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Bug 557285 - [RFE] Need to add time keeping abstraction
Summary: [RFE] Need to add time keeping abstraction
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: libvirt
Version: 6.0
Hardware: All
OS: Linux
high
medium
Target Milestone: beta
: ---
Assignee: Laine Stump
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2010-01-20 22:11 UTC by Dor Laor
Modified: 2013-01-09 21:17 UTC (History)
12 users (show)

Fixed In Version: libvirt-0.7.8-0.pre20100330.el6
Doc Type: Enhancement
Doc Text:
Clone Of:
Environment:
Last Closed: 2010-07-02 19:28:33 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)

Description Dor Laor 2010-01-20 22:11:46 UTC 
Description of problem:
KVM does not really virtualize the tsc. Basically today we just wrap it with a delta. It might be suffice and good enough for most application but might be a problem is guest kernel/apps will need a very accurate tsc readings.

The solution is to add an abstraction about tsc virtualization - it can be:
 - 'normal' - the default like today
 - 'ideal' - trap every tsc read and fully emulate it.

Zach can provide further information. Also need to see if we need a new bug for live migration when the tsc frequency changes among the hosts.
Comment 2 RHEL Program Management 2010-01-20 22:35:52 UTC 
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release.  Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release.  This request is not yet committed for
inclusion.
Comment 5 Daniel Berrangé 2010-03-05 14:38:25 UTC 
A proposal for modelling this in libvirt XML is posted upstream.

http://www.redhat.com/archives/libvir-list/2010-March/msg00304.html

Would appreciate feedback from the KVM team that this is an accurate representation of & solution to the problem.
Comment 6 Daniel Berrangé 2010-03-05 14:39:21 UTC 
NB, this proposal also covers the RTC/PIT missed tick hacks in KVM.
Comment 7 Hugh Brock 2010-03-15 19:16:41 UTC 
With the design settled, reassigning to Laine for the implementation.
Comment 8 Bill Burns 2010-03-26 00:05:28 UTC 
*** Bug 576973 has been marked as a duplicate of this bug. ***
Comment 9 Laine Stump 2010-03-26 18:57:28 UTC 
libvirt support for the XML and qemu backend described in the aforementioned email has been posted upstream:

https://www.redhat.com/archives/libvir-list/2010-March/msg01289.html

The vmware and xen backends have not yet been implemented.
Comment 10 Daniel Veillard 2010-03-30 21:20:59 UTC 
libvirt-0.7.8-0.pre20100330.el6 was built in RHEL-6-candidate with
the patches

Daniel
Comment 13 dyuan 2010-06-22 10:51:10 UTC 
Test with libvirt-0.8.1-9.el6 and qemu-kvm-0.12.1.2-2.77.el6

# virsh start demo
error: Failed to start domain demo
error: internal error Process exited while reading console log output: qemu-kvm: -rtc base=localtime,driftfix=slew: Invalid parameter 'driftfix'

Test with the following lines in xml:
  <clock offset='localtime'>
    <timer name='rtc' tickpolicy='catchup' wallclock='guest'/>
  </clock>

got xml description from: 
http://www.redhat.com/archives/libvir-list/2010-March/msg00304.html


# tail -f /var/log/libvirt/qemu/demo.log
==> /var/log/libvirt/qemu/demo.log <==
LC_ALL=C PATH=/sbin:/usr/sbin:/bin:/usr/bin QEMU_AUDIO_DRV=none /usr/libexec/qemu-kvm -S -M rhel6.0.0 -enable-kvm -m 2048 -smp 33,sockets=33,cores=1,threads=1 -name demo -uuid 80f9fa13-41d0-c352-b9d1-939937668a16 -nodefaults -chardev socket,id=monitor,path=/var/lib/libvirt/qemu/rhel68.monitor,server,nowait -mon chardev=monitor,mode=control -rtc base=localtime,driftfix=slew -boot c -drive file=/mnt/vol/rhel6_x86_64.img,if=none,id=drive-ide0-0-0,boot=on,cache=none -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -netdev tap,fd=20,id=hostnet0,vhost=on,vhostfd=21 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=52:54:00:35:17:aa,bus=pci.0,addr=0x4 -chardev pty,id=serial0 -device isa-serial,chardev=serial0 -usb -vnc 127.0.0.1:1 -k en-us -vga cirrus -device AC97,id=sound0,bus=pci.0,addr=0x5 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 
qemu-kvm: -rtc base=localtime,driftfix=slew: Invalid parameter 'driftfix'


Test with name='pit' and name='hpet', no error output.
<timer name='pit' tickpolicy='delay'/>
<timer name='hpet' present='no'/>
Comment 14 Daniel Berrangé 2010-06-22 11:04:06 UTC 
libvirt is operating correctly there. The problem reported is a QEMU bug

https://bugzilla.redhat.com/show_bug.cgi?id=606733
Comment 16 Yan Tian 2010-06-23 02:37:43 UTC 
Verified this bug with Comment 14.
Comment 17 releng-rhel@redhat.com 2010-07-02 19:28:33 UTC 
Red Hat Enterprise Linux Beta 2 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.
Comment 18 Nan Zhang 2010-09-08 10:24:17 UTC 
Verified with libvirt-0.8.1-27.el6.x86_64 & qemu-kvm-0.12.1.2-2.113.el6.x86_64.

1. Test with the XML:
  <clock offset='localtime'>
    <timer name='rtc' tickpolicy='catchup' track='guest'/>
  </clock>

# virsh start rhel6
Domain rhel6 started

# tail /var/log/libvirt/qemu/rhel6.log
...
-rtc base=localtime,clock=vm,driftfix=slew
...

2. Test with the XML:
  <clock offset='localtime'>
    <timer name='pit' tickpolicy='delay' />
  </clock>

# virsh start rhel6
Domain rhel6 started

# tail /var/log/libvirt/qemu/rhel6.log
...
-rtc base=localtime -no-kvm-pit-reinjection
...

3. Test with the XML:
  <clock offset='localtime'>
    <timer name='hpet' present='no'/>
  </clock>

# virsh start rhel6
Domain rhel6 started

# tail /var/log/libvirt/qemu/rhel6.log
...
-rtc base=localtime
...
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