Re: [PATCH v3 1/1] hw/s390x: modularize virtio-gpu-ccw

[Halil Pasic <pasic@linux.ibm.com>]

On Tue, 9 Mar 2021 13:21:14 +0000
Daniel P. Berrangé <berrange@redhat.com> wrote:

> > Well, yes, in a non-modular world this will work perfectly fine.  We
> > only compile objects actually supported into the system emulator.
> > 
> > With modular builds we have the situation that we have shared modules
> > which may or may not work in specific system emulators, for example
> > hw-display-virtio-gpu-pci.so or the ccw module added by this patch,
> > because the given system emulator doesn't provide the needed support.
> > We have some which don't support pci (avr for example).  Likewise ccw
> > is supported by s390x only.  
> 
> We could solve this by having a different location for loading modules
> for each target.
> 
>   *  /usr/$LIB/qemu/
> 
>     All the real .so's go in here as today
> 
>   *  /usr/$LIB/qemu/$TARGET
> 
>     Populated with symlinks to the .so's in the parent dir,
>     but /only/ those which are valid for this $TARGET
> 
> Then change QEMU  to load from the second dir.

I like the idea. I also prefer not trying to load a module X
that we know is not supported with, and ain't going to work with
target Y, over doing the load and making something fail afterwards.

I've not only started working on this, but I already have something
kind of works. But I'm not quite satisfied with it. I will spend some
more cycles before sending it out, but I doubt I will be able to get it
in a 'looks nice' shape. Thanks you!

Regards,
Halil