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Date: Mon, 10 Jul 2017 10:59:43 -0300
From: Eduardo Habkost <ehabkost@redhat.com>
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Subject: Re: [Qemu-devel] change x86 default machine type to Q35?
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To: Marcel Apfelbaum <marcel@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Thomas Huth <thuth@redhat.com>, Chao Peng <chao.p.peng@linux.intel.com>, qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, "Tian, Kevin" <kevin.tian@intel.com>, Laszlo Ersek <lersek@redhat.com>

On Mon, Jul 10, 2017 at 10:42:26AM +0300, Marcel Apfelbaum wrote:
> On 07/07/2017 21:03, Eduardo Habkost wrote:
> > On Fri, Jul 07, 2017 at 06:17:57PM +0300, Michael S. Tsirkin wrote:
> > > On Fri, Jul 07, 2017 at 10:39:49AM -0300, Eduardo Habkost wrote:
> > > > On Wed, Jul 05, 2017 at 12:32:10PM +0300, Marcel Apfelbaum wrote:
[...]
> > > > > 
> > > > > The upper layers should manage the defaults by themselves so
> > > > > are not supposed to be affected.
> > > > 
> > > > But they would be.  libvirt uses the default machine-type from
> > > > QEMU.
> > > 
> > > How about extending the command for supported machines with a
> > > recommended machine type, and teaching libvirt to use that?
> > 
> > I don't think QEMU has enough information to decide if it should
> > recommend "q35" or "pc".
> 
> We don't really need a complicated rule set, we would just recommend q35
> by default. Libvirt will try to create the default machine and if fails
> for some reason (what would it be?) it can switch to PC.
> 
> The advanced logic would be "old systems should use PC", where old
> means Windows XP and before and so on. But this logic should appear
> in management layers above.

In this case, is there any difference between "changing the
default to q35" and "recommending q35", for libvirt users?

-- 
Eduardo