Re: [Qemu-devel] [RFC 08/13] pc: add writeonly 'cpu' property to PCMachine

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Thu, Jan 19, 2017 at 04:04:23PM +0100, Igor Mammedov wrote:
> On Wed, 18 Jan 2017 16:57:13 -0200
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
> > On Wed, Jan 18, 2017 at 06:13:24PM +0100, Igor Mammedov wrote:
> > > it will allow generic numa code to set cpu to numa node mapping
> > > in target independent manner in the next patch.
> > > 
> > > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > > ---
> > >  hw/i386/pc.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > >  1 file changed, 56 insertions(+)
> > > 
> > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > > index f8ea635..1d33a5e 100644
> > > --- a/hw/i386/pc.c
> > > +++ b/hw/i386/pc.c
> > > @@ -2201,6 +2201,56 @@ static void pc_machine_set_pit(Object *obj, bool value, Error **errp)
> > >      pcms->pit = value;
> > >  }
> > >  
> > > +static void pc_machine_set_cpu(Object *obj, Visitor *v, const char *name,
> > > +                               void *opaque, Error **errp)
> > > +{
> > > +    uint32_t apic_id;
> > > +    X86CPUTopoInfo topo;
> > > +    CPUArchId *cpu_slot;
> > > +    Error *local_err = NULL;
> > > +    CpuInstanceProperties *cpu_props = NULL;
> > > +    PCMachineState *pcms = PC_MACHINE(obj);
> > > +    MachineClass *mc = MACHINE_GET_CLASS(obj);
> > > +
> > > +    visit_type_CpuInstanceProperties(v, name, &cpu_props, &local_err);
> > > +    if (local_err) {
> > > +        goto out;
> > > +    }
> > > +
> > > +    if (!cpu_props->has_node_id) {
> > > +        error_setg(&local_err, "node-id property is not specified");
> > > +        goto out;
> > > +    }
> > > +
> > > +    /*
> > > +     * make sure that possible_cpus is initialized
> > > +     * as property setter might be called before machine init is called
> > > +     */
> > > +    mc->possible_cpu_arch_ids(MACHINE(obj));
> > > +
> > > +    topo.pkg_id = cpu_props->socket_id;
> > > +    topo.core_id = cpu_props->core_id;
> > > +    topo.smt_id = cpu_props->thread_id;
> > > +    apic_id = apicid_from_topo_ids(smp_cores, smp_threads, &topo);
> > > +    cpu_slot = pc_find_cpu_slot(pcms, apic_id, NULL);  
> > 
> > If we make TYPE_MACHINE provide an API to query CPU slots, e.g.:
> >   CPUArchId *machine_find_cpu_slot(MachineState *m, CpuInstanceProperties *props)
> so if there is no objections, 
> I'll move possible_cpus to MachineState
> and add to MachineClass above callback so target machine
> would be able to provide arch specific lookup function.
> it should work for both x86 and ARM.

The need for possible_cpus in MachineState for sPAPR isn't immediately
apparent to me. In the context of this new numa "cpu" property, PC target
seems to use possible_cpus to store and later lookup the numa node id for
a given CPU. Wondering if that could be achieved w/o needing possible_cpus
in MachineState ?

Regards,
Bharata.