Re: [Qemu-devel] [Qemu-ppc] [PATCH] spapr: move registration of "host" CPU core type to machine code

[Greg Kurz]

On Mon, 25 Sep 2017 17:48:57 +0200
Greg Kurz <address@hidden> wrote:

> On Mon, 25 Sep 2017 15:41:34 +0200
> Igor Mammedov <address@hidden> wrote:
> 
> > On Mon, 25 Sep 2017 11:47:33 +0200
> > Greg Kurz <address@hidden> wrote:
> >   
> > > The CPU core abstraction belongs to the machine code. This also gets
> > > rid of some code duplication.
> > > 
> > > Signed-off-by: Greg Kurz <address@hidden>
> > > ---
> > > 
> > > hw/ppc/spapr_cpu_core.h is also included elsewhere in target/ppc/kvm.c
> > > but this is already handled by the following cleanup patch:
> > > 
> > > https://patchwork.ozlabs.org/patch/817598/
> > > ---
> > >  hw/ppc/spapr.c                  |    4 ++++
> > >  hw/ppc/spapr_cpu_core.c         |   34 ++++++++++++++++++++++------------
> > >  include/hw/ppc/spapr_cpu_core.h |    2 +-
> > >  target/ppc/kvm.c                |   12 ------------
> > >  4 files changed, 27 insertions(+), 25 deletions(-)
> > > 
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index 0ce3ec87ac59..e82c8532ffb0 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -2349,6 +2349,10 @@ static void ppc_spapr_init(MachineState *machine)
> > >      }
> > >  
> > >      /* init CPUs */
> > > +    if (kvm_enabled()) {
> > > +        spapr_cpu_core_register_host_type();
> > > +    }    
> > why don't we create it statically in hw/ppc/spapr_cpu_core.c
> > like it's done in x86, i.e.
> > 
> >   static void x86_cpu_register_types(void)                                  
> >        
> >   {                                                                         
> >        
> >   ...                              
> >   #ifdef CONFIG_KVM                                                         
> >        
> >       type_register_static(&host_x86_cpu_type_info);                        
> >        
> >   #endif                                                                    
> >        
> >   } 
> >   type_init(x86_cpu_register_types)
> > 
> > and do the same for host CPU as well?
> >   
> 
> Hi Igor,
> 
> Not sure yet why we use dynamic types, but I'd be glad to dig a bit more.

So the problem is that it was decided to make the host CPU class a
subclass of the host's CPU model, and this requires all the CPU model
classes to be registered beforehand.

commit 5ba4576b858c0d6056f59abb7e17a2b63f7905f3
Author: Andreas Färber <address@hidden>
Date:   Sat Feb 23 11:22:12 2013 +0000

    target-ppc: Make host CPU a subclass of the host's CPU model
    
    This avoids assigning individual class fields and contributors
    forgetting to add field assignments in KVM-only code.
    
    ppc_cpu_class_find_by_pvr() requires the CPU model classes to be
    registered, so defer host CPU type registration to kvm_arch_init().
    
    Only register the host CPU type if there is a class with matching PVR.
    This lets us drop error handling from instance_init.
    
    Signed-off-by: Andreas Färber <address@hidden>
    Signed-off-by: Alexander Graf <address@hidden>

I can't think of an alternate way to do this. Any suggestion ?

> Maybe I'll do this in a followup patch though, since the present patch
> is mostly about not referencing sPAPRCPUCore from the KVM code anymore.
> 
> > my gripe with 'dynamic' types is that it creates problems
> > if one needs to access type information before type is created.
> > In my use-case it's before machine_init() is called but
> > after kvm is initialized, so I was sort of 'fine' with way
> > it's currently handled /i.e. still too much convoluted with
> > aliases redefinition and all but sort of 'manageable' /.
> > 
> > However I'd very much prefer static type info so it
> > could be used regardless of place/time it's accessed.
> >   
> 
> I agree that it would be better.
> 
> > I can add a couple patches to that effect into upcomming
> > cpu_model removal series, if that's ok for PPC folks.
> >   
> 
> Oh, and can you share an url to see how it looks like ?
> 
> Cheers,
> 
> --
> Greg
> 
> >   
> > > +
> > >      if (machine->cpu_model == NULL) {
> > >          machine->cpu_model = kvm_enabled() ? "host" : 
> > > smc->tcg_default_cpu;
> > >      }
> > > diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> > > index c08ee7571a50..6e224ba029ec 100644
> > > --- a/hw/ppc/spapr_cpu_core.c
> > > +++ b/hw/ppc/spapr_cpu_core.c
> > > @@ -317,7 +317,7 @@ static Property spapr_cpu_core_properties[] = {
> > >      DEFINE_PROP_END_OF_LIST()
> > >  };
> > >  
> > > -void spapr_cpu_core_class_init(ObjectClass *oc, void *data)
> > > +static void spapr_cpu_core_class_init(ObjectClass *oc, void *data)
> > >  {
> > >      DeviceClass *dc = DEVICE_CLASS(oc);
> > >      sPAPRCPUCoreClass *scc = SPAPR_CPU_CORE_CLASS(oc);
> > > @@ -337,6 +337,20 @@ static const TypeInfo spapr_cpu_core_type_info = {
> > >      .class_size = sizeof(sPAPRCPUCoreClass),
> > >  };
> > >  
> > > +static void spapr_cpu_core_register_type(const char *model_name)
> > > +{
> > > +    TypeInfo type_info = {
> > > +        .parent = TYPE_SPAPR_CPU_CORE,
> > > +        .instance_size = sizeof(sPAPRCPUCore),
> > > +        .class_init = spapr_cpu_core_class_init,
> > > +        .class_data = (void *) model_name,
> > > +    };
> > > +
> > > +    type_info.name = g_strdup_printf("%s-"TYPE_SPAPR_CPU_CORE, 
> > > model_name);
> > > +    type_register(&type_info);
> > > +    g_free((void *)type_info.name);
> > > +}
> > > +
> > >  static void spapr_cpu_core_register_types(void)
> > >  {
> > >      int i;
> > > @@ -344,18 +358,14 @@ static void spapr_cpu_core_register_types(void)
> > >      type_register_static(&spapr_cpu_core_type_info);
> > >  
> > >      for (i = 0; i < ARRAY_SIZE(spapr_core_models); i++) {
> > > -        TypeInfo type_info = {
> > > -            .parent = TYPE_SPAPR_CPU_CORE,
> > > -            .instance_size = sizeof(sPAPRCPUCore),
> > > -            .class_init = spapr_cpu_core_class_init,
> > > -            .class_data = (void *) spapr_core_models[i],
> > > -        };
> > > -
> > > -        type_info.name = g_strdup_printf("%s-" TYPE_SPAPR_CPU_CORE,
> > > -                                         spapr_core_models[i]);
> > > -        type_register(&type_info);
> > > -        g_free((void *)type_info.name);
> > > +        spapr_cpu_core_register_type(spapr_core_models[i]);
> > >      }
> > > +
> > > +}
> > > +
> > > +void spapr_cpu_core_register_host_type(void)
> > > +{
> > > +    spapr_cpu_core_register_type("host");
> > >  }
> > >  
> > >  type_init(spapr_cpu_core_register_types)
> > > diff --git a/include/hw/ppc/spapr_cpu_core.h 
> > > b/include/hw/ppc/spapr_cpu_core.h
> > > index 93051e9ecf56..e3e906343048 100644
> > > --- a/include/hw/ppc/spapr_cpu_core.h
> > > +++ b/include/hw/ppc/spapr_cpu_core.h
> > > @@ -36,5 +36,5 @@ typedef struct sPAPRCPUCoreClass {
> > >  } sPAPRCPUCoreClass;
> > >  
> > >  char *spapr_get_cpu_core_type(const char *model);
> > > -void spapr_cpu_core_class_init(ObjectClass *oc, void *data);
> > > +void spapr_cpu_core_register_host_type(void);
> > >  #endif
> > > diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> > > index 5b281b2f1b6d..8dd80993ec9e 100644
> > > --- a/target/ppc/kvm.c
> > > +++ b/target/ppc/kvm.c
> > > @@ -37,7 +37,6 @@
> > >  #include "hw/sysbus.h"
> > >  #include "hw/ppc/spapr.h"
> > >  #include "hw/ppc/spapr_vio.h"
> > > -#include "hw/ppc/spapr_cpu_core.h"
> > >  #include "hw/ppc/ppc.h"
> > >  #include "sysemu/watchdog.h"
> > >  #include "trace.h"
> > > @@ -2502,17 +2501,6 @@ static int kvm_ppc_register_host_cpu_type(void)
> > >      oc = object_class_by_name(type_info.name);
> > >      g_assert(oc);
> > >  
> > > -#if defined(TARGET_PPC64)
> > > -    type_info.name = g_strdup_printf("%s-"TYPE_SPAPR_CPU_CORE, "host");
> > > -    type_info.parent = TYPE_SPAPR_CPU_CORE,
> > > -    type_info.instance_size = sizeof(sPAPRCPUCore);
> > > -    type_info.instance_init = NULL;
> > > -    type_info.class_init = spapr_cpu_core_class_init;
> > > -    type_info.class_data = (void *) "host";
> > > -    type_register(&type_info);
> > > -    g_free((void *)type_info.name);
> > > -#endif
> > > -
> > >      /*
> > >       * Update generic CPU family class alias (e.g. on a POWER8NVL host,
> > >       * we want "POWER8" to be a "family" alias that points to the current
> > > 
> > >     
> >   
> 
> 
> 



-- 
Gregory Kurz                                     address@hidden
                                                 address@hidden
Software Engineer @ IBM/LTC                      http://www.ibm.com
Tel 33-5-6218-1607

"Anarchy is about taking complete responsibility for yourself."
        Alan Moore.