Re: [Qemu-devel] [PATCH v3 30/30] target/s390x: update maximum TCG model to z800

[David Hildenbrand]

On 01.06.2017 10:38, David Hildenbrand wrote:
> On 01.06.2017 00:01, Aurelien Jarno wrote:
>> At the same time fix the TCG version of get_max_cpu_model to return the
>> maximum model like on KVM. Remove the ETF2 and long-displacement
> 
> I don't understand the part
> "fix the TCG version of get_max_cpu_model to return the maximum model
> like on KVM".
> 
> Can you elaborate?
> 
>> facilities from the additional features as it is included in the z800.
>>
>> Signed-off-by: Aurelien Jarno <address@hidden>
>> ---
>>  target/s390x/cpu_models.c | 13 ++++++-------
>>  1 file changed, 6 insertions(+), 7 deletions(-)
>>
>> diff --git a/target/s390x/cpu_models.c b/target/s390x/cpu_models.c
>> index fc3cb25cc3..c13bbd852c 100644
>> --- a/target/s390x/cpu_models.c
>> +++ b/target/s390x/cpu_models.c
>> @@ -668,8 +668,6 @@ static void add_qemu_cpu_model_features(S390FeatBitmap 
>> fbm)
>>      static const int feats[] = {
>>          S390_FEAT_STFLE,
>>          S390_FEAT_EXTENDED_IMMEDIATE,
>> -        S390_FEAT_EXTENDED_TRANSLATION_2,
>> -        S390_FEAT_LONG_DISPLACEMENT,
>>          S390_FEAT_LONG_DISPLACEMENT_FAST,
>>          S390_FEAT_ETF2_ENH,
>>          S390_FEAT_STORE_CLOCK_FAST,
>> @@ -696,9 +694,9 @@ static S390CPUModel *get_max_cpu_model(Error **errp)
>>      if (kvm_enabled()) {
>>          kvm_s390_get_host_cpu_model(&max_model, errp);
>>      } else {
>> -        /* TCG emulates a z900 (with some optional additional features) */
>> -        max_model.def = &s390_cpu_defs[0];
>> -        bitmap_copy(max_model.features, max_model.def->default_feat,
>> +        /* TCG emulates a z800 (with some optional additional features) */
>> +        max_model.def = s390_find_cpu_def(0x2066, 7, 3, NULL);
>> +        bitmap_copy(max_model.features, max_model.def->full_feat,
>>                      S390_FEAT_MAX);

This is most likely wrong: you're indicating features here that are not
available on tcg. esp. S390_FEAT_SIE_F2 and friends.

I think should only copy the base features and add whatever else is
available via add_qemu_cpu_model_features() as already done.

>>          add_qemu_cpu_model_features(max_model.features);
>>      }
>> @@ -956,8 +954,9 @@ static void s390_qemu_cpu_model_initfn(Object *obj)
>>      S390CPU *cpu = S390_CPU(obj);
>>  
>>      cpu->model = g_malloc0(sizeof(*cpu->model));
>> -    /* TCG emulates a z900 (with some optional additional features) */
>> -    memcpy(&s390_qemu_cpu_defs, &s390_cpu_defs[0], 
>> sizeof(s390_qemu_cpu_defs));
>> +    /* TCG emulates a z800 (with some optional additional features) */
>> +    memcpy(&s390_qemu_cpu_defs, s390_find_cpu_def(0x2066, 7, 3, NULL),
>> +           sizeof(s390_qemu_cpu_defs));
> 
> No changing the qemu model without compatibility handling.
> 
Please have a look at the following mail for a possible solution:

https://lists.gnu.org/archive/html/qemu-devel/2017-05/msg06030.html

This could be moved to a separate patch. So this patch really should
just care about the maximum model, not the qemu model.

-- 

Thanks,

David