** Changed in: linux (Ubuntu Focal)
       Status: New => In Progress

** Changed in: linux (Ubuntu Jammy)
       Status: New => In Progress

** Changed in: linux (Ubuntu Lunar)
       Status: New => In Progress

** Changed in: linux (Ubuntu Mantic)
       Status: New => In Progress

** Changed in: linux (Ubuntu Noble)
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/2047382

Title:
  Hotplugging SCSI disk in QEMU VM fails

Status in linux package in Ubuntu:
  In Progress
Status in linux source package in Focal:
  In Progress
Status in linux source package in Jammy:
  In Progress
Status in linux source package in Lunar:
  In Progress
Status in linux source package in Mantic:
  In Progress
Status in linux source package in Noble:
  In Progress

Bug description:
  [Impact]
  Hot-plugging SCSI disks for QEMU VMs booting with UEFI and using guest 
kernels >= 6.5 might be broken.
  The inconsistency suggests a potential race condition.

  [Fix]
  Reverting the two specified commits appears to restore reliability.
  ==========
  cc22522fd55e2 PCI: acpiphp: Use pci_assign_unassigned_bridge_resources() only 
for non-root bus
  40613da52b13f PCI: acpiphp: Reassign resources on bridge if necessary
  ==========

  Upstream has resolved the issue by reverting both commits through a commit 
placed below.
  ==========
  5df12742b7e3a Revert "PCI: acpiphp: Reassign resources on bridge if necessary
  ==========

  [Test Plan]
  1. Create a VM
  virt-install --name scsi_test --memory 2048 --vcpus 2 --boot uefi --disk 
path=/home/ubuntu/mantic-server-cloudimg-amd64.img,size=20,format=qcow2,bus=virtio
  -os-variant=ubuntu18.04 --graphics spice --network bridge=virbr0
  2. Prepare two XMLs for adding two disk devices
  # cat disk_X.xml
  <disk type='file' device='disk'>
    <driver name='qemu' type='raw'/>
    <source file='XXX.img'/>
    <target dev='vdX' bus='virtio'/>
  </disk>
  3. Hotplug disks and check for success
  virsh attach-device scsi_test disk_X.xml

  [Where problems could occur]
  The patch reverts two commits that previously addressed long-standing issues 
related to hotplugging devices with large BARs.
  While this reversion may reintroduce legacy issues, it does not introduce new 
problems.
  The associated risks are deemed low, making it worthwhile to address timing 
issues during the hotplugging of SCSI disks in QEMU VM.

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