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Date: Mon, 2 Mar 2015 17:43:52 +0100
From: Michael Mueller <mimu@linux.vnet.ibm.com>
To: Andreas =?UTF-8?B?RsOkcmJlcg==?= <afaerber@suse.de>
Cc: qemu-devel@nongnu.org, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>,
        Peter Crosthwaite <peter.crosthwaite@xilinx.com>,
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        Gleb Natapov <gleb@kernel.org>, Alexander Graf <agraf@suse.de>,
        Eduardo Habkost <ehabkost@redhat.com>, linux-kernel@vger.kernel.org,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        "Jason J. Herne" <jjherne@linux.vnet.ibm.com>,
        Cornelia Huck <cornelia.huck@de.ibm.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Alistair Francis <alistair.francis@xilinx.com>,
        Richard Henderson <rth@twiddle.net>
Subject: Re: [Qemu-devel] [PATCH v3 01/16] Introduce probe mode for machine
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On Mon, 02 Mar 2015 14:57:21 +0100
Andreas Färber <afaerber@suse.de> wrote:

> >  int configure_accelerator(MachineState *ms)
> >  {
> > -    const char *p;
> > +    const char *p, *name;
> >      char buf[10];
> >      int ret;
> >      bool accel_initialised = false;
> >      bool init_failed = false;
> >      AccelClass *acc = NULL;
> > +    ObjectClass *oc;
> > +    bool probe_mode = false;
> >  
> >      p = qemu_opt_get(qemu_get_machine_opts(), "accel");
> >      if (p == NULL) {
> > -        /* Use the default "accelerator", tcg */
> > -        p = "tcg";
> > +        oc = (ObjectClass *) MACHINE_GET_CLASS(current_machine);
> > +        name = object_class_get_name(oc);
> > +        probe_mode = !strcmp(name, "none" TYPE_MACHINE_SUFFIX);
> > +        if (probe_mode) {
> > +            /* Use these accelerators in probe mode, tcg should be last */
> > +            p = probe_mode_accels;
> > +        } else {
> > +            /* Use the default "accelerator", tcg */
> > +            p = "tcg";
> > +        }
> >      }  
> 
> Can't we instead use an explicit ,accel=probe or ,accel=auto?
> That would then obsolete the next patch.

How would you express the following with the accel=<pseudo-accel> approach?

-probe -machine s390-ccw,accel=kvm 

Using machine "none" as default with tcg as last accelerator initialized should not break
anything.

-M none

The return code of configure_accelerator() is ignored anyway.

Thanks,
Michael