Was this problem already reported upstream and a fix made available?
Btw. the latest (and wit that GA) kernel of 20.04 is: 5.4.0-26
** Also affects: ubuntu-z-systems
Importance: Undecided
Status: New
** Changed in: ubuntu-z-systems
Importance: Undecided => Medium
** Changed in: ubuntu-z-systems
Status: New => Incomplete
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https://bugs.launchpad.net/bugs/1874647
Title:
[Ubuntu 20.04] Stale libvirt cache leads to VM startup failures
Status in Ubuntu on IBM z Systems:
Incomplete
Status in linux package in Ubuntu:
New
Bug description:
Stale libvirt cache leads to VM startup failures
Contact Information = Viktor Mihajlovski <mihaj...@de.ibm.com>
---Additional Hardware Info---
Z15 with IBM Secute Execution
---uname output---
Linux linux02 5.4.0-21-generic #25-Ubuntu SMP Sat Mar 28 13:10:00 UTC 2020
s390x s390x s390x GNU/Linux
Machine Type = 8562 (IBM Z15)
---Debugger---
A debugger is not configured
---Steps to Reproduce---
1. Install Ubuntu 20.04 in the LPAR
2. Modify the host kernel command line in /etc/zipl.conf to include
prot_virt=1, run zipl and reboot.
3. Define at least one KVM guest with host CPU model and start and stop it
4. Define a secure KVM guest using the host CPU model and start and stop it.
5. Change back the host kernel command line, re-run zipl, reboot.
6. Try to start the first KVM guest, which fails with a message like:
error: internal error: qemu unexpectedly closed the monitor:
2020-04-23T13:55:30.889152Z qemu-system-s390x: Some features requested in the
CPU model are not available in the configuration: unpack
The reason for that is that libvirt caches the domaincapabilities
reported during the first boot and doesn't update them after the
reboot in step 5 even though changing the prot_virt= in the command
line changes the CPU features as reported by domcapabilities. So even
though the guest may not require the unpack feature, libvirt
constructs a CPU model which can't be satisfied on this configuration.
The issue also occurs the other way around, going from prot_virt=0 to
prot_virt=1, in which case the guest will fail to boot as it requires
the unpack feature.
Manually removing the content of /var/cache/libvirt/qemu/capabilities/
will force libvirt to refresh it's capabilities cache and temporarily
resolve the situation.
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