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/trace/irq_vectors.h> 34/* 35 * Some notes on x86 processor bugs affecting SMP operation: 36 * 37 * Pentium, Pentium Pro, II, III (and all CPUs) have bugs. 38 * The Linux implications for SMP are handled as follows: 39 * 40 * Pentium III / [Xeon] 41 * None of the E1AP-E3AP errata are visible to the user. 42 * 43 * E1AP. see PII A1AP 44 * E2AP. see PII A2AP 45 * E3AP. see PII A3AP 46 * 47 * Pentium II / [Xeon] 48 * None of the A1AP-A3AP errata are visible to the user. 49 * 50 * A1AP. see PPro 1AP 51 * A2AP. see PPro 2AP 52 * A3AP. see PPro 7AP 53 * 54 * Pentium Pro 55 * None of 1AP-9AP errata are visible to the normal user, 56 * except occasional delivery of 'spurious interrupt' as trap #15. 57 * This is very rare and a non-problem. 58 * 59 * 1AP. Linux maps APIC as non-cacheable 60 * 2AP. worked around in hardware 61 * 3AP. fixed in C0 and above steppings microcode update. 62 * Linux does not use excessive STARTUP_IPIs. 63 * 4AP. worked around in hardware 64 * 5AP. symmetric IO mode (normal Linux operation) not affected. 65 * 'noapic' mode has vector 0xf filled out properly. 66 * 6AP. 'noapic' mode might be affected - fixed in later steppings 67 * 7AP. We do not assume writes to the LVT deassering IRQs 68 * 8AP. We do not enable low power mode (deep sleep) during MP bootup 69 * 9AP. We do not use mixed mode 70 * 71 * Pentium 72 * There is a marginal case where REP MOVS on 100MHz SMP 73 * machines with B stepping processors can fail. XXX should provide 74 * an L1cache=Writethrough or L1cache=off option. 75 * 76 * B stepping CPUs may hang. There are hardware work arounds 77 * for this. We warn about it in case your board doesn't have the work 78 * arounds. Basically that's so I can tell anyone with a B stepping 79 * CPU and SMP problems "tough". 80 * 81 * Specific items [From Pentium Processor Specification Update] 82 * 83 * 1AP. Linux doesn't use remote read 84 * 2AP. Linux doesn't trust APIC errors 85 * 3AP. We work around this 86 * 4AP. Linux never generated 3 interrupts of the same priority 87 * to cause a lost local interrupt. 88 * 5AP. Remote read is never used 89 * 6AP. not affected - worked around in hardware 90 * 7AP. not affected - worked around in hardware 91 * 8AP. worked around in hardware - we get explicit CS errors if not 92 * 9AP. only 'noapic' mode affected. Might generate spurious 93 * interrupts, we log only the first one and count the 94 * rest silently. 95 * 10AP. not affected - worked around in hardware 96 * 11AP. Linux reads the APIC between writes to avoid this, as per 97 * the documentation. Make sure you preserve this as it affects 98 * the C stepping chips too. 99 * 12AP. not affected - worked around in hardware 100 * 13AP. not affected - worked around in hardware 101 * 14AP. we always deassert INIT during bootup 102 * 15AP. not affected - worked around in hardware 103 * 16AP. not affected - worked around in hardware 104 * 17AP. not affected - worked around in hardware 105 * 18AP. not affected - worked around in hardware 106 * 19AP. not affected - worked around in BIOS 107 * 108 * If this sounds worrying believe me these bugs are either ___RARE___, 109 * or are signal timing bugs worked around in hardware and there's 110 * about nothing of note with C stepping upwards. 111 */ 112 113static atomic_t stopping_cpu = ATOMIC_INIT(-1); 114static bool smp_no_nmi_ipi = false; 115 116/* 117 * this function sends a 'reschedule' IPI to another CPU. 118 * it goes straight through and wastes no time serializing 119 * anything. Worst case is that we lose a reschedule ... 120 */ 121static void native_smp_send_reschedule(int cpu) 122{ 123 if (unlikely(cpu_is_offline(cpu))) { 124 WARN_ON(1); 125 return; 126 } 127 apic->send_IPI_mask(cpumask_of(cpu), RESCHEDULE_VECTOR); 128} 129 130void native_send_call_func_single_ipi(int cpu) 131{ 132 apic->send_IPI_mask(cpumask_of(cpu), CALL_FUNCTION_SINGLE_VECTOR); 133} 134 135void native_send_call_func_ipi(const struct cpumask *mask) 136{ 137 cpumask_var_t allbutself; 138 139 if (!alloc_cpumask_var(&allbutself, GFP_ATOMIC)) { 140 apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR); 141 return; 142 } 143 144 cpumask_copy(allbutself, cpu_online_mask); 145 cpumask_clear_cpu(smp_processor_id(), allbutself); 146 147 if (cpumask_equal(mask, allbutself) && 148 cpumask_equal(cpu_online_mask, cpu_callout_mask)) 149 apic->send_IPI_allbutself(CALL_FUNCTION_VECTOR); 150 else 151 apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR); 152 153 free_cpumask_var(allbutself); 154} 155 156static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs) 157{ 158 /* We are registered on stopping cpu too, avoid spurious NMI */ 159 if (raw_smp_processor_id() == atomic_read(&stopping_cpu)) 160 return NMI_HANDLED; 161 162 stop_this_cpu(NULL); 163 164 return NMI_HANDLED; 165} 166 167/* 168 * this function calls the 'stop' function on all other CPUs in the system. 169 */ 170 171asmlinkage __visible void smp_reboot_interrupt(void) 172{ 173 ack_APIC_irq(); 174 irq_enter(); 175 stop_this_cpu(NULL); 176 irq_exit(); 177} 178 179static void native_stop_other_cpus(int wait) 180{ 181 unsigned long flags; 182 unsigned long timeout; 183 184 if (reboot_force) 185 return; 186 187 /* 188 * Use an own vector here because smp_call_function 189 * does lots of things not suitable in a panic situation. 190 */ 191 192 /* 193 * We start by using the REBOOT_VECTOR irq. 194 * The irq is treated as a sync point to allow critical 195 * regions of code on other cpus to release their spin locks 196 * and re-enable irqs. Jumping straight to an NMI might 197 * accidentally cause deadlocks with further shutdown/panic 198 * code. By syncing, we give the cpus up to one second to 199 * finish their work before we force them off with the NMI. 200 */ 201 if (num_online_cpus() > 1) { 202 /* did someone beat us here? */ 203 if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1) 204 return; 205 206 /* sync above data before sending IRQ */ 207 wmb(); 208 209 apic->send_IPI_allbutself(REBOOT_VECTOR); 210 211 /* 212 * Don't wait longer than a second if the caller 213 * didn't ask us to wait. 214 */ 215 timeout = USEC_PER_SEC; 216 while (num_online_cpus() > 1 && (wait || timeout--)) 217 udelay(1); 218 } 219 220 /* if the REBOOT_VECTOR didn't work, try with the NMI */ 221 if ((num_online_cpus() > 1) && (!smp_no_nmi_ipi)) { 222 if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback, 223 NMI_FLAG_FIRST, "smp_stop")) 224 /* Note: we ignore failures here */ 225 /* Hope the REBOOT_IRQ is good enough */ 226 goto finish; 227 228 /* sync above data before sending IRQ */ 229 wmb(); 230 231 pr_emerg("Shutting down cpus with NMI\n"); 232 233 apic->send_IPI_allbutself(NMI_VECTOR); 234 235 /* 236 * Don't wait longer than a 10 ms if the caller 237 * didn't ask us to wait. 238 */ 239 timeout = USEC_PER_MSEC * 10; 240 while (num_online_cpus() > 1 && (wait || timeout--)) 241 udelay(1); 242 } 243 244finish: 245 local_irq_save(flags); 246 disable_local_APIC(); 247 local_irq_restore(flags); 248} 249 250/* 251 * Reschedule call back. 252 */ 253static inline void __smp_reschedule_interrupt(void) 254{ 255 inc_irq_stat(irq_resched_count); 256 scheduler_ipi(); 257} 258 259__visible void smp_reschedule_interrupt(struct pt_regs *regs) 260{ 261 ack_APIC_irq(); 262 __smp_reschedule_interrupt(); 263 /* 264 * KVM uses this interrupt to force a cpu out of guest mode 265 */ 266} 267 268static inline void smp_entering_irq(void) 269{ 270 ack_APIC_irq(); 271 irq_enter(); 272} 273 274__visible void smp_trace_reschedule_interrupt(struct pt_regs *regs) 275{ 276 /* 277 * Need to call irq_enter() before calling the trace point. 278 * __smp_reschedule_interrupt() calls irq_enter/exit() too (in 279 * scheduler_ipi(). This is OK, since those functions are allowed 280 * to nest. 281 */ 282 smp_entering_irq(); 283 trace_reschedule_entry(RESCHEDULE_VECTOR); 284 __smp_reschedule_interrupt(); 285 trace_reschedule_exit(RESCHEDULE_VECTOR); 286 exiting_irq(); 287 /* 288 * KVM uses this interrupt to force a cpu out of guest mode 289 */ 290} 291 292static inline void __smp_call_function_interrupt(void) 293{ 294 generic_smp_call_function_interrupt(); 295 inc_irq_stat(irq_call_count); 296} 297 298__visible void smp_call_function_interrupt(struct pt_regs *regs) 299{ 300 smp_entering_irq(); 301 __smp_call_function_interrupt(); 302 exiting_irq(); 303} 304 305__visible void smp_trace_call_function_interrupt(struct pt_regs *regs) 306{ 307 smp_entering_irq(); 308 trace_call_function_entry(CALL_FUNCTION_VECTOR); 309 __smp_call_function_interrupt(); 310 trace_call_function_exit(CALL_FUNCTION_VECTOR); 311 exiting_irq(); 312} 313 314static inline void __smp_call_function_single_interrupt(void) 315{ 316 generic_smp_call_function_single_interrupt(); 317 inc_irq_stat(irq_call_count); 318} 319 320__visible void smp_call_function_single_interrupt(struct pt_regs *regs) 321{ 322 smp_entering_irq(); 323 __smp_call_function_single_interrupt(); 324 exiting_irq(); 325} 326 327__visible void smp_trace_call_function_single_interrupt(struct pt_regs *regs) 328{ 329 smp_entering_irq(); 330 trace_call_function_single_entry(CALL_FUNCTION_SINGLE_VECTOR); 331 __smp_call_function_single_interrupt(); 332 trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR); 333 exiting_irq(); 334} 335 336static int __init nonmi_ipi_setup(char *str) 337{ 338 smp_no_nmi_ipi = true; 339 return 1; 340} 341 342__setup("nonmi_ipi", nonmi_ipi_setup); 343 344struct smp_ops smp_ops = { 345 .smp_prepare_boot_cpu = native_smp_prepare_boot_cpu, 346 .smp_prepare_cpus = native_smp_prepare_cpus, 347 .smp_cpus_done = native_smp_cpus_done, 348 349 .stop_other_cpus = native_stop_other_cpus, 350 .smp_send_reschedule = native_smp_send_reschedule, 351 352 .cpu_up = native_cpu_up, 353 .cpu_die = native_cpu_die, 354 .cpu_disable = native_cpu_disable, 355 .play_dead = native_play_dead, 356 357 .send_call_func_ipi = native_send_call_func_ipi, 358 .send_call_func_single_ipi = native_send_call_func_single_ipi, 359}; 360EXPORT_SYMBOL_GPL(smp_ops); 361