[libvirt] [RFC PATCH 00/12] qemu: add support to hot-plug/unplug cpu device

[Zhu Guihua]

On Thu, 2015-01-22 at 10:06 +0000, Daniel P. Berrange wrote:
> On Thu, Jan 22, 2015 at 04:55:02PM +0800, Zhu Guihua wrote:
> > On Wed, 2015-01-21 at 09:42 +0000, Daniel P. Berrange wrote:
> > > On Wed, Jan 21, 2015 at 04:00:52PM +0800, Zhu Guihua wrote:
> > > > If you apply the folowing patchset
> > > > [PATCH v3 0/7] cpu: add device_add foo-x86_64-cpu support
> > > > https://lists.nongnu.org/archive/html/qemu-devel/2015-01/msg01552.html,
> > > > and [PATCH v2 00/11] cpu: add i386 cpu hot remove support
> > > > https://lists.nongnu.org/archive/html/qemu-devel/2015-01/msg01557.html,
> > > > qemu can support hotplug and hot-unplug cpu device.
> > > > 
> > > > So this patch series will make libvirt support hotplug and hot-unplug cpu
> > > > device for qemu driver, and now only supports one cpu driver which is
> > > > 'qemu64-x86_64-cpu'.
> > > > 
> > > > The cpu device's xml like this:
> > > > <cpu driver='qemu64-x86_64-cpu' apic_id='3'>
> > > 
> > > Do we really need to expose this 'qemu64-x86_64-cpu' string to apps.
> > > It feels like a rather low level QEMU private implementation detail
> > > to me that apps should not need to know or care about. I think libvirt
> > > should always just do the right thing to make cpu hotplug work.
> > > 
> > 
> > There is a need to use more cpu model. 
> > 'qemu64-x86_64-cpu' is only one example, we will realize more driver in
> > future.
> 
> Can you give an example of why we will need more than one model ? It seems
> pretty crazy to me that we will need to specify two CPU models for CPUs,
> both "Nehalem" / "Opteron" / etc and this new CPU model. It makes little
> sense from the user / app POV IMHO.
> 

In future, this will become an advanced feature for specific user. If
user may not specific a model, we will specific a default model.

I think this feature is mainly for test environment. If you want to test
different cpu model's performance, this feature will be essential.

Regards,
Zhu

> Regards,
> Daniel