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? Thomas
