Re: [Qemu-devel] [PATCH v5 1/6] machine: Convert the valid cpu types to use cpu_model

From: Eduardo Habkost <ehabkost@redhat.com>
To: Igor Mammedov <imammedo@redhat.com>
Cc: marcel@redhat.com, peter.maydell@linaro.org,
	"Philippe Mathieu-Daudé" <philmd@redhat.com>,
	qemu-devel@nongnu.org, alistair23@gmail.com
Subject: Re: [Qemu-devel] [PATCH v5 1/6] machine: Convert the valid cpu types to use cpu_model
Date: Tue, 18 Jun 2019 10:55:16 -0300	[thread overview]
Message-ID: <20190618135516.GH19178@habkost.net> (raw)
In-Reply-To: <20190618133410.18b93bcd@redhat.com>

On Tue, Jun 18, 2019 at 01:34:10PM +0200, Igor Mammedov wrote:
> On Mon, 17 Jun 2019 13:27:00 -0300
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
> > On Mon, Jun 17, 2019 at 05:33:43PM +0200, Igor Mammedov wrote:
> > > On Mon, 17 Jun 2019 17:15:21 +0200
> > > Philippe Mathieu-Daudé <philmd@redhat.com> wrote:  
> > [...]
> > > > Yes. Eduardo and you should write some lines to explain this, and then
> > > > we will follow :)  
> > > Unfortunately I don't recall details anymore. One could check out all
> > > implementations of class_by_name callbacks to find out current state.  
> > 
> > See this message for a summary of existing class_by_name quirks:
> > 
> >   https://www.mail-archive.com/qemu-devel@nongnu.org/msg615503.html
> >   Date: Wed, 08 May 2019 10:34:44 +0200
> >   Message-ID: <877eb173a3.fsf@dusky.pond.sub.org>
> >   Subject: Re: [Qemu-devel] [PATCH 0/7] Delete 16 *_cpu_class_by_name() functions
> > 
> > I'm unsure about Igor's suggestion to get rid of CPU model names
> > and use only QOM type names in external interfaces.  In either
> > case, we can still simplify the rules rules and reduce the amount
> > of arch-specific code.
> as far as we have cpu_class_by_name, we have to watch over that
> new patches/targets won't add some custom handling/fallbac/whatnot.

We can get rid of CPUClass::cpu_class_by_name() without changing
the external interfaces provided by QEMU.

I don't have a strong opinion about using only QOM types at -cpu,
yet.  But first we need to get rid of the arch-specific CPU model
name exceptions enumerated at the URL above (which would be very
welcome).

> 
> On contrary -device works just with type names for all devices,
> applying the same to -cpu which is basically translator
>    model->type[,-global type.foo,...]
> would be consistent with -device and less confusing for everyone
> (not counting significant code reduction).
> It would certainly simplify contributing new targets as contributor
> won't have to care about cpu model naming and do something about it.
> 
> This option wasn't considered before because we didn't have deprecation
> back then, but now it opens possibility to simplify qemu and consolidate
> naming. (we probably would be able to fold '-cpu help' into '-device help'
> as well).
> 

-- 
Eduardo