Re: [Qemu-arm] [Qemu-devel] [PATCH RFC 05/16] hw/core/machine: add smp properites

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

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On Tue, Jun 14, 2016 at 08:08:07AM +0200, Andrew Jones wrote:
> On Tue, Jun 14, 2016 at 12:00:26PM +1000, David Gibson wrote:
> > On Fri, Jun 10, 2016 at 07:40:16PM +0200, Andrew Jones wrote:
> > > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > > ---
> > >  hw/core/machine.c   | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> > >  include/hw/boards.h |  6 ++++
> > >  2 files changed, 87 insertions(+)
> > > 
> > > diff --git a/hw/core/machine.c b/hw/core/machine.c
> > > index 3dce9020e510a..2625044002e57 100644
> > > --- a/hw/core/machine.c
> > > +++ b/hw/core/machine.c
> > > @@ -172,6 +172,53 @@ static void machine_set_dumpdtb(Object *obj, const char *value, Error **errp)
> > >      ms->dumpdtb = g_strdup(value);
> > >  }
> > >  
> > > +static void machine_get_smp(Object *obj, Visitor *v, const char *name,
> > > +                            void *opaque, Error **errp)
> > > +{
> > > +    MachineState *ms = MACHINE(obj);
> > > +    int64_t value;
> > > +
> > > +    if (strncmp(name, "sockets", 7) == 0) {
> > > +        value = ms->sockets;
> > > +    } else if (strncmp(name, "cores", 5) == 0) {
> > > +        value = ms->cores;
> > > +    } else if (strncmp(name, "threads", 7) == 0) {
> > > +        value = ms->threads;
> > > +    } else if (strncmp(name, "maxcpus", 7) == 0) {
> > > +        value = ms->maxcpus;
> > > +    } else if (strncmp(name, "cpus", 4) == 0) {
> > > +        value = ms->cpus;
> > > +    }
> > > +
> > > +    visit_type_int(v, name, &value, errp);
> > > +}
> > 
> > Any particular for multiplexing all the set / get, rather than having
> > separate callbacks for each property?
> 
> Not really. This way just makes denser code. But I'll go whichever
> direction people prefer.

I'd prefer not to have the multiplexer, but I don't care that much.

> Actually I should probably add an
> else { error_report(...) } in either case, which means the multifunction
> direction would still contain strncmps.

Hrm.. that would seem an odd choice to me if you didn't have the
multiplex.  Not including the strncmp() means you can change the
property name (or add aliases) in a single place, without changing the
callback functions.

Note also that the current set of strncmp()s is only correct because
there is a limited set of things bound to this callback.  Remember
that strncmp(name, "sockets", 7) will match "socketsfoo".

> > > +
> > > +static void machine_set_smp(Object *obj, Visitor *v, const char *name,
> > > +                            void *opaque, Error **errp)
> > > +{
> > > +    MachineState *ms = MACHINE(obj);
> > > +    Error *error = NULL;
> > > +    int64_t value;
> > > +
> > > +    visit_type_int(v, name, &value, &error);
> > > +    if (error) {
> > > +        error_propagate(errp, error);
> > > +        return;
> > > +    }
> > > +
> > > +    if (strncmp(name, "sockets", 7) == 0) {
> > > +        ms->sockets = value;
> > > +    } else if (strncmp(name, "cores", 5) == 0) {
> > > +        ms->cores = value;;
> > > +    } else if (strncmp(name, "threads", 7) == 0) {
> > > +        ms->threads = value;
> > > +    } else if (strncmp(name, "maxcpus", 7) == 0) {
> > > +        ms->maxcpus = value;
> > > +    } else if (strncmp(name, "cpus", 4) == 0) {
> > > +        ms->cpus = value;
> > > +    }
> > > +}
> > > +
> > >  static void machine_get_phandle_start(Object *obj, Visitor *v,
> > >                                        const char *name, void *opaque,
> > >                                        Error **errp)
> > > @@ -368,8 +415,18 @@ static void machine_init_notify(Notifier *notifier, void *data)
> > >      foreach_dynamic_sysbus_device(error_on_sysbus_device, NULL);
> > >  }
> > >  
> > > +static void machine_set_smp_parameters(MachineState *ms)
> > > +{
> > > +    if (ms->sockets != -1 || ms->cores != -1 || ms->threads != -1 ||
> > > +        ms->maxcpus != -1 || ms->cpus != -1) {
> > > +        error_report("warning: cpu topology: "
> > > +                     "machine properties currently ignored");
> > > +    }
> > > +}
> > > +
> > >  static void machine_pre_init(MachineState *ms)
> > >  {
> > > +    machine_set_smp_parameters(ms);
> > >  }
> > >  
> > >  static void machine_class_init(ObjectClass *oc, void *data)
> > > @@ -403,6 +460,11 @@ static void machine_initfn(Object *obj)
> > >      ms->dump_guest_core = true;
> > >      ms->mem_merge = true;
> > >      ms->enable_graphics = true;
> > > +    ms->sockets = -1;
> > > +    ms->cores = -1;
> > > +    ms->threads = -1;
> > > +    ms->maxcpus = -1;
> > > +    ms->cpus = -1;
> > >  
> > >      object_property_add_str(obj, "accel",
> > >                              machine_get_accel, machine_set_accel, NULL);
> > > @@ -462,6 +524,25 @@ static void machine_initfn(Object *obj)
> > >      object_property_set_description(obj, "dt-compatible",
> > >                                      "Overrides the \"compatible\" property of the dt root node",
> > >                                      NULL);
> > > +    object_property_add(obj, "sockets", "int", machine_get_smp,
> > > +                        machine_set_smp, NULL, NULL, NULL);
> > > +    object_property_set_description(obj, "sockets", "Number of sockets", NULL);
> > > +    object_property_add(obj, "cores", "int", machine_get_smp,
> > > +                        machine_set_smp, NULL, NULL, NULL);
> > > +    object_property_set_description(obj, "cores",
> > > +                                    "Number of cores per socket", NULL);
> > > +    object_property_add(obj, "threads", "int", machine_get_smp,
> > > +                        machine_set_smp, NULL, NULL, NULL);
> > > +    object_property_set_description(obj, "threads",
> > > +                                    "Number of threads per core", NULL);
> > > +    object_property_add(obj, "maxcpus", "int", machine_get_smp,
> > > +                        machine_set_smp, NULL, NULL, NULL);
> > > +    object_property_set_description(obj, "maxcpus", "Maximum number of cpus",
> > > +                                    NULL);
> > > +    object_property_add(obj, "cpus", "int", machine_get_smp,
> > > +                        machine_set_smp, NULL, NULL, NULL);
> > > +    object_property_set_description(obj, "cpus", "Number of online cpus",
> > > +                                    NULL);
> > >      object_property_add_bool(obj, "dump-guest-core",
> > >                               machine_get_dump_guest_core,
> > >                               machine_set_dump_guest_core,
> > > diff --git a/include/hw/boards.h b/include/hw/boards.h
> > > index 4e8dc68b07a24..53adbfe2a3099 100644
> > > --- a/include/hw/boards.h
> > > +++ b/include/hw/boards.h
> > > @@ -166,6 +166,12 @@ struct MachineState {
> > >      char *initrd_filename;
> > >      const char *cpu_model;
> > >      AccelState *accelerator;
> > > +
> > > +    int sockets;
> > > +    int cores;
> > > +    int threads;
> > > +    int maxcpus;
> > > +    int cpus;
> > 
> > Hrm.. as the tests added in earlier patches highlight, essentially one
> > of these properties is redundant.  Is there a reason to include them
> > all, rather than to pick one to drop?
> 
> Well, IMO, only maxcpus could be dropped. I'd prefer not to though
> because it's a convenient state to have pre-calculated, and possibly
> error prone to leave to all users to re-calculate.

Sorry, to clarify.  I have no problem with having all 5 variables,
with one precalculated from the others.  What I'm not convinced is a
good idea is exposing all 5 as settable properties.

-- 
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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