Re: [Qemu-devel] [Qemu-ppc] [PATCH 1/1] ppc: spapr: Move VCPU ID calculation into sPAPR

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

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On Mon, Sep 04, 2017 at 12:18:57PM +0200, Greg Kurz wrote:
> On Thu, 31 Aug 2017 16:38:46 +1000
> Sam Bobroff <sam.bobroff@au1.ibm.com> wrote:
> 
> > Move the calculation of a CPU's VCPU ID out of the generic PPC code
> > (ppc_cpu_realizefn()) and into sPAPR specific code
> > (spapr_cpu_core_realize()) where it belongs.
> > 
> > Unfortunately, due to the way things are ordered, we still need to
> > default the VCPU ID in ppc_cpu_realizfn() but at least doing that
> > doesn't require any interaction with sPAPR.
> > 
> > Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
> > ---
> > This is follow up work arising from my work to clean up the way CPU VCPU IDs are
> > handled on PowerPC. It had looked like it would be difficult to move the actual
> > VCPU ID calculation out of generic code but it turned out to be OK.
> > 
> > It's based on dgibson/ppc-for-2.11.
> > 
> 
> According to what we currently have in the generic code, this should be:
> 
> ((cc->core_id + i) / smp_threads) * spapr->vsmt + ((cc->core_id + i) % smp_threads)
> 
> but since cc->core_id is a multiple of smp_threads and i < cc->nr_threads <= smp_threads,
> then we can indeed simplify the computation as you did. :)

Right, I suggested this simplication on just that basis.

Applied to ppc-for-2.11.

> 
> \o/
> 
> Reviewed-by: Greg Kurz <groug@kaod.org>
> 
> > +        if (kvm_enabled() && !kvm_vcpu_id_is_valid(cpu->vcpu_id)) {
> > +            error_setg(&local_err, "Can't create CPU with id %d in KVM",
> > +                       cpu->vcpu_id);
> > +            error_append_hint(&local_err, "Adjust the number of cpus to %d "
> > +                              "or try to raise the number of threads per core\n",
> > +                              cpu->vcpu_id * smp_threads / spapr->vsmt);
> > +            goto err;
> > +        }
> > +
> >  
> >          /* Set NUMA node for the threads belonged to core  */
> >          cpu->node_id = sc->node_id;
> > diff --git a/target/ppc/translate_init.c b/target/ppc/translate_init.c
> > index 7f6a349e43..1f7286c893 100644
> > --- a/target/ppc/translate_init.c
> > +++ b/target/ppc/translate_init.c
> > @@ -9903,28 +9903,15 @@ static void ppc_cpu_realizefn(DeviceState *dev, Error **errp)
> >      PowerPCCPU *cpu = POWERPC_CPU(dev);
> >      PowerPCCPUClass *pcc = POWERPC_CPU_GET_CLASS(cpu);
> >      Error *local_err = NULL;
> > -#if !defined(CONFIG_USER_ONLY)
> > -    int max_smt = kvmppc_smt_threads();
> > -#endif
> >  
> >      cpu_exec_realizefn(cs, &local_err);
> >      if (local_err != NULL) {
> >          error_propagate(errp, local_err);
> >          return;
> >      }
> > -
> > -#if !defined(CONFIG_USER_ONLY)
> > -    cpu->vcpu_id = (cs->cpu_index / smp_threads) * max_smt
> > -        + (cs->cpu_index % smp_threads);
> > -
> > -    if (kvm_enabled() && !kvm_vcpu_id_is_valid(cpu->vcpu_id)) {
> > -        error_setg(errp, "Can't create CPU with id %d in KVM", cpu->vcpu_id);
> > -        error_append_hint(errp, "Adjust the number of cpus to %d "
> > -                          "or try to raise the number of threads per core\n",
> > -                          cpu->vcpu_id * smp_threads / max_smt);
> > -        goto unrealize;
> > +    if (cpu->vcpu_id == UNASSIGNED_CPU_INDEX) {
> > +        cpu->vcpu_id = cs->cpu_index;
> >      }
> > -#endif
> >  
> >      if (tcg_enabled()) {
> >          if (ppc_fixup_cpu(cpu) != 0) {
> > @@ -10625,6 +10612,7 @@ static void ppc_cpu_initfn(Object *obj)
> >      CPUPPCState *env = &cpu->env;
> >  
> >      cs->env_ptr = env;
> > +    cpu->vcpu_id = UNASSIGNED_CPU_INDEX;
> >  
> >      env->msr_mask = pcc->msr_mask;
> >      env->mmu_model = pcc->mmu_model;
> 



-- 
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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