Re: proposal: deprecate -readconfig/-writeconfig

[Paolo Bonzini]

On 14/05/20 17:34, Daniel P. Berrangé wrote:
> Yeah, the key thing is that you really want to be able to provide the
> whole initial config in one go as an atomic action. I don't want to
> issue 100 individual QMP commands to load each initial device.

Why?  I think if we do something like the qemu-vm-$TARGET that you
propose below, there's absolutely no difference between the two.

Then you'd have a

qemu-run /some/file.yaml

(notice the lack of $TARGET) that takes care of starting the VM.

> I tend to think we'd be better served by focusing on introducing a new set
> of binaries,  qemu-vm-$TARGET, which exclusively use a new config syntax,
> free of any legacy baggage present in qemu-system-$TARGET.
> 
> Work on qemu-vm-$TARGET will involve refactoring, and that will certainly
> risk causing bugs in qemu-system-$TARGET. The premise though is that this
> risk is lower, than if we tried to retrofit a new config syuntax directly
> into qemu-system-$TARGET.
> 
> In particular I think it is basically impossible to do any meaningful
> changes in the main() method of softmmu/vl.c, due to the fragile ordering
> for creation of various different devices/backends, and its interaction
> with the argv parsing. By using a new qemu-vm-$TARGET we can have a new
> softmmu/vm.c, instead of vl.c. We'll still likely need to modify parts of
> vl.c to use new/changed API calls, but that's less distruptive, as we
> can leave the crazy logic for ordering of device creation untouched.

Agreed.

Paolo