hotplug-cpu.c

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/*
 * 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/interrupt.h>
#include <linux/delay.h>
#include <linux/sched.h>    /* for idle_task_exit */
#include <linux/cpu.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 <asm/xics.h>
#include "plpar_wrappers.h"
#include "offline_states.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 DEFINE_PER_CPU(enum cpu_state_vals, preferred_offline_state) =
                            CPU_STATE_OFFLINE;
static DEFINE_PER_CPU(enum cpu_state_vals, current_state) = CPU_STATE_OFFLINE;

static enum cpu_state_vals default_offline_state = CPU_STATE_OFFLINE;

static int cede_offline_enabled __read_mostly = 1;

/*
 * Enable/disable cede_offline when available.
 */
static int __init setup_cede_offline(char *str)
{
    if (!strcmp(str, "off"))
        cede_offline_enabled = 0;
    else if (!strcmp(str, "on"))
        cede_offline_enabled = 1;
    else
        return 0;
    return 1;
}

__setup("cede_offline=", setup_cede_offline);

enum cpu_state_vals get_cpu_current_state(int cpu)
{
    return per_cpu(current_state, cpu);
}

void set_cpu_current_state(int cpu, enum cpu_state_vals state)
{
    per_cpu(current_state, cpu) = state;
}

enum cpu_state_vals get_preferred_offline_state(int cpu)
{
    return per_cpu(preferred_offline_state, cpu);
}

void set_preferred_offline_state(int cpu, enum cpu_state_vals state)
{
    per_cpu(preferred_offline_state, cpu) = state;
}

void set_default_offline_state(int cpu)
{
    per_cpu(preferred_offline_state, cpu) = default_offline_state;
}

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)
{
    unsigned int cpu = smp_processor_id();
    unsigned int hwcpu = hard_smp_processor_id();
    u8 cede_latency_hint = 0;

    local_irq_disable();
    idle_task_exit();
    xics_teardown_cpu();

    if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
        set_cpu_current_state(cpu, CPU_STATE_INACTIVE);
        if (ppc_md.suspend_disable_cpu)
            ppc_md.suspend_disable_cpu();

        cede_latency_hint = 2;

        get_lppaca()->idle = 1;
        if (!get_lppaca()->shared_proc)
            get_lppaca()->donate_dedicated_cpu = 1;

        while (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
            extended_cede_processor(cede_latency_hint);
        }

        if (!get_lppaca()->shared_proc)
            get_lppaca()->donate_dedicated_cpu = 0;
        get_lppaca()->idle = 0;

        if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) {
            unregister_slb_shadow(hwcpu);

            /*
             * Call to start_secondary_resume() will not return.
             * Kernel stack will be reset and start_secondary()
             * will be called to continue the online operation.
             */
            start_secondary_resume();
        }
    }

    /* Requested state is CPU_STATE_OFFLINE at this point */
    WARN_ON(get_preferred_offline_state(cpu) != CPU_STATE_OFFLINE);

    set_cpu_current_state(cpu, CPU_STATE_OFFLINE);
    unregister_slb_shadow(hwcpu);
    rtas_stop_self();

    /* Should never get here... */
    BUG();
    for(;;);
}

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

    set_cpu_online(cpu, false);
    vdso_data->processorCount--;

    /*fix boot_cpuid here*/
    if (cpu == boot_cpuid)
        boot_cpuid = cpumask_any(cpu_online_mask);

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

/*
 * pseries_cpu_die: Wait for the cpu to die.
 * @cpu: logical processor id of the CPU whose death we're awaiting.
 *
 * This function is called from the context of the thread which is performing
 * the cpu-offline. Here we wait for long enough to allow the cpu in question
 * to self-destroy so that the cpu-offline thread can send the CPU_DEAD
 * notifications.
 *
 * OTOH, pseries_mach_cpu_die() is called by the @cpu when it wants to
 * self-destruct.
 */
static void pseries_cpu_die(unsigned int cpu)
{
    int tries;
    int cpu_status = 1;
    unsigned int pcpu = get_hard_smp_processor_id(cpu);

    if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
        cpu_status = 1;
        for (tries = 0; tries < 5000; tries++) {
            if (get_cpu_current_state(cpu) == CPU_STATE_INACTIVE) {
                cpu_status = 0;
                break;
            }
            msleep(1);
        }
    } else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {

        for (tries = 0; tries < 25; tries++) {
            cpu_status = smp_query_cpu_stopped(pcpu);
            if (cpu_status == QCSS_STOPPED ||
                cpu_status == QCSS_HARDWARE_ERROR)
                break;
            cpu_relax();
        }
    }

    if (cpu_status != 0) {
        printk("Querying DEAD? cpu %i (%i) shows %i\n",
               cpu, pcpu, cpu_status);
    }

    /* Isolation and deallocation are definitely 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_mask 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_var_t candidate_mask, tmp;
    int err = -ENOSPC, len, nthreads, i;
    const u32 *intserv;

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

    zalloc_cpumask_var(&candidate_mask, GFP_KERNEL);
    zalloc_cpumask_var(&tmp, GFP_KERNEL);

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

    cpu_maps_update_begin();

    BUG_ON(!cpumask_subset(cpu_present_mask, cpu_possible_mask));

    /* Get a bitmap of unoccupied slots. */
    cpumask_xor(candidate_mask, cpu_possible_mask, cpu_present_mask);
    if (cpumask_empty(candidate_mask)) {
        /* 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,
               cpumask_weight(cpu_possible_mask));
        goto out_unlock;
    }

    while (!cpumask_empty(tmp))
        if (cpumask_subset(tmp, candidate_mask))
            /* Found a range where we can insert the new cpu(s) */
            break;
        else
            cpumask_shift_left(tmp, tmp, nthreads);

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

    for_each_cpu(cpu, tmp) {
        BUG_ON(cpu_present(cpu));
        set_cpu_present(cpu, true);
        set_hard_smp_processor_id(cpu, *intserv++);
    }
    err = 0;
out_unlock:
    cpu_maps_update_done();
    free_cpumask_var(candidate_mask);
    free_cpumask_var(tmp);
    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));
            set_cpu_present(cpu, false);
            set_hard_smp_processor_id(cpu, -1);
            break;
        }
        if (cpu >= nr_cpu_ids)
            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 = 0;

    switch (action) {
    case PSERIES_RECONFIG_ADD:
        err = pseries_add_processor(node);
        break;
    case PSERIES_RECONFIG_REMOVE:
        pseries_remove_processor(node);
        break;
    }
    return notifier_from_errno(err);
}

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

#define MAX_CEDE_LATENCY_LEVELS     4
#define CEDE_LATENCY_PARAM_LENGTH   10
#define CEDE_LATENCY_PARAM_MAX_LENGTH   \
    (MAX_CEDE_LATENCY_LEVELS * CEDE_LATENCY_PARAM_LENGTH * sizeof(char))
#define CEDE_LATENCY_TOKEN      45

static char cede_parameters[CEDE_LATENCY_PARAM_MAX_LENGTH];

static int parse_cede_parameters(void)
{
    memset(cede_parameters, 0, CEDE_LATENCY_PARAM_MAX_LENGTH);
    return rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
             NULL,
             CEDE_LATENCY_TOKEN,
             __pa(cede_parameters),
             CEDE_LATENCY_PARAM_MAX_LENGTH);
}

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

    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);
        cpu_maps_update_begin();
        if (cede_offline_enabled && parse_cede_parameters() == 0) {
            default_offline_state = CPU_STATE_INACTIVE;
            for_each_online_cpu(cpu)
                set_default_offline_state(cpu);
        }
        cpu_maps_update_done();
    }

    return 0;
}
arch_initcall(pseries_cpu_hotplug_init);