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Date: Wed, 25 Jul 2018 17:14:38 -0300
From: Eduardo Habkost <ehabkost@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v1] s390x/cpu_models: Add "-cpu max" support
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To: David Hildenbrand <david@redhat.com>
Cc: qemu-s390x@nongnu.org, qemu-devel@nongnu.org, Richard Henderson <rth@twiddle.net>, Alexander Graf <agraf@suse.de>, Cornelia Huck <cohuck@redhat.com>, Christian Borntraeger <borntraeger@de.ibm.com>, Thomas Huth <thuth@redhat.com>, Chris Venteicher <cventeic@redhat.com>, Collin Walling <walling@linux.ibm.com>, Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= <berrange@redhat.com>

On Wed, Jul 25, 2018 at 07:50:21PM +0200, David Hildenbrand wrote:
> On 25.07.2018 19:09, Eduardo Habkost wrote:
[...]
> >> +    if (local_err) {
> >> +        g_assert(kvm_enabled());
> >> +        error_report_err(local_err);
> >> +        /* fallback to unsupported CPU models */
> >> +        return;
> > 
> > What about moving this outside instance_init?
> 
> To which place for example? We at least have to copy the CPU model
> for each and every CPU instance (so we can modify it without side
> effects using properties).

To any code that will look at cpu->model.

You are wrapping an interface that needs to report errors
(kvm_s390_get_host_cpu_model()) behind an interface that is not
able to report errors (object_new()).  There's nothing that
requires you to do that, does it?  You are free to provide an API
that is actually able to report errors, instead of relying on
object_new() only.

But I understand that the QOM/qdev API doesn't make that job
easy.  On x86 we have X86CPU::max_features and
X86CPU::user_features because of that.

-- 
Eduardo