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

[Aurelien Jarno]

On 2017-06-01 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?

Currently get_max_cpu_model returns the features of the base model, so
for example the one of a z900 even on a z800. This makes impossible to
enable the features that are provided by a z800 like etf2 or ldisp.

For what I understand from the KVM code (but I haven't tested), the
function return all the features that are supported by the current CPU,
not all the features that are supported by the base model of the current
CPU.


> > 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);
> >          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.

This patch series is based on the patch from Thomas Huth. It means the
QEMU model is still based on a z900, but that it is possible to enable
some more features like etf2.

Aurelien

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
address@hidden                 http://www.aurel32.net