[libvirt] HELP: after host upgrade to F11, guest runs extremely slow

Gerry Reno greno at verizon.net
Tue May 26 16:26:24 UTC 2009

Chris Lalancette wrote:
> Gerry Reno wrote:
>> Gerry Reno wrote:
>>> Gerry Reno wrote:
>>>> Daniel P. Berrange wrote:
>>>>> On Sat, May 23, 2009 at 03:43:12PM -0400, Gerry Reno wrote:
>>>>>> I upgraded the host from F10 to F11 (x86_64) with no issues.  Now when I 
>>>>>> start a F10 (i386) guest it runs very very slow.  I also see messages on 
>>>>>> the guest boot console about "clocksource tsc unstable" and some kernel 
>>>>>> oops.  Once it got far enough to start network I logged in and checked 
>>>>>> the clocksource and it currently is 'acpi_pm' even though the kernel 
>>>>>> line says clocksource=pit.  The available clocksources are acpi_pm, 
>>>>>> jiffies, and tsc.  I do not see 'pit' in the list.  How do I fix this issue?
>>>>> If the guest runs 'extrememly' slowly then the most like thing is that 
>>>>> it has fallen back to using QEMU emulation, instead of KVM hardware
>>>>> acceleration. Check the /var/log/libvirt/qemu/$GUEST.log to see if there
>>>>> is any mesage about not being able to open /dev/kvm.  Also make sure that
>>>>> KVM modules are loaded, and that 'virsh capabilities' lists KVM as a valid
>>>>> domain.
>>>>> Daniel
>>>> Ok, I checked the guest log and it says:
>>>> /dev/kvm: no such file or directory.
>>>> So how do I make this node?  Shouldn't libvirt have made it for us?
>>> Ok, once I got both kernel modules loaded, it created the /dev/kvm
>>> device and now everything runs fine.
>> Well, not quite so fine.  If I reboot the machine then the kvm modules
>> are no longer loaded.  How do I keep these modules loaded?
> I'm assuming that you haven't installed qemu from the F-11 packages.  If you
> install the qemu-system-x86 on F-11, it comes with a file
> /etc/sysconfig/modules/kvm.modules.  On bootup, any scripts in that directory
> are executed, and that command automatically loads the appropriate modules for
> you.  If you don't want to install the F-11 qemu-system-x86 package for some
> reason, you'll have to arrange to do the same with a custom script in that
> directory, or just in /etc/rc.d/rc.local.
Thanks Chris.  I found an update to the 'qemu' package and ran 'yum 
update qemu'.  After the update then this file: 
/etc/sysconfig/modules/kvm.modules  was added.  Now the kvm modules stay 
loaded across reboots.  I wonder why the F11 upgrade didn't bring in 
this package?  Maybe it's not on the DVD.


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