Re: [libvirt] [Qemu-devel] [uq/master PATCH 0/7] x86 CPU subclasses, take 7

Eduardo Habkost
2014-01-31T19:08:12Z

On Fri, Jan 31, 2014 at 11:56:18AM -0700, Eric Blake wrote:
> On 01/31/2014 11:51 AM, Eduardo Habkost wrote:
>
> >> Allowing -device may be okay, since in the (very?) long term -device
> >> can be replaced by -object. But -object is definitive.
> >
> > OK, one additional reason to try device_add first.
> >
> > But then we have one additional problem:
> >
> > * We want to allow libvirt to probe for CPU model information when
> > running QEMU using "-machine none" (because libvirt already does
> > that, and we don't want to require libvirt to run QEMU multiple
> > times)
> > * "device_add driver=<model>-x86_64-cpu" requires an icc-bus to be present
> > * -machine none doesn't have any bus
> > * I don't see a way to create an icc-bus through QMP (is there a way?)
>
> Is the icc-bus something that makes sense for all architectures, so that
> libvirt could just blindly request a command line that uses '-machine
> none' but also instantiates the icc-bus? Even if icc-bus is
> x86-specific, libvirt DOES have some notion of what architecture a qemu
> executable will be targetting, and could modify the command line based
> on what architecture it guesses the binary will support, if only for the
> purpose of minimizing qemu invocations for its probe of supported cpus.

I don't know if it is possible to instantiate icc-bus from the
command-line if using -machine none, either. Does anybody know if it's
already possible?

--
Eduardo