** Also affects: ubuntu-z-systems
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1755712
Title:
KVM: multiple epoch facility bugs
Status in Ubuntu on IBM z Systems:
New
Status in linux package in Ubuntu:
New
Bug description:
The bionic 4.15 kernel contains KVM/s390 support for the multiple epoch
facility.
This code has some bugs which can result in hanging guests when running the
guest on a z14 with a recent guest kernel (containing
6e2ef5e4f6cc57344762932d70d38ba4ec65fa8b s390/time: add support for the TOD
clock epoch extension)
The following upstream commits are necessary to fix the multi epoch facility
0e7def5fb0dc KVM: s390: provide only a single function for setting the tod
(fix SCK)
1575767ef3cf KVM: s390: consider epoch index on TOD clock syncs
d16b52cb9cdb KVM: s390: consider epoch index on hotplugged CPUs
5fe01793dd95 KVM: s390: take care of clock-comparator sign control
As an alternative 4.15.8 also contains these fixes.
---uname output---
4.15
---Additional Hardware Info---
Z14 LPAR
Machine Type = IBM z14
---System Hang---
A simple test case to trigger the hang of guests:
qemu-system-s390x -drive file=/data/bionic-server-
s390x.iso,if=none,id=d1 -nographic -enable-kvm -device virtio-scsi-ccw
-device scsi-cd,drive=d1 -m 1G -cpu z14,mepoch=on
it hangs
just before printing the network dialog.
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