Re: [Qemu-devel] [RFC PATCH v1 07/10] spapr: Represent boot CPUs as spapr-cpu-core devices

[David Gibson]

On Fri, Mar 04, 2016 at 12:24:18PM +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.
> 
> Also prevent topologies that have or can result in incomplete cores.
> 
> Signed-off-by: Bharata B Rao <address@hidden>
> ---
>  hw/ppc/spapr.c          | 85 
> ++++++++++++++++++++++++++++++++++++++++++-------
>  hw/ppc/spapr_cpu_core.c |  9 ++++++
>  include/hw/ppc/spapr.h  |  4 +++
>  3 files changed, 87 insertions(+), 11 deletions(-)
> 
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index e9d4abf..5acb612 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>
>  
> @@ -1614,8 +1615,11 @@ static void spapr_boot_set(void *opaque, const char 
> *boot_device,
>      machine->boot_order = g_strdup(boot_device);
>  }
>  
> -static void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu,
> -                           Error **errp)
> +/*
> + * TODO: Check if some of these can be moved to rtas_start_cpu() where
> + * a few other things required for hotplugged CPUs are being done.
> + */
> +void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp)
>  {
>      CPUPPCState *env = &cpu->env;
>  
> @@ -1643,7 +1647,6 @@ static void spapr_cpu_init(sPAPRMachineState *spapr, 
> PowerPCCPU *cpu,
>      }
>  
>      xics_cpu_setup(spapr->icp, cpu);
> -
>      qemu_register_reset(spapr_cpu_reset, cpu);
>  }
>  
> @@ -1720,6 +1723,28 @@ 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);
> +
> +    /*
> +     * Allow the link to be unset when the core is unplugged.
> +     */
> +    if (!val) {
> +        return;
> +    }
> +
> +    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 +1753,6 @@ 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 +1766,20 @@ 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;
> +
> +    if (smp_cpus % smp_threads) {
> +        error_report("smp_cpus (%u) must be multiple of threads (%u)",
> +                     smp_cpus, smp_threads);
> +        exit(1);
> +    }
> +
> +    if (max_cpus % smp_threads) {
> +        error_report("max_cpus (%u) must be multiple of threads (%u)",
> +                     max_cpus, smp_threads);
> +        exit(1);
> +    }
>  
>      msi_supported = true;
>  
> @@ -1800,13 +1838,37 @@ 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_new0(Object *, spapr_max_cores);
> +
> +    for (i = 0; i < spapr_max_cores; i++) {
> +        char name[32];
> +
> +        /*
> +         * Create links from machine objects to all possible cores.
> +         */
> +        snprintf(name, sizeof(name), "%s[%d]", SPAPR_MACHINE_CPU_CORE_PROP, 
> i);
> +        object_property_add_link(OBJECT(spapr), name, TYPE_SPAPR_CPU_CORE,
> +                                 (Object **)&spapr->cores[i],
> +                                 spapr_cpu_core_allow_set_link,
> +                                 OBJ_PROP_LINK_UNREF_ON_RELEASE,
> +                                 &error_fatal);

These links no longer make sense to me.  When it was a set of links to
the hotpluggable units on the machine, I could see why they might be
useful.  But now that they're links explicitly to *core* which are
only the hotpluggable units on certain platforms, I don't see why
these are useful.

Could we maybe not create the links for now, and add them in a later
patch if they do turn out to be useful for something?

> +        /*
> +         * Create cores and set link from machine object to core object for
> +         * boot time CPUs and realize them.
> +         */
> +        if (i < spapr_cores) {
> +            Object *core  = object_new(TYPE_SPAPR_CPU_CORE);
> +
> +            object_property_set_str(core, machine->cpu_model, "cpu_model",
> +                                    &error_fatal);
> +            object_property_set_int(core, smp_threads, "nr_threads",
> +                                    &error_fatal);
> +            object_property_set_str(core, name, CPU_CORE_SLOT_PROP,
> +                                    &error_fatal);
> +            object_property_set_bool(core, true, "realized", &error_fatal);
>          }
> -        spapr_cpu_init(spapr, cpu, &error_fatal);
>      }
>  
>      if (kvm_enabled()) {
> @@ -2259,7 +2321,8 @@ 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_SPAPR_CPU_CORE)) {
>          return HOTPLUG_HANDLER(machine);
>      }
>      return NULL;
> diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
> index 3f3440c..9ddf3ce 100644
> --- a/hw/ppc/spapr_cpu_core.c
> +++ b/hw/ppc/spapr_cpu_core.c
> @@ -17,11 +17,20 @@
>  static int spapr_cpu_core_realize_child(Object *child, void *opaque)
>  {
>      Error **errp = opaque;
> +    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
> +    CPUState *cs = CPU(child);
> +    PowerPCCPU *cpu = POWERPC_CPU(cs);
>  
>      object_property_set_bool(child, true, "realized", errp);
>      if (*errp) {
>          return 1;
>      }
> +
> +    spapr_cpu_init(spapr, cpu, errp);
> +    if (*errp) {
> +        return 1;
> +    }
> +

Doesn't this change belong in the previous patch, which created the
spapr core type?

>      return 0;
>  }
>  
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 098d85d..06e6cec 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 */
> @@ -585,6 +588,7 @@ void spapr_hotplug_req_add_by_count(sPAPRDRConnectorType 
> drc_type,
>                                         uint32_t count);
>  void spapr_hotplug_req_remove_by_count(sPAPRDRConnectorType drc_type,
>                                            uint32_t count);
> +void spapr_cpu_init(sPAPRMachineState *spapr, PowerPCCPU *cpu, Error **errp);
>  
>  /* rtas-configure-connector state */
>  struct sPAPRConfigureConnectorState {

-- 
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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