------- Comment From [email protected] 2025-04-29 08:24 EDT-------
Hi, since there hasn't been movement for a while, it has been pointed out to me
that
sharing a udev rule proposal regarding the issue might help;
How about sth like below?
SUBSYSTEM=="cpu", ACTION=="add", CONST{arch}=="s390*",
ATTR{configure}=="1", TEST=="online", ATTR{online}!="1",
ATTR{online}="1"
rule above should automatically hotplug any CPUs added to the system in
configured
state.
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https://bugs.launchpad.net/bugs/2078347
Title:
[UBUNTU 24.04] Udev/rules: Missing rules causes newly added CPUs to
stay offline
Status in Ubuntu on IBM z Systems:
New
Status in linux package in Ubuntu:
New
Bug description:
---Problem
Description----------------------------------------------------------------------------------
Adding a configured CPU to a system (LPAR, ZVM or KVM) leaves that CPU
configured but hotplugged off.
# lscpu -e
CPU NODE DRAWER BOOK SOCKET CORE L1d:L1i:L2 ONLINE CONFIGURED POLARIZATION
ADDRESS
0 0 0 0 0 0 0:0:0 yes yes horizontal 0
1 0 0 0 1 1 1:1:1 yes yes horizontal 1
2 0 0 0 2 2 2:2:2 yes yes horizontal 2
3 0 0 0 3 3 3:3:3 yes yes horizontal 3
4 0 0 0 4 4 4:4:4 yes yes horizontal 4
5 0 0 0 5 5 5:5:5 yes yes horizontal 5
6 - - - - - - no yes horizontal 6
7 - - - - - - no yes horizontal 7
---Debugger---
A debugger is not configured
Machine Type = z/VM, LPAR
---uname output---
6.8.0-41-generic #41-Ubuntu SMP Fri Aug 2 19:51:49 UTC 2024 s390x s390x
s390x GNU/Linux
---Steps to Reproduce---
Easiest way to reproduce is using a KVM guest to add new CPUs.
1. Before adding CPUs:
$ virsh dumpxml vm
<domain type='kvm' id='106'>
...
<vcpu placement='static' current='6'>8</vcpu>
<vcpus>
<vcpu id='0' enabled='yes' hotpluggable='no' order='1'/>
<vcpu id='1' enabled='yes' hotpluggable='no' order='2'/>
<vcpu id='2' enabled='yes' hotpluggable='yes' order='3'/>
<vcpu id='3' enabled='yes' hotpluggable='yes' order='4'/>
<vcpu id='4' enabled='yes' hotpluggable='yes' order='5'/>
<vcpu id='5' enabled='yes' hotpluggable='yes' order='6'/>
<vcpu id='6' enabled='no' hotpluggable='yes'/>
<vcpu id='7' enabled='no' hotpluggable='yes'/>
2. Attempt to add CPUs to the guest in a "running" state.
$ virsh setvcpus vm 8 --live
3. The guest XML is updated :
...
<vcpu placement='static'>8</vcpu>
<vcpus>
<vcpu id='0' enabled='yes' hotpluggable='no' order='1'/>
<vcpu id='1' enabled='yes' hotpluggable='no' order='2'/>
<vcpu id='2' enabled='yes' hotpluggable='yes' order='3'/>
<vcpu id='3' enabled='yes' hotpluggable='yes' order='4'/>
<vcpu id='4' enabled='yes' hotpluggable='yes' order='5'/>
<vcpu id='5' enabled='yes' hotpluggable='yes' order='6'/>
<vcpu id='6' enabled='yes' hotpluggable='yes' order='7'/>
<vcpu id='7' enabled='yes' hotpluggable='yes' order='8'/>
</vcpus>
4. But inside the guest, the CPUs are in offline state:
$ lscpu -e
CPU NODE DRAWER BOOK SOCKET CORE L1d:L1i:L2 ONLINE CONFIGURED POLARIZATION
ADDRESS
0 0 0 0 0 0 0:0:0 yes yes horizontal 0
1 0 0 0 1 1 1:1:1 yes yes horizontal 1
2 0 0 0 2 2 2:2:2 yes yes horizontal 2
3 0 0 0 3 3 3:3:3 yes yes horizontal 3
4 0 0 0 4 4 4:4:4 yes yes horizontal 4
5 0 0 0 5 5 5:5:5 yes yes horizontal 5
6 - - - - - - no yes horizontal 6
7 - - - - - - no yes horizontal 7
5. Post rebooting the guest, the CPUs are online:
$ virsh reboot vm
Inside the guest:
$ lscpu -e
CPU NODE DRAWER BOOK SOCKET CORE L1d:L1i:L2 ONLINE CONFIGURED POLARIZATION
ADDRESS
0 0 0 0 0 0 0:0:0 yes yes horizontal 0
1 0 0 0 1 1 1:1:1 yes yes horizontal 1
2 0 0 0 2 2 2:2:2 yes yes horizontal 2
3 0 0 0 3 3 3:3:3 yes yes horizontal 3
4 0 0 0 4 4 4:4:4 yes yes horizontal 4
5 0 0 0 5 5 5:5:5 yes yes horizontal 5
6 0 0 0 6 6 6:6:6 yes yes horizontal 6
7 0 0 0 7 7 7:7:7 yes yes horizontal 7
The CPUs should be online after adding them to the system.
Other distros already have a udev rule to circumvent this under;
/etc/udev/rules.d/
The rule does a check if a newly added CPUs are configured but not online,
then hotplugs it to make it online. If CPUs are NOT configured then they should
stay offline.
Contact Information = [email protected]
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