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hotplug-cpu.c

/*
 * pseries CPU Hotplug infrastructure.
 *
 * Split out from arch/powerpc/platforms/pseries/setup.c
 *  arch/powerpc/kernel/rtas.c, and arch/powerpc/platforms/pseries/smp.c
 *
 * Peter Bergner, IBM   March 2001.
 * Copyright (C) 2001 IBM.
 * Dave Engebretsen, Peter Bergner, and
 * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
 * Plus various changes from other IBM teams...
 *
 * Copyright (C) 2006 Michael Ellerman, IBM Corporation
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/cpu.h>
#include <asm/system.h>
#include <asm/prom.h>
#include <asm/rtas.h>
#include <asm/firmware.h>
#include <asm/machdep.h>
#include <asm/vdso_datapage.h>
#include <asm/pSeries_reconfig.h>
#include "xics.h"
#include "plpar_wrappers.h"

/* This version can't take the spinlock, because it never returns */
static struct rtas_args rtas_stop_self_args = {
      .token = RTAS_UNKNOWN_SERVICE,
      .nargs = 0,
      .nret = 1,
      .rets = &rtas_stop_self_args.args[0],
};

static void rtas_stop_self(void)
{
      struct rtas_args *args = &rtas_stop_self_args;

      local_irq_disable();

      BUG_ON(args->token == RTAS_UNKNOWN_SERVICE);

      printk("cpu %u (hwid %u) Ready to die...\n",
             smp_processor_id(), hard_smp_processor_id());
      enter_rtas(__pa(args));

      panic("Alas, I survived.\n");
}

static void pseries_mach_cpu_die(void)
{
      local_irq_disable();
      idle_task_exit();
      xics_teardown_cpu();
      unregister_slb_shadow(hard_smp_processor_id(), __pa(get_slb_shadow()));
      rtas_stop_self();
      /* Should never get here... */
      BUG();
      for(;;);
}

static int qcss_tok;    /* query-cpu-stopped-state token */

/* Get state of physical CPU.
 * Return codes:
 *    0     - The processor is in the RTAS stopped state
 *    1     - stop-self is in progress
 *    2     - The processor is not in the RTAS stopped state
 *    -1    - Hardware Error
 *    -2    - Hardware Busy, Try again later.
 */
static int query_cpu_stopped(unsigned int pcpu)
{
      int cpu_status, status;

      status = rtas_call(qcss_tok, 1, 2, &cpu_status, pcpu);
      if (status != 0) {
            printk(KERN_ERR
                   "RTAS query-cpu-stopped-state failed: %i\n", status);
            return status;
      }

      return cpu_status;
}

static int pseries_cpu_disable(void)
{
      int cpu = smp_processor_id();

      cpu_clear(cpu, cpu_online_map);
      vdso_data->processorCount--;

      /*fix boot_cpuid here*/
      if (cpu == boot_cpuid)
            boot_cpuid = any_online_cpu(cpu_online_map);

      /* FIXME: abstract this to not be platform specific later on */
      xics_migrate_irqs_away();
      return 0;
}

static void pseries_cpu_die(unsigned int cpu)
{
      int tries;
      int cpu_status;
      unsigned int pcpu = get_hard_smp_processor_id(cpu);

      for (tries = 0; tries < 25; tries++) {
            cpu_status = query_cpu_stopped(pcpu);
            if (cpu_status == 0 || cpu_status == -1)
                  break;
            msleep(200);
      }
      if (cpu_status != 0) {
            printk("Querying DEAD? cpu %i (%i) shows %i\n",
                   cpu, pcpu, cpu_status);
      }

      /* Isolation and deallocation are definatly done by
       * drslot_chrp_cpu.  If they were not they would be
       * done here.  Change isolate state to Isolate and
       * change allocation-state to Unusable.
       */
      paca[cpu].cpu_start = 0;
}

/*
 * Update cpu_present_map and paca(s) for a new cpu node.  The wrinkle
 * here is that a cpu device node may represent up to two logical cpus
 * in the SMT case.  We must honor the assumption in other code that
 * the logical ids for sibling SMT threads x and y are adjacent, such
 * that x^1 == y and y^1 == x.
 */
static int pseries_add_processor(struct device_node *np)
{
      unsigned int cpu;
      cpumask_t candidate_map, tmp = CPU_MASK_NONE;
      int err = -ENOSPC, len, nthreads, i;
      const u32 *intserv;

      intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
      if (!intserv)
            return 0;

      nthreads = len / sizeof(u32);
      for (i = 0; i < nthreads; i++)
            cpu_set(i, tmp);

      cpu_maps_update_begin();

      BUG_ON(!cpus_subset(cpu_present_map, cpu_possible_map));

      /* Get a bitmap of unoccupied slots. */
      cpus_xor(candidate_map, cpu_possible_map, cpu_present_map);
      if (cpus_empty(candidate_map)) {
            /* If we get here, it most likely means that NR_CPUS is
             * less than the partition's max processors setting.
             */
            printk(KERN_ERR "Cannot add cpu %s; this system configuration"
                   " supports %d logical cpus.\n", np->full_name,
                   cpus_weight(cpu_possible_map));
            goto out_unlock;
      }

      while (!cpus_empty(tmp))
            if (cpus_subset(tmp, candidate_map))
                  /* Found a range where we can insert the new cpu(s) */
                  break;
            else
                  cpus_shift_left(tmp, tmp, nthreads);

      if (cpus_empty(tmp)) {
            printk(KERN_ERR "Unable to find space in cpu_present_map for"
                   " processor %s with %d thread(s)\n", np->name,
                   nthreads);
            goto out_unlock;
      }

      for_each_cpu_mask(cpu, tmp) {
            BUG_ON(cpu_isset(cpu, cpu_present_map));
            cpu_set(cpu, cpu_present_map);
            set_hard_smp_processor_id(cpu, *intserv++);
      }
      err = 0;
out_unlock:
      cpu_maps_update_done();
      return err;
}

/*
 * Update the present map for a cpu node which is going away, and set
 * the hard id in the paca(s) to -1 to be consistent with boot time
 * convention for non-present cpus.
 */
static void pseries_remove_processor(struct device_node *np)
{
      unsigned int cpu;
      int len, nthreads, i;
      const u32 *intserv;

      intserv = of_get_property(np, "ibm,ppc-interrupt-server#s", &len);
      if (!intserv)
            return;

      nthreads = len / sizeof(u32);

      cpu_maps_update_begin();
      for (i = 0; i < nthreads; i++) {
            for_each_present_cpu(cpu) {
                  if (get_hard_smp_processor_id(cpu) != intserv[i])
                        continue;
                  BUG_ON(cpu_online(cpu));
                  cpu_clear(cpu, cpu_present_map);
                  set_hard_smp_processor_id(cpu, -1);
                  break;
            }
            if (cpu == NR_CPUS)
                  printk(KERN_WARNING "Could not find cpu to remove "
                         "with physical id 0x%x\n", intserv[i]);
      }
      cpu_maps_update_done();
}

static int pseries_smp_notifier(struct notifier_block *nb,
                        unsigned long action, void *node)
{
      int err = NOTIFY_OK;

      switch (action) {
      case PSERIES_RECONFIG_ADD:
            if (pseries_add_processor(node))
                  err = NOTIFY_BAD;
            break;
      case PSERIES_RECONFIG_REMOVE:
            pseries_remove_processor(node);
            break;
      default:
            err = NOTIFY_DONE;
            break;
      }
      return err;
}

static struct notifier_block pseries_smp_nb = {
      .notifier_call = pseries_smp_notifier,
};

static int __init pseries_cpu_hotplug_init(void)
{
      struct device_node *np;
      const char *typep;

      for_each_node_by_name(np, "interrupt-controller") {
            typep = of_get_property(np, "compatible", NULL);
            if (strstr(typep, "open-pic")) {
                  of_node_put(np);

                  printk(KERN_INFO "CPU Hotplug not supported on "
                        "systems using MPIC\n");
                  return 0;
            }
      }

      rtas_stop_self_args.token = rtas_token("stop-self");
      qcss_tok = rtas_token("query-cpu-stopped-state");

      if (rtas_stop_self_args.token == RTAS_UNKNOWN_SERVICE ||
                  qcss_tok == RTAS_UNKNOWN_SERVICE) {
            printk(KERN_INFO "CPU Hotplug not supported by firmware "
                        "- disabling.\n");
            return 0;
      }

      ppc_md.cpu_die = pseries_mach_cpu_die;
      smp_ops->cpu_disable = pseries_cpu_disable;
      smp_ops->cpu_die = pseries_cpu_die;

      /* Processors can be added/removed only on LPAR */
      if (firmware_has_feature(FW_FEATURE_LPAR))
            pSeries_reconfig_notifier_register(&pseries_smp_nb);

      return 0;
}
arch_initcall(pseries_cpu_hotplug_init);

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