Re: [Qemu-devel] [PATCH 1/1] Support default interface types per QEMUMachine

[Anthony Liguori]

On 04/26/2012 11:11 AM, Andreas Färber wrote:
> Am 26.04.2012 17:48, schrieb Anthony Liguori:
> > On 04/26/2012 10:23 AM, Christian Borntraeger wrote:
> > > From: Einar Lueck<address@hidden>
> > >
> > > There are QEMUMachines that have neither IF_IDE nor IF_SCSI as a
> > > default/standard interface to their block devices / drives. Therefore,
> > > this patch introduces a new field def_blk_if per QEMUMachine struct.
> > > The prior use_scsi field becomes thereby obsolete and is replaced through
> > > .def_blk_if = IF_SCSI.
> >
> > I'd prefer a less cryptic name along with a reasonable default.  If 0
> > isn't the right thing for IF_*, we could use another enum.
> >
> > Looking briefly, it seems like both IF_SCSI and IF_IDE could be a
> > reasonable default.
>
> Not so long ago you told me that the whole machine should go into
> configuration files... If we do start drilling up QEMUMachine now, we
> should seriously QOM'ify it for 1.2.

QOM represents logic objects.  It's a data model and when we model hardware, we 
can model something concrete (because hardware for the most part has a physical 
implementation).

Machines are entirely a QEMU concept.  There's logic in the machines that will 
never be able to be expressed in a config file.  Machines make decisions about 
things like what the best NIC to use is.  There's no way to model "the best nic" 
in QOM.

Now a machine should *only* do things that can be done through a config file. 
IOW, the output of the machine function could be a config file that is then used 
to do a bunch of QOM operations.  That's perhaps a simplification but you get 
the general idea hopefully.

But I don't see a tremendous amount of value in just making QEMUMachine an 
Object.  I can certainly be convinced otherwise, but it's not obvious to me how 
it would be helpful.

Regards,

Anthony Liguori

> Andreas