Re: [Qemu-devel] [RFC v3 2/2] spapr: implement query-hotpluggable-cpus QMP command

[David Gibson <dgibson@redhat.com>]

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On Wed, 16 Mar 2016 10:49:41 +0530
Bharata B Rao <bharata@linux.vnet.ibm.com> wrote:

> On Tue, Mar 15, 2016 at 02:24:08PM +0100, Igor Mammedov wrote:
> > it returns a list of present/possible to hotplug CPU
> > objects with a list of properties to use with
> > device_add.
> > 
> > in spapr case returned list would looks like:  
> > -> { "execute": "query-hotpluggable-cpus" }  
> > <- {"return": [
> >      { "props": { "core": 1 }, "type": "spapr-cpu-core",
> >        "vcpus-count": 2 },
> >      { "props": { "core": 0 }, "type": "spapr-cpu-core",
> >        "vcpus-count": 2,
> >        "qom-path": "/machine/unattached/device[0]"}
> >    ]}'
> > 
> > TODO:
> >   add 'node' property for core <-> numa node mapping
> > 
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > ---
> > it's only compile tested
> > ---
> >  hw/ppc/spapr.c | 32 ++++++++++++++++++++++++++++++++
> >  1 file changed, 32 insertions(+)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index b1e9ba2..e1ce983 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -65,6 +65,7 @@
> >  #include "hw/compat.h"
> >  #include "qemu-common.h"
> >  #include "hw/ppc/spapr_cpu_core.h"
> > +#include "qmp-commands.h"
> > 
> >  #include <libfdt.h>
> > 
> > @@ -2399,6 +2400,37 @@ static unsigned spapr_cpu_index_to_socket_id(unsigned cpu_index)
> >      return cpu_index / smp_threads / smp_cores;
> >  }
> > 
> > +HotpluggableCPUList *qmp_query_hotpluggable_cpus(Error **errp)
> > +{
> > +    int i;
> > +    HotpluggableCPUList *head = NULL;
> > +    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> > +    int spapr_max_cores = max_cpus / smp_threads;
> > +
> > +    for (i = 0; i < spapr_max_cores; i++) {
> > +        HotpluggableCPUList *list_item = g_new0(typeof(*list_item), 1);
> > +        HotpluggableCPU *cpu_item = g_new0(typeof(*cpu_item), 1);
> > +        CpuInstanceProperties *cpu_props = g_new0(typeof(*cpu_props), 1);
> > +
> > +        cpu_item->type = g_strdup(TYPE_SPAPR_CPU_CORE);
> > +        cpu_item->vcpus_count = smp_threads;  
> 
> Shouldn't this be fetched from "threads" property of the core device
> instead of directly using smp_threads ? But again, what that would mean
> for not-yet-plugged in cores and how to get that for them is a question.

Yeah, I think Igor's patch is correct here.  The information flow goes
the other direction: the machine type code advertises smp_threads here,
which management then passes back to the device_add spapr-core in the
threads property.

-- 
David Gibson <dgibson@redhat.com>
Senior Software Engineer, Virtualization, Red Hat

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