Re: [Qemu-devel] [PATCH v3] s390x/ccw: create s390 phb for compat reasons as well

[David Hildenbrand <david@redhat.com>]

On 18.09.2017 10:55, Cornelia Huck wrote:
> d32bd032d8 ("s390x/ccw: create s390 phb conditionally") made
> registering the s390 pci host bridge conditional on presense
> of the zpci facility bit. Sadly, that breaks migration from
> machines that did not use the cpu model (2.7 and previous).
> 
> Create the s390 phb for pre-cpu model machines as well: We can
> tweak s390_has_feat() to always indicate the zpci facility bit
> when no cpu model is available (on 2.7 and previous compat machines).
> 
> Fixes: d32bd032d8 ("s390x/ccw: create s390 phb conditionally")
> Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
> 
> v2->v3:
> - no longer RFC (I tested a bit more)
> - removed unrelated hunk
> - more verbose patch description
> 
> I'll wait a bit for more acks/reviews and will probably send a pull
> request for s390x tomorrow or so before the amount of queued patches
> gets out of hand...
> 
> ---
>  target/s390x/cpu_models.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/target/s390x/cpu_models.c b/target/s390x/cpu_models.c
> index c295e641e6..5169379db5 100644
> --- a/target/s390x/cpu_models.c
> +++ b/target/s390x/cpu_models.c
> @@ -196,6 +196,9 @@ bool s390_has_feat(S390Feat feat)
>              }
>          }
>  #endif
> +        if (feat == S390_FEAT_ZPCI) {
> +            return true;
> +        }
>          return 0;
>      }
>      return test_bit(feat, cpu->model->features);
> 

1. cpu->model will always be set for QEMU, so you can move that into the
ifdef, next do the other checks. You can even send a cleanup to remove
the if (kvm_enabled()) check.

2. "return pci_available" ?

-- 

Thanks,

David