From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39608) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fXqUV-000458-Ds for qemu-devel@nongnu.org; Tue, 26 Jun 2018 12:06:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fXqUS-00080f-AT for qemu-devel@nongnu.org; Tue, 26 Jun 2018 12:06:50 -0400 Date: Tue, 26 Jun 2018 13:06:23 -0300 From: Eduardo Habkost Message-ID: <20180626160623.GT7451@localhost.localdomain> References: <20180622193522.GI7451@localhost.localdomain> <743d495e-51cd-8c8e-293e-026b8dece74a@redhat.com> <87lgb3xsv8.fsf@dusky.pond.sub.org> <4292432f-5f26-6925-4c14-ad1370e36e5b@redhat.com> <20180625173056.GM7451@localhost.localdomain> <97504b42-9ebe-45c5-6ff3-b43102c8374a@redhat.com> <20180625195126.GN7451@localhost.localdomain> <20180626122908.GQ7451@localhost.localdomain> <577768c0-5205-2fb4-209f-845332fe158d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <577768c0-5205-2fb4-209f-845332fe158d@redhat.com> Subject: Re: [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Markus Armbruster , Thomas Huth , zhang.zhanghailiang@huawei.com, Ben Warren , qemu-trivial@nongnu.org, Cornelia Huck , qemu-devel@nongnu.org, Stefan Hajnoczi On Tue, Jun 26, 2018 at 03:05:33PM +0200, Paolo Bonzini wrote: > 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. Not changing the default is different from promising we will keep ABI compatibility if the accelerator is omitted. I just want to get rid of the latter. > > (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. We can keep trying to not break it when "-accel tcg" is explicitly provided. -- Eduardo