[virt-tools-list] [PATCH v2 3/3] Add support for cpu host-passthrough mode

[Cole Robinson]

On 04/12/2013 05:50 AM, Guannan Ren wrote:
> On 04/11/2013 01:45 PM, Hu Tao wrote:
>> From: Ken ICHIKAWA <ichikawa.ken at jp.fujitsu.com>
>>
>> We couldn't use host-passthrough mode for virtual cpu from
>> virt-manager so far. This patch enables virt-manager to
>> configure host-passthrough mode.
>>
>> Signed-off-by: Ken ICHIKAWA <ichikawa.ken at jp.fujitsu.com>
>> ---
>>   ui/vmm-details.ui      | 21 +++++++++++++++++++--
>>   virtManager/details.py | 23 ++++++++++++++++++++++-
>>   virtManager/domain.py  | 13 ++++++++++---
>>   3 files changed, 51 insertions(+), 6 deletions(-)
>>
>> diff --git a/ui/vmm-details.ui b/ui/vmm-details.ui
>> index ad0652d..b1a70b3 100644
>> --- a/ui/vmm-details.ui
>> +++ b/ui/vmm-details.ui
>> @@ -2314,6 +2314,23 @@ I/O:</property>
>>                                               <property
>> name="can_focus">False</property>
>>                                               <property
>> name="spacing">6</property>
>>                                               <child>
>> +                                              <object
>> class="GtkCheckButton" id="host-passthrough-enable">
>> +                                                <property name="label"
>> translatable="yes">Use host-passthrough mode</property>
>> +                                                <property
>> name="visible">True</property>
>> +                                                <property
>> name="can_focus">True</property>
>> +                                                <property
>> name="receives_default">False</property>
>> +                                                <property
>> name="use_action_appearance">False</property>
>> +                                                <property
>> name="active">True</property>
>> +                                                <property
>> name="draw_indicator">True</property>
>> +                                                <signal name="toggled"
>> handler="on_host_passthrough_enable_toggled" swapped="no"/>
>> +                                              </object>
>> +                                              <packing>
>> +                                                <property
>> name="expand">True</property>
>> +                                                <property
>> name="fill">True</property>
>> +                                                <property
>> name="position">0</property>
>> +                                              </packing>
>> +                                            </child>
>> +                                            <child>
>>                                                 <object class="GtkTable"
>> id="table15">
>>                                                   <property
>> name="visible">True</property>
>>                                                   <property
>> name="can_focus">False</property>
>> @@ -2428,7 +2445,7 @@ I/O:</property>
>>                                                 <packing>
>>                                                   <property
>> name="expand">False</property>
>>                                                   <property
>> name="fill">True</property>
>> -                                                <property
>> name="position">0</property>
>> +                                                <property
>> name="position">1</property>
>>                                                 </packing>
>>                                               </child>
>>                                               <child>
>> @@ -2499,7 +2516,7 @@ I/O:</property>
>>                                                 <packing>
>>                                                   <property
>> name="expand">False</property>
>>                                                   <property
>> name="fill">True</property>
>> -                                                <property
>> name="position">1</property>
>> +                                                <property
>> name="position">2</property>
>>                                                 </packing>
>>                                               </child>
>>                                             </object>
> 
>           There are four modes we can let user choose:
>           default(qemu64)
>           custom
>           host-model
>           host-passthrough(cpu -host)
> 
>           Currently, the virt-manager supports
>           default mode(by default)
>           custom(choose from a ComboBox)
>           host-model(Copy host CPU configuration Button)
> 
>           My idea is to use ComboBox which gives a list of these four modes,
> if the custom mode is selected,
>           then, the model and feature is activated next, guiding user to
> choose cpu model and features.
>           Or, the RadioButton is also an idea, but I prefer the ComboBox.
> 
>           By the way, for the CheckButton in this patch, I found the UI become
> not very smooth, can you do
>           a little modification to make it perfect, although it look perfect
> in glade-3.
> 

So here I'm not sure we even want host-passthrough in the virt-manager UI. I
know it's valuable and useful, but there's the problem that libvirt 'taints'
the VM when you set this flag. This doesn't really have any functional effect,
but it basically means that libvirt devs consider this option to be not all
that supportable. Exposing it in the UI seems like going against libvirt's wishes.

It's also quite hard to explain host-model vs host-passthrough to an end user.
We could just throw them in a combo box, but I guarantee it will have people
asking over and over what the difference between host-model and
host-passthrough is.

I'm fine with allowing this via virt-install though.

I'm not sure what the end result UI should be here. If we use host-model when
libvirt is new enough, the current UI doesn't quite fit, because we don't know
what libvirt cpu model and feature flags we are going to get until we define
the VM, so hitting the 'copy' button won't update the UI. I guess we could
change it to a checkbox.

Also, I don't know if host-model allows add/removing extra CPU flags, so if
host-model is selected, we might want to disable the feature list and model
drop down to make it clear they aren't editable. They should still be viewable
though so users can see the exact configuration.

- Cole