Bug 866999 - CPU topology is missing in capabilities XML when libvirt fails to detect host CPU model
CPU topology is missing in capabilities XML when libvirt fails to detect host...
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: libvirt (Show other bugs)
Unspecified Unspecified
high Severity high
: rc
: ---
Assigned To: Jiri Denemark
Virtualization Bugs
: ZStream
Depends On:
Blocks: 868972 876475
  Show dependency treegraph
Reported: 2012-10-16 09:59 EDT by Yaniv Bronhaim
Modified: 2013-02-21 02:10 EST (History)
13 users (show)

See Also:
Fixed In Version: libvirt-0.10.2-5.el6
Doc Type: Bug Fix
Doc Text:
When libvirt could not find a suitable CPU model for a host CPU, it would not provide the CPU topology in host capabilities even though the topology was detected correctly. Consequently, applications that work with the host CPU topology but not with the CPU model could not see the topology in host capabilities. With this update, the host capabilities XML description contains the host CPU topology even if the host CPU model is unknown.
Story Points: ---
Clone Of:
: 876475 (view as bug list)
Last Closed: 2013-02-21 02:10:12 EST
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Yaniv Bronhaim 2012-10-16 09:59:34 EDT
Description of problem:
Running vdsm gets exception while reading libvirt capabilities

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

How reproducible:
service vdsmd start

Steps to Reproduce:
1. install and run vdsm, it reproduce during vdsm startup
Actual results:
when running virsh -r capabilities we see no parameters under topology tag:
      <cells num='1'>
        <cell id='0'>
          <cpus num='1'>
            <cpu id='0'/>

vdsm throws exception and fails to start:

MainThread::ERROR::2012-10-16 15:42:44,001::vdsm::84::vds::(run) Exception raised
Traceback (most recent call last):
  File "/usr/share/vdsm/vdsm", line 82, in run
  File "/usr/share/vdsm/vdsm", line 50, in serve_clients
    cif = clientIF.getInstance(log)
  File "/usr/share/vdsm/clientIF.py", line 126, in getInstance
    cls._instance = clientIF(log)
  File "/usr/share/vdsm/clientIF.py", line 93, in __init__
  File "/usr/share/vdsm/caps.py", line 88, in __init__
    self._topology = _getCpuTopology(capabilities)
  File "/usr/lib64/python2.6/site-packages/vdsm/utils.py", line 822, in __call__
    value = self.func(*args)
  File "/usr/share/vdsm/caps.py", line 116, in _getCpuTopology
    'sockets': int(cpu.getElementsByTagName('topology')[0].
IndexError: list index out of range

Expected results:
topology should have the attributes cells, sockets, cores and threads in libvirt capabilities xml.

Additional info:
Comment 2 Jiri Denemark 2012-10-16 13:57:35 EDT
_getCpuTopology is a function from vdsm, which parses cpu topology from /capabilities/host/cpu/topology in libvirt's capabilities XML. The /capabilities/host/topology element shown in bug description is a NUMA topology. While vdsm can use virNodeGetInfo to get the CPU topology (rather than parsing it from capabilities), I agree that we have a bug in libvirt. When host CPU model cannot be detected for some reason, we won't provide the topology even though it's known.
Comment 3 Jiri Denemark 2012-10-18 09:02:15 EDT
Patch sent upstream for review: https://www.redhat.com/archives/libvir-list/2012-October/msg00976.html
Comment 4 Jiri Denemark 2012-10-18 10:06:04 EDT
Fixed upstream by v0.10.2-199-gf1c7010:

commit f1c70100409562c3f402392aa667732e5f89a2c4
Author: Jiri Denemark <jdenemar@redhat.com>
Date:   Tue Oct 16 21:11:29 2012 +0200

    qemu: Always format CPU topology
    When libvirt cannot find a suitable CPU model for host CPU (easily
    reproducible by running libvirt in a guest), it would not provide CPU
    topology in capabilities XML either. Even though CPU topology is known
    and can be queried by virNodeGetInfo. With this patch, CPU topology will
    always be provided in capabilities XML regardless on the presence of CPU
Comment 6 Dan Kenigsberg 2012-10-21 06:31:07 EDT
Requesting rhel-6.3.z so that we can test rhev-3.1.0 on virtual hosts which tickle this bug.
Comment 9 hongming 2012-10-25 02:17:59 EDT
Verify it as follows, the result is expected. Move its status to VERIFIED.


Login one RHEL6.3 guest ,run the following commands.

# virsh nodeinfo
CPU model:           x86_64
CPU(s):              4
CPU frequency:       3092 MHz
CPU socket(s):       1
Core(s) per socket:  4
Thread(s) per core:  1
NUMA cell(s):        1
Memory size:         1020340 KiB

# virsh capabilities

      <topology sockets='1' cores='4' threads='1'/>
      <cells num='1'>
        <cell id='0'>
          <cpus num='4'>
            <cpu id='0'/>
            <cpu id='1'/>
            <cpu id='2'/>
            <cpu id='3'/>

Comment 15 errata-xmlrpc 2013-02-21 02:10:12 EST
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.


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