linux/arch/powerpc/platforms/pseries/smp.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * SMP support for pSeries machines.
   4 *
   5 * Dave Engebretsen, Peter Bergner, and
   6 * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
   7 *
   8 * Plus various changes from other IBM teams...
   9 */
  10
  11
  12#include <linux/kernel.h>
  13#include <linux/sched.h>
  14#include <linux/smp.h>
  15#include <linux/interrupt.h>
  16#include <linux/delay.h>
  17#include <linux/init.h>
  18#include <linux/spinlock.h>
  19#include <linux/cache.h>
  20#include <linux/err.h>
  21#include <linux/device.h>
  22#include <linux/cpu.h>
  23#include <linux/pgtable.h>
  24
  25#include <asm/ptrace.h>
  26#include <linux/atomic.h>
  27#include <asm/irq.h>
  28#include <asm/page.h>
  29#include <asm/io.h>
  30#include <asm/prom.h>
  31#include <asm/smp.h>
  32#include <asm/paca.h>
  33#include <asm/machdep.h>
  34#include <asm/cputable.h>
  35#include <asm/firmware.h>
  36#include <asm/rtas.h>
  37#include <asm/vdso_datapage.h>
  38#include <asm/cputhreads.h>
  39#include <asm/xics.h>
  40#include <asm/xive.h>
  41#include <asm/dbell.h>
  42#include <asm/plpar_wrappers.h>
  43#include <asm/code-patching.h>
  44#include <asm/svm.h>
  45#include <asm/kvm_guest.h>
  46
  47#include "pseries.h"
  48
  49/*
  50 * The Primary thread of each non-boot processor was started from the OF client
  51 * interface by prom_hold_cpus and is spinning on secondary_hold_spinloop.
  52 */
  53static cpumask_var_t of_spin_mask;
  54
  55/* Query where a cpu is now.  Return codes #defined in plpar_wrappers.h */
  56int smp_query_cpu_stopped(unsigned int pcpu)
  57{
  58        int cpu_status, status;
  59        int qcss_tok = rtas_token("query-cpu-stopped-state");
  60
  61        if (qcss_tok == RTAS_UNKNOWN_SERVICE) {
  62                printk_once(KERN_INFO
  63                        "Firmware doesn't support query-cpu-stopped-state\n");
  64                return QCSS_HARDWARE_ERROR;
  65        }
  66
  67        status = rtas_call(qcss_tok, 1, 2, &cpu_status, pcpu);
  68        if (status != 0) {
  69                printk(KERN_ERR
  70                       "RTAS query-cpu-stopped-state failed: %i\n", status);
  71                return status;
  72        }
  73
  74        return cpu_status;
  75}
  76
  77/**
  78 * smp_startup_cpu() - start the given cpu
  79 *
  80 * At boot time, there is nothing to do for primary threads which were
  81 * started from Open Firmware.  For anything else, call RTAS with the
  82 * appropriate start location.
  83 *
  84 * Returns:
  85 *      0       - failure
  86 *      1       - success
  87 */
  88static inline int smp_startup_cpu(unsigned int lcpu)
  89{
  90        int status;
  91        unsigned long start_here =
  92                        __pa(ppc_function_entry(generic_secondary_smp_init));
  93        unsigned int pcpu;
  94        int start_cpu;
  95
  96        if (cpumask_test_cpu(lcpu, of_spin_mask))
  97                /* Already started by OF and sitting in spin loop */
  98                return 1;
  99
 100        pcpu = get_hard_smp_processor_id(lcpu);
 101
 102        /* Check to see if the CPU out of FW already for kexec */
 103        if (smp_query_cpu_stopped(pcpu) == QCSS_NOT_STOPPED){
 104                cpumask_set_cpu(lcpu, of_spin_mask);
 105                return 1;
 106        }
 107
 108        /* 
 109         * If the RTAS start-cpu token does not exist then presume the
 110         * cpu is already spinning.
 111         */
 112        start_cpu = rtas_token("start-cpu");
 113        if (start_cpu == RTAS_UNKNOWN_SERVICE)
 114                return 1;
 115
 116        status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, pcpu);
 117        if (status != 0) {
 118                printk(KERN_ERR "start-cpu failed: %i\n", status);
 119                return 0;
 120        }
 121
 122        return 1;
 123}
 124
 125static void smp_setup_cpu(int cpu)
 126{
 127        if (xive_enabled())
 128                xive_smp_setup_cpu();
 129        else if (cpu != boot_cpuid)
 130                xics_setup_cpu();
 131
 132        if (firmware_has_feature(FW_FEATURE_SPLPAR))
 133                vpa_init(cpu);
 134
 135        cpumask_clear_cpu(cpu, of_spin_mask);
 136}
 137
 138static int smp_pSeries_kick_cpu(int nr)
 139{
 140        if (nr < 0 || nr >= nr_cpu_ids)
 141                return -EINVAL;
 142
 143        if (!smp_startup_cpu(nr))
 144                return -ENOENT;
 145
 146        /*
 147         * The processor is currently spinning, waiting for the
 148         * cpu_start field to become non-zero After we set cpu_start,
 149         * the processor will continue on to secondary_start
 150         */
 151        paca_ptrs[nr]->cpu_start = 1;
 152
 153        return 0;
 154}
 155
 156static int pseries_smp_prepare_cpu(int cpu)
 157{
 158        if (xive_enabled())
 159                return xive_smp_prepare_cpu(cpu);
 160        return 0;
 161}
 162
 163/* Cause IPI as setup by the interrupt controller (xics or xive) */
 164static void (*ic_cause_ipi)(int cpu) __ro_after_init;
 165
 166/* Use msgsndp doorbells target is a sibling, else use interrupt controller */
 167static void dbell_or_ic_cause_ipi(int cpu)
 168{
 169        if (doorbell_try_core_ipi(cpu))
 170                return;
 171
 172        ic_cause_ipi(cpu);
 173}
 174
 175static int pseries_cause_nmi_ipi(int cpu)
 176{
 177        int hwcpu;
 178
 179        if (cpu == NMI_IPI_ALL_OTHERS) {
 180                hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS;
 181        } else {
 182                if (cpu < 0) {
 183                        WARN_ONCE(true, "incorrect cpu parameter %d", cpu);
 184                        return 0;
 185                }
 186
 187                hwcpu = get_hard_smp_processor_id(cpu);
 188        }
 189
 190        if (plpar_signal_sys_reset(hwcpu) == H_SUCCESS)
 191                return 1;
 192
 193        return 0;
 194}
 195
 196static __init void pSeries_smp_probe(void)
 197{
 198        if (xive_enabled())
 199                xive_smp_probe();
 200        else
 201                xics_smp_probe();
 202
 203        /* No doorbell facility, must use the interrupt controller for IPIs */
 204        if (!cpu_has_feature(CPU_FTR_DBELL))
 205                return;
 206
 207        /* Doorbells can only be used for IPIs between SMT siblings */
 208        if (!cpu_has_feature(CPU_FTR_SMT))
 209                return;
 210
 211        check_kvm_guest();
 212
 213        if (is_kvm_guest()) {
 214                /*
 215                 * KVM emulates doorbells by disabling FSCR[MSGP] so msgsndp
 216                 * faults to the hypervisor which then reads the instruction
 217                 * from guest memory, which tends to be slower than using XIVE.
 218                 */
 219                if (xive_enabled())
 220                        return;
 221
 222                /*
 223                 * XICS hcalls aren't as fast, so we can use msgsndp (which
 224                 * also helps exercise KVM emulation), however KVM can't
 225                 * emulate secure guests because it can't read the instruction
 226                 * out of their memory.
 227                 */
 228                if (is_secure_guest())
 229                        return;
 230        }
 231
 232        /*
 233         * Under PowerVM, FSCR[MSGP] is enabled as guest vCPU siblings are
 234         * gang scheduled on the same physical core, so doorbells are always
 235         * faster than the interrupt controller, and they can be used by
 236         * secure guests.
 237         */
 238
 239        ic_cause_ipi = smp_ops->cause_ipi;
 240        smp_ops->cause_ipi = dbell_or_ic_cause_ipi;
 241}
 242
 243static struct smp_ops_t pseries_smp_ops = {
 244        .message_pass   = NULL, /* Use smp_muxed_ipi_message_pass */
 245        .cause_ipi      = NULL, /* Filled at runtime by pSeries_smp_probe() */
 246        .cause_nmi_ipi  = pseries_cause_nmi_ipi,
 247        .probe          = pSeries_smp_probe,
 248        .prepare_cpu    = pseries_smp_prepare_cpu,
 249        .kick_cpu       = smp_pSeries_kick_cpu,
 250        .setup_cpu      = smp_setup_cpu,
 251        .cpu_bootable   = smp_generic_cpu_bootable,
 252};
 253
 254/* This is called very early */
 255void __init smp_init_pseries(void)
 256{
 257        int i;
 258
 259        pr_debug(" -> smp_init_pSeries()\n");
 260        smp_ops = &pseries_smp_ops;
 261
 262        alloc_bootmem_cpumask_var(&of_spin_mask);
 263
 264        /*
 265         * Mark threads which are still spinning in hold loops
 266         *
 267         * We know prom_init will not have started them if RTAS supports
 268         * query-cpu-stopped-state.
 269         */
 270        if (rtas_token("query-cpu-stopped-state") == RTAS_UNKNOWN_SERVICE) {
 271                if (cpu_has_feature(CPU_FTR_SMT)) {
 272                        for_each_present_cpu(i) {
 273                                if (cpu_thread_in_core(i) == 0)
 274                                        cpumask_set_cpu(i, of_spin_mask);
 275                        }
 276                } else
 277                        cpumask_copy(of_spin_mask, cpu_present_mask);
 278
 279                cpumask_clear_cpu(boot_cpuid, of_spin_mask);
 280        }
 281
 282        /* Non-lpar has additional take/give timebase */
 283        if (rtas_token("freeze-time-base") != RTAS_UNKNOWN_SERVICE) {
 284                smp_ops->give_timebase = rtas_give_timebase;
 285                smp_ops->take_timebase = rtas_take_timebase;
 286        }
 287
 288        pr_debug(" <- smp_init_pSeries()\n");
 289}
 290