arch/x86/kernel/smp.c

   1 /*
   2  *      Intel SMP support routines.
   3  *
   4  *      (c) 1995 Alan Cox, Building #3 <alan@lxorguk.ukuu.org.uk>
   5  *      (c) 1998-99, 2000, 2009 Ingo Molnar <mingo@redhat.com>
   6  *      (c) 2002,2003 Andi Kleen, SuSE Labs.
   7  *
   8  *      i386 and x86_64 integration by Glauber Costa <gcosta@redhat.com>
   9  *
  10  *      This code is released under the GNU General Public License version 2 or
  11  *      later.
  12  */
  13
  14 #include <linux/init.h>
  15
  16 #include <linux/mm.h>
  17 #include <linux/delay.h>
  18 #include <linux/spinlock.h>
  19 #include <linux/export.h>
  20 #include <linux/kernel_stat.h>
  21 #include <linux/mc146818rtc.h>
  22 #include <linux/cache.h>
  23 #include <linux/interrupt.h>
  24 #include <linux/cpu.h>
  25 #include <linux/gfp.h>
  26
  27 #include <asm/mtrr.h>
  28 #include <asm/tlbflush.h>
  29 #include <asm/mmu_context.h>
  30 #include <asm/proto.h>
  31 #include <asm/apic.h>
  32 #include <asm/nmi.h>
  33 #include <asm/mce.h>
  34 #include <asm/kexec.h>
  35 #include <asm/virtext.h>
  36
  37 /*
  38  *      Some notes on x86 processor bugs affecting SMP operation:
  39  *
  40  *      Pentium, Pentium Pro, II, III (and all CPUs) have bugs.
  41  *      The Linux implications for SMP are handled as follows:
  42  *
  43  *      Pentium III / [Xeon]
  44  *              None of the E1AP-E3AP errata are visible to the user.
  45  *
  46  *      E1AP.   see PII A1AP
  47  *      E2AP.   see PII A2AP
  48  *      E3AP.   see PII A3AP
  49  *
  50  *      Pentium II / [Xeon]
  51  *              None of the A1AP-A3AP errata are visible to the user.
  52  *
  53  *      A1AP.   see PPro 1AP
  54  *      A2AP.   see PPro 2AP
  55  *      A3AP.   see PPro 7AP
  56  *
  57  *      Pentium Pro
  58  *              None of 1AP-9AP errata are visible to the normal user,
  59  *      except occasional delivery of 'spurious interrupt' as trap #15.
  60  *      This is very rare and a non-problem.
  61  *
  62  *      1AP.    Linux maps APIC as non-cacheable
  63  *      2AP.    worked around in hardware
  64  *      3AP.    fixed in C0 and above steppings microcode update.
  65  *              Linux does not use excessive STARTUP_IPIs.
  66  *      4AP.    worked around in hardware
  67  *      5AP.    symmetric IO mode (normal Linux operation) not affected.
  68  *              'noapic' mode has vector 0xf filled out properly.
  69  *      6AP.    'noapic' mode might be affected - fixed in later steppings
  70  *      7AP.    We do not assume writes to the LVT deassering IRQs
  71  *      8AP.    We do not enable low power mode (deep sleep) during MP bootup
  72  *      9AP.    We do not use mixed mode
  73  *
  74  *      Pentium
  75  *              There is a marginal case where REP MOVS on 100MHz SMP
  76  *      machines with B stepping processors can fail. XXX should provide
  77  *      an L1cache=Writethrough or L1cache=off option.
  78  *
  79  *              B stepping CPUs may hang. There are hardware work arounds
  80  *      for this. We warn about it in case your board doesn't have the work
  81  *      arounds. Basically that's so I can tell anyone with a B stepping
  82  *      CPU and SMP problems "tough".
  83  *
  84  *      Specific items [From Pentium Processor Specification Update]
  85  *
  86  *      1AP.    Linux doesn't use remote read
  87  *      2AP.    Linux doesn't trust APIC errors
  88  *      3AP.    We work around this
  89  *      4AP.    Linux never generated 3 interrupts of the same priority
  90  *              to cause a lost local interrupt.
  91  *      5AP.    Remote read is never used
  92  *      6AP.    not affected - worked around in hardware
  93  *      7AP.    not affected - worked around in hardware
  94  *      8AP.    worked around in hardware - we get explicit CS errors if not
  95  *      9AP.    only 'noapic' mode affected. Might generate spurious
  96  *              interrupts, we log only the first one and count the
  97  *              rest silently.
  98  *      10AP.   not affected - worked around in hardware
  99  *      11AP.   Linux reads the APIC between writes to avoid this, as per
 100  *              the documentation. Make sure you preserve this as it affects
 101  *              the C stepping chips too.
 102  *      12AP.   not affected - worked around in hardware
 103  *      13AP.   not affected - worked around in hardware
 104  *      14AP.   we always deassert INIT during bootup
 105  *      15AP.   not affected - worked around in hardware
 106  *      16AP.   not affected - worked around in hardware
 107  *      17AP.   not affected - worked around in hardware
 108  *      18AP.   not affected - worked around in hardware
 109  *      19AP.   not affected - worked around in BIOS
 110  *
 111  *      If this sounds worrying believe me these bugs are either ___RARE___,
 112  *      or are signal timing bugs worked around in hardware and there's
 113  *      about nothing of note with C stepping upwards.
 114  */
 115
 116 static atomic_t stopping_cpu = ATOMIC_INIT(-1);
 117 static bool smp_no_nmi_ipi = false;
 118
 119 /*
 120  * this function sends a 'reschedule' IPI to another CPU.
 121  * it goes straight through and wastes no time serializing
 122  * anything. Worst case is that we lose a reschedule ...
 123  */
 124 static void native_smp_send_reschedule(int cpu)
 125 {
 126         if (unlikely(cpu_is_offline(cpu))) {
 127                 WARN(1, "sched: Unexpected reschedule of offline CPU#%d!\n", cpu);
 128                 return;
 129         }
 130         apic->send_IPI(cpu, RESCHEDULE_VECTOR);
 131 }
 132
 133 void native_send_call_func_single_ipi(int cpu)
 134 {
 135         apic->send_IPI(cpu, CALL_FUNCTION_SINGLE_VECTOR);
 136 }
 137
 138 void native_send_call_func_ipi(const struct cpumask *mask)
 139 {
 140         cpumask_var_t allbutself;
 141
 142         if (!alloc_cpumask_var(&allbutself, GFP_ATOMIC)) {
 143                 apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR);
 144                 return;
 145         }
 146
 147         cpumask_copy(allbutself, cpu_online_mask);
 148         cpumask_clear_cpu(smp_processor_id(), allbutself);
 149
 150         if (cpumask_equal(mask, allbutself) &&
 151             cpumask_equal(cpu_online_mask, cpu_callout_mask))
 152                 apic->send_IPI_allbutself(CALL_FUNCTION_VECTOR);
 153         else
 154                 apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR);
 155
 156         free_cpumask_var(allbutself);
 157 }
 158
 159 static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
 160 {
 161         /* We are registered on stopping cpu too, avoid spurious NMI */
 162         if (raw_smp_processor_id() == atomic_read(&stopping_cpu))
 163                 return NMI_HANDLED;
 164
 165         cpu_emergency_vmxoff();
 166         stop_this_cpu(NULL);
 167
 168         return NMI_HANDLED;
 169 }
 170
 171 /*
 172  * this function calls the 'stop' function on all other CPUs in the system.
 173  */
 174
 175 asmlinkage __visible void smp_reboot_interrupt(void)
 176 {
 177         ipi_entering_ack_irq();
 178         cpu_emergency_vmxoff();
 179         stop_this_cpu(NULL);
 180         irq_exit();
 181 }
 182
 183 static void native_stop_other_cpus(int wait)
 184 {
 185         unsigned long flags;
 186         unsigned long timeout;
 187
 188         if (reboot_force)
 189                 return;
 190
 191         /*
 192          * Use an own vector here because smp_call_function
 193          * does lots of things not suitable in a panic situation.
 194          */
 195
 196         /*
 197          * We start by using the REBOOT_VECTOR irq.
 198          * The irq is treated as a sync point to allow critical
 199          * regions of code on other cpus to release their spin locks
 200          * and re-enable irqs.  Jumping straight to an NMI might
 201          * accidentally cause deadlocks with further shutdown/panic
 202          * code.  By syncing, we give the cpus up to one second to
 203          * finish their work before we force them off with the NMI.
 204          */
 205         if (num_online_cpus() > 1) {
 206                 /* did someone beat us here? */
 207                 if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1)
 208                         return;
 209
 210                 /* sync above data before sending IRQ */
 211                 wmb();
 212
 213                 apic->send_IPI_allbutself(REBOOT_VECTOR);
 214
 215                 /*
 216                  * Don't wait longer than a second if the caller
 217                  * didn't ask us to wait.
 218                  */
 219                 timeout = USEC_PER_SEC;
 220                 while (num_online_cpus() > 1 && (wait || timeout--))
 221                         udelay(1);
 222         }
 223
 224         /* if the REBOOT_VECTOR didn't work, try with the NMI */
 225         if ((num_online_cpus() > 1) && (!smp_no_nmi_ipi))  {
 226                 if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
 227                                          NMI_FLAG_FIRST, "smp_stop"))
 228                         /* Note: we ignore failures here */
 229                         /* Hope the REBOOT_IRQ is good enough */
 230                         goto finish;
 231
 232                 /* sync above data before sending IRQ */
 233                 wmb();
 234
 235                 pr_emerg("Shutting down cpus with NMI\n");
 236
 237                 apic->send_IPI_allbutself(NMI_VECTOR);
 238
 239                 /*
 240                  * Don't wait longer than a 10 ms if the caller
 241                  * didn't ask us to wait.
 242                  */
 243                 timeout = USEC_PER_MSEC * 10;
 244                 while (num_online_cpus() > 1 && (wait || timeout--))
 245                         udelay(1);
 246         }
 247
 248 finish:
 249         local_irq_save(flags);
 250         disable_local_APIC();
 251         mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
 252         local_irq_restore(flags);
 253 }
 254
 255 /*
 256  * Reschedule call back.
 257  */
 258 static inline void __smp_reschedule_interrupt(void)
 259 {
 260         inc_irq_stat(irq_resched_count);
 261         scheduler_ipi();
 262 }
 263
 264 __visible void __irq_entry smp_reschedule_interrupt(struct pt_regs *regs)
 265 {
 266         ack_APIC_irq();
 267         __smp_reschedule_interrupt();
 268         /*
 269          * KVM uses this interrupt to force a cpu out of guest mode
 270          */
 271 }
 272
 273 __visible void __irq_entry smp_trace_reschedule_interrupt(struct pt_regs *regs)
 274 {
 275         /*
 276          * Need to call irq_enter() before calling the trace point.
 277          * __smp_reschedule_interrupt() calls irq_enter/exit() too (in
 278          * scheduler_ipi(). This is OK, since those functions are allowed
 279          * to nest.
 280          */
 281         ipi_entering_ack_irq();
 282         __smp_reschedule_interrupt();
 283         exiting_irq();
 284         /*
 285          * KVM uses this interrupt to force a cpu out of guest mode
 286          */
 287 }
 288
 289 static inline void __smp_call_function_interrupt(void)
 290 {
 291         generic_smp_call_function_interrupt();
 292         inc_irq_stat(irq_call_count);
 293 }
 294
 295 __visible void __irq_entry smp_call_function_interrupt(struct pt_regs *regs)
 296 {
 297         ipi_entering_ack_irq();
 298         __smp_call_function_interrupt();
 299         exiting_irq();
 300 }
 301
 302 __visible void __irq_entry
 303 smp_trace_call_function_interrupt(struct pt_regs *regs)
 304 {
 305         ipi_entering_ack_irq();
 306         __smp_call_function_interrupt();
 307         exiting_irq();
 308 }
 309
 310 static inline void __smp_call_function_single_interrupt(void)
 311 {
 312         generic_smp_call_function_single_interrupt();
 313         inc_irq_stat(irq_call_count);
 314 }
 315
 316 __visible void __irq_entry
 317 smp_call_function_single_interrupt(struct pt_regs *regs)
 318 {
 319         ipi_entering_ack_irq();
 320         __smp_call_function_single_interrupt();
 321         exiting_irq();
 322 }
 323
 324 __visible void __irq_entry
 325 smp_trace_call_function_single_interrupt(struct pt_regs *regs)
 326 {
 327         ipi_entering_ack_irq();
 328         __smp_call_function_single_interrupt();
 329         exiting_irq();
 330 }
 331
 332 static int __init nonmi_ipi_setup(char *str)
 333 {
 334         smp_no_nmi_ipi = true;
 335         return 1;
 336 }
 337
 338 __setup("nonmi_ipi", nonmi_ipi_setup);
 339
 340 struct smp_ops smp_ops = {
 341         .smp_prepare_boot_cpu   = native_smp_prepare_boot_cpu,
 342         .smp_prepare_cpus       = native_smp_prepare_cpus,
 343         .smp_cpus_done          = native_smp_cpus_done,
 344
 345         .stop_other_cpus        = native_stop_other_cpus,
 346 #if defined(CONFIG_KEXEC_CORE)
 347         .crash_stop_other_cpus  = kdump_nmi_shootdown_cpus,
 348 #endif
 349         .smp_send_reschedule    = native_smp_send_reschedule,
 350
 351         .cpu_up                 = native_cpu_up,
 352         .cpu_die                = native_cpu_die,
 353         .cpu_disable            = native_cpu_disable,
 354         .play_dead              = native_play_dead,
 355
 356         .send_call_func_ipi     = native_send_call_func_ipi,
 357         .send_call_func_single_ipi = native_send_call_func_single_ipi,
 358 };
 359 EXPORT_SYMBOL_GPL(smp_ops);