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From: Thomas Huth <thuth@redhat.com>
Message-ID: <c10c2ffa-7ee2-5106-07d1-528df939d6ad@redhat.com>
Date: Fri, 22 Jun 2018 21:19:56 +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>, Paolo Bonzini <pbonzini@redhat.com>
Cc: Cornelia Huck <cohuck@redhat.com>, Markus Armbruster <armbru@redhat.com>, "=?UTF-8?Q?Daniel_P._Berrang=c3=a9?=" <berrange@redhat.com>, zhang.zhanghailiang@huawei.com, Ben Warren <ben@skyportsystems.com>, qemu-trivial@nongnu.org, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

On 22.06.2018 20:11, Eduardo Habkost wrote:
> On Tue, Jun 19, 2018 at 06:16:33PM +0200, Paolo Bonzini wrote:
>> On 19/06/2018 17:15, Cornelia Huck wrote:
>>>> Why does a user have to know how to enable KVM?  Oh, because our default
>>>> is "run this guest much slower than necessary".  Great!
>>> Should we try again to default to a better accelerator, if possible? I
>>> don't quite recall why we didn't do so the last time that came up...
>>> was it tests?
>>
>> My plan was to create qemu-{kvm,hax,hvf,whpx} binaries that default to a
>> better accelerator, and leave qemu-system-* as defaulting to TCG.  This
>> matches what distributions already do.
> 
> Why is this better than using KVM by default if it's available?

The answer is (as almost always): Compatibility with migration. Nobody
dares to sacrifice that chicken :-(

 Thomas