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/trace/irq_vectors.h> 35 #include <asm/kexec.h> 36 #include <asm/virtext.h> 37 38 /* 39 * Some notes on x86 processor bugs affecting SMP operation: 40 * 41 * Pentium, Pentium Pro, II, III (and all CPUs) have bugs. 42 * The Linux implications for SMP are handled as follows: 43 * 44 * Pentium III / [Xeon] 45 * None of the E1AP-E3AP errata are visible to the user. 46 * 47 * E1AP. see PII A1AP 48 * E2AP. see PII A2AP 49 * E3AP. see PII A3AP 50 * 51 * Pentium II / [Xeon] 52 * None of the A1AP-A3AP errata are visible to the user. 53 * 54 * A1AP. see PPro 1AP 55 * A2AP. see PPro 2AP 56 * A3AP. see PPro 7AP 57 * 58 * Pentium Pro 59 * None of 1AP-9AP errata are visible to the normal user, 60 * except occasional delivery of 'spurious interrupt' as trap #15. 61 * This is very rare and a non-problem. 62 * 63 * 1AP. Linux maps APIC as non-cacheable 64 * 2AP. worked around in hardware 65 * 3AP. fixed in C0 and above steppings microcode update. 66 * Linux does not use excessive STARTUP_IPIs. 67 * 4AP. worked around in hardware 68 * 5AP. symmetric IO mode (normal Linux operation) not affected. 69 * 'noapic' mode has vector 0xf filled out properly. 70 * 6AP. 'noapic' mode might be affected - fixed in later steppings 71 * 7AP. We do not assume writes to the LVT deassering IRQs 72 * 8AP. We do not enable low power mode (deep sleep) during MP bootup 73 * 9AP. We do not use mixed mode 74 * 75 * Pentium 76 * There is a marginal case where REP MOVS on 100MHz SMP 77 * machines with B stepping processors can fail. XXX should provide 78 * an L1cache=Writethrough or L1cache=off option. 79 * 80 * B stepping CPUs may hang. There are hardware work arounds 81 * for this. We warn about it in case your board doesn't have the work 82 * arounds. Basically that's so I can tell anyone with a B stepping 83 * CPU and SMP problems "tough". 84 * 85 * Specific items [From Pentium Processor Specification Update] 86 * 87 * 1AP. Linux doesn't use remote read 88 * 2AP. Linux doesn't trust APIC errors 89 * 3AP. We work around this 90 * 4AP. Linux never generated 3 interrupts of the same priority 91 * to cause a lost local interrupt. 92 * 5AP. Remote read is never used 93 * 6AP. not affected - worked around in hardware 94 * 7AP. not affected - worked around in hardware 95 * 8AP. worked around in hardware - we get explicit CS errors if not 96 * 9AP. only 'noapic' mode affected. Might generate spurious 97 * interrupts, we log only the first one and count the 98 * rest silently. 99 * 10AP. not affected - worked around in hardware 100 * 11AP. Linux reads the APIC between writes to avoid this, as per 101 * the documentation. Make sure you preserve this as it affects 102 * the C stepping chips too. 103 * 12AP. not affected - worked around in hardware 104 * 13AP. not affected - worked around in hardware 105 * 14AP. we always deassert INIT during bootup 106 * 15AP. not affected - worked around in hardware 107 * 16AP. not affected - worked around in hardware 108 * 17AP. not affected - worked around in hardware 109 * 18AP. not affected - worked around in hardware 110 * 19AP. not affected - worked around in BIOS 111 * 112 * If this sounds worrying believe me these bugs are either ___RARE___, 113 * or are signal timing bugs worked around in hardware and there's 114 * about nothing of note with C stepping upwards. 115 */ 116 117 static atomic_t stopping_cpu = ATOMIC_INIT(-1); 118 static bool smp_no_nmi_ipi = false; 119 120 /* 121 * this function sends a 'reschedule' IPI to another CPU. 122 * it goes straight through and wastes no time serializing 123 * anything. Worst case is that we lose a reschedule ... 124 */ 125 static void native_smp_send_reschedule(int cpu) 126 { 127 if (unlikely(cpu_is_offline(cpu))) { 128 WARN(1, "sched: Unexpected reschedule of offline CPU#%d!\n", cpu); 129 return; 130 } 131 apic->send_IPI(cpu, RESCHEDULE_VECTOR); 132 } 133 134 void native_send_call_func_single_ipi(int cpu) 135 { 136 apic->send_IPI(cpu, CALL_FUNCTION_SINGLE_VECTOR); 137 } 138 139 void native_send_call_func_ipi(const struct cpumask *mask) 140 { 141 cpumask_var_t allbutself; 142 143 if (!alloc_cpumask_var(&allbutself, GFP_ATOMIC)) { 144 apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR); 145 return; 146 } 147 148 cpumask_copy(allbutself, cpu_online_mask); 149 cpumask_clear_cpu(smp_processor_id(), allbutself); 150 151 if (cpumask_equal(mask, allbutself) && 152 cpumask_equal(cpu_online_mask, cpu_callout_mask)) 153 apic->send_IPI_allbutself(CALL_FUNCTION_VECTOR); 154 else 155 apic->send_IPI_mask(mask, CALL_FUNCTION_VECTOR); 156 157 free_cpumask_var(allbutself); 158 } 159 160 static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs) 161 { 162 /* We are registered on stopping cpu too, avoid spurious NMI */ 163 if (raw_smp_processor_id() == atomic_read(&stopping_cpu)) 164 return NMI_HANDLED; 165 166 cpu_emergency_vmxoff(); 167 stop_this_cpu(NULL); 168 169 return NMI_HANDLED; 170 } 171 172 /* 173 * this function calls the 'stop' function on all other CPUs in the system. 174 */ 175 176 asmlinkage __visible void smp_reboot_interrupt(void) 177 { 178 ipi_entering_ack_irq(); 179 cpu_emergency_vmxoff(); 180 stop_this_cpu(NULL); 181 irq_exit(); 182 } 183 184 static void native_stop_other_cpus(int wait) 185 { 186 unsigned long flags; 187 unsigned long timeout; 188 189 if (reboot_force) 190 return; 191 192 /* 193 * Use an own vector here because smp_call_function 194 * does lots of things not suitable in a panic situation. 195 */ 196 197 /* 198 * We start by using the REBOOT_VECTOR irq. 199 * The irq is treated as a sync point to allow critical 200 * regions of code on other cpus to release their spin locks 201 * and re-enable irqs. Jumping straight to an NMI might 202 * accidentally cause deadlocks with further shutdown/panic 203 * code. By syncing, we give the cpus up to one second to 204 * finish their work before we force them off with the NMI. 205 */ 206 if (num_online_cpus() > 1) { 207 /* did someone beat us here? */ 208 if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1) 209 return; 210 211 /* sync above data before sending IRQ */ 212 wmb(); 213 214 apic->send_IPI_allbutself(REBOOT_VECTOR); 215 216 /* 217 * Don't wait longer than a second if the caller 218 * didn't ask us to wait. 219 */ 220 timeout = USEC_PER_SEC; 221 while (num_online_cpus() > 1 && (wait || timeout--)) 222 udelay(1); 223 } 224 225 /* if the REBOOT_VECTOR didn't work, try with the NMI */ 226 if ((num_online_cpus() > 1) && (!smp_no_nmi_ipi)) { 227 if (register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback, 228 NMI_FLAG_FIRST, "smp_stop")) 229 /* Note: we ignore failures here */ 230 /* Hope the REBOOT_IRQ is good enough */ 231 goto finish; 232 233 /* sync above data before sending IRQ */ 234 wmb(); 235 236 pr_emerg("Shutting down cpus with NMI\n"); 237 238 apic->send_IPI_allbutself(NMI_VECTOR); 239 240 /* 241 * Don't wait longer than a 10 ms if the caller 242 * didn't ask us to wait. 243 */ 244 timeout = USEC_PER_MSEC * 10; 245 while (num_online_cpus() > 1 && (wait || timeout--)) 246 udelay(1); 247 } 248 249 finish: 250 local_irq_save(flags); 251 disable_local_APIC(); 252 mcheck_cpu_clear(this_cpu_ptr(&cpu_info)); 253 local_irq_restore(flags); 254 } 255 256 /* 257 * Reschedule call back. KVM uses this interrupt to force a cpu out of 258 * guest mode 259 */ 260 __visible void __irq_entry smp_reschedule_interrupt(struct pt_regs *regs) 261 { 262 ack_APIC_irq(); 263 inc_irq_stat(irq_resched_count); 264 kvm_set_cpu_l1tf_flush_l1d(); 265 266 if (trace_resched_ipi_enabled()) { 267 /* 268 * scheduler_ipi() might call irq_enter() as well, but 269 * nested calls are fine. 270 */ 271 irq_enter(); 272 trace_reschedule_entry(RESCHEDULE_VECTOR); 273 scheduler_ipi(); 274 trace_reschedule_exit(RESCHEDULE_VECTOR); 275 irq_exit(); 276 return; 277 } 278 scheduler_ipi(); 279 } 280 281 __visible void __irq_entry smp_call_function_interrupt(struct pt_regs *regs) 282 { 283 ipi_entering_ack_irq(); 284 trace_call_function_entry(CALL_FUNCTION_VECTOR); 285 inc_irq_stat(irq_call_count); 286 generic_smp_call_function_interrupt(); 287 trace_call_function_exit(CALL_FUNCTION_VECTOR); 288 exiting_irq(); 289 } 290 291 __visible void __irq_entry smp_call_function_single_interrupt(struct pt_regs *r) 292 { 293 ipi_entering_ack_irq(); 294 trace_call_function_single_entry(CALL_FUNCTION_SINGLE_VECTOR); 295 inc_irq_stat(irq_call_count); 296 generic_smp_call_function_single_interrupt(); 297 trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR); 298 exiting_irq(); 299 } 300 301 static int __init nonmi_ipi_setup(char *str) 302 { 303 smp_no_nmi_ipi = true; 304 return 1; 305 } 306 307 __setup("nonmi_ipi", nonmi_ipi_setup); 308 309 struct smp_ops smp_ops = { 310 .smp_prepare_boot_cpu = native_smp_prepare_boot_cpu, 311 .smp_prepare_cpus = native_smp_prepare_cpus, 312 .smp_cpus_done = native_smp_cpus_done, 313 314 .stop_other_cpus = native_stop_other_cpus, 315 #if defined(CONFIG_KEXEC_CORE) 316 .crash_stop_other_cpus = kdump_nmi_shootdown_cpus, 317 #endif 318 .smp_send_reschedule = native_smp_send_reschedule, 319 320 .cpu_up = native_cpu_up, 321 .cpu_die = native_cpu_die, 322 .cpu_disable = native_cpu_disable, 323 .play_dead = native_play_dead, 324 325 .send_call_func_ipi = native_send_call_func_ipi, 326 .send_call_func_single_ipi = native_send_call_func_single_ipi, 327 }; 328 EXPORT_SYMBOL_GPL(smp_ops); 329