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Date: Tue, 11 Jul 2017 11:47:52 -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: Gerd Hoffmann <kraxel@redhat.com>
Cc: Thomas Huth <thuth@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, "Tian, Kevin" <kevin.tian@intel.com>, libvir-list@redhat.com, qemu-devel@nongnu.org, Chao Peng <chao.p.peng@linux.intel.com>, Marcel Apfelbaum <marcel@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Laszlo Ersek <lersek@redhat.com>, Laine Stump <laine@redhat.com>

On Tue, Jul 11, 2017 at 10:13:05AM +0200, Gerd Hoffmann wrote:
>   Hi,
>=20
> >=A0Concerning QEMU, could we maybe simply emit a warning a la
> >=20
> > =A0"you did not specify a machine type with the -M option, so you are
> > =A0 currently running the the 'pc' machine type. Please note that
> > future
> > =A0 versions of QEMU might use the 'q35' machine type instead. If you
> > =A0 require the 'pc' machine type for your setting, then please speci=
fy
> > =A0 it with the -M option."
>=20
> Warnings tend to get ignored until things are actually break, so I
> don't think this helps much.  I think simply not having a default
> machine type (as already suggested elsewhere in this thread) is the
> best way to deal with this.  That way we don't silently change
> behavior.  It also is in line with what we have on arm where we already
> require the user to explicitly pick a machine type.

If we do that, we probably should wait for libvirt to adapt and
choose its own default.  Current libvirt would pick an arbitrary
machine-type (the first one in the query-machines list) as the
default.

--=20
Eduardo