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

[Eduardo Habkost <ehabkost@redhat.com>]

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.

-- 
Eduardo