Re: [Qemu-devel] [PATCH] Support for loading devices as dynamic libraries

[Dominik Żeromski]

2012/8/25 Stefan Hajnoczi <address@hidden>
>
> On Sat, Aug 25, 2012 at 12:10 PM, Dominik Żeromski <address@hidden>
> wrote:
> > Adding support for loading DSO with -device option.
> >
> > Example Makefile for out of tree modules:
>
> QEMU does not have a stable ABI for devices.  There is a lot of device
> model refactoring happening right now for multithreaded MMIO/PIO
> dispatch and taking advantage of QEMU Object Model.  A stable ABI
> hinders those kinds of improvements.
>
> Send device model patches upstream.  That way you avoid the
> maintenance overhead of out-of-tree modules and the QEMU community
> doesn't need to provide a stable ABI.
>

I think that QEMU is a great tool, not only for server virtualization
but also for embedded software and hardware development.

I agree that it would be hard to maintain stable ABI, but this is a
usability feature for device developers, not QEMU developers. I can
imagine use cases where one team works on a hardware emulator and
wants to share it with driver team. Driver team doesn't care about how
QEMU works, how to configure, compile it and then use it. They
probably use qemu-kvm and libvirt provided by some Linux distribution.
The distro qemu-kvm does not change much so it wouldn't be a problem
for emulator team to fix eventual ABI problems. Distributing device as
dynamic library is simply easier for both teams.

-Dominik