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Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not sho
From: |
Daniel P . Berrangé |
Subject: |
Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore |
Date: |
Tue, 26 Jun 2018 17:10:38 +0100 |
User-agent: |
Mutt/1.10.0 (2018-05-17) |
On Tue, Jun 26, 2018 at 01:06:23PM -0300, Eduardo Habkost wrote:
> 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 guess the key question is what is the risk of causing problems if we
switch from tcg to kvm:tcg when accelerator is omitted ?
Based on what I've seen the likely troublespot would be people who are
using QEMU inside a guest with nested-virt enabled. Some nested-virt
impls are buggy and will cause L2 guest hangs, or worse L1 host crashes.
Then again we're not causing that brokenness - just revealing what
already exists.
Regards,
Daniel
--
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- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, (continued)
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Paolo Bonzini, 2018/06/22
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Markus Armbruster, 2018/06/25
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Paolo Bonzini, 2018/06/25
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Eduardo Habkost, 2018/06/25
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Paolo Bonzini, 2018/06/25
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Eduardo Habkost, 2018/06/25
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Paolo Bonzini, 2018/06/26
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Eduardo Habkost, 2018/06/26
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Paolo Bonzini, 2018/06/26
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Eduardo Habkost, 2018/06/26
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore,
Daniel P . Berrangé <=
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Paolo Bonzini, 2018/06/27
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Eduardo Habkost, 2018/06/27
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Thomas Huth, 2018/06/26
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Cornelia Huck, 2018/06/26
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Eduardo Habkost, 2018/06/26
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Markus Armbruster, 2018/06/26
- Re: [Qemu-trivial] [Qemu-devel] [RFC PATCH 4/4] qemu-options: Do not show -enable-kvm and -enable-hax in the docs anymore, Paolo Bonzini, 2018/06/27
Re: [Qemu-trivial] [PATCH 0/4] Clean up accelerator options, Stefan Hajnoczi, 2018/06/13