[libvirt] [Qemu-devel] CPU models and feature probing (was Re: [PATCH qom-cpu 00/16 v10] target-i386: convert CPU) features into properties

[Eduardo Habkost]

On Tue, Feb 11, 2014 at 07:58:30AM -0800, Anthony Liguori wrote:
> On Tue, Feb 11, 2014 at 7:25 AM, Eduardo Habkost <ehabkost at redhat.com> wrote:
> > On Tue, Feb 11, 2014 at 06:31:35AM -0800, Anthony Liguori wrote:
> >> On Fri, Feb 7, 2014 at 2:55 AM, Paolo Bonzini <pbonzini at redhat.com> wrote:
> >> > Il 07/02/2014 11:16, Eduardo Habkost ha scritto:
> >> >
> >> >> You are not alone. I remember we spent lots of time trying to convince
> >> >> Anthony to allow global properties and compat_props affect dynamic
> >> >> properties not just static properties, and static properties were a big
> >> >> deal due to reasons I didn't understand completely. Now I am hearing the
> >> >> opposite message, and I don't understand the reasons for the change of
> >> >> plans. I am confused.
> >> >
> >> >
> >> > Picture me confused as well, but at the same I think I understand the
> >> > reasons for the change of plans.
> >>
> >> There's no real convincing.  It's just a question of code.
> >
> > I am sure there's a lot of convincing involved, even after the code is
> > written (in this case, 15 months after the code was written).
> 
> N.B. the code you refer to doesn't "make global propeties and
> compat_props affect dynamic properties."  It converts CPU properties
> to static properties which I'm pretty sure I said many times is a
> perfectly reasonable thing to do.

Exactly. Have you read the rest of this thread?

> 
> >> There are
> >> no defaults in classes for dynamic properties to modify.  compat_props
> >> are a nice mechanism, making them work for all properties is a
> >> reasonable thing to do.
> >
> > That's exactly the opposite of what you said before[1]. But that isn't
> > supposed to be a problem, I understand there may be change of plans (we
> > should be able to change our minds).
> 
> I think you're confusing a few things.  You cannot make dynamic
> properties work with globals today.  Globals change class default
> values and there are no class defaults for dynamic properties.[*]

They work today. Not that people _should_ use -global with them, but it
works. All we really needed (before this series) was to make
compat_props and -cpu be able to affect the dynamic properties.

> 
> There's a perfectly valid discussion to have about whether we should
> even have dynamic properties.  It's certainly been a long time since
> they were introduced and they haven't made their way into all that
> many devices so it's reasonable to say that perhaps we'd be better off
> without them.  I would not object to a patch series that moved
> properties to classes entirely provided it removed existing uses of
> dynamic properties and didn't just introduce yet another mechanism.

That sounds like the opposite of what I have been reading in this
thread. Now I am even more confused.

> 
> But compat properties as a concept could be made to work with dynamic
> properties.  They would have to be evaluated after instance init.
> There's quite a few places they would end up touching I suspect.

They already work.

-- 
Eduardo