2 * SMP initialisation and IPI support
3 * Based on arch/arm/kernel/smp.c
5 * Copyright (C) 2012 ARM Ltd.
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
20 #include <linux/acpi.h>
21 #include <linux/delay.h>
22 #include <linux/init.h>
23 #include <linux/spinlock.h>
24 #include <linux/sched/mm.h>
25 #include <linux/sched/hotplug.h>
26 #include <linux/sched/task_stack.h>
27 #include <linux/interrupt.h>
28 #include <linux/cache.h>
29 #include <linux/profile.h>
30 #include <linux/errno.h>
32 #include <linux/err.h>
33 #include <linux/cpu.h>
34 #include <linux/smp.h>
35 #include <linux/seq_file.h>
36 #include <linux/irq.h>
37 #include <linux/percpu.h>
38 #include <linux/clockchips.h>
39 #include <linux/completion.h>
41 #include <linux/irq_work.h>
43 #include <asm/alternative.h>
44 #include <asm/atomic.h>
45 #include <asm/cacheflush.h>
47 #include <asm/cputype.h>
48 #include <asm/cpu_ops.h>
49 #include <asm/mmu_context.h>
51 #include <asm/pgtable.h>
52 #include <asm/pgalloc.h>
53 #include <asm/processor.h>
54 #include <asm/smp_plat.h>
55 #include <asm/sections.h>
56 #include <asm/tlbflush.h>
57 #include <asm/ptrace.h>
60 #define CREATE_TRACE_POINTS
61 #include <trace/events/ipi.h>
63 DEFINE_PER_CPU_READ_MOSTLY(int, cpu_number
);
64 EXPORT_PER_CPU_SYMBOL(cpu_number
);
67 * as from 2.5, kernels no longer have an init_tasks structure
68 * so we need some other way of telling a new secondary core
69 * where to place its SVC stack
71 struct secondary_data secondary_data
;
72 /* Number of CPUs which aren't online, but looping in kernel text. */
73 int cpus_stuck_in_kernel
;
84 #ifdef CONFIG_ARM64_VHE
86 /* Whether the boot CPU is running in HYP mode or not*/
87 static bool boot_cpu_hyp_mode
;
89 static inline void save_boot_cpu_run_el(void)
91 boot_cpu_hyp_mode
= is_kernel_in_hyp_mode();
94 static inline bool is_boot_cpu_in_hyp_mode(void)
96 return boot_cpu_hyp_mode
;
100 * Verify that a secondary CPU is running the kernel at the same
101 * EL as that of the boot CPU.
103 void verify_cpu_run_el(void)
105 bool in_el2
= is_kernel_in_hyp_mode();
106 bool boot_cpu_el2
= is_boot_cpu_in_hyp_mode();
108 if (in_el2
^ boot_cpu_el2
) {
109 pr_crit("CPU%d: mismatched Exception Level(EL%d) with boot CPU(EL%d)\n",
112 boot_cpu_el2
? 2 : 1);
118 static inline void save_boot_cpu_run_el(void) {}
121 #ifdef CONFIG_HOTPLUG_CPU
122 static int op_cpu_kill(unsigned int cpu
);
124 static inline int op_cpu_kill(unsigned int cpu
)
132 * Boot a secondary CPU, and assign it the specified idle task.
133 * This also gives us the initial stack to use for this CPU.
135 static int boot_secondary(unsigned int cpu
, struct task_struct
*idle
)
137 if (cpu_ops
[cpu
]->cpu_boot
)
138 return cpu_ops
[cpu
]->cpu_boot(cpu
);
143 static DECLARE_COMPLETION(cpu_running
);
145 int __cpu_up(unsigned int cpu
, struct task_struct
*idle
)
151 * We need to tell the secondary core where to find its stack and the
154 secondary_data
.task
= idle
;
155 secondary_data
.stack
= task_stack_page(idle
) + THREAD_START_SP
;
156 update_cpu_boot_status(CPU_MMU_OFF
);
157 __flush_dcache_area(&secondary_data
, sizeof(secondary_data
));
160 * Now bring the CPU into our world.
162 ret
= boot_secondary(cpu
, idle
);
165 * CPU was successfully started, wait for it to come online or
168 wait_for_completion_timeout(&cpu_running
,
169 msecs_to_jiffies(1000));
171 if (!cpu_online(cpu
)) {
172 pr_crit("CPU%u: failed to come online\n", cpu
);
176 pr_err("CPU%u: failed to boot: %d\n", cpu
, ret
);
179 secondary_data
.task
= NULL
;
180 secondary_data
.stack
= NULL
;
181 status
= READ_ONCE(secondary_data
.status
);
184 if (status
== CPU_MMU_OFF
)
185 status
= READ_ONCE(__early_cpu_boot_status
);
189 pr_err("CPU%u: failed in unknown state : 0x%lx\n",
193 if (!op_cpu_kill(cpu
)) {
194 pr_crit("CPU%u: died during early boot\n", cpu
);
198 pr_crit("CPU%u: may not have shut down cleanly\n", cpu
);
199 case CPU_STUCK_IN_KERNEL
:
200 pr_crit("CPU%u: is stuck in kernel\n", cpu
);
201 cpus_stuck_in_kernel
++;
203 case CPU_PANIC_KERNEL
:
204 panic("CPU%u detected unsupported configuration\n", cpu
);
212 * This is the secondary CPU boot entry. We're using this CPUs
213 * idle thread stack, but a set of temporary page tables.
215 asmlinkage
void secondary_start_kernel(void)
217 struct mm_struct
*mm
= &init_mm
;
220 cpu
= task_cpu(current
);
221 set_my_cpu_offset(per_cpu_offset(cpu
));
224 * All kernel threads share the same mm context; grab a
225 * reference and switch to it.
228 current
->active_mm
= mm
;
231 * TTBR0 is only used for the identity mapping at this stage. Make it
232 * point to zero page to avoid speculatively fetching new entries.
234 cpu_uninstall_idmap();
237 trace_hardirqs_off();
240 * If the system has established the capabilities, make sure
241 * this CPU ticks all of those. If it doesn't, the CPU will
242 * fail to come online.
244 check_local_cpu_capabilities();
246 if (cpu_ops
[cpu
]->cpu_postboot
)
247 cpu_ops
[cpu
]->cpu_postboot();
250 * Log the CPU info before it is marked online and might get read.
255 * Enable GIC and timers.
257 notify_cpu_starting(cpu
);
259 store_cpu_topology(cpu
);
262 * OK, now it's safe to let the boot CPU continue. Wait for
263 * the CPU migration code to notice that the CPU is online
264 * before we continue.
266 pr_info("CPU%u: Booted secondary processor [%08x]\n",
267 cpu
, read_cpuid_id());
268 update_cpu_boot_status(CPU_BOOT_SUCCESS
);
269 set_cpu_online(cpu
, true);
270 complete(&cpu_running
);
273 local_async_enable();
276 * OK, it's off to the idle thread for us
278 cpu_startup_entry(CPUHP_AP_ONLINE_IDLE
);
281 #ifdef CONFIG_HOTPLUG_CPU
282 static int op_cpu_disable(unsigned int cpu
)
285 * If we don't have a cpu_die method, abort before we reach the point
286 * of no return. CPU0 may not have an cpu_ops, so test for it.
288 if (!cpu_ops
[cpu
] || !cpu_ops
[cpu
]->cpu_die
)
292 * We may need to abort a hot unplug for some other mechanism-specific
295 if (cpu_ops
[cpu
]->cpu_disable
)
296 return cpu_ops
[cpu
]->cpu_disable(cpu
);
302 * __cpu_disable runs on the processor to be shutdown.
304 int __cpu_disable(void)
306 unsigned int cpu
= smp_processor_id();
309 ret
= op_cpu_disable(cpu
);
314 * Take this CPU offline. Once we clear this, we can't return,
315 * and we must not schedule until we're ready to give up the cpu.
317 set_cpu_online(cpu
, false);
320 * OK - migrate IRQs away from this CPU
322 irq_migrate_all_off_this_cpu();
327 static int op_cpu_kill(unsigned int cpu
)
330 * If we have no means of synchronising with the dying CPU, then assume
331 * that it is really dead. We can only wait for an arbitrary length of
332 * time and hope that it's dead, so let's skip the wait and just hope.
334 if (!cpu_ops
[cpu
]->cpu_kill
)
337 return cpu_ops
[cpu
]->cpu_kill(cpu
);
341 * called on the thread which is asking for a CPU to be shutdown -
342 * waits until shutdown has completed, or it is timed out.
344 void __cpu_die(unsigned int cpu
)
348 if (!cpu_wait_death(cpu
, 5)) {
349 pr_crit("CPU%u: cpu didn't die\n", cpu
);
352 pr_notice("CPU%u: shutdown\n", cpu
);
355 * Now that the dying CPU is beyond the point of no return w.r.t.
356 * in-kernel synchronisation, try to get the firwmare to help us to
357 * verify that it has really left the kernel before we consider
358 * clobbering anything it might still be using.
360 err
= op_cpu_kill(cpu
);
362 pr_warn("CPU%d may not have shut down cleanly: %d\n",
367 * Called from the idle thread for the CPU which has been shutdown.
369 * Note that we disable IRQs here, but do not re-enable them
370 * before returning to the caller. This is also the behaviour
371 * of the other hotplug-cpu capable cores, so presumably coming
372 * out of idle fixes this.
376 unsigned int cpu
= smp_processor_id();
382 /* Tell __cpu_die() that this CPU is now safe to dispose of */
383 (void)cpu_report_death();
386 * Actually shutdown the CPU. This must never fail. The specific hotplug
387 * mechanism must perform all required cache maintenance to ensure that
388 * no dirty lines are lost in the process of shutting down the CPU.
390 cpu_ops
[cpu
]->cpu_die(cpu
);
397 * Kill the calling secondary CPU, early in bringup before it is turned
400 void cpu_die_early(void)
402 int cpu
= smp_processor_id();
404 pr_crit("CPU%d: will not boot\n", cpu
);
406 /* Mark this CPU absent */
407 set_cpu_present(cpu
, 0);
409 #ifdef CONFIG_HOTPLUG_CPU
410 update_cpu_boot_status(CPU_KILL_ME
);
411 /* Check if we can park ourselves */
412 if (cpu_ops
[cpu
] && cpu_ops
[cpu
]->cpu_die
)
413 cpu_ops
[cpu
]->cpu_die(cpu
);
415 update_cpu_boot_status(CPU_STUCK_IN_KERNEL
);
420 static void __init
hyp_mode_check(void)
422 if (is_hyp_mode_available())
423 pr_info("CPU: All CPU(s) started at EL2\n");
424 else if (is_hyp_mode_mismatched())
425 WARN_TAINT(1, TAINT_CPU_OUT_OF_SPEC
,
426 "CPU: CPUs started in inconsistent modes");
428 pr_info("CPU: All CPU(s) started at EL1\n");
431 void __init
smp_cpus_done(unsigned int max_cpus
)
433 pr_info("SMP: Total of %d processors activated.\n", num_online_cpus());
434 setup_cpu_features();
436 apply_alternatives_all();
439 void __init
smp_prepare_boot_cpu(void)
441 set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
443 * Initialise the static keys early as they may be enabled by the
447 cpuinfo_store_boot_cpu();
448 save_boot_cpu_run_el();
450 * Run the errata work around checks on the boot CPU, once we have
451 * initialised the cpu feature infrastructure from
452 * cpuinfo_store_boot_cpu() above.
454 update_cpu_errata_workarounds();
457 static u64 __init
of_get_cpu_mpidr(struct device_node
*dn
)
463 * A cpu node with missing "reg" property is
464 * considered invalid to build a cpu_logical_map
467 cell
= of_get_property(dn
, "reg", NULL
);
469 pr_err("%s: missing reg property\n", dn
->full_name
);
473 hwid
= of_read_number(cell
, of_n_addr_cells(dn
));
475 * Non affinity bits must be set to 0 in the DT
477 if (hwid
& ~MPIDR_HWID_BITMASK
) {
478 pr_err("%s: invalid reg property\n", dn
->full_name
);
485 * Duplicate MPIDRs are a recipe for disaster. Scan all initialized
486 * entries and check for duplicates. If any is found just ignore the
487 * cpu. cpu_logical_map was initialized to INVALID_HWID to avoid
488 * matching valid MPIDR values.
490 static bool __init
is_mpidr_duplicate(unsigned int cpu
, u64 hwid
)
494 for (i
= 1; (i
< cpu
) && (i
< NR_CPUS
); i
++)
495 if (cpu_logical_map(i
) == hwid
)
501 * Initialize cpu operations for a logical cpu and
502 * set it in the possible mask on success
504 static int __init
smp_cpu_setup(int cpu
)
506 if (cpu_read_ops(cpu
))
509 if (cpu_ops
[cpu
]->cpu_init(cpu
))
512 set_cpu_possible(cpu
, true);
517 static bool bootcpu_valid __initdata
;
518 static unsigned int cpu_count
= 1;
522 * acpi_map_gic_cpu_interface - parse processor MADT entry
524 * Carry out sanity checks on MADT processor entry and initialize
525 * cpu_logical_map on success
528 acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt
*processor
)
530 u64 hwid
= processor
->arm_mpidr
;
532 if (!(processor
->flags
& ACPI_MADT_ENABLED
)) {
533 pr_debug("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid
);
537 if (hwid
& ~MPIDR_HWID_BITMASK
|| hwid
== INVALID_HWID
) {
538 pr_err("skipping CPU entry with invalid MPIDR 0x%llx\n", hwid
);
542 if (is_mpidr_duplicate(cpu_count
, hwid
)) {
543 pr_err("duplicate CPU MPIDR 0x%llx in MADT\n", hwid
);
547 /* Check if GICC structure of boot CPU is available in the MADT */
548 if (cpu_logical_map(0) == hwid
) {
550 pr_err("duplicate boot CPU MPIDR: 0x%llx in MADT\n",
554 bootcpu_valid
= true;
555 early_map_cpu_to_node(0, acpi_numa_get_nid(0, hwid
));
559 if (cpu_count
>= NR_CPUS
)
562 /* map the logical cpu id to cpu MPIDR */
563 cpu_logical_map(cpu_count
) = hwid
;
566 * Set-up the ACPI parking protocol cpu entries
567 * while initializing the cpu_logical_map to
568 * avoid parsing MADT entries multiple times for
569 * nothing (ie a valid cpu_logical_map entry should
570 * contain a valid parking protocol data set to
571 * initialize the cpu if the parking protocol is
572 * the only available enable method).
574 acpi_set_mailbox_entry(cpu_count
, processor
);
576 early_map_cpu_to_node(cpu_count
, acpi_numa_get_nid(cpu_count
, hwid
));
582 acpi_parse_gic_cpu_interface(struct acpi_subtable_header
*header
,
583 const unsigned long end
)
585 struct acpi_madt_generic_interrupt
*processor
;
587 processor
= (struct acpi_madt_generic_interrupt
*)header
;
588 if (BAD_MADT_GICC_ENTRY(processor
, end
))
591 acpi_table_print_madt_entry(header
);
593 acpi_map_gic_cpu_interface(processor
);
598 #define acpi_table_parse_madt(...) do { } while (0)
602 * Enumerate the possible CPU set from the device tree and build the
603 * cpu logical map array containing MPIDR values related to logical
604 * cpus. Assumes that cpu_logical_map(0) has already been initialized.
606 static void __init
of_parse_and_init_cpus(void)
608 struct device_node
*dn
;
610 for_each_node_by_type(dn
, "cpu") {
611 u64 hwid
= of_get_cpu_mpidr(dn
);
613 if (hwid
== INVALID_HWID
)
616 if (is_mpidr_duplicate(cpu_count
, hwid
)) {
617 pr_err("%s: duplicate cpu reg properties in the DT\n",
623 * The numbering scheme requires that the boot CPU
624 * must be assigned logical id 0. Record it so that
625 * the logical map built from DT is validated and can
628 if (hwid
== cpu_logical_map(0)) {
630 pr_err("%s: duplicate boot cpu reg property in DT\n",
635 bootcpu_valid
= true;
636 early_map_cpu_to_node(0, of_node_to_nid(dn
));
639 * cpu_logical_map has already been
640 * initialized and the boot cpu doesn't need
641 * the enable-method so continue without
647 if (cpu_count
>= NR_CPUS
)
650 pr_debug("cpu logical map 0x%llx\n", hwid
);
651 cpu_logical_map(cpu_count
) = hwid
;
653 early_map_cpu_to_node(cpu_count
, of_node_to_nid(dn
));
660 * Enumerate the possible CPU set from the device tree or ACPI and build the
661 * cpu logical map array containing MPIDR values related to logical
662 * cpus. Assumes that cpu_logical_map(0) has already been initialized.
664 void __init
smp_init_cpus(void)
669 of_parse_and_init_cpus();
672 * do a walk of MADT to determine how many CPUs
673 * we have including disabled CPUs, and get information
674 * we need for SMP init
676 acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_INTERRUPT
,
677 acpi_parse_gic_cpu_interface
, 0);
679 if (cpu_count
> nr_cpu_ids
)
680 pr_warn("Number of cores (%d) exceeds configured maximum of %d - clipping\n",
681 cpu_count
, nr_cpu_ids
);
683 if (!bootcpu_valid
) {
684 pr_err("missing boot CPU MPIDR, not enabling secondaries\n");
689 * We need to set the cpu_logical_map entries before enabling
690 * the cpus so that cpu processor description entries (DT cpu nodes
691 * and ACPI MADT entries) can be retrieved by matching the cpu hwid
692 * with entries in cpu_logical_map while initializing the cpus.
693 * If the cpu set-up fails, invalidate the cpu_logical_map entry.
695 for (i
= 1; i
< nr_cpu_ids
; i
++) {
696 if (cpu_logical_map(i
) != INVALID_HWID
) {
697 if (smp_cpu_setup(i
))
698 cpu_logical_map(i
) = INVALID_HWID
;
703 void __init
smp_prepare_cpus(unsigned int max_cpus
)
707 unsigned int this_cpu
;
711 this_cpu
= smp_processor_id();
712 store_cpu_topology(this_cpu
);
713 numa_store_cpu_info(this_cpu
);
716 * If UP is mandated by "nosmp" (which implies "maxcpus=0"), don't set
717 * secondary CPUs present.
723 * Initialise the present map (which describes the set of CPUs
724 * actually populated at the present time) and release the
725 * secondaries from the bootloader.
727 for_each_possible_cpu(cpu
) {
729 per_cpu(cpu_number
, cpu
) = cpu
;
731 if (cpu
== smp_processor_id())
737 err
= cpu_ops
[cpu
]->cpu_prepare(cpu
);
741 set_cpu_present(cpu
, true);
742 numa_store_cpu_info(cpu
);
746 void (*__smp_cross_call
)(const struct cpumask
*, unsigned int);
748 void __init
set_smp_cross_call(void (*fn
)(const struct cpumask
*, unsigned int))
750 __smp_cross_call
= fn
;
753 static const char *ipi_types
[NR_IPI
] __tracepoint_string
= {
754 #define S(x,s) [x] = s
755 S(IPI_RESCHEDULE
, "Rescheduling interrupts"),
756 S(IPI_CALL_FUNC
, "Function call interrupts"),
757 S(IPI_CPU_STOP
, "CPU stop interrupts"),
758 S(IPI_TIMER
, "Timer broadcast interrupts"),
759 S(IPI_IRQ_WORK
, "IRQ work interrupts"),
760 S(IPI_WAKEUP
, "CPU wake-up interrupts"),
763 static void smp_cross_call(const struct cpumask
*target
, unsigned int ipinr
)
765 trace_ipi_raise(target
, ipi_types
[ipinr
]);
766 __smp_cross_call(target
, ipinr
);
769 void show_ipi_list(struct seq_file
*p
, int prec
)
773 for (i
= 0; i
< NR_IPI
; i
++) {
774 seq_printf(p
, "%*s%u:%s", prec
- 1, "IPI", i
,
775 prec
>= 4 ? " " : "");
776 for_each_online_cpu(cpu
)
777 seq_printf(p
, "%10u ",
778 __get_irq_stat(cpu
, ipi_irqs
[i
]));
779 seq_printf(p
, " %s\n", ipi_types
[i
]);
783 u64
smp_irq_stat_cpu(unsigned int cpu
)
788 for (i
= 0; i
< NR_IPI
; i
++)
789 sum
+= __get_irq_stat(cpu
, ipi_irqs
[i
]);
794 void arch_send_call_function_ipi_mask(const struct cpumask
*mask
)
796 smp_cross_call(mask
, IPI_CALL_FUNC
);
799 void arch_send_call_function_single_ipi(int cpu
)
801 smp_cross_call(cpumask_of(cpu
), IPI_CALL_FUNC
);
804 #ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
805 void arch_send_wakeup_ipi_mask(const struct cpumask
*mask
)
807 smp_cross_call(mask
, IPI_WAKEUP
);
811 #ifdef CONFIG_IRQ_WORK
812 void arch_irq_work_raise(void)
814 if (__smp_cross_call
)
815 smp_cross_call(cpumask_of(smp_processor_id()), IPI_IRQ_WORK
);
820 * ipi_cpu_stop - handle IPI from smp_send_stop()
822 static void ipi_cpu_stop(unsigned int cpu
)
824 set_cpu_online(cpu
, false);
833 * Main handler for inter-processor interrupts
835 void handle_IPI(int ipinr
, struct pt_regs
*regs
)
837 unsigned int cpu
= smp_processor_id();
838 struct pt_regs
*old_regs
= set_irq_regs(regs
);
840 if ((unsigned)ipinr
< NR_IPI
) {
841 trace_ipi_entry_rcuidle(ipi_types
[ipinr
]);
842 __inc_irq_stat(cpu
, ipi_irqs
[ipinr
]);
852 generic_smp_call_function_interrupt();
862 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
865 tick_receive_broadcast();
870 #ifdef CONFIG_IRQ_WORK
878 #ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
880 WARN_ONCE(!acpi_parking_protocol_valid(cpu
),
881 "CPU%u: Wake-up IPI outside the ACPI parking protocol\n",
887 pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu
, ipinr
);
891 if ((unsigned)ipinr
< NR_IPI
)
892 trace_ipi_exit_rcuidle(ipi_types
[ipinr
]);
893 set_irq_regs(old_regs
);
896 void smp_send_reschedule(int cpu
)
898 smp_cross_call(cpumask_of(cpu
), IPI_RESCHEDULE
);
901 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
902 void tick_broadcast(const struct cpumask
*mask
)
904 smp_cross_call(mask
, IPI_TIMER
);
908 void smp_send_stop(void)
910 unsigned long timeout
;
912 if (num_online_cpus() > 1) {
915 cpumask_copy(&mask
, cpu_online_mask
);
916 cpumask_clear_cpu(smp_processor_id(), &mask
);
918 if (system_state
== SYSTEM_BOOTING
||
919 system_state
== SYSTEM_RUNNING
)
920 pr_crit("SMP: stopping secondary CPUs\n");
921 smp_cross_call(&mask
, IPI_CPU_STOP
);
924 /* Wait up to one second for other CPUs to stop */
925 timeout
= USEC_PER_SEC
;
926 while (num_online_cpus() > 1 && timeout
--)
929 if (num_online_cpus() > 1)
930 pr_warning("SMP: failed to stop secondary CPUs %*pbl\n",
931 cpumask_pr_args(cpu_online_mask
));
937 int setup_profiling_timer(unsigned int multiplier
)
942 static bool have_cpu_die(void)
944 #ifdef CONFIG_HOTPLUG_CPU
945 int any_cpu
= raw_smp_processor_id();
947 if (cpu_ops
[any_cpu
]->cpu_die
)
953 bool cpus_are_stuck_in_kernel(void)
955 bool smp_spin_tables
= (num_possible_cpus() > 1 && !have_cpu_die());
957 return !!cpus_stuck_in_kernel
|| smp_spin_tables
;