1235180 – guest will have broken settings if we cold-unplug a vcpu which included in some domain vcpu sched

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Bug 1235180 - guest will have broken settings if we cold-unplug a vcpu which included in some domain vcpu sched

Summary: guest will have broken settings if we cold-unplug a vcpu which included in so...

Keywords:
Status:	CLOSED ERRATA
Alias:	None
Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	libvirt
Sub Component:
Version:	7.2
Hardware:	x86_64
OS:	Linux
Priority:	medium
Severity:	medium
Target Milestone:	rc
Target Release:	---
Assignee:	Peter Krempa
QA Contact:	Virtualization Bugs
Docs Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+	depends on / blocked

Reported:	2015-06-24 08:30 UTC by Luyao Huang
Modified:	2016-11-03 18:19 UTC (History)
CC List:	4 users (show)
Fixed In Version:	libvirt-1.3.2-1.el7
Doc Type:	Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed:	2016-11-03 18:19:11 UTC
Target Upstream Version:
Embargoed:

Attachments	(Terms of Use)

Links
System	ID	Private	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHSA-2016:2577	0	normal	SHIPPED_LIVE	Moderate: libvirt security, bug fix, and enhancement update	2016-11-03 12:07:06 UTC

Description Luyao Huang 2015-06-24 08:30:03 UTC

Description of problem:
guest will have broken settings if we delete a vcpu which included in some domain vcpu sched

Version-Release number of selected component (if applicable):
libvirt-1.2.16-1.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. prepare a guest like this:

  <vcpu placement='static' cpuset='0-1'>5</vcpu>
...
  <cputune>
    <emulatorpin cpuset='1-3'/>
    <vcpusched vcpus='0-2,4' scheduler='idle'/>
    <iothreadsched iothreads='1-2' scheduler='idle'/>
  </cputune>

2. use setvcpus remove vcpu 4:

# virsh setvcpus test4 --maximum 4 --config


3. recheck xml

  <vcpu placement='static' cpuset='0-1'>4</vcpu>
...
  <cputune>
    <emulatorpin cpuset='1-3'/>
    <vcpusched vcpus='0-2,4' scheduler='idle'/>
    <iothreadsched iothreads='1-2' scheduler='idle'/>
  </cputune>


4. restart libvirtd and check guest
# service libvirtd restart
Redirecting to /bin/systemctl restart  libvirtd.service

# virsh dumpxml test4
error: failed to get domain 'test4'
error: Domain not found: no domain with matching name 'test4'

Actual results:
guest will have broken settings if we delete a vcpu which included in some domain vcpu sched

Expected results:
remove the use of vcpu 4 in vcpusched in step 3

Additional info:

Comment 1 Peter Krempa 2015-06-24 08:46:05 UTC

I'm working on a refactor of data structures that hold info for vCPUs so this bug should be fixed along with that series.

Comment 3 Peter Krempa 2016-02-08 09:55:32 UTC

Fixed upstream:

commit 99c5fe0e7c26c08103415248ffef1f5acb81ddc7
Author: Peter Krempa <pkrempa>
Date:   Tue Jan 12 13:12:05 2016 +0100

    conf: Don't store vcpusched orthogonally to other vcpu info
    
    Due to bad design the vcpu sched element is orthogonal to the way how
    the data belongs to the corresponding objects. Now that vcpus are a
    struct that allow to store other info too, let's convert the data to the
    sane structure.
    
    The helpers for the conversion are made universal so that they can be
    reused for iothreads too.
    
    This patch also resolves https://bugzilla.redhat.com/show_bug.cgi?id=1235180
    since with the correct storage approach you can't have dangling data.

v1.3.1-159-g99c5fe0

Comment 5 Luyao Huang 2016-08-15 09:09:35 UTC

Verify this bug on libvirt-2.0.0-5.el7.x86_64:

1. prepare a guest xml like this:

# virsh dumpxml r7
...
  <vcpu placement='static'>20</vcpu>
  <iothreads>1</iothreads>
  <cputune>
    <vcpusched vcpus='0-2,18' scheduler='idle'/>
    <iothreadsched iothreads='1' scheduler='idle'/>
  </cputune>
...
  <cpu mode='host-model'>
    <model fallback='allow'/>
    <numa>
      <cell id='0' cpus='0-4' memory='524288' unit='KiB' memAccess='shared'/>
      <cell id='1' cpus='5-8' memory='524288' unit='KiB' memAccess='shared'/>
    </numa>
  </cpu>

2. use setvcpus remove some vcpus:

# virsh setvcpus r7 10 --config --maximum

3. recheck xml:

# virsh dumpxml r7
...
  <vcpu placement='static'>10</vcpu>
  <iothreads>1</iothreads>
  <cputune>
    <vcpusched vcpus='0-2' scheduler='idle'/>
    <iothreadsched iothreads='1' scheduler='idle'/>
  </cputune>
...

4. restart libvirtd and recheck guest xml:

# service libvirtd restart
Redirecting to /bin/systemctl restart  libvirtd.service

# virsh dumpxml r7
...
  <vcpu placement='static'>10</vcpu>
  <iothreads>1</iothreads>
  <cputune>
    <vcpusched vcpus='0-2' scheduler='idle'/>
    <iothreadsched iothreads='1' scheduler='idle'/>
  </cputune>
...

Comment 7 errata-xmlrpc 2016-11-03 18:19:11 UTC

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.

https://rhn.redhat.com/errata/RHSA-2016-2577.html

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