Re: [Qemu-devel] [RFC PATCH v2 3/5] spapr: Set stable_cpu_id for threads of CPU cores

[David Gibson]

On Thu, Jul 07, 2016 at 06:11:31PM +0200, Greg Kurz wrote:
> On Thu,  7 Jul 2016 20:20:23 +0530
> Bharata B Rao <address@hidden> wrote:
> 
> > Conditonally set stable_cpu_id for CPU threads that are created as part
> > of spapr CPU cores. The use of stable_cpu_id is enabled for pseries-2.7
> > onwards.
> > 
> 
> The last sentence is a bit confusing since the enablement actually happens
> in patch 5/5.
> 
> > Signed-off-by: Bharata B Rao <address@hidden>
> > ---
> >  hw/ppc/spapr_cpu_core.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> > index b104778..0ec3513 100644
> > --- a/hw/ppc/spapr_cpu_core.c
> > +++ b/hw/ppc/spapr_cpu_core.c
> > @@ -293,8 +293,15 @@ static void spapr_cpu_core_realize(DeviceState *dev, 
> > Error **errp)
> >      for (i = 0; i < cc->nr_threads; i++) {
> >          char id[32];
> >          obj = sc->threads + i * size;
> > +        CPUState *cs;
> >  
> >          object_initialize(obj, size, typename);
> > +        cs = CPU(obj);
> > +
> > +        /* Use core_id (which is actually cpu_dt_id) as stable CPU id */
> 
> It isn't what I had in mind. More something like below:
> 
> In ppc_spapr_init():
> 
>     for (i = 0; i < spapr_max_cores; i++) {
>         spapr->cores[i]->stable_id = i * smp_threads;
>     }
> 
> 
> In spapr_cpu_core_realize():
> 
>     for (j = 0; j < cc->nr_threads; j++) {
>         stable_cpu_id = cc->stable_id + j;
>     }
> 
> So we need to introduce cc->stable_id.

No, we don't.  Cores have had a stable ID since they were introduced.

Instead we should be setting the thread stable ids based on the core
stable id.

> I think stable_cpu_id is the prerequisite to compute both cpu_dt_id and 
> instance_id.
> 
> Makes sense ?
> 
> > +        if (cs->has_stable_cpu_id) {
> > +            cs->stable_cpu_id = cc->core_id + i;
> > +        }
> >          snprintf(id, sizeof(id), "thread[%d]", i);
> >          object_property_add_child(OBJECT(sc), id, obj, &local_err);
> >          if (local_err) {
> 

-- 
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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