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

[David Hildenbrand <david@redhat.com>]

On 18.09.2017 14:11, Cornelia Huck wrote:
> On Mon, 18 Sep 2017 14:03:20 +0200
> David Hildenbrand <david@redhat.com> wrote:
> 
>> 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.
> 
> I prefer it the way it is now. There's nothing kvm specific about that
> bit, and cpu->model always being set is not really obvious.
> 

I's already kvm specific as this can never happen with TCG :)

But whatever you prefer. This is good enough to fix the problem.


-- 

Thanks,

David