[fedora-virt] how can i verify that HW extensions are being used?

Bill Davidsen davidsen at tmr.com
Thu Apr 16 13:44:30 UTC 2009

Eduardo Habkost wrote:
> On Thu, Apr 16, 2009 at 07:48:52AM -0400, Robert P. J. Day wrote:
>>   apparently, i made one lame-brained move yesterday that almost
>> certainly caused my VM to run thigh-suckingly slowly.  following the
>> linux KVM FAQ, i wanted to configure KVM so i could run it as a
>> non-root user.  to that end, i
>>   * created a "kvm" group,
>>   * added my user account to the kvm group, and
>>   * added the rules file /etc/udev/rules.d/60-kvm.rules:
>>     KERNEL=="kvm", GROUP="kvm"
>>   i re-initialized udev with:
>>   # udevadm control --reload-rules   (right?)
>> unloaded my kvm modules (kvm and kvm_amd), reloaded them and, sure
>> enough, my new /dev/kvm device file had a group affiliation of kvm.
>> excellent, i thought, and away i went ... with still painfully slow
>> performance, until i realized that i was still in my original desktop
>> session which *wasn't* considered part of the kvm group.  so a quick
>> logout, log back in and things were much better.
>>   *that's* the sort of thing i'm trying to document as i write all of
>> this up -- those slight oversights which no one bothers to mention
>> that eventually bite you in the butt.  in any event, back to my
>> original question -- what could i have checked that would have told
>> me, no, you are *not* taking advantage of the AMD-V HW virt
>> extensions?  after all, my modules were loaded, /dev/kvm existed, it
>> clearly had the right group, but (and correct me if i'm wrong) i was
>> obviously not getting the benefit of HVM because my desktop session
>> wasn't considered part of the "kvm" group.
> If you are using qemu directly, go to the monitor (ctrl-alt-f2) and type
> "info kvm", and you can be sure if kvm is being used or not.
> But you shouldn't be using qemu directly and use libvirt/virt-manager
> instead. ;) However, I don't know what is the right command to check if
> kvm is actually being used for a libvirt-managed guest.
Actually, that's one of the reasons I usually don't use a VMM, is just 
because I want to be able to get to KVM. And I have had far better luck 
using SVN for console than VNC, another minor issue.

bill davidsen <davidsen at tmr.com>
  CTO TMR Associates, Inc

"You are disgraced professional losers. And by the way, give us our money back."
    - Representative Earl Pomeroy,  Democrat of North Dakota
on the A.I.G. executives who were paid bonuses  after a federal bailout.

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