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 #include <linux/kexec.h>
25
26 #include <asm/mtrr.h>
27 #include <asm/tlbflush.h>
28 #include <asm/mmu_context.h>
29 #include <asm/proto.h>
30 #include <asm/apic.h>
31 #include <asm/cpu.h>
32 #include <asm/idtentry.h>
33 #include <asm/nmi.h>
34 #include <asm/mce.h>
35 #include <asm/trace/irq_vectors.h>
36 #include <asm/kexec.h>
37 #include <asm/reboot.h>
38
39 /*
40 * Some notes on x86 processor bugs affecting SMP operation:
41 *
42 * Pentium, Pentium Pro, II, III (and all CPUs) have bugs.
43 * The Linux implications for SMP are handled as follows:
44 *
45 * Pentium III / [Xeon]
46 * None of the E1AP-E3AP errata are visible to the user.
47 *
48 * E1AP. see PII A1AP
49 * E2AP. see PII A2AP
50 * E3AP. see PII A3AP
51 *
52 * Pentium II / [Xeon]
53 * None of the A1AP-A3AP errata are visible to the user.
54 *
55 * A1AP. see PPro 1AP
56 * A2AP. see PPro 2AP
57 * A3AP. see PPro 7AP
58 *
59 * Pentium Pro
60 * None of 1AP-9AP errata are visible to the normal user,
61 * except occasional delivery of 'spurious interrupt' as trap #15.
62 * This is very rare and a non-problem.
63 *
64 * 1AP. Linux maps APIC as non-cacheable
65 * 2AP. worked around in hardware
66 * 3AP. fixed in C0 and above steppings microcode update.
67 * Linux does not use excessive STARTUP_IPIs.
68 * 4AP. worked around in hardware
69 * 5AP. symmetric IO mode (normal Linux operation) not affected.
70 * 'noapic' mode has vector 0xf filled out properly.
71 * 6AP. 'noapic' mode might be affected - fixed in later steppings
72 * 7AP. We do not assume writes to the LVT deasserting IRQs
73 * 8AP. We do not enable low power mode (deep sleep) during MP bootup
74 * 9AP. We do not use mixed mode
75 *
76 * Pentium
77 * There is a marginal case where REP MOVS on 100MHz SMP
78 * machines with B stepping processors can fail. XXX should provide
79 * an L1cache=Writethrough or L1cache=off option.
80 *
81 * B stepping CPUs may hang. There are hardware work arounds
82 * for this. We warn about it in case your board doesn't have the work
83 * arounds. Basically that's so I can tell anyone with a B stepping
84 * CPU and SMP problems "tough".
85 *
86 * Specific items [From Pentium Processor Specification Update]
87 *
88 * 1AP. Linux doesn't use remote read
89 * 2AP. Linux doesn't trust APIC errors
90 * 3AP. We work around this
91 * 4AP. Linux never generated 3 interrupts of the same priority
92 * to cause a lost local interrupt.
93 * 5AP. Remote read is never used
94 * 6AP. not affected - worked around in hardware
95 * 7AP. not affected - worked around in hardware
96 * 8AP. worked around in hardware - we get explicit CS errors if not
97 * 9AP. only 'noapic' mode affected. Might generate spurious
98 * interrupts, we log only the first one and count the
99 * rest silently.
100 * 10AP. not affected - worked around in hardware
101 * 11AP. Linux reads the APIC between writes to avoid this, as per
102 * the documentation. Make sure you preserve this as it affects
103 * the C stepping chips too.
104 * 12AP. not affected - worked around in hardware
105 * 13AP. not affected - worked around in hardware
106 * 14AP. we always deassert INIT during bootup
107 * 15AP. not affected - worked around in hardware
108 * 16AP. not affected - worked around in hardware
109 * 17AP. not affected - worked around in hardware
110 * 18AP. not affected - worked around in hardware
111 * 19AP. not affected - worked around in BIOS
112 *
113 * If this sounds worrying believe me these bugs are either ___RARE___,
114 * or are signal timing bugs worked around in hardware and there's
115 * about nothing of note with C stepping upwards.
116 */
117
118 static atomic_t stopping_cpu = ATOMIC_INIT(-1);
119 static bool smp_no_nmi_ipi = false;
120
smp_stop_nmi_callback(unsigned int val,struct pt_regs * regs)121 static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs)
122 {
123 /* We are registered on stopping cpu too, avoid spurious NMI */
124 if (raw_smp_processor_id() == atomic_read(&stopping_cpu))
125 return NMI_HANDLED;
126
127 cpu_emergency_disable_virtualization();
128 stop_this_cpu(NULL);
129
130 return NMI_HANDLED;
131 }
132
133 /*
134 * this function calls the 'stop' function on all other CPUs in the system.
135 */
DEFINE_IDTENTRY_SYSVEC(sysvec_reboot)136 DEFINE_IDTENTRY_SYSVEC(sysvec_reboot)
137 {
138 apic_eoi();
139 cpu_emergency_disable_virtualization();
140 stop_this_cpu(NULL);
141 }
142
register_stop_handler(void)143 static int register_stop_handler(void)
144 {
145 return register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback,
146 NMI_FLAG_FIRST, "smp_stop");
147 }
148
native_stop_other_cpus(int wait)149 static void native_stop_other_cpus(int wait)
150 {
151 unsigned int cpu = smp_processor_id();
152 unsigned long flags, timeout;
153
154 if (reboot_force)
155 return;
156
157 /* Only proceed if this is the first CPU to reach this code */
158 if (atomic_cmpxchg(&stopping_cpu, -1, cpu) != -1)
159 return;
160
161 /* For kexec, ensure that offline CPUs are out of MWAIT and in HLT */
162 if (kexec_in_progress)
163 smp_kick_mwait_play_dead();
164
165 /*
166 * 1) Send an IPI on the reboot vector to all other CPUs.
167 *
168 * The other CPUs should react on it after leaving critical
169 * sections and re-enabling interrupts. They might still hold
170 * locks, but there is nothing which can be done about that.
171 *
172 * 2) Wait for all other CPUs to report that they reached the
173 * HLT loop in stop_this_cpu()
174 *
175 * 3) If #2 timed out send an NMI to the CPUs which did not
176 * yet report
177 *
178 * 4) Wait for all other CPUs to report that they reached the
179 * HLT loop in stop_this_cpu()
180 *
181 * #3 can obviously race against a CPU reaching the HLT loop late.
182 * That CPU will have reported already and the "have all CPUs
183 * reached HLT" condition will be true despite the fact that the
184 * other CPU is still handling the NMI. Again, there is no
185 * protection against that as "disabled" APICs still respond to
186 * NMIs.
187 */
188 cpumask_copy(&cpus_stop_mask, cpu_online_mask);
189 cpumask_clear_cpu(cpu, &cpus_stop_mask);
190
191 if (!cpumask_empty(&cpus_stop_mask)) {
192 apic_send_IPI_allbutself(REBOOT_VECTOR);
193
194 /*
195 * Don't wait longer than a second for IPI completion. The
196 * wait request is not checked here because that would
197 * prevent an NMI shutdown attempt in case that not all
198 * CPUs reach shutdown state.
199 */
200 timeout = USEC_PER_SEC;
201 while (!cpumask_empty(&cpus_stop_mask) && timeout--)
202 udelay(1);
203 }
204
205 /* if the REBOOT_VECTOR didn't work, try with the NMI */
206 if (!cpumask_empty(&cpus_stop_mask)) {
207 /*
208 * If NMI IPI is enabled, try to register the stop handler
209 * and send the IPI. In any case try to wait for the other
210 * CPUs to stop.
211 */
212 if (!smp_no_nmi_ipi && !register_stop_handler()) {
213 pr_emerg("Shutting down cpus with NMI\n");
214
215 for_each_cpu(cpu, &cpus_stop_mask)
216 __apic_send_IPI(cpu, NMI_VECTOR);
217 }
218 /*
219 * Don't wait longer than 10 ms if the caller didn't
220 * request it. If wait is true, the machine hangs here if
221 * one or more CPUs do not reach shutdown state.
222 */
223 timeout = USEC_PER_MSEC * 10;
224 while (!cpumask_empty(&cpus_stop_mask) && (wait || timeout--))
225 udelay(1);
226 }
227
228 local_irq_save(flags);
229 disable_local_APIC();
230 mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
231 local_irq_restore(flags);
232
233 /*
234 * Ensure that the cpus_stop_mask cache lines are invalidated on
235 * the other CPUs. See comment vs. SME in stop_this_cpu().
236 */
237 cpumask_clear(&cpus_stop_mask);
238 }
239
240 /*
241 * Reschedule call back. KVM uses this interrupt to force a cpu out of
242 * guest mode.
243 */
DEFINE_IDTENTRY_SYSVEC_SIMPLE(sysvec_reschedule_ipi)244 DEFINE_IDTENTRY_SYSVEC_SIMPLE(sysvec_reschedule_ipi)
245 {
246 apic_eoi();
247 trace_reschedule_entry(RESCHEDULE_VECTOR);
248 inc_irq_stat(irq_resched_count);
249 scheduler_ipi();
250 trace_reschedule_exit(RESCHEDULE_VECTOR);
251 }
252
DEFINE_IDTENTRY_SYSVEC(sysvec_call_function)253 DEFINE_IDTENTRY_SYSVEC(sysvec_call_function)
254 {
255 apic_eoi();
256 trace_call_function_entry(CALL_FUNCTION_VECTOR);
257 inc_irq_stat(irq_call_count);
258 generic_smp_call_function_interrupt();
259 trace_call_function_exit(CALL_FUNCTION_VECTOR);
260 }
261
DEFINE_IDTENTRY_SYSVEC(sysvec_call_function_single)262 DEFINE_IDTENTRY_SYSVEC(sysvec_call_function_single)
263 {
264 apic_eoi();
265 trace_call_function_single_entry(CALL_FUNCTION_SINGLE_VECTOR);
266 inc_irq_stat(irq_call_count);
267 generic_smp_call_function_single_interrupt();
268 trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR);
269 }
270
nonmi_ipi_setup(char * str)271 static int __init nonmi_ipi_setup(char *str)
272 {
273 smp_no_nmi_ipi = true;
274 return 1;
275 }
276
277 __setup("nonmi_ipi", nonmi_ipi_setup);
278
279 struct smp_ops smp_ops = {
280 .smp_prepare_boot_cpu = native_smp_prepare_boot_cpu,
281 .smp_prepare_cpus = native_smp_prepare_cpus,
282 .smp_cpus_done = native_smp_cpus_done,
283
284 .stop_other_cpus = native_stop_other_cpus,
285 #if defined(CONFIG_KEXEC_CORE)
286 .crash_stop_other_cpus = kdump_nmi_shootdown_cpus,
287 #endif
288 .smp_send_reschedule = native_smp_send_reschedule,
289
290 .kick_ap_alive = native_kick_ap,
291 .cpu_disable = native_cpu_disable,
292 .play_dead = native_play_dead,
293
294 .send_call_func_ipi = native_send_call_func_ipi,
295 .send_call_func_single_ipi = native_send_call_func_single_ipi,
296 };
297 EXPORT_SYMBOL_GPL(smp_ops);
298