libvirt users - Nov 2015 - Re: How to disable kvm_steal_time feature

Hi.

I would like to workaround a bug, when after live-migration of KVM 
guest, there is a 100% steal time shown in guest.

I've read, that disabling 'kvm_steal_time' feature should workarund
this
bug, but i can't find a way to disable it in libvirt's domain xml file.

Tried in <cpu> section:
<feature policy='disable' name='kvm_steal_time'/>
but that doesn't work.

Also, couldn't find any related information in libvirt documentation. 
Google helps neither.

How can I disable this feature?

Thanks in advance.
Piotr Rybicki

On Fri, Nov 20, 2015 at 04:31:56PM +0100, Piotr Rybicki
wrote:
>Hi.
>
>I would like to workaround a bug, when after live-migration of KVM
>guest, there is a 100% steal time shown in guest.
>
>I've read, that disabling 'kvm_steal_time' feature should
workarund
>this bug, but i can't find a way to disable it in libvirt's domain
xml
>file.
>
There is no support for that in libvirt.  Either we must addit ad a
feature (patches welcome), but if that's there just for a workaround,
I would suggest chasing the original bug.

If you just want to check that the workaround works, you could check
how the '-cpu ' parameter looks like when the domain is running and
then use the unsupported way of adding parameters to the qemu
commandline to specify the -cpu parameter again (qemu should use the
last one, so it should work), something like this:

<domain type='kvm'
xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
...
  <qemu:commandline>
    <qemu:arg value='-cpu'/>
    <qemu:arg value='${CPU_SPEC},-kvm_steal_time'/>
  </qemu:commandline>
</domain>

where ${CPU_SPEC} is the next parameter after the '-cpu' one from the
command line, so for qemu command line similar to this:

  qemu-kvm ... -cpu Nehalem,+feat,something ...

the line in XML would be:

  <qemu:arg value='Nehalem,+feat,something,-kvm_steal_time'/>

HTH,

Martin
>Tried in <cpu> section:
><feature policy='disable' name='kvm_steal_time'/>
>but that doesn't work.
>
>Also, couldn't find any related information in libvirt documentation.
>Google helps neither.
>
>How can I disable this feature?
>
>Thanks in advance.
>Piotr Rybicki
>
>_______________________________________________
>libvirt-users mailing list
>libvirt-users@redhat.com
>https://www.redhat.com/mailman/listinfo/libvirt-users

27 нояб. 2015 г. 14:15 пользователь "Martin Kletzander"
<mkletzan@redhat.com>
написал:
>
> On Fri, Nov 20, 2015 at 04:31:56PM +0100, Piotr Rybicki wrote:
>>
>> Hi.
>>
>> I would like to workaround a bug, when after live-migration of KVM
>> guest, there is a 100% steal time shown in guest.
>>
>> I've read, that disabling 'kvm_steal_time' feature should
workarund
>> this bug, but i can't find a way to disable it in libvirt's
domain xml
>> file.
>>
>
> There is no support for that in libvirt.  Either we must addit ad a
> feature (patches welcome), but if that's there just for a workaround,
> I would suggest chasing the original bug.
>
> If you just want to check that the workaround works, you could check
> how the '-cpu ' parameter looks like when the domain is running and
> then use the unsupported way of adding parameters to the qemu
> commandline to specify the -cpu parameter again (qemu should use the
> last one, so it should work), something like this:
>
> <domain type='kvm'
xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0
'>
> ...
>  <qemu:commandline>
>    <qemu:arg value='-cpu'/>
>    <qemu:arg value='${CPU_SPEC},-kvm_steal_time'/>
>  </qemu:commandline>
> </domain>
>
> where ${CPU_SPEC} is the next parameter after the '-cpu' one from
the
> command line, so for qemu command line similar to this:
>
>  qemu-kvm ... -cpu Nehalem,+feat,something ...
>
> the line in XML would be:
>
>  <qemu:arg value='Nehalem,+feat,something,-kvm_steal_time'/>
>
> HTH,
>
> Martin
>
>> Tried in <cpu> section:
>> <feature policy='disable' name='kvm_steal_time'/>
>> but that doesn't work.
>>
>> Also, couldn't find any related information in libvirt
documentation.
>> Google helps neither.
>>
>> How can I disable this feature?
>>
>> Thanks in advance.
>> Piotr Rybicki
>>
>>
Does it possible to calculate steal time for  vm if I have libvirt and
domain stats?
_______________________________________________
>> libvirt-users mailing list
>> libvirt-users@redhat.com
>> https://www.redhat.com/mailman/listinfo/libvirt-users
>
>
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> libvirt-users@redhat.com
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