arch/x86/kernel/smp.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      Intel SMP support routines.
   4  *
   5  *      (c) 1995 Alan Cox, Building #3 <alan@lxorguk.ukuu.org.uk>
   6  *      (c) 1998-99, 2000, 2009 Ingo Molnar <mingo@redhat.com>
   7  *      (c) 2002,2003 Andi Kleen, SuSE Labs.
   8  *
   9  *      i386 and x86_64 integration by Glauber Costa <gcosta@redhat.com>
  10  */
  11
  12 #include <linux/init.h>
  13
  14 #include <linux/mm.h>
  15 #include <linux/delay.h>
  16 #include <linux/spinlock.h>
  17 #include <linux/export.h>
  18 #include <linux/kernel_stat.h>
  19 #include <linux/mc146818rtc.h>
  20 #include <linux/cache.h>
  21 #include <linux/interrupt.h>
  22 #include <linux/cpu.h>
  23 #include <linux/gfp.h>
  24
  25 #include <asm/mtrr.h>
  26 #include <asm/tlbflush.h>
  27 #include <asm/mmu_context.h>
  28 #include <asm/proto.h>
  29 #include <asm/apic.h>
  30 #include <asm/nmi.h>
  31 #include <asm/mce.h>
  32 #include <asm/trace/irq_vectors.h>
  33 #include <asm/kexec.h>
  34 #include <asm/virtext.h>
  35
  36 /*
  37  *      Some notes on x86 processor bugs affecting SMP operation:
  38  *
  39  *      Pentium, Pentium Pro, II, III (and all CPUs) have bugs.
  40  *      The Linux implications for SMP are handled as follows:
  41  *
  42  *      Pentium III / [Xeon]
  43  *              None of the E1AP-E3AP errata are visible to the user.
  44  *
  45  *      E1AP.   see PII A1AP
  46  *      E2AP.   see PII A2AP
  47  *      E3AP.   see PII A3AP
  48  *
  49  *      Pentium II / [Xeon]
  50  *              None of the A1AP-A3AP errata are visible to the user.
  51  *
  52  *      A1AP.   see PPro 1AP
  53  *      A2AP.   see PPro 2AP
  54  *      A3AP.   see PPro 7AP
  55  *
  56  *      Pentium Pro
  57  *              None of 1AP-9AP errata are visible to the normal user,
  58  *      except occasional delivery of 'spurious interrupt' as trap #15.
  59  *      This is very rare and a non-problem.
  60  *
  61  *      1AP.    Linux maps APIC as non-cacheable
  62  *      2AP.    worked around in hardware
  63  *      3AP.    fixed in C0 and above steppings microcode update.
  64  *              Linux does not use excessive STARTUP_IPIs.
  65  *      4AP.    worked around in hardware
  66  *      5AP.    symmetric IO mode (normal Linux operation) not affected.
  67  *              'noapic' mode has vector 0xf filled out properly.
  68  *      6AP.    'noapic' mode might be affected - fixed in later steppings
  69  *      7AP.    We do not assume writes to the LVT deassering IRQs
  70  *      8AP.    We do not enable low power mode (deep sleep) during MP bootup
  71  *      9AP.    We do not use mixed mode
  72  *
  73  *      Pentium
  74  *              There is a marginal case where REP MOVS on 100MHz SMP
  75  *      machines with B stepping processors can fail. XXX should provide
  76  *      an L1cache=Writethrough or L1cache=off option.
  77  *
  78  *              B stepping CPUs may hang. There are hardware work arounds
  79  *      for this. We warn about it in case your board doesn't have the work
  80  *      arounds. Basically that's so I can tell anyone with a B stepping
  81  *      CPU and SMP problems "tough".
  82  *
  83  *      Specific items [From Pentium Processor Specification Update]
  84  *
  85  *      1AP.    Linux doesn't use remote read
  86  *      2AP.    Linux doesn't trust APIC errors
  87  *      3AP.    We work around this
  88  *      4AP.    Linux never generated 3 interrupts of the same priority
  89  *              to cause a lost local interrupt.
  90  *      5AP.    Remote read is never used
  91  *      6AP.    not affected - worked around in hardware
  92  *      7AP.    not affected - worked around in hardware
  93  *      8AP.    worked around in hardware - we get explicit CS errors if not
  94  *      9AP.    only 'noapic' mode affected. Might generate spurious
  95  *              interrupts, we log only the first one and count the
  96  *              rest silently.
  97  *      10AP.   not affected - worked around in hardware
  98  *      11AP.   Linux reads the APIC between writes to avoid this, as per
  99  *              the documentation. Make sure you preserve this as it affects
 100  *              the C stepping chips too.
 101  *      12AP.   not affected - worked around in hardware
 102  *      13AP.   not affected - worked around in hardware
 103  *      14AP.   we always deassert INIT during bootup
 104  *      15AP.   not affected - worked around in hardware
 105  *      16AP.   not affected - worked around in hardware
 106  *      17AP.   not affected - worked around in hardware
 107  *      18AP.   not affected - worked around in hardware
 108  *      19AP.   not affected - worked around in BIOS
 109  *
 110  *      If this sounds worrying believe me these bugs are either ___RARE___,
 111  *      or are signal timing bugs worked around in hardware and there's
 112  *      about nothing of note with C stepping upwards.
 113  */
 114
 115 static atomic_t stopping_cpu = ATOMIC_INIT(-1);
 116 static bool smp_no_nmi_ipi = false;
 117
 118 /*
 119  * this function sends a 'reschedule' IPI to another CPU.
 120  * it goes straight through and wastes no time serializing
 121  * anything. Worst case is that we lose a reschedule ...
 122  */
 123 static void native_smp_send_reschedule(int cpu)
 124 {
 125         if (unlikely(cpu_is_offline(cpu))) {
 126                 WARN(1, "sched: Unexpected reschedule of offline CPU#%d!\n", cpu);
 127                 return;
 128         }
 129         apic->send_IPI(cpu, RESCHEDULE_VECTOR);
 130 }
 131
 132 void native_send_call_func_single_ipi(int cpu)
 133 {
 134         apic->send_IPI(cpu, CALL_FUNCTION_SINGLE_VECTOR);
 135 }
 136
 137 void native_send_call_func_ipi(const struct cpumask *mask)
 138 {
 139         cpumask_var_t allbutself;
 140
 141         if (!alloc_cpumask_var(&allbutself, GFP_ATOMIC)) {
 142                 apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR);
 143                 return;
 144         }
 145
 146         cpumask_copy(allbutself, cpu_online_mask);
 147         __cpumask_clear_cpu(smp_processor_id(), allbutself);
 148
 149         if (cpumask_equal(mask, allbutself) &&
 150             cpumask_equal(cpu_online_mask, cpu_callout_mask))
 151                 apic->send_IPI_allbutself(CALL_FUNCTION_VECTOR);
 152         else
 153                 apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR);
 154
 155         free_cpumask_var(allbutself);
 156 }
 157
 158 static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
 159 {
 160         /* We are registered on stopping cpu too, avoid spurious NMI */
 161         if (raw_smp_processor_id() == atomic_read(&stopping_cpu))
 162                 return NMI_HANDLED;
 163
 164         cpu_emergency_vmxoff();
 165         stop_this_cpu(NULL);
 166
 167         return NMI_HANDLED;
 168 }
 169
 170 /*
 171  * this function calls the 'stop' function on all other CPUs in the system.
 172  */
 173
 174 asmlinkage __visible void smp_reboot_interrupt(void)
 175 {
 176         ipi_entering_ack_irq();
 177         cpu_emergency_vmxoff();
 178         stop_this_cpu(NULL);
 179         irq_exit();
 180 }
 181
 182 static void native_stop_other_cpus(int wait)
 183 {
 184         unsigned long flags;
 185         unsigned long timeout;
 186
 187         if (reboot_force)
 188                 return;
 189
 190         /*
 191          * Use an own vector here because smp_call_function
 192          * does lots of things not suitable in a panic situation.
 193          */
 194
 195         /*
 196          * We start by using the REBOOT_VECTOR irq.
 197          * The irq is treated as a sync point to allow critical
 198          * regions of code on other cpus to release their spin locks
 199          * and re-enable irqs.  Jumping straight to an NMI might
 200          * accidentally cause deadlocks with further shutdown/panic
 201          * code.  By syncing, we give the cpus up to one second to
 202          * finish their work before we force them off with the NMI.
 203          */
 204         if (num_online_cpus() > 1) {
 205                 /* did someone beat us here? */
 206                 if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1)
 207                         return;
 208
 209                 /* sync above data before sending IRQ */
 210                 wmb();
 211
 212                 apic->send_IPI_allbutself(REBOOT_VECTOR);
 213
 214                 /*
 215                  * Don't wait longer than a second if the caller
 216                  * didn't ask us to wait.
 217                  */
 218                 timeout = USEC_PER_SEC;
 219                 while (num_online_cpus() > 1 && (wait || timeout--))
 220                         udelay(1);
 221         }
 222
 223         /* if the REBOOT_VECTOR didn't work, try with the NMI */
 224         if ((num_online_cpus() > 1) && (!smp_no_nmi_ipi))  {
 225                 if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
 226                                          NMI_FLAG_FIRST, "smp_stop"))
 227                         /* Note: we ignore failures here */
 228                         /* Hope the REBOOT_IRQ is good enough */
 229                         goto finish;
 230
 231                 /* sync above data before sending IRQ */
 232                 wmb();
 233
 234                 pr_emerg("Shutting down cpus with NMI\n");
 235
 236                 apic->send_IPI_allbutself(NMI_VECTOR);
 237
 238                 /*
 239                  * Don't wait longer than a 10 ms if the caller
 240                  * didn't ask us to wait.
 241                  */
 242                 timeout = USEC_PER_MSEC * 10;
 243                 while (num_online_cpus() > 1 && (wait || timeout--))
 244                         udelay(1);
 245         }
 246
 247 finish:
 248         local_irq_save(flags);
 249         disable_local_APIC();
 250         mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
 251         local_irq_restore(flags);
 252 }
 253
 254 /*
 255  * Reschedule call back. KVM uses this interrupt to force a cpu out of
 256  * guest mode
 257  */
 258 __visible void __irq_entry smp_reschedule_interrupt(struct pt_regs *regs)
 259 {
 260         ack_APIC_irq();
 261         inc_irq_stat(irq_resched_count);
 262         kvm_set_cpu_l1tf_flush_l1d();
 263
 264         if (trace_resched_ipi_enabled()) {
 265                 /*
 266                  * scheduler_ipi() might call irq_enter() as well, but
 267                  * nested calls are fine.
 268                  */
 269                 irq_enter();
 270                 trace_reschedule_entry(RESCHEDULE_VECTOR);
 271                 scheduler_ipi();
 272                 trace_reschedule_exit(RESCHEDULE_VECTOR);
 273                 irq_exit();
 274                 return;
 275         }
 276         scheduler_ipi();
 277 }
 278
 279 __visible void __irq_entry smp_call_function_interrupt(struct pt_regs *regs)
 280 {
 281         ipi_entering_ack_irq();
 282         trace_call_function_entry(CALL_FUNCTION_VECTOR);
 283         inc_irq_stat(irq_call_count);
 284         generic_smp_call_function_interrupt();
 285         trace_call_function_exit(CALL_FUNCTION_VECTOR);
 286         exiting_irq();
 287 }
 288
 289 __visible void __irq_entry smp_call_function_single_interrupt(struct pt_regs *r)
 290 {
 291         ipi_entering_ack_irq();
 292         trace_call_function_single_entry(CALL_FUNCTION_SINGLE_VECTOR);
 293         inc_irq_stat(irq_call_count);
 294         generic_smp_call_function_single_interrupt();
 295         trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR);
 296         exiting_irq();
 297 }
 298
 299 static int __init nonmi_ipi_setup(char *str)
 300 {
 301         smp_no_nmi_ipi = true;
 302         return 1;
 303 }
 304
 305 __setup("nonmi_ipi", nonmi_ipi_setup);
 306
 307 struct smp_ops smp_ops = {
 308         .smp_prepare_boot_cpu   = native_smp_prepare_boot_cpu,
 309         .smp_prepare_cpus       = native_smp_prepare_cpus,
 310         .smp_cpus_done          = native_smp_cpus_done,
 311
 312         .stop_other_cpus        = native_stop_other_cpus,
 313 #if defined(CONFIG_KEXEC_CORE)
 314         .crash_stop_other_cpus  = kdump_nmi_shootdown_cpus,
 315 #endif
 316         .smp_send_reschedule    = native_smp_send_reschedule,
 317
 318         .cpu_up                 = native_cpu_up,
 319         .cpu_die                = native_cpu_die,
 320         .cpu_disable            = native_cpu_disable,
 321         .play_dead              = native_play_dead,
 322
 323         .send_call_func_ipi     = native_send_call_func_ipi,
 324         .send_call_func_single_ipi = native_send_call_func_single_ipi,
 325 };
 326 EXPORT_SYMBOL_GPL(smp_ops);