Re: [Qemu-devel] [RFC PATCH v0 3/6] spapr: Represent boot CPUs as spapr-cpu-core devices

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

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On Thu, Feb 25, 2016 at 09:52:39PM +0530, Bharata B Rao wrote:
> Initialize boot CPUs as spapr-cpu-core devices and create links from
> machine object to these core devices. These links can be considered
> as CPU slots in which core devices will get hot-plugged. spapr-cpu-core
> device's slot property indicates the slot where it is plugged. Information
> about all the CPU slots can be obtained by walking these links.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> ---
>  hw/ppc/spapr.c         | 65 +++++++++++++++++++++++++++++++++++++++++++-------
>  include/hw/ppc/spapr.h |  3 +++
>  2 files changed, 60 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index e214a34..1f0d232 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -64,6 +64,7 @@
>  
>  #include "hw/compat.h"
>  #include "qemu-common.h"
> +#include "hw/ppc/spapr_cpu_core.h"
>  
>  #include <libfdt.h>
>  
> @@ -1720,6 +1721,21 @@ static void spapr_validate_node_memory(MachineState *machine, Error **errp)
>      }
>  }
>  
> +/*
> + * Check to see if core is being hot-plugged into an already populated slot.
> + */
> +static void spapr_cpu_core_allow_set_link(Object *obj, const char *name,
> +                                          Object *val, Error **errp)
> +{
> +    Object *core = object_property_get_link(qdev_get_machine(), name, NULL);
> +
> +    if (core) {
> +        char *path = object_get_canonical_path(core);
> +        error_setg(errp, "Slot %s already populated with %s", name, path);
> +        g_free(path);
> +    }
> +}
> +
>  /* pSeries LPAR / sPAPR hardware init */
>  static void ppc_spapr_init(MachineState *machine)
>  {
> @@ -1728,7 +1744,6 @@ static void ppc_spapr_init(MachineState *machine)
>      const char *kernel_filename = machine->kernel_filename;
>      const char *kernel_cmdline = machine->kernel_cmdline;
>      const char *initrd_filename = machine->initrd_filename;
> -    PowerPCCPU *cpu;
>      PCIHostState *phb;
>      int i;
>      MemoryRegion *sysmem = get_system_memory();
> @@ -1742,6 +1757,8 @@ static void ppc_spapr_init(MachineState *machine)
>      long load_limit, fw_size;
>      bool kernel_le = false;
>      char *filename;
> +    int spapr_cores = smp_cpus / smp_threads;
> +    int spapr_max_cores = max_cpus / smp_threads;
>  
>      msi_supported = true;
>  
> @@ -1800,13 +1817,38 @@ static void ppc_spapr_init(MachineState *machine)
>      if (machine->cpu_model == NULL) {
>          machine->cpu_model = kvm_enabled() ? "host" : "POWER7";
>      }
> -    for (i = 0; i < smp_cpus; i++) {
> -        cpu = cpu_ppc_init(machine->cpu_model);
> -        if (cpu == NULL) {
> -            error_report("Unable to find PowerPC CPU definition");
> -            exit(1);
> +
> +    spapr->cores = g_malloc0(spapr_max_cores * sizeof(Object));
> +
> +    for (i = 0; i < spapr_max_cores; i++) {
> +        Object *spapr_cpu_core  = object_new(TYPE_SPAPR_CPU_CORE);

So.. if I understand correctly this will always construct maxcpus
threads at startup.  I's just that the ones beyond initial cpus won't
be realized.  Was that your intention?  I thought the plan was to only
construct the hotplugged cpus when they were hotplugged (in contrast
to my earlier proposal).

> +        char name[32];
> +
> +        object_property_set_str(spapr_cpu_core, machine->cpu_model, "cpu_model",
> +                                &error_fatal);
> +        object_property_set_int(spapr_cpu_core, smp_threads, "nr_threads",
> +                                &error_fatal);
> +        /*
> +         * Create links from machine objects to all possible cores.
> +         */
> +        snprintf(name, sizeof(name), "%s[%d]", SPAPR_MACHINE_CPU_CORE_PROP, i);

Why do SPAPR_MACHINE_CPU_CORE_PROP and SPAPR_CPU_CORE_SLOT_PROP get
#defines, but the other properties get bare strings?  I find the bare
strings are usually easier to follow.

> +        object_property_add_link(OBJECT(spapr), name, TYPE_SPAPR_CPU_CORE,
> +                                 (Object **)&spapr->cores[i],
> +                                 spapr_cpu_core_allow_set_link, 0,
> +                                 &error_fatal);
> +
> +        /*
> +         * Set the link from machine object to core object for all
> +         * boot time CPUs specified with -smp and realize them.
> +         * For rest of the hotpluggable cores this is happens from
> +         * the core hotplug/realization path.
> +         */
> +        if (i < spapr_cores) {
> +            object_property_set_str(spapr_cpu_core, name,
> +                                    SPAPR_CPU_CORE_SLOT_PROP, &error_fatal);
> +            object_property_set_bool(spapr_cpu_core, true, "realized",
> +                                     &error_fatal);
>          }
> -        spapr_cpu_init(spapr, cpu, &error_fatal);
>      }
>  
>      if (kvm_enabled()) {
> @@ -2209,6 +2251,7 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
>                                        DeviceState *dev, Error **errp)
>  {
>      sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(qdev_get_machine());
> +    sPAPRMachineState *ms = SPAPR_MACHINE(hotplug_dev);
>  
>      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
>          int node;
> @@ -2245,6 +2288,11 @@ static void spapr_machine_device_plug(HotplugHandler *hotplug_dev,
>          }
>  
>          spapr_memory_plug(hotplug_dev, dev, node, errp);
> +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
> +        CPUState *cs = CPU(dev);
> +        PowerPCCPU *cpu = POWERPC_CPU(cs);
> +
> +        spapr_cpu_init(ms, cpu, errp);

I tend to thin the spapr_cpu_init() should be done from the core's
create_threads() function, but I'm willing to be persuaded otherwise.

>      }
>  }
>  
> @@ -2259,7 +2307,8 @@ static void spapr_machine_device_unplug(HotplugHandler *hotplug_dev,
>  static HotplugHandler *spapr_get_hotpug_handler(MachineState *machine,
>                                               DeviceState *dev)
>  {
> -    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM) ||
> +        object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
>          return HOTPLUG_HANDLER(machine);
>      }
>      return NULL;
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 098d85d..20b3417 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -79,8 +79,11 @@ struct sPAPRMachineState {
>      /*< public >*/
>      char *kvm_type;
>      MemoryHotplugState hotplug_memory;
> +    Object *cores;
>  };
>  
> +#define SPAPR_MACHINE_CPU_CORE_PROP "core"
> +
>  #define H_SUCCESS         0
>  #define H_BUSY            1        /* Hardware busy -- retry later */
>  #define H_CLOSED          2        /* Resource closed */

-- 
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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