Re: [Qemu-devel] [Xen-devel] [PATCH] Remove hardcoded xen-platform device initialization

[Paolo Bonzini]

Il 14/06/2013 10:11, Paul Durrant ha scritto:
> I think we're still going to need -M xenpv, I think; it's quite
> distinct from pc.

Of course!  Even more: "-M xenpv" should be reused on ARM.

> I guess we could use -M pc for HVM and gate the
> accel code as you suggest but, if that's the way we're going, it
> would seem more logical just to ditch the accel code for xenpv
> completely (assuming we can do all we need from the machine init) and
> then use -M pc -accel=xen for HVM guests going forward.

There is common code between pv and fv, and that one definitely belongs
in xen_init.  Most fv-only code probably should be in pc_init.  The rest
should move to xen_init though, because it would apply just as well for
example to Q35.  It's a bit ugly to have fv-only code there, but it's
better than having a Xen-specific machine type.  Xen/KVM/TCG should be
as similar as possible at the QEMU level, any difference should be
handled in the toolstack.

> But that does
> rather screw up my autodiscovery plans because I would not know, for
> a given qemu binary, which machine type to use.

There's no need for that.  4.4 can just use "-M pc" unconditionally,
<=4.3 will just use "-M xenfv" unconditionally.

> If I create a new
> xenfv-2.0 machine type though I *can* do auto discovery... in which
> case do we need the -accel=xen option at all?

Yes.  Please try not do things differently from other accelerators.

Paolo