Re: [Qemu-devel] [PATCH 17/23] ppc: spapr: use generic cpu_model parsing

[David Gibson]

On Thu, Oct 05, 2017 at 06:24:44PM +0200, Igor Mammedov wrote:
> use generic cpu_model parsing introduced by
>  (6063d4c0f vl.c: convert cpu_model to cpu type and set of global properties 
> before machine_init())
> 
> it allows to:
>   * replace sPAPRMachineClass::tcg_default_cpu with
>     MachineClass::default_cpu_type
>   * drop cpu_parse_cpu_model() from hw/ppc/spapr.c and reuse
>     one in vl.c
>   * simplify spapr_get_cpu_core_type() by removing
>     not needed anymore recurrsion since alias look up
>     happens earlier at vl.c and spapr_get_cpu_core_type()
>     works only with resulted from that cpu type.
>   * spapr no more needs to parse/depend on being phased out
>     MachineState::cpu_model, all tha parsing done by generic
>     code and target specific callback.
> 
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
> PS:
>   patch is a little bit big but it's hard to split it due
>   to dependencies, so pls bear with it.

[snip]
> -static int kvm_ppc_register_host_cpu_type(void)
> +static int kvm_ppc_register_host_cpu_type(MachineState *ms)
>  {
>      TypeInfo type_info = {
>          .name = TYPE_HOST_POWERPC_CPU,
>          .class_init = kvmppc_host_cpu_class_init,
>      };
> +    MachineClass *mc = MACHINE_GET_CLASS(ms);
>      PowerPCCPUClass *pvr_pcc;
>      ObjectClass *oc;
>      DeviceClass *dc;
> @@ -2504,6 +2505,8 @@ static int kvm_ppc_register_host_cpu_type(void)
>      }
>      type_info.parent = object_class_get_name(OBJECT_CLASS(pvr_pcc));
>      type_register(&type_info);
> +    /* override TCG default cpu type with 'host' cpu model */
> +    mc->default_cpu_type = TYPE_HOST_POWERPC_CPU;

Ugh.  I dislike this, it changes the default cpu type to 'host' for
*all* machine types, whereas previously it was just true for pseries.
That wasn't by accident.

In general, I think we want there to be a single default CPU type for
a machine, regardless of TCG vs. KVM.  This is particularly true for
many of the ppc machine types - they will only work with a CPU in the
right "family" (e500 / 440 / POWERx, wahtever); in many of these cases
KVM PR is usable, but using -cpu host could easily break the machine
type.

'pseries' is different, it (and only it) can be used with KVM HV - and
usually is.  And KVM HV *only* works with -cpu host, due to hardware
limitations.

>      oc = object_class_by_name(type_info.name);
>      g_assert(oc);
> diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
> index 5ee91e8..a968e86 100644
> --- a/target/ppc/translate_init.c
> +++ b/target/ppc/translate_init.c
> @@ -10277,6 +10277,19 @@ PowerPCCPUClass *ppc_cpu_class_by_pvr_mask(uint32_t 
> pvr)
>      return pcc;
>  }
>  
> +static const char *ppc_cpu_lookup_alias(const char *alias)
> +{
> +    int ai;
> +
> +    for (ai = 0; ppc_cpu_aliases[ai].alias != NULL; ai++) {
> +        if (strcmp(ppc_cpu_aliases[ai].alias, alias) == 0) {
> +            return ppc_cpu_aliases[ai].model;
> +        }
> +    }
> +
> +    return NULL;
> +}
> +
>  static ObjectClass *ppc_cpu_class_by_name(const char *name)
>  {
>      char *cpu_model, *typename;
> @@ -10370,19 +10383,6 @@ static void ppc_cpu_parse_featurestr(const char 
> *typename, char *features,
>      pcc->parent_parse_features(typename, features, errp);
>  }
>  
> -const char *ppc_cpu_lookup_alias(const char *alias)
> -{
> -    int ai;
> -
> -    for (ai = 0; ppc_cpu_aliases[ai].alias != NULL; ai++) {
> -        if (strcmp(ppc_cpu_aliases[ai].alias, alias) == 0) {
> -            return ppc_cpu_aliases[ai].model;
> -        }
> -    }
> -
> -    return NULL;
> -}
> -

This code motion of ppc_cpu_lookup_alias appears to be unrelated to
the rest of the patch.

>  PowerPCCPUClass *ppc_cpu_get_family_class(PowerPCCPUClass *pcc)
>  {
>      ObjectClass *oc = OBJECT_CLASS(pcc);

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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