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Bug 624983

Summary: QEMU should support the newer set of MSRs for kvmclock
Product: Red Hat Enterprise Linux 6 Reporter: Shirley Zhou <szhou>
Component: qemu-kvmAssignee: Eduardo Habkost <ehabkost>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: medium Docs Contact:
Priority: high    
Version: 6.0CC: arozansk, gcosta, juzhang, lihuang, mjenner, mkenneth, mshao, qcai, qzhang, szhou, tburke, virt-maint
Target Milestone: rcKeywords: Triaged
Target Release: 6.1   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: qemu-kvm-0.12.1.2-2.188.el6 Doc Type: Bug Fix
Doc Text:
Cause: A set if MSRs used by kvmclock was deprecated in favour of a new set of registers. Consequence: qemu-kvm didn't support the new set of registers, and guests that used only the new set wouldn't be able to use kvmclock. Change: the new set of kvmclock registers is now supported. Result: guests that use only the new set of kvmclock registers will be able to use kvmclock too.
 Story Points: ---
Clone Of: 592296 Environment:
Last Closed: 2011-12-06 15:43:09 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 592296    
Bug Blocks: 580951, 743047    

Comment 11 Qunfang Zhang 2011-09-16 07:14:20 UTC 
Verified on kernel-2.6.32-196.el6.x86_64 and qemu-kvm-0.12.1.2-2.189.el6.

Steps:
1. Boot a RHEL6.2 guest. (guest kernel version: kernel-2.6.32-196.el6.x86_64)
2. Check dmesg info of guest:
# dmesg | grep kvm
kvm-clock: Using msrs 4b564d01 and 4b564d00
kvm-clock: cpu 0, msr 0:1c1df81, boot clock
kvm-clock: cpu 0, msr 0:28215f81, primary cpu clock
kvm-clock: cpu 1, msr 0:28315f81, secondary cpu clock
Switching to clocksource kvm-clock

It already uses the newer sets of MSRs (4b564d01 and 4b564d00) for kvmclock.

So, this bug is fixed.
Comment 12 Qunfang Zhang 2011-09-16 07:18:08 UTC 
Based on Comment 11. This issue can be reproduced on qemu-kvm-0.12.1.2-2.185.el6.

Boot the same guest and check the dmesg info of guest:

# dmesg | grep kvm
kvm-clock: Using msrs 12 and 11
kvm-clock: cpu 0, msr 0:1c1df81, boot clock
kvm-clock: cpu 0, msr 0:28215f81, primary cpu clock
kvm-clock: cpu 1, msr 0:28315f81, secondary cpu clock
Switching to clocksource kvm-clock

It is using the old MSRs 12 and 11.
Comment 14 Eduardo Habkost 2011-11-17 18:15:11 UTC 
    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
Cause: A set if MSRs used by kvmclock was deprecated in favour of a new set of registers.

Consequence: qemu-kvm didn't support the new set of registers, and guests that used only the new set wouldn't be able to use kvmclock.

Change: the new set of kvmclock registers is now supported.

Result: guests that use only the new set of kvmclock registers will be able to use kvmclock too.
Comment 15 errata-xmlrpc 2011-12-06 15:43:09 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.

http://rhn.redhat.com/errata/RHSA-2011-1531.html