Public bug reported:
[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 a disk device
# cat disk.xml
<disk type='file' device='disk'>
<driver name='qemu' type='raw'/>
<source file='XXX.img'/>
<target dev='vdX' bus='virtio'/>
</disk>
3. Hotplug the disk and check for success
virsh attach-device scsi_test XXX.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.
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Chengen Du (chengendu)
Status: New
** Affects: linux (Ubuntu Focal)
Importance: Undecided
Assignee: Chengen Du (chengendu)
Status: New
** Affects: linux (Ubuntu Jammy)
Importance: Undecided
Assignee: Chengen Du (chengendu)
Status: New
** Affects: linux (Ubuntu Lunar)
Importance: Undecided
Assignee: Chengen Du (chengendu)
Status: New
** Affects: linux (Ubuntu Mantic)
Importance: Undecided
Assignee: Chengen Du (chengendu)
Status: New
** Affects: linux (Ubuntu Noble)
Importance: Undecided
Assignee: Chengen Du (chengendu)
Status: New
** Also affects: linux (Ubuntu Noble)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Mantic)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Jammy)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Lunar)
Importance: Undecided
Status: New
** Also affects: linux (Ubuntu Focal)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Focal)
Assignee: (unassigned) => Chengen Du (chengendu)
** Changed in: linux (Ubuntu Jammy)
Assignee: (unassigned) => Chengen Du (chengendu)
** Changed in: linux (Ubuntu Lunar)
Assignee: (unassigned) => Chengen Du (chengendu)
** Changed in: linux (Ubuntu Mantic)
Assignee: (unassigned) => Chengen Du (chengendu)
** Changed in: linux (Ubuntu Noble)
Assignee: (unassigned) => Chengen Du (chengendu)
--
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/2047382
Title:
Hotplugging SCSI disk in QEMU VM fails
Status in linux package in Ubuntu:
New
Status in linux source package in Focal:
New
Status in linux source package in Jammy:
New
Status in linux source package in Lunar:
New
Status in linux source package in Mantic:
New
Status in linux source package in Noble:
New
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 a disk device
# cat disk.xml
<disk type='file' device='disk'>
<driver name='qemu' type='raw'/>
<source file='XXX.img'/>
<target dev='vdX' bus='virtio'/>
</disk>
3. Hotplug the disk and check for success
virsh attach-device scsi_test XXX.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.
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2047382/+subscriptions
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