QEMU pegs CPU at 100% when running a Focal guest image

Bug #1874005 reported by Juerg Haefliger
This bug affects 1 person
Affects Status Importance Assigned to Milestone
linux (Ubuntu)

Bug Description


Running a VM with a guest kernel >=5.2 results in the QEMU process pegging the CPU at 100%. Sometimes it recovers but most of the times the QEMU process just hangs, libvirt times out trying to talk to it and it can't be killed.

[Test Case]

Spin up a libvirt VM that runs a kernel >=5.2. Sometimes it takes a couple of VM reboots but the QEMU process will eventually hang with 100% CPU utilization.


Cherry pick commit 53a712bae5dd ("powerpc/powernv/idle: Restore AMR/UAMOR/AMOR after idle").

[Regression Potential]

Moderate. The commit is in 5.2 and is a clean cherry-pick but it's POWER assembly voodoo.

[Original Description]

Running a Focal guest image with a 5.4 kernel on a POWER9 Bionic host with kernel 4.15 leads to the QEMU process pegging the CPU at 100%.

Juerg Haefliger (juergh)
no longer affects: linux-raspi2 (Ubuntu)
Changed in linux (Ubuntu Bionic):
status: New → Confirmed
description: updated
summary: - QEMU pegs cpu at 100% when running a Focal guest image
+ QEMU pegs CPU at 100% when running a Focal guest image
description: updated
Revision history for this message
Ubuntu Kernel Bot (ubuntu-kernel-bot) wrote : Missing required logs.

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1874005

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

Changed in linux (Ubuntu):
status: New → Incomplete
tags: added: focal
Juerg Haefliger (juergh)
Changed in linux (Ubuntu):
status: Incomplete → Confirmed
Juerg Haefliger (juergh)
description: updated
Changed in linux (Ubuntu Bionic):
status: Confirmed → In Progress
Changed in linux (Ubuntu):
status: Confirmed → Invalid
Changed in linux (Ubuntu Bionic):
status: In Progress → Fix Committed
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