Re: [Qemu-devel] [RFC PATCH v0 2/6] spapr: CPU core device

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

On Fri, Feb 26, 2016 at 01:57:44PM +1100, David Gibson wrote:
> On Thu, Feb 25, 2016 at 09:52:38PM +0530, Bharata B Rao wrote:
> > Add sPAPR specific CPU core device that is based on generic CPU core device.
> > Creating this core device will result in creation of all the CPU thread
> > devices that are part of this core.
> > 
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> 
> Looks good overall, a few minor points below.
> 
> > ---
> >  hw/ppc/Makefile.objs            |   1 +
> >  hw/ppc/spapr_cpu_core.c         | 210 ++++++++++++++++++++++++++++++++++++++++
> >  include/hw/ppc/spapr_cpu_core.h |  32 ++++++
> >  3 files changed, 243 insertions(+)
> >  create mode 100644 hw/ppc/spapr_cpu_core.c
> >  create mode 100644 include/hw/ppc/spapr_cpu_core.h
> > 
> > diff --git a/hw/ppc/Makefile.objs b/hw/ppc/Makefile.objs
> > index c1ffc77..5cc6608 100644
> > --- a/hw/ppc/Makefile.objs
> > +++ b/hw/ppc/Makefile.objs
> > @@ -4,6 +4,7 @@ obj-y += ppc.o ppc_booke.o
> >  obj-$(CONFIG_PSERIES) += spapr.o spapr_vio.o spapr_events.o
> >  obj-$(CONFIG_PSERIES) += spapr_hcall.o spapr_iommu.o spapr_rtas.o
> >  obj-$(CONFIG_PSERIES) += spapr_pci.o spapr_rtc.o spapr_drc.o spapr_rng.o
> > +obj-$(CONFIG_PSERIES) += spapr_cpu_core.o
> >  ifeq ($(CONFIG_PCI)$(CONFIG_PSERIES)$(CONFIG_LINUX), yyy)
> >  obj-y += spapr_pci_vfio.o
> >  endif
> > diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> > new file mode 100644
> > index 0000000..c44eb61
> > --- /dev/null
> > +++ b/hw/ppc/spapr_cpu_core.c
> > @@ -0,0 +1,210 @@
> > +/*
> > + * sPAPR CPU core device, acts as container of CPU thread devices.
> > + *
> > + * Copyright (C) 2016 Bharata B Rao <bharata@linux.vnet.ibm.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> > + * See the COPYING file in the top-level directory.
> > + */
> > +#include "hw/cpu/core.h"
> > +#include "hw/ppc/spapr_cpu_core.h"
> > +#include "hw/ppc/spapr.h"
> > +#include "hw/boards.h"
> > +#include "qemu/error-report.h"
> > +#include "qapi/visitor.h"
> > +#include <sysemu/cpus.h>
> > +
> > +static int spapr_cpu_core_realize_child(Object *child, void *opaque)
> > +{
> > +    Error **errp = opaque;
> > +
> > +    object_property_set_bool(child, true, "realized", errp);
> > +    if (*errp) {
> > +        return 1;
> > +    }
> > +    return 0;
> > +}
> > +
> > +static void spapr_cpu_core_realize(DeviceState *dev, Error **errp)
> > +{
> > +    sPAPRCPUCore *core = SPAPR_CPU_CORE(OBJECT(dev));
> > +    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> > +    Error *local_err = NULL;
> > +
> > +    if (!core->nr_threads) {
> > +        error_setg(errp, "nr_threads property can't be 0");
> > +        return;
> > +    }
> > +
> > +    if (!core->cpu_model) {
> > +        error_setg(errp, "cpu_model property isn't set");
> > +        return;
> > +    }
> > +
> > +    /*
> > +     * TODO: If slot isn't specified, plug this core into
> > +     * an existing empty slot.
> > +     */
> > +    if (!core->slot) {
> > +        error_setg(errp, "slot property isn't set");
> > +        return;
> > +    }
> > +
> > +    object_property_set_link(OBJECT(spapr), OBJECT(core), core->slot,
> > +                             &local_err);
> > +    if (local_err) {
> > +        error_propagate(errp, local_err);
> > +        return;
> > +    }
> > +
> > +    object_child_foreach(OBJECT(dev), spapr_cpu_core_realize_child, errp);
> > +}
> > +
> > +/*
> > + * This creates the CPU threads for a given @core.
> > + *
> > + * In order to create the threads, we need two inputs - number of
> > + * threads and the cpu_model. These are set as core object's properties.
> > + * When both of them become available/set, this routine will be called from
> > + * either property's set handler to create the threads.
> > + *
> > + * TODO: Dependence of threads creation on two properties is resulting
> > + * in this not-so-clean way of creating threads from either of the
> > + * property setters based on the order in which they get set. Check if
> > + * this can be handled in a better manner.
> > + */
> > +static void spapr_cpu_core_create_threads(sPAPRCPUCore *core, Error **errp)
> > +{
> > +    int i;
> > +
> > +    for (i = 0; i < core->nr_threads; i++) {
> > +        char id[32];
> > +        char type[32];
> > +
> > +        snprintf(type, sizeof(type), "%s-%s", core->cpu_model,
> > +                 TYPE_POWERPC_CPU);
> 
> I think you want to use cpu_class_by_name() rather than explicitly
> constructing the class name here.

Good point, started using ObjectClass.

> 
> > +        object_initialize(&core->threads[i], sizeof(core->threads[i]), type);
> > +
> > +        snprintf(id, sizeof(id), "thread[%d]", i);
> > +        object_property_add_child(OBJECT(core), id, OBJECT(&core->threads[i]),
> > +                                  errp);
> > +    }
> > +}
> > +
> > +static char *spapr_cpu_core_prop_get_slot(Object *obj, Error **errp)
> > +{
> > +    sPAPRCPUCore *core = SPAPR_CPU_CORE(obj);
> > +
> > +    return core->slot;
> > +}
> > +
> > +static void spapr_cpu_core_prop_set_slot(Object *obj, const char *val,
> > +                                              Error **errp)
> > +{
> > +    sPAPRCPUCore *core = SPAPR_CPU_CORE(obj);
> > +
> > +    core->slot = g_strdup(val);
> > +}
> > +
> > +static char *spapr_cpu_core_prop_get_cpu_model(Object *obj, Error **errp)
> > +{
> > +    sPAPRCPUCore *core = SPAPR_CPU_CORE(obj);
> > +
> > +    return core->cpu_model;
> > +}
> > +
> > +static void spapr_cpu_core_prop_set_cpu_model(Object *obj, const char *val,
> > +                                              Error **errp)
> > +{
> > +    sPAPRCPUCore *core = SPAPR_CPU_CORE(obj);
> > +    MachineState *machine = MACHINE(qdev_get_machine());
> > +
> > +    /*
> > +     * cpu_model can't be different from what is specified with -cpu
> > +     */
> > +    if (strcmp(val, machine->cpu_model)) {
> > +       error_setg(errp, "cpu_model should be %s", machine->cpu_model);
> > +       return;
> > +    }
> 
> I'm not sure if this is the right place to test this.  Possibly it
> should be tested in the machine hotplug handler instead.

Not sure about the right place to validate this and nr_threads property. But
it essentially boils down to backing out from property setter after
object init vs backing out during realization.

Regards,
Bharata.