Re: [Qemu-devel] [PATCH v7 0/9] Add limited support of VMware's hyper-call rpc

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jun 17, 2015 at 01:34:33PM -0400, Don Slutz wrote:
> On 06/17/15 13:25, Paolo Bonzini wrote:
> > 
> > 
> > On 17/06/2015 19:14, Paolo Bonzini wrote:
> >>
> >>
> >> On 17/06/2015 19:03, Don Slutz wrote:
> >>> On 06/17/15 12:29, Michael S. Tsirkin wrote:
> >>>> On Wed, Jun 17, 2015 at 06:17:19PM +0200, Paolo Bonzini wrote:
> >>>>>
> >>>>>
> >>>>> On 17/06/2015 16:29, Michael S. Tsirkin wrote:
> >>>>>> On Wed, Jun 17, 2015 at 04:27:13PM +0200, Paolo Bonzini wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>> On 17/06/2015 16:18, Michael S. Tsirkin wrote:
> >>>>>>>>>> Yes, that's what was done for parallel and pcspk as well.  There's no
> >>>>>>>>>> infrastructure to avoid it.
> >>>>>>>>>>
> >>>>>>>>>> Paolo
> >>>>>>>> How do you mean? We have multiple ways to keep devices
> >>>>>>>> compatible with old versions.
> >>>>>>>> Set a new property to skip the extra stuff.
> >>>>>>>
> >>>>>>> Not if the device didn't have a vmstate at all, unfortunately.
> >>>>>>
> >>>>>> Skip creating the device completely for old machine types.
> >>>>>
> >>>>> Which device?  The vmstate is tied to the same device that has always
> >>>>> been created.
> >>>>
> >>>> Just disable the new functionality. Make it behave in
> >>>> a compatible way.
> >>>>
> >>>>>  we enable this thing by default (why do we?)
> >>>>
> >>>> Sigh. There is a very simple way to add a device in qemu: let user
> >>>> request it with -device.  If one does this, one gets to maintain the
> >>>> resulting mess without bothering with pc maintainers in any way.
> >>>>
> >>>> But of course, everyone implementing a new feature feels it's such a
> >>>> great thing, and completel zero risk, it must be part of the default
> >>>> machine. Guess what, one then gets to bother with versioning from day 0.
> >>>>
> >>>>>>>> this seems like a big deal ...
> >>>>>>>
> >>>>>>> The PC speaker device is also enabled by default.
> >>>>>>
> >>>>>> This is historical, isn't it?
> >>>>>
> >>>>> Yes, but it has broken 2.3->2.2 migration.
> >>>>>
> >>>>> Let's just stop fighting windmills.
> >>>>>
> >>>>> Paolo
> >>>>
> >>>> I don't see what you are saying. Suddenly guest visible
> >>>> changes within a machine type are ok?
> >>>>
> >>>> So we have a bug, need to fix it, preferably before piling up
> >>>> more features. The best way imho is for 2.4 to avoid
> >>>> this device unless requested explicitly.
> >>>>
> >>>
> >>> My take on this is that Michael would like me to have a vmport_rpc=on
> >>> option, just like vmport=on (which already exists).  With a default of off.
> >>
> >> It wouldn't be enough, because dc->vmsd would be non-NULL anyway.
> >>
> >> (But yes, that option would be a good thing anyway).
> > 
> > Even better would be to have a "-global vmport.rpc=no" option.  It would
> > be simpler to disable it in existing machine types.
> > 
> 
> Either way I can avoid the device creation... Unless I hear otherwise I
> will go the global way.  Since the default would be no, should I also
> make the default =yes for the 2.4 pc?
> 
>    -Don Slutz
> 
>    -Don Slutz

Can you use -device vmport_rpc, and avoid adding code to the default pc?

> > Paolo
> >