Re: [Qemu-devel] [PATCH RFC v2 0/9] s390x: zPCI detangling

[Cornelia Huck <cohuck@redhat.com>]

On Tue, 18 Jul 2017 16:24:46 +0200
Cornelia Huck <cohuck@redhat.com> wrote:

> Next try of the zPCI detangling, taking cpu models into account.
> 
> The goal of this is twofold:
> - Being able to disable PCI support in a build completely, as for v1.
> - Properly fencing off PCI if the relevant facility bit is not provided.
> 
> The second one leads to an interesting usability problem: -device help
> still shows the various pci devices, but you cannot add them if the
> cpu model does not include zpci, due to the phb not being instantiated.
> The user is presented with
> 
> qemu-system-s390x: -device virtio-rng-pci: No 'PCI' bus found for device 'virtio-rng-pci'
> 
> ...which is not very helpful, as it does not point to the root cause (no
> zpci in the cpu model, and therefore no pci at all). Not sure how one can
> communicate this root cause, ideas welcome.

An idea on how to improve this would still be welcome :)

> 
> A cross-check with the zpci documentation would also be good, as it is
> not public.
> 
> Changes v1->v2:
> - add hw/s390x/s390-pci-stub.c to get rid of the ifdeffery
> - use the cpumodel to decide whether the guest can use pci instructions or
>   not; also use this in the sclp and ioinst code
> 
> Branch in git:
> 
> git://github.com/cohuck/qemu no-zpci-cpumodel

I've updated this with the various feedback I got, but probably will
not have time to do more until next week.

> 
> Cornelia Huck (9):
>   kvm: remove hard dependency on pci
>   s390x/pci: add stubs
>   s390x: chsc nt2 events are pci-only
>   s390x/pci: do not advertise pci on non-pci builds
>   s390x/ccw: create s390 phb conditionally
>   s390x/sclp: properly guard pci-specific functions
>   s390x/pci: fence off instructions for non-pci
>   s390x/kvm: msi route fixup for non-pci
>   s390x: refine pci dependencies
> 
>  default-configs/s390x-softmmu.mak |  2 +-
>  hw/pci/pci-stub.c                 | 12 ++++++
>  hw/s390x/Makefile.objs            |  3 +-
>  hw/s390x/s390-pci-bus.c           |  4 +-
>  hw/s390x/s390-pci-bus.h           |  4 +-
>  hw/s390x/s390-pci-stub.c          | 74 ++++++++++++++++++++++++++++++++
>  hw/s390x/s390-virtio-ccw.c        | 12 +++---
>  hw/s390x/sclp.c                   | 19 +++++++--
>  target/s390x/ioinst.c             | 16 +++++++
>  target/s390x/kvm.c                | 89 +++++++++++++++++++++++++++------------
>  10 files changed, 193 insertions(+), 42 deletions(-)
>  create mode 100644 hw/s390x/s390-pci-stub.c
>