Re: Building QEMU as a shared library

[Peter Maydell]

On Wed, 15 Dec 2021 at 08:18, Amir Gonnen <amir.gonnen@neuroblade.ai> wrote:
> My goal is to simulate a mixed architecture system.
>
> Today QEMU strongly assumes that the simulated system is a *single 
> architecture*.
> Changing this assumption and supporting mixed architecture in QEMU proved to 
> be
> non-trivial and may require significant development effort. Common code such 
> as
> TCG and others explicitly include architecture specific header files, for 
> example.

Yeah. This is definitely something we'd like to fix some day. It's
the approach I would prefer for getting multi-architecture machines.

> Instead, I would like to suggest a new approach we use at Neuroblade to 
> achieve this:
> Build QEMU as a shared library that can be loaded and used directly in a 
> larger simulation.
> Today we build qemu-system-nios2 shared library and load it from 
> qemu-system-x86_64 in order
> to simulate an x86_64 system that also consists of multiple nios2 cores.
> In our simulation, two independent "main" functions are running on different 
> threads, and
> simulation synchronization is reduced to synchronizing threads.

I agree with Stefan that you should go ahead and send the code as
an RFC patchset, but I feel like there is a lot of work required
to really get the codebase into a state where it is a clean
shared library...

-- PMM