Re: [Qemu-devel] [PATCH v3 4/9] s390x/pci: do not advertise pci on non-pci builds

[Thomas Huth <thuth@redhat.com>]

On 26.07.2017 11:28, David Hildenbrand wrote:
> On 25.07.2017 17:33, Cornelia Huck wrote:
>> Only set the zpci feature bit on builds that actually support pci.
>>
>> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
>> ---
>>  hw/s390x/s390-pci-bus.c  | 5 +++++
>>  hw/s390x/s390-pci-bus.h  | 1 +
>>  hw/s390x/s390-pci-stub.c | 4 ++++
>>  target/s390x/kvm.c       | 2 +-
>>  4 files changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
>> index c57f6ebae0..7b30d4c7bd 100644
>> --- a/hw/s390x/s390-pci-bus.c
>> +++ b/hw/s390x/s390-pci-bus.c
>> @@ -34,6 +34,11 @@
>>          }                                                         \
>>      } while (0)
>>  
>> +void pci_enable_zpci_feature(S390CPUModel *model)
>> +{
>> +    set_bit(S390_FEAT_ZPCI, model->features);
>> +}
>> +
>>  S390pciState *s390_get_phb(void)
>>  {
>>      static S390pciState *phb;
>> diff --git a/hw/s390x/s390-pci-bus.h b/hw/s390x/s390-pci-bus.h
>> index 5df6292509..d8796536b0 100644
>> --- a/hw/s390x/s390-pci-bus.h
>> +++ b/hw/s390x/s390-pci-bus.h
>> @@ -333,4 +333,5 @@ S390PCIBusDevice *s390_pci_find_dev_by_fid(S390pciState *s, uint32_t fid);
>>  S390PCIBusDevice *s390_pci_find_next_avail_dev(S390pciState *s,
>>                                                 S390PCIBusDevice *pbdev);
>>  
>> +void pci_enable_zpci_feature(S390CPUModel *model);
>>  #endif
>> diff --git a/hw/s390x/s390-pci-stub.c b/hw/s390x/s390-pci-stub.c
>> index cc7278a865..8ceaf482e7 100644
>> --- a/hw/s390x/s390-pci-stub.c
>> +++ b/hw/s390x/s390-pci-stub.c
>> @@ -72,3 +72,7 @@ S390PCIBusDevice *s390_pci_find_dev_by_idx(S390pciState *s, uint32_t idx)
>>  {
>>      return NULL;
>>  }
>> +
>> +void pci_enable_zpci_feature(S390CPUModel *model)
>> +{
>> +}
>> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
>> index c4c5791d27..866ac3d414 100644
>> --- a/target/s390x/kvm.c
>> +++ b/target/s390x/kvm.c
>> @@ -2662,7 +2662,7 @@ void kvm_s390_get_host_cpu_model(S390CPUModel *model, Error **errp)
>>      }
>>  
>>      /* We emulate a zPCI bus and AEN, therefore we don't need HW support */
>> -    set_bit(S390_FEAT_ZPCI, model->features);
>> +    pci_enable_zpci_feature(model);
> 
> While I see how this solves the problem, I don't really like it. If
> there is a function "save_the_world()" I expect it to save the world in
> all scenarios ;)
> 
> What about the same approach but rather
> 
> if(pci_configured())
> 	set_bit(S390_FEAT_ZPCI, model->features);

Or maybe something like this (without introducing new functions):

    if (object_class_by_name(TYPE_S390_PCI_HOST_BRIDGE)) {
        set_bit(S390_FEAT_ZPCI, model->features);
    }

?

I haven't tested this, though, but I think it should work since the
S390_PCI classes are only compiled in if CONFIG_PCI=y.

 Thomas