Bug 1462183 - [RFE] warn the user if trying to use hyperthreading on unsupported architecture
[RFE] warn the user if trying to use hyperthreading on unsupported architecture
Status: NEW
Product: ovirt-engine
Classification: oVirt
Component: BLL.Virt (Show other bugs)
x86_64 Linux
medium Severity medium (vote)
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Assigned To: Michal Skrivanek
meital avital
: FutureFeature
Depends On:
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Reported: 2017-06-16 07:50 EDT by jiyan
Modified: 2017-09-28 04:54 EDT (History)
7 users (show)

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oVirt Team: Virt
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rule-engine: planning_ack?
rule-engine: devel_ack?
rule-engine: testing_ack?

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Logs for the needinfo (11.21 MB, application/x-tar)
2017-06-19 00:46 EDT, jiyan
no flags Details

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Description jiyan 2017-06-16 07:50:28 EDT
Description of problem:
The cpu topology shows in guest by command 'lscpu' is different from the configuration in RHV-M and libvirt dumpxml file in register host 

Version-Release number of selected component (if applicable):
RHV-M server:

RHV-M register host:

How reproducible:

Steps to Reproduce:
1. In the RHV-M GUI, remove 'CPU' filter from 'none' scheduling policy, and make'cluster' select the 'none' scheduling policy.

2. In the RHV-M GUI, configure the data center with hosts and storage, then New a vm called vm1, confirm the vm can start successfully.

3. Configure 'system' configuration of vm as following, and check the vm can start the vm normally.
  Total Virtual CPUs:100
  Virtual Sockets:5
  Cores per Virtual Socket:4
  threads per Core:5

4.After step3 check the libvirt dumpxml file in register host and execute command 'lscpu' in guest:
In Host check libvirt dumpxml:
<vcpu placement='static' current='100'>160</vcpu>
  <cpu mode='custom' match='exact' check='full'>
    <topology sockets='8' cores='4' threads='5'/>

In vm/Guest:
CPU(s):                100
On-line CPU(s) list:   0-99
Thread(s) per core:    1
Core(s) per socket:    20
Socket(s):             5

Actual results:
As step-4 shows.

Expected results:
The cpu topology shows in guest by command 'lscpu',the configuration in RHV-M and libvirt dumpxml file in register host should be consistent.

Additional info:
Comment 2 jiyan 2017-06-19 00:46 EDT
Created attachment 1289009 [details]
Logs for the needinfo

The attachment includes the following files:
Comment 3 Tomas Jelinek 2017-06-21 05:13:21 EDT
so, the qemu cmdline looks like:
-smp 100,maxcpus=160,sockets=8,cores=4,threads=5

(the sockets = 8 is there to allow hotplug)

The problem here is that the architecture is AMD which does not support hyperthreading, so qemu changes the "Thread(s) per core" to 1 and manipulates the "Core(s) per socket:" and "Socket(s):" to match the configured num of CPUs.

Turning this into an RFE to warn when the user when he is trying to use hyperthreading on an unsupported architecture.

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