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[OpenStack Infra <1948705@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.opendev.org/c/openstack/nova/+/815373
Committed: https://opendev.org/openstack/nova/commit/16f7c601b63bd1e7ca13917261300a7064ec72bc
Submitter: "Zuul (22348)"
Branch:    master

commit 16f7c601b63bd1e7ca13917261300a7064ec72bc
Author: Gustavo Santos <gustavofaganello.santos@xxxxxxxxxxxxx>
Date:   Mon Oct 25 16:32:10 2021 -0300

    Reattach mdevs to guest on resume
    
    When suspending a VM in OpenStack, Nova detaches all the mediated
    devices from the guest machine, but does not reattach them on the resume
    operation. This patch makes Nova reattach the mdevs that were detached
    when the guest was suspended.
    
    This behavior is due to libvirt not supporting the hot-unplug of
    mediated devices at the time the feature was being developed. The
    limitation has been lifted since then, and now we have to amend the
    resume function so it will reattach the mediated devices that were
    detached on suspension.
    
    Closes-bug: #1948705
    
    Signed-off-by: Gustavo Santos <gustavofaganello.santos@xxxxxxxxxxxxx>
    Change-Id: I083929f36d9e78bf7713a87cae6d581e0d946867


** Changed in: nova
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1948705

Title:
  vGPU instance is not reattached to guest on resume

Status in OpenStack Compute (nova):
  Fix Released

Bug description:
  Description
  ===========
  When suspending a guest with a vGPU instance attached to it, Nova asks libvirt to detach that device, since the guest can't be suspended otherwise. When resuming that guest, however, it comes back without the vGPU instance previously attached to it.

  This happens because, at the time the feature was developed, libvirt
  did not support hot unplugging mediated devices [1]. That limitation
  has been lifted since then, and the resume operation needs to be
  modified in order to reattach the mediated device (vGPU instance) that
  was detached on suspend.

  [1]
  https://opendev.org/openstack/nova/src/branch/master/nova/virt/libvirt/driver.py#L8003

  Steps to reproduce
  ==================
  1 - Set up the environment in order to provide vGPU capabilities to Nova;
  2 - Spawn an instance using a flavor that asks for a vGPU;
  3 - Suspend the instance;
  4 - Resume the instance;

  
  Expected result
  ===============
  After resuming the instance, it should still have a vGPU instance attached.

  
  Actual result
  =============
  The instance comes back without a vGPU attached.

  
  Environment
  ===========
  - Tested on StarlingX OpenStack - Ussuri; master code still does not provide a fix.
  - Libvirt v4.7.0 + KVM.

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