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Bug 880017 - libvirt should check if vcpu topology is right
Summary: libvirt should check if vcpu topology is right
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: libvirt
Version: 6.4
Hardware: Unspecified
OS: Unspecified
medium
medium
Target Milestone: rc
: ---
Assignee: Gunannan Ren
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks: 965465
TreeView+ depends on / blocked
 
Reported: 2012-11-26 02:26 UTC by hongming
Modified: 2013-12-23 12:15 UTC (History)
7 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
: 965465 (view as bug list)
Environment:
Last Closed: 2013-05-30 08:18:46 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description hongming 2012-11-26 02:26:53 UTC 
Description of problem:
libvirt should check if vcpu topology is right. If the wrong vcpu topology is given in xml , the wrong arguments also be passed to qemu-kvm.

vcpu number = sockets*cores*threads


Version-Release number of selected component (if applicable):
libvirt-0.10.2-9.el6.x86_64


How reproducible:
100% 

Steps to Reproduce:
1.# virsh start rhel63
Domain rhel63 started

2.# virsh dumpxml rhel63
<domain type='kvm' id='104'>
  .......
  <vcpu placement='static'>4</vcpu>
   ......
  <cpu>
    <topology sockets='1' cores='4' threads='2'/> 
  </cpu>


3.# ps -ef|grep qemu-kvm
qemu     21296     1 14 16:41 ?        00:00:17 /usr/libexec/qemu-kvm -name rhel63 -S -M rhel6.4.0 -enable-kvm -m 1024 -smp 4,sockets=1,cores=4,threads=2
......


4 Login guest

# lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    1
Core(s) per socket:    4
CPU socket(s):         1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 13
Stepping:              3
CPU MHz:               3092.974
BogoMIPS:              6185.94
Hypervisor vendor:     KVM
Virtualization type:   full
L1d cache:             32K
L1i cache:             32K
L2 cache:              4096K
NUMA node0 CPU(s):     0-3

  
Actual results:
Wrong vcpu topology can be given in xml and passed to qemu-kvm

Expected results:
libvirt should check if vcpu topology is right.

Additional info:
Comment 3 Gunannan Ren 2013-05-30 08:18:46 UTC 
Actually, QEMU can calculate from the values in smp, sockets, cores, threads to emulate how many physical processor, how many cores does each of physical processors contain and how many multi-threading logical processors does each core supports.

The algorithm was explain in my email
https://www.redhat.com/archives/libvir-list/2013-May/thread.html

The results can be verified by using cpuid tool
So I don't think this is a bug. If anything wrong during testing, please reopen this bug again.
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