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 /*
  34  *      Some notes on x86 processor bugs affecting SMP operation:
  35  *
  36  *      Pentium, Pentium Pro, II, III (and all CPUs) have bugs.
  37  *      The Linux implications for SMP are handled as follows:
  38  *
  39  *      Pentium III / [Xeon]
  40  *              None of the E1AP-E3AP errata are visible to the user.
  41  *
  42  *      E1AP.   see PII A1AP
  43  *      E2AP.   see PII A2AP
  44  *      E3AP.   see PII A3AP
  45  *
  46  *      Pentium II / [Xeon]
  47  *              None of the A1AP-A3AP errata are visible to the user.
  48  *
  49  *      A1AP.   see PPro 1AP
  50  *      A2AP.   see PPro 2AP
  51  *      A3AP.   see PPro 7AP
  52  *
  53  *      Pentium Pro
  54  *              None of 1AP-9AP errata are visible to the normal user,
  55  *      except occasional delivery of 'spurious interrupt' as trap #15.
  56  *      This is very rare and a non-problem.
  57  *
  58  *      1AP.    Linux maps APIC as non-cacheable
  59  *      2AP.    worked around in hardware
  60  *      3AP.    fixed in C0 and above steppings microcode update.
  61  *              Linux does not use excessive STARTUP_IPIs.
  62  *      4AP.    worked around in hardware
  63  *      5AP.    symmetric IO mode (normal Linux operation) not affected.
  64  *              'noapic' mode has vector 0xf filled out properly.
  65  *      6AP.    'noapic' mode might be affected - fixed in later steppings
  66  *      7AP.    We do not assume writes to the LVT deassering IRQs
  67  *      8AP.    We do not enable low power mode (deep sleep) during MP bootup
  68  *      9AP.    We do not use mixed mode
  69  *
  70  *      Pentium
  71  *              There is a marginal case where REP MOVS on 100MHz SMP
  72  *      machines with B stepping processors can fail. XXX should provide
  73  *      an L1cache=Writethrough or L1cache=off option.
  74  *
  75  *              B stepping CPUs may hang. There are hardware work arounds
  76  *      for this. We warn about it in case your board doesn't have the work
  77  *      arounds. Basically that's so I can tell anyone with a B stepping
  78  *      CPU and SMP problems "tough".
  79  *
  80  *      Specific items [From Pentium Processor Specification Update]
  81  *
  82  *      1AP.    Linux doesn't use remote read
  83  *      2AP.    Linux doesn't trust APIC errors
  84  *      3AP.    We work around this
  85  *      4AP.    Linux never generated 3 interrupts of the same priority
  86  *              to cause a lost local interrupt.
  87  *      5AP.    Remote read is never used
  88  *      6AP.    not affected - worked around in hardware
  89  *      7AP.    not affected - worked around in hardware
  90  *      8AP.    worked around in hardware - we get explicit CS errors if not
  91  *      9AP.    only 'noapic' mode affected. Might generate spurious
  92  *              interrupts, we log only the first one and count the
  93  *              rest silently.
  94  *      10AP.   not affected - worked around in hardware
  95  *      11AP.   Linux reads the APIC between writes to avoid this, as per
  96  *              the documentation. Make sure you preserve this as it affects
  97  *              the C stepping chips too.
  98  *      12AP.   not affected - worked around in hardware
  99  *      13AP.   not affected - worked around in hardware
 100  *      14AP.   we always deassert INIT during bootup
 101  *      15AP.   not affected - worked around in hardware
 102  *      16AP.   not affected - worked around in hardware
 103  *      17AP.   not affected - worked around in hardware
 104  *      18AP.   not affected - worked around in hardware
 105  *      19AP.   not affected - worked around in BIOS
 106  *
 107  *      If this sounds worrying believe me these bugs are either ___RARE___,
 108  *      or are signal timing bugs worked around in hardware and there's
 109  *      about nothing of note with C stepping upwards.
 110  */
 111
 112 /*
 113  * this function sends a 'reschedule' IPI to another CPU.
 114  * it goes straight through and wastes no time serializing
 115  * anything. Worst case is that we lose a reschedule ...
 116  */
 117 static void native_smp_send_reschedule(int cpu)
 118 {
 119         if (unlikely(cpu_is_offline(cpu))) {
 120                 WARN_ON(1);
 121                 return;
 122         }
 123         apic->send_IPI_mask(cpumask_of(cpu), RESCHEDULE_VECTOR);
 124 }
 125
 126 void native_send_call_func_single_ipi(int cpu)
 127 {
 128         apic->send_IPI_mask(cpumask_of(cpu), CALL_FUNCTION_SINGLE_VECTOR);
 129 }
 130
 131 void native_send_call_func_ipi(const struct cpumask *mask)
 132 {
 133         cpumask_var_t allbutself;
 134
 135         if (!alloc_cpumask_var(&allbutself, GFP_ATOMIC)) {
 136                 apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR);
 137                 return;
 138         }
 139
 140         cpumask_copy(allbutself, cpu_online_mask);
 141         cpumask_clear_cpu(smp_processor_id(), allbutself);
 142
 143         if (cpumask_equal(mask, allbutself) &&
 144             cpumask_equal(cpu_online_mask, cpu_callout_mask))
 145                 apic->send_IPI_allbutself(CALL_FUNCTION_VECTOR);
 146         else
 147                 apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR);
 148
 149         free_cpumask_var(allbutself);
 150 }
 151
 152 static atomic_t stopping_cpu = ATOMIC_INIT(-1);
 153
 154 static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
 155 {
 156         /* We are registered on stopping cpu too, avoid spurious NMI */
 157         if (raw_smp_processor_id() == atomic_read(&stopping_cpu))
 158                 return NMI_HANDLED;
 159
 160         stop_this_cpu(NULL);
 161
 162         return NMI_HANDLED;
 163 }
 164
 165 static void native_nmi_stop_other_cpus(int wait)
 166 {
 167         unsigned long flags;
 168         unsigned long timeout;
 169
 170         if (reboot_force)
 171                 return;
 172
 173         /*
 174          * Use an own vector here because smp_call_function
 175          * does lots of things not suitable in a panic situation.
 176          */
 177         if (num_online_cpus() > 1) {
 178                 /* did someone beat us here? */
 179                 if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1)
 180                         return;
 181
 182                 if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
 183                                          NMI_FLAG_FIRST, "smp_stop"))
 184                         /* Note: we ignore failures here */
 185                         return;
 186
 187                 /* sync above data before sending NMI */
 188                 wmb();
 189
 190                 apic->send_IPI_allbutself(NMI_VECTOR);
 191
 192                 /*
 193                  * Don't wait longer than a second if the caller
 194                  * didn't ask us to wait.
 195                  */
 196                 timeout = USEC_PER_SEC;
 197                 while (num_online_cpus() > 1 && (wait || timeout--))
 198                         udelay(1);
 199         }
 200
 201         local_irq_save(flags);
 202         disable_local_APIC();
 203         local_irq_restore(flags);
 204 }
 205
 206 /*
 207  * this function calls the 'stop' function on all other CPUs in the system.
 208  */
 209
 210 asmlinkage void smp_reboot_interrupt(void)
 211 {
 212         ack_APIC_irq();
 213         irq_enter();
 214         stop_this_cpu(NULL);
 215         irq_exit();
 216 }
 217
 218 static void native_irq_stop_other_cpus(int wait)
 219 {
 220         unsigned long flags;
 221         unsigned long timeout;
 222
 223         if (reboot_force)
 224                 return;
 225
 226         /*
 227          * Use an own vector here because smp_call_function
 228          * does lots of things not suitable in a panic situation.
 229          * On most systems we could also use an NMI here,
 230          * but there are a few systems around where NMI
 231          * is problematic so stay with an non NMI for now
 232          * (this implies we cannot stop CPUs spinning with irq off
 233          * currently)
 234          */
 235         if (num_online_cpus() > 1) {
 236                 apic->send_IPI_allbutself(REBOOT_VECTOR);
 237
 238                 /*
 239                  * Don't wait longer than a second if the caller
 240                  * didn't ask us to wait.
 241                  */
 242                 timeout = USEC_PER_SEC;
 243                 while (num_online_cpus() > 1 && (wait || timeout--))
 244                         udelay(1);
 245         }
 246
 247         local_irq_save(flags);
 248         disable_local_APIC();
 249         local_irq_restore(flags);
 250 }
 251
 252 static void native_smp_disable_nmi_ipi(void)
 253 {
 254         smp_ops.stop_other_cpus = native_irq_stop_other_cpus;
 255 }
 256
 257 /*
 258  * Reschedule call back.
 259  */
 260 void smp_reschedule_interrupt(struct pt_regs *regs)
 261 {
 262         ack_APIC_irq();
 263         inc_irq_stat(irq_resched_count);
 264         scheduler_ipi();
 265         /*
 266          * KVM uses this interrupt to force a cpu out of guest mode
 267          */
 268 }
 269
 270 void smp_call_function_interrupt(struct pt_regs *regs)
 271 {
 272         ack_APIC_irq();
 273         irq_enter();
 274         generic_smp_call_function_interrupt();
 275         inc_irq_stat(irq_call_count);
 276         irq_exit();
 277 }
 278
 279 void smp_call_function_single_interrupt(struct pt_regs *regs)
 280 {
 281         ack_APIC_irq();
 282         irq_enter();
 283         generic_smp_call_function_single_interrupt();
 284         inc_irq_stat(irq_call_count);
 285         irq_exit();
 286 }
 287
 288 static int __init nonmi_ipi_setup(char *str)
 289 {
 290         native_smp_disable_nmi_ipi();
 291         return 1;
 292 }
 293
 294 __setup("nonmi_ipi", nonmi_ipi_setup);
 295
 296 struct smp_ops smp_ops = {
 297         .smp_prepare_boot_cpu   = native_smp_prepare_boot_cpu,
 298         .smp_prepare_cpus       = native_smp_prepare_cpus,
 299         .smp_cpus_done          = native_smp_cpus_done,
 300
 301         .stop_other_cpus        = native_nmi_stop_other_cpus,
 302         .smp_send_reschedule    = native_smp_send_reschedule,
 303
 304         .cpu_up                 = native_cpu_up,
 305         .cpu_die                = native_cpu_die,
 306         .cpu_disable            = native_cpu_disable,
 307         .play_dead              = native_play_dead,
 308
 309         .send_call_func_ipi     = native_send_call_func_ipi,
 310         .send_call_func_single_ipi = native_send_call_func_single_ipi,
 311 };
 312 EXPORT_SYMBOL_GPL(smp_ops);