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From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <577768c0-5205-2fb4-209f-845332fe158d@redhat.com>
Date: Tue, 26 Jun 2018 15:05:33 +0200
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Subject: Re: [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show
 -enable-kvm and -enable-hax in the docs anymore
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To: Eduardo Habkost <ehabkost@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>, Thomas Huth <thuth@redhat.com>, zhang.zhanghailiang@huawei.com, Ben Warren <ben@skyportsystems.com>, qemu-trivial@nongnu.org, Cornelia Huck <cohuck@redhat.com>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

On 26/06/2018 14:29, Eduardo Habkost wrote:
> On Tue, Jun 26, 2018 at 07:57:18AM +0200, Paolo Bonzini wrote:
>> On 25/06/2018 21:51, Eduardo Habkost wrote:
>>> In either case, I'm not arguing (yet) for changing the default
>>> upstream.  I'm just arguing for upstream QEMU to not make any
>>> promises about the default.
>>
>> It would be a guest ABI breakage for TCG guests, so it would only apply
>> to new machine types.  I don't think it's worth the complication.
> 
> That's exactly the point: I want to stop promising a stable guest
> ABI when the accelerator is omitted, because I see no benefit in
> wasting energy on this.

On the other hand I see no benefit in changing a default that people are
obviously not using (since most people use KVM, not TCG).  Distros will
keep shipping, and people will keep using qemu-kvm even if we change the
default.

> (I don't think we ever kept the guest ABI correctly with TCG, by
> the way.)

It would not be any different from KVM.  Less tested and likely to be
more buggy, yes, but not particularly harder.

Paolo