[libvirt] [PATCH 0/4] Add new APIs and virsh commands to get/set cpu mode

Daniel P. Berrange berrange at redhat.com
Mon Dec 10 13:55:11 UTC 2012


On Mon, Dec 10, 2012 at 02:52:33PM +0100, Jiri Denemark wrote:
> On Mon, Dec 10, 2012 at 09:28:06 +0100, Viktor Mihajlovski wrote:
> > On 12/10/2012 06:19 AM, Ichikawa, Ken wrote:
> > > This patchset adds new APIs virDomainGetCPUMode and virDomainSetCPUMode,
> > > and adds new virsh commands cpu-getmode and cpu-setmode by using these APIs.
> > >
> > > virDomainGetCPUMode allows to get cpu mode of a running or persistent domain.
> > > virDomainSetCPUMode allows to set cpu mode of a persistent domain.
> 
> This proposal does not make any sense to me. In general, we don't provide APIs
> that duplicate what we can already do by changing domain XML. Since
> virDomainSetCPUMode can only affect persistent config (you cannot unplug the
> old CPU and plug the new one while the domain is running), the API does not
> add anything what could not be done with virDomainDefineXML.
> 
> > > These APIs and virsh commands are useful because:
> > >   - No longer need to mess around with XML for changing cpu mode.
> > >   - People who want more performance can change cpu mode easily.
> 
> There's libvirt-gconfig for those who don't want to mess with XML.
> 
> > >   - If there is a person who has a trouble with host-mode and
> > >     host-passthrough, we can help easily by one-liner like
> > >       "# virsh cpu-setmode <domain> custom"
> > >     Then, default cpu is used after next boot.
> 
> However, default CPU is most likely not what anyone would want. It's better to
> use one of the predefined models that.
> 
> Anyway, if an easy way to change the CPU mode is required, a patch
> implementing new virsh command that would fetch domain XML, update it, and
> define back could be acceptable (I think we have some of these in virsh
> already), but NACK to these new APIs.

Agreed, NACK to this proposal

Daniel
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