Re: [PATCH 0/4] modules: add support for target-specific modules.

[Gerd Hoffmann]

On Mon, Jun 14, 2021 at 10:19:27PM +0000, José Ricardo Ziviani wrote:
> Hello Gerd,
> 
> On sexta-feira, 11 de junho de 2021 10:03:21 -03 Gerd Hoffmann wrote:
> >   Hi,
> > 
> > > Are there any pending patches to handle the remaining tcg dependencies
> > > in qemu?  When trying to build tcg modular (more than only
> > > tcg-accel-ops*) I get lots of unresolved symbols to tcg bits which are
> > > referenced directly (in cpu.c, gdbstub.c, monitor, ...).
> > > 
> > > The CONFIG_TCG=n case is handled either with stubs or with #ifdef
> > > CONFIG_TCG, which doesn't fly for modular tcg ...
> > 
> > So, enough for today, to be continued next week.
> > Work branch pushed to
> >     https://git.kraxel.org/cgit/qemu/log/?h=sirius/modinfo-playground
> > 
> > Topmost patch doesn't compile but shows the build changes.
> 
> I cloned your 'sirius/modinfo-playground-good' and started playing with the 
> command line options to build these modules. I would like to suggest to 
> change 
> the current "--enable-X" with "--X=[enabled,disabled,module]", that seems to 
> make more sense for these modules. For instance:

Hmm, what would be the use case?  Right now qemu has the all-or-nothing
approach for modules, i.e. if modules are enabled everything we can
build as module will be built as module, and I havn't seen any drawbacks
so far.  So, why would one compile parts of qemu as module and other
parts not?

Also: when changing this I think it would be good to maintain backward
compatibility and use something like this:

  --enable-tcg=builtin
  --enable-tcg=module
  --enable-tcg (use default, probably "module" when modules
                are enabled and "builtin" otherwise)
  --disable-tcg

take care,
  Gerd