Re: [Qemu-devel] [RFC PATCH v0 4/8] spapr: Introduce CPU core device

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

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On Mon, Feb 22, 2016 at 07:44:40AM +0100, Andreas Färber wrote:
> Am 22.02.2016 um 06:01 schrieb Bharata B Rao:
> > sPAPR CPU core device is a container of CPU thread devices. CPU hotplug is
> > performed in the granularity of CPU core device by setting the "realized"
> > property of this device to "true". When hotplugged, CPU core creates CPU
> > thread devices.
> > 
> > TODO: Right now allows for only homogeneous configurations as we depend
> > on global smp_threads and machine->cpu_model.
> > 
> > Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> > ---
> >  hw/ppc/Makefile.objs               |  1 +
> >  hw/ppc/spapr_cpu_package.c         | 50 ++++++++++++++++++++++++++++++++++++++
> >  include/hw/ppc/spapr_cpu_package.h | 26 ++++++++++++++++++++
> >  3 files changed, 77 insertions(+)
> >  create mode 100644 hw/ppc/spapr_cpu_package.c
> >  create mode 100644 include/hw/ppc/spapr_cpu_package.h
> > 
> > diff --git a/hw/ppc/Makefile.objs b/hw/ppc/Makefile.objs
> > index c1ffc77..3000982 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_package.o
> >  ifeq ($(CONFIG_PCI)$(CONFIG_PSERIES)$(CONFIG_LINUX), yyy)
> >  obj-y += spapr_pci_vfio.o
> >  endif
> > diff --git a/hw/ppc/spapr_cpu_package.c b/hw/ppc/spapr_cpu_package.c
> > new file mode 100644
> > index 0000000..3120a16
> > --- /dev/null
> > +++ b/hw/ppc/spapr_cpu_package.c
> > @@ -0,0 +1,50 @@
> > +/*
> > + * sPAPR CPU package 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/package.h"
> > +#include "hw/ppc/spapr_cpu_package.h"
> > +#include "hw/boards.h"
> > +#include <sysemu/cpus.h>
> > +#include "qemu/error-report.h"
> > +
> > +static void spapr_cpu_package_instance_init(Object *obj)
> > +{
> > +    int i;
> > +    CPUState *cpu;
> > +    MachineState *machine = MACHINE(qdev_get_machine());
> > +    sPAPRCPUPackage *package = SPAPR_CPU_PACKAGE(obj);
> > +
> > +    /* Create as many CPU threads as specified in the topology */
> > +    for (i = 0; i < smp_threads; i++) {
> > +        cpu = cpu_generic_init(machine->cpu_type, machine->cpu_model);
> 
> No, no, no. This is horribly violating QOM design.

Ok.. why?  There does not, to me, seem to be any remotely easily
discoverable means of finding out what QOM design principles are.

It also would have been nice if you weighed in on my RFC this code is
based on.

> Please compare the x86 RFC.

Where do I find this?

From all I could tell there just seemed to be a lot of spinning of
wheels on the cpu hotplug stuff, which is why I made the cpu-packages
proposal to try and move things forward.

There's been a lot of "don't do it like that" but precious little
"here's how you _should_ do it" that actually addresses the needs of
the various platforms.

-- 
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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