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Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models |
Date: |
Tue, 23 Jun 2015 17:32:42 +0200 |
On Tue, Jun 23, 2015 at 12:08:28PM -0300, Eduardo Habkost wrote:
> On Tue, Jun 23, 2015 at 02:32:00PM +0200, Andreas Färber wrote:
> > Am 08.06.2015 um 22:18 schrieb Jiri Denemark:
> > >> To help libvirt in the transition, a x86-cpu-model-dump script is
> > >> provided,
> > >> that will generate a config file that can be loaded using -readconfig,
> > >> based on
> > >> the -cpu and -machine options provided in the command-line.
> > >
> > > Thanks Eduardo, I never was a big fan of moving (or copying) all the CPU
> > > configuration data to libvirt, but now I think it actually makes sense.
> > > We already have a partial copy of CPU model definitions in libvirt
> > > anyway, but as QEMU changes some CPU models in some machine types (and
> > > libvirt does not do that) we have no real control over the guest CPU
> > > configuration. While what we really want is full control to enforce
> > > stable guest ABI.
> >
> > That sounds like FUD to me. Any concrete data points where QEMU does not
> > have a stable ABI for x86 CPUs? That's what we have the pc*-x.y machines
> > for.
>
> What Jiri is saying that the CPUs change depending on -mmachine, not
> that the ABI is broken by a given machine.
>
> The problem here is that libvirt needs to provide CPU models whose
> runnability does not depend on the machine-type. If users have a VM that
> is running in a host and the VM machine-type changes,
How does it change, and why?
> the VM should be
> still runnable in that host. QEMU doesn't provide that, our CPU models
> may change when we introduce new machine-types, so we are giving them a
> mechanism that allows libvirt to implement the policy they need.
I don't mind wrt CPU specifically, but we absolutely do change guest ABI
in many ways when we change machine types.
> --
> Eduardo
- [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Eduardo Habkost, 2015/06/08
- [Qemu-devel] [PATCH 1/2] target-i386: Introduce "-cpu custom", Eduardo Habkost, 2015/06/08
- [Qemu-devel] [PATCH 2/2] scripts: x86-cpu-model-dump script, Eduardo Habkost, 2015/06/08
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Jiri Denemark, 2015/06/08
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Daniel P. Berrange, 2015/06/09
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Andreas Färber, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Eduardo Habkost, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Eduardo Habkost, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Andreas Färber, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Daniel P. Berrange, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Michael S. Tsirkin, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Eduardo Habkost, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Andreas Färber, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Eduardo Habkost, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Andreas Färber, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Daniel P. Berrange, 2015/06/23
- Re: [Qemu-devel] [PATCH 0/2] target-i386: "custom" CPU model + script to dump existing CPU models, Andreas Färber, 2015/06/23