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/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  */
  53 static cpumask_var_t of_spin_mask;
  54
  55 /* Query where a cpu is now.  Return codes #defined in plpar_wrappers.h */
  56 int 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  */
  88 static 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
 125 static 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
 138 static 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
 156 static 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) */
 164 static void (*ic_cause_ipi)(int cpu) __ro_after_init;
 165
 166 /* Use msgsndp doorbells target is a sibling, else use interrupt controller */
 167 static 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
 175 static 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
 196 static __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
 243 static 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 */
 255 void __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 }