arch/powerpc/platforms/pseries/smp.c

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