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Bug 1525182

Summary:	Should rebuild QEMU capabilities on KVM hosts if kernel version changes
Product:	Red Hat Enterprise Linux 7	Reporter:	Paolo Bonzini <pbonzini>
Component:	libvirt	Assignee:	Jiri Denemark <jdenemar>
Status:	CLOSED ERRATA	QA Contact:	Luyao Huang <lhuang>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	7.5	CC:	dyuan, lmen, lmiksik, mtessun, pbonzini, rbalakri, xuzhang, yalzhang, zpeng
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	libvirt-3.9.0-9.el7	Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2018-04-10 11:02:08 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Paolo Bonzini 2017-12-12 17:46:36 UTC

A new kernel version can make new CPUID bits show up in KVM's capabilities.  So "uname -r" should be stored in the QEMU capabilities cache and checked at libvirt startup.

Comment 2 Jiri Denemark 2018-01-22 10:47:47 UTC

Patch sent upstream for review: https://www.redhat.com/archives/libvir-list/2018-January/msg00657.html

Comment 3 Jiri Denemark 2018-01-22 13:13:46 UTC

The patch is now pushed upstream as

commit 52b7d910b6b0ceeff50866774adba6efab55b2c0
Refs: v4.0.0-6-g52b7d910b6
Author:     Jiri Denemark <jdenemar>
AuthorDate: Mon Jan 22 11:37:04 2018 +0100
Commit:     Jiri Denemark <jdenemar>
CommitDate: Mon Jan 22 14:11:58 2018 +0100

    qemu: Refresh caps cache after booting a different kernel

    Whenever a different kernel is booted, some capabilities related to KVM
    (such as CPUID bits) may change. We need to refresh the cache to see the
    changes.

    Signed-off-by: Jiri Denemark <jdenemar>
    Reviewed-by: Daniel P. Berrange <berrange>

Comment 6 Luyao Huang 2018-01-24 02:37:48 UTC

Verify this bug with libvirt-3.9.0-9.el7.x86_64:

1. check caps file timestamp:

# ll /var/cache/libvirt/qemu/capabilities/3c76bc41d59c0c7314b1ae8e63f4f765d2cf16abaeea081b3ca1f5d8732f7bb1.xml 
-rw-------. 1 root root 51770 Jan 23 21:11 /var/cache/libvirt/qemu/capabilities/3c76bc41d59c0c7314b1ae8e63f4f765d2cf16abaeea081b3ca1f5d8732f7bb1.xml


2. check the kernel version in caps file:

# cat /var/cache/libvirt/qemu/capabilities/3c76bc41d59c0c7314b1ae8e63f4f765d2cf16abaeea081b3ca1f5d8732f7bb1.xml

...
  <kernelVersion>3.10.0-837.el7.x86_64 #1 SMP Tue Jan 23 13:31:59 UTC 2018</kernelVersion>
...

3. install a new kernel and reboot:

4. check the caps file timestamp:

# ll /var/cache/libvirt/qemu/capabilities/3c76bc41d59c0c7314b1ae8e63f4f765d2cf16abaeea081b3ca1f5d8732f7bb1.xml
-rw-------. 1 root root 51770 Jan 23 21:28 /var/cache/libvirt/qemu/capabilities/3c76bc41d59c0c7314b1ae8e63f4f765d2cf16abaeea081b3ca1f5d8732f7bb1.xml

5. check the kernel  version in caps file:

  <kernelVersion>3.10.0-831.el7.x86_64 #1 SMP Wed Jan 17 15:59:59 EST 2018</kernelVersion>

6. restart libvirtd and recheck the caps file timestamp:

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

# ll /var/cache/libvirt/qemu/capabilities/3c76bc41d59c0c7314b1ae8e63f4f765d2cf16abaeea081b3ca1f5d8732f7bb1.xml 
-rw-------. 1 root root 51770 Jan 23 21:28 /var/cache/libvirt/qemu/capabilities/3c76bc41d59c0c7314b1ae8e63f4f765d2cf16abaeea081b3ca1f5d8732f7bb1.xml

Comment 10 errata-xmlrpc 2018-04-10 11:02:08 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://access.redhat.com/errata/RHEA-2018:0704