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

Eduardo Habkost ehabkost at redhat.com
Thu Apr 16 13:09:48 UTC 2009

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.


More information about the Fedora-virt mailing list