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

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Jul 07, 2016 at 08:20:23PM +0530, Bharata B Rao 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.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
>  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 */
> +        if (cs->has_stable_cpu_id) {
> +            cs->stable_cpu_id = cc->core_id + i;
> +        }

Testing cs->has_stable_cpu_id here in machine type specific code seems
really weird.  It's the machine type that knows whether it has a
stable ID to give to the CPU or not, rather than the other way around.

Since we haven't yet had a release with cpu cores, I think the right
thing is for cpu_core to unconditionally set the stable ID (and set
has_stable_id to true).  The backup path that does thread-based cpu
init, can set has_stable_id to false (if that's not the default).

>          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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