[Qemu-devel] Re: [PATCH] Patches from PyQemu project

[Brian Johnson]

Anthony Liguori wrote:
> On Mon, 2007-09-03 at 18:41 +0300, Blue Swirl wrote:
> > Sorry to ruin your GSoC project, but the plugin system was discussed
> > last year, please see this thread:
> > http://thread.gmane.org/gmane.comp.emulators.qemu/14341/focus=14473
>
> I've always agreed that allowing plugins was not a good idea.  However,
> I had a different thought recently.
>
> While I don't think there's much of a reason to allow plugins for QEMU,
> it would be interesting to make some of QEMU's device emulation into
> more a of a library that could be used by other programs.
>
> With things like KVM making it relatively simple to do CPU emulation, if
> QEMU's device emulation was available as a library (even a GPL library),
> it would be pretty easy to do interesting things without forking QEMU
> which is what everyone seems to be doing these days.

Yes -- it would be valuable to have QEMU's devices available as a 
separate library(ies), with a simple, well-defined API.  Some of us use 
other CPU emulators (yes, yes, I know we should emulate all 
architectures under qemu, but that's not always easy :) and would love 
to use qemu's device emulations.

> My initial thought is to make the libraries at the individual device
> level.

It would be good to have a general mechanism for bus providers, 
interrupts, APICs, chipsets, etc. as well, so we could emulate fancier 
architectures than a simple PC (or simple Sparc/MIPS/ARM/etc. box.)  For 
instance, I'd like to emulate multiple PCIe host bridges, each with an 
APIC and multiple cards, which might contain PCI-to-PCI bridges.  And 
I'd like to emulate NUMA systems with many memory controllers and a 
complex memory map, with multiple sets of chipset registers.  I don't 
expect qemu to do this off the shelf, but I'd like to avoid hardcoding 
PC assumptions into the device libraries, so I can code the fancy 
machines myself and use the I/O as-is.

Any more thoughts on how to structure the libraries?

Brian J. Johnson