-device-role-tagging.html

** Changed in: nova
       Status: In Progress => Won't Fix

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https://bugs.launchpad.net/bugs/1961567

Title:
  attached PCI devices may change addresses after reboot

Status in OpenStack Compute (nova):
  Won't Fix

Bug description:
  When attaching PCI devices to the instance (e.g. via PCI passthru),
  the final order and addresses of devices as seen from inside the
  instance can change between reboots:

  E.g. these are the snippets from qemu command line args as seen thru
  `ps`:

  -device vfio-pci,host=5e:00.1,id=hostdev0,bus=pci.0,addr=0x6 -device
  vfio-pci,host=5e:00.0,id=hostdev1,bus=pci.0,addr=0x7

  after hard reboot:
  -device vfio-pci,host=5e:00.0,id=hostdev0,bus=pci.0,addr=0x6 -device vfio-pci,host=5e:00.1,id=hostdev1,bus=pci.0,addr=0x7

  For some VNF workloads this poses a problem. Instead of forcing the
  app authors to build complex udev setups inside instances, let's
  simply order the list always by the pci address.

  
  Note that this particular issue was caught in Queens release running under Python2. Unfortunately I do not have means to reproduce that on newer OpenStack, but even if it turns out this is auto-fixed by oredered-by-default dicts in py3.7+, we still support py36.

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