Re: [Qemu-devel] in a device or CPU instance init/realize, can I rely on something having the BQL or equivalent?

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 8 Dec 2017 14:14:22 -0200
Eduardo Habkost <ehabkost@redhat.com> wrote:

> On Fri, Dec 08, 2017 at 03:50:50PM +0100, Igor Mammedov wrote:
> > On Fri, 8 Dec 2017 13:19:27 +0000
> > Peter Maydell <peter.maydell@linaro.org> wrote:
> >   
> > > On 8 December 2017 at 13:16, Igor Mammedov <imammedo@redhat.com> wrote:  
> > > > TBH:
> > > >  I do not recall why we have x86 max/host cpu types do feature
> > > >  loading at realize time instead of at class init like the rest
> > > >  of static cpu types.    
> > > 
> > > class init is too early, IIRC -- it's before KVM has been set up at all.  
> > 
> > that shouldn't be an issue as kvm_ppc_register_host_cpu_type() demonstrates
> > (i.e. an additional class init at kvm/tcg init time),  
> 
> It is possible, but IMO it's not a good idea.  We should be able
> to enumerate all CPU types before the accelerator has been
> initialized, so query-cpu-definitions and "-cpu help" will always
> work.
> 
> 
> > 
> > so it might be some compat issue or just legacy approach why it
> > havn't been rewritten to class_init for x86 the way PPC does.
> > But Eduardo probably knows better if there is anything left that
> > prevents using class init there.  
> 
> It's the opposite: x86 "host" CPU model used to work the same way
> as PPC, but we changed it so all classes are registered at
> type_init()-time.
Is it for libvirt convenience, so that it would be able to cache
all supported cpus regardless of whether they would actually work
or not?