On Mon, 11 Feb 2019 12:17:26 +0100 Thomas Huth <th...@redhat.com> wrote:
> On 2019-02-11 12:04, Cornelia Huck wrote: > > On Mon, 11 Feb 2019 11:54:45 +0100 > > Thomas Huth <th...@redhat.com> wrote: > > > >> On 2019-02-11 11:48, Cornelia Huck wrote: > >>> On Fri, 1 Feb 2019 09:23:56 +0100 > >>> Cornelia Huck <coh...@redhat.com> wrote: > >>> > >>>> On Fri, 1 Feb 2019 07:46:40 +0100 > >>>> Thomas Huth <th...@redhat.com> wrote: > >>> > >>>>> So I see two options now: > >>>>> > >>>>> 1) Finally really make the device optional, at least for new machine > >>>>> types, so we can really disable CONFIG_PCI and get a working executable. > >>>>> > >>>>> 2) Scratch the idea completely to make this optional, always link the > >>>>> s390-pci-bus.o and s390-pci-inst.o files unconditionally, and remove the > >>>>> s390-pci-stub.c file. > >>>>> > >>>>> I assume options 2 is preferred, since we likely rather want to move > >>>>> into the PCI direction in the long run, instead of ignoring it... > >>>> > >>>> I think both options are viable, but option 1 is of course more work. > >>>> The win there is that we could disable an entire subsystem. > >>>> > >>>> I guess that the basic questions are: How important is it that > >>>> subsystems can be compiled out, and do we see a use case for a pci-less > >>>> s390 machine in the future? We really don't want to spend much time on > >>>> something of dubious use... > >>> > >>> Any thoughts on this? > >>> > >>> I'm currently tending towards option 2 (and can cook up a patch for > >>> that). Unless someone is already working on option 1 :) > >> > >> Since nobody currently has a need to completely disable PCI, I think we > >> should go with option 2. > > > > Hm... I'm wondering if we also should move S390_FEAT_ZPCI from the max > > cpu model to the qemu cpu model (is there any reason not to turn it on > > by default in tcg?) > > Migration compatibility? Wouldn't that cause problems when migrating > back to older versions of QEMU? Not sure. But we can still do that in a follow-on patch, if wanted.
