[libvirt] Fwd: How do you disable hpet in a kvm?

[Laine Stump]

On 06/08/2010 03:59 PM, Richard W.M. Jones wrote:
> Forwarding to libvir-list.
>
> The KVM developers have been recommending that all guests use -no-hpet
> flag.  Indeed, we've been adding this flag in libguestfs for quite a
> long time.  However I notice that libvirt [in Rawhide] does not
> include this flag for my guests.
>    

-no-hpet isn't in the commandline by default, but can be added with the 
following bit of xml in the domain definition:

<clock>
<timer name='hpet' present='no'/>
</clock>

(if there is an existing <clock> section, you should add the "<timer 
name= ...>" to that, rather than creating a new one).

That functionality is in libvirt as of version 0.8.0.

Actually, I just realized while loking back through the code that the 
intent was for -no-hpet to be set if
<timer name='hpet'/> is given with *no* "present" attribute (and if qemu 
supports it, of course), but that isn't being done, so I'm filing a bug 
for that. (the idea is that then the xml for all domains can just say 
"<timer name='hpet'/>" and the option will be added when qemu supports 
it, and it will be silently ignored when it doesn't support it.

> Rich.
>
> ----- Forwarded message from "Frederick N. Brier"<fnbrier at gmail.com>  -----
>
> Subject: [fedora-virt] How do you disable hpet in a kvm?
> Date: Tue, 08 Jun 2010 14:15:06 -0400
> To: virt at lists.fedoraproject.org
>
> I installed PBX In A Flash (PIAF) as a VM on a Fedora 11 64 bit host.
> PIAF is a 32 bit CentOS 5.2 distro for running Asterisk.  I, like many
> others, am getting the error message "rtc: lost some interrupts at 1024hz"
> repeating over and over on the console.  Some people have apparently gotten
> rid of this error message by disabling hpet in the BIOS.  However, this is
> a VM (kvm).
>
> I tried adding nohpet as a kernel parameter in /boot/grub/menu.lst, but
> that effects the linux OS, not the BIOS.  It did not fix it.
>
> I found references to a -no-hpet qemu parameter.  However, I cannot find
> how to set it in a VM created using virt-manager and an ISO image.  In the
> /etc/libvirt of the host I found XML configuration files describing the
> VMs.  These appear to be the same as those created using the virsh dumpxml
> command.  There does not appear to be an XML element as there is for acpi
> and apic.  The man page describing the XML format does not have an HPET
> related option.  I could not find an example or sample of it being disabled
> in a libvirt XML file.  Nor does there appear to be a schema (xsd or dtd)
> for the libvirt file format, which might have had an hpet element or
> attribute.
>
> Ideally, is there a way to disable HPET in the BIOS for a specific VM, and
> not all VMs.  Thank you.
>
> Fred
> //
>
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> ----- End forwarded message -----
>
>