Re: [Qemu-devel] [PATCH] kvm: Set default accelerator to "kvm" if the host supports it

[Anthony Liguori <anthony@codemonkey.ws>]

"Daniel P. Berrange" <berrange@redhat.com> writes:

> On Mon, Oct 01, 2012 at 06:43:00PM +0200, Andreas Färber wrote:
>> Hello Jan,
>> 
>> Am 01.10.2012 16:34, schrieb Jan Kiszka:
>> > If we built a target for a host that supports KVM in principle, set the
>> > 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.
>> 
>> 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 on
>> 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.

But libguest can set it's accelerator option to whatever it wants.

If your running QEMU under a VM, it's pretty reasonable to have to use a
special option IMHO.

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

Except if a user expects good network performance and can't
understand why they're getting 100kb/s.

Regards,

Anthony Liguori

>
> Daniel
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