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Date: Mon, 1 Oct 2012 17:47:30 +0100
From: "Daniel P. Berrange" <berrange@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] kvm: Set default accelerator to "kvm" if
 the host supports it
Reply-To: "Daniel P. Berrange" <berrange@redhat.com>
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To: Andreas =?utf-8?Q?F=C3=A4rber?= <afaerber@suse.de>
Cc: kvm <kvm@vger.kernel.org>, Scott Moser <smoser@ubuntu.com>, Jan Kiszka <jan.kiszka@siemens.com>, Marcelo Tosatti <mtosatti@redhat.com>, Michael Tokarev <mjt@tls.msk.ru>, qemu-devel <qemu-devel@nongnu.org>, Bruce Rogers <brogers@suse.com>, Avi Kivity <avi@redhat.com>, Anthony Liguori <anthony@codemonkey.ws>, Cole Robinson <crobinso@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>

On Mon, Oct 01, 2012 at 06:43:00PM +0200, Andreas F=C3=A4rber wrote:
> Hello Jan,
>=20
> Am 01.10.2012 16:34, schrieb Jan Kiszka:
> > If we built a target for a host that supports KVM in principle, set t=
he
> > default accelerator to KVM as well. This also means the start of QEMU
> > will fail to start if KVM support turns out to be unavailable at
> > runtime.
>=20
> From a distro point of view this of course means that we will build
> against KVM and that the new KVM default will start to fail for users o=
n
> very old hardware. Can't we do a runtime check to select the default?

NB, this is *not* only about old hardware. There are plenty of users who
use QEMU inside VMs. One very common usage I know of is image building
tools which are run inside Amazon VMs, using libguestfs & QEMU.

IMHO, default to KVM, fallback to TCG is the most friendly default
behaviour.

Daniel
--=20
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