Re: [Qemu-devel] [PATCH for-2.11 v4 08/25] s390x: replace cpu_s390x_init() with cpu_generic_init()

[Igor Mammedov]

On Thu, 31 Aug 2017 15:44:38 +0200
David Hildenbrand <address@hidden> wrote:

> On 31.08.2017 15:19, Igor Mammedov wrote:
> > cpu_s390x_init() is used only *-user targets indirectly
> > via cpu_init() macro and has a hack to assign ids to created
> > cpus (I'm not sure if 'id' really matters to *-user emulation).  
> 
> It only has one cpu, right? With the below mentioned patch, the default
> "id"/ (the cpu_addr) will be 0. So you can create one CPU without any
> hacks. Or can it create more than 1?
As I understand it creates only one cpu,
but then there is fork related cpu_copy() which creates a cpu
and the rewrites new CPUArchState with old cpu data

    CPUState *new_cpu = cpu_init(cpu_model);                                    
 
    CPUArchState *new_env = new_cpu->env_ptr;                                   
 
    ...                                                    
    memcpy(new_env, env, sizeof(CPUArchState));

so I couldn't decide if id is of importance for *-user target
(well, I'm not really interested in *-user), and opted for
keeping current behavior (i.e. not breaking) in this patch
just without cpu_s390x_init().

So if 'id' isn't really needed for  *-user target, hunk 2 could be
dropped but it ought to be another patch on top as this change isn't
related to the topic of this patch/series.
 

> > So to on safe side, instead of having custom wrapper to do numbering
> > replace it with cpu_generic_init() and use S390CPUClass::next_cpu_id
> > which could serve the same purpose as static variable and move cpu->id
> > initialization to s390_cpu_initfn for CONFIG_USER_ONLY use-case.
> > 
> > PS:
> > ifdef is ugly but it allows us to hide s390x detail that isn't
> > set by *-user targets and reuse generic cpu creation utility
> > for btoh machine and user emulation.
> > 
> > Signed-off-by: Igor Mammedov <address@hidden>
> > Acked-by: Cornelia Huck <address@hidden>
> > ---
> > v2:
> >   - fix merge conflict in target/s390x/cpu.h caused by moving
> >     cpu_init/cpu_s390x_init with the file in commit
> >     (c862bddbc target/s390x: cleanup cpu.h)
> > 
> > CC: Cornelia Huck <address@hidden>
> > CC: address@hidden
> > CC: Eduardo Habkost <address@hidden>
> > 
> > perhaps cpu->id isn't need by CONFIG_USER_ONLY but I'd leave to it
> > s390x maintainers to deal with it.  
> 
> Will most probably be dropped in
> 
> https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg06158.html
> 
> > ---
> >  target/s390x/cpu.h    |  3 +--
> >  target/s390x/cpu.c    |  7 +++++++
> >  target/s390x/helper.c | 14 --------------
> >  3 files changed, 8 insertions(+), 16 deletions(-)
> > 
> > diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
> > index 4ec3380..0bd97a5 100644
> > --- a/target/s390x/cpu.h
> > +++ b/target/s390x/cpu.h
> > @@ -688,8 +688,7 @@ const char *s390_default_cpu_model_name(void);
> >  
> >  
> >  /* helper.c */
> > -S390CPU *cpu_s390x_init(const char *cpu_model);
> > -#define cpu_init(model) CPU(cpu_s390x_init(model))
> > +#define cpu_init(cpu_model) cpu_generic_init(TYPE_S390_CPU, cpu_model)
> >  S390CPU *s390x_new_cpu(const char *cpu_model, int64_t id, Error **errp);
> >  /* you can call this signal handler from your SIGBUS and SIGSEGV
> >     signal handlers to inform the virtual CPU of exceptions. non zero
> > diff --git a/target/s390x/cpu.c b/target/s390x/cpu.c
> > index 7267b60..74b3e4f 100644
> > --- a/target/s390x/cpu.c
> > +++ b/target/s390x/cpu.c
> > @@ -306,6 +306,13 @@ static void s390_cpu_initfn(Object *obj)
> >          inited = true;
> >          s390x_translate_init();
> >      }
> > +
> > +#if defined(CONFIG_USER_ONLY)
> > +    {
> > +        S390CPUClass *scc = S390_CPU_GET_CLASS(obj);
> > +        cpu->id = scc->next_cpu_id;
> > +    }
> > +#endif
> >  }
> >  
> >  static void s390_cpu_finalize(Object *obj)
> > diff --git a/target/s390x/helper.c b/target/s390x/helper.c
> > index 3adb9de..ba29504 100644
> > --- a/target/s390x/helper.c
> > +++ b/target/s390x/helper.c
> > @@ -129,20 +129,6 @@ out:
> >      return cpu;
> >  }
> >  
> > -S390CPU *cpu_s390x_init(const char *cpu_model)
> > -{
> > -    Error *err = NULL;
> > -    S390CPU *cpu;
> > -    /* Use to track CPU ID for linux-user only */
> > -    static int64_t next_cpu_id;
> > -
> > -    cpu = s390x_new_cpu(cpu_model, next_cpu_id++, &err);
> > -    if (err) {
> > -        error_report_err(err);
> > -    }
> > -    return cpu;
> > -}
> > -
> >  #ifndef CONFIG_USER_ONLY
> >  
> >  hwaddr s390_cpu_get_phys_page_debug(CPUState *cs, vaddr vaddr)
> >   
> 
>