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1 /*
2  * Xen SMP support
3  *
4  * This file implements the Xen versions of smp_ops.  SMP under Xen is
5  * very straightforward.  Bringing a CPU up is simply a matter of
6  * loading its initial context and setting it running.
7  *
8  * IPIs are handled through the Xen event mechanism.
9  *
10  * Because virtual CPUs can be scheduled onto any real CPU, there's no
11  * useful topology information for the kernel to make use of.  As a
12  * result, all CPUs are treated as if they're single-core and
13  * single-threaded.
14  */
15 #include <linux/sched.h>
16 #include <linux/err.h>
17 #include <linux/slab.h>
18 #include <linux/smp.h>
19 #include <linux/irq_work.h>
20
21 #include <asm/paravirt.h>
22 #include <asm/desc.h>
23 #include <asm/pgtable.h>
24 #include <asm/cpu.h>
25
26 #include <xen/interface/xen.h>
27 #include <xen/interface/vcpu.h>
28
29 #include <asm/xen/interface.h>
30 #include <asm/xen/hypercall.h>
31
32 #include <xen/xen.h>
33 #include <xen/page.h>
34 #include <xen/events.h>
35
36 #include <xen/hvc-console.h>
37 #include "xen-ops.h"
38 #include "mmu.h"
39
40 cpumask_var_t xen_cpu_initialized_map;
41
42 static DEFINE_PER_CPU(int, xen_resched_irq);
43 static DEFINE_PER_CPU(int, xen_callfunc_irq);
44 static DEFINE_PER_CPU(int, xen_callfuncsingle_irq);
45 static DEFINE_PER_CPU(int, xen_irq_work);
46 static DEFINE_PER_CPU(int, xen_debug_irq) = -1;
47
48 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);
49 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id);
50 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
51
52 /*
53  * Reschedule call back.
54  */
55 static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
56 {
57         inc_irq_stat(irq_resched_count);
58         scheduler_ipi();
59
60         return IRQ_HANDLED;
61 }
62
63 static void __cpuinit cpu_bringup(void)
64 {
65         int cpu;
66
67         cpu_init();
68         touch_softlockup_watchdog();
69         preempt_disable();
70
71         xen_enable_sysenter();
72         xen_enable_syscall();
73
74         cpu = smp_processor_id();
75         smp_store_cpu_info(cpu);
76         cpu_data(cpu).x86_max_cores = 1;
77         set_cpu_sibling_map(cpu);
78
79         xen_setup_cpu_clockevents();
80
81         notify_cpu_starting(cpu);
82
83         set_cpu_online(cpu, true);
84
85         this_cpu_write(cpu_state, CPU_ONLINE);
86
87         wmb();
88
89         /* We can take interrupts now: we're officially "up". */
90         local_irq_enable();
91
92         wmb();                  /* make sure everything is out */
93 }
94
95 static void __cpuinit cpu_bringup_and_idle(void)
96 {
97         cpu_bringup();
98         cpu_idle();
99 }
100
101 static int xen_smp_intr_init(unsigned int cpu)
102 {
103         int rc;
104         const char *resched_name, *callfunc_name, *debug_name;
105
106         resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
107         rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
108                                     cpu,
109                                     xen_reschedule_interrupt,
110                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
111                                     resched_name,
112                                     NULL);
113         if (rc < 0)
114                 goto fail;
115         per_cpu(xen_resched_irq, cpu) = rc;
116
117         callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
118         rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
119                                     cpu,
120                                     xen_call_function_interrupt,
121                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
122                                     callfunc_name,
123                                     NULL);
124         if (rc < 0)
125                 goto fail;
126         per_cpu(xen_callfunc_irq, cpu) = rc;
127
128         debug_name = kasprintf(GFP_KERNEL, "debug%d", cpu);
129         rc = bind_virq_to_irqhandler(VIRQ_DEBUG, cpu, xen_debug_interrupt,
130                                      IRQF_DISABLED | IRQF_PERCPU | IRQF_NOBALANCING,
131                                      debug_name, NULL);
132         if (rc < 0)
133                 goto fail;
134         per_cpu(xen_debug_irq, cpu) = rc;
135
136         callfunc_name = kasprintf(GFP_KERNEL, "callfuncsingle%d", cpu);
137         rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_SINGLE_VECTOR,
138                                     cpu,
139                                     xen_call_function_single_interrupt,
140                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
141                                     callfunc_name,
142                                     NULL);
143         if (rc < 0)
144                 goto fail;
145         per_cpu(xen_callfuncsingle_irq, cpu) = rc;
146
147         callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
148         rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
149                                     cpu,
150                                     xen_irq_work_interrupt,
151                                     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
152                                     callfunc_name,
153                                     NULL);
154         if (rc < 0)
155                 goto fail;
156         per_cpu(xen_irq_work, cpu) = rc;
157
158         return 0;
159
160  fail:
161         if (per_cpu(xen_resched_irq, cpu) >= 0)
162                 unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
163         if (per_cpu(xen_callfunc_irq, cpu) >= 0)
164                 unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
165         if (per_cpu(xen_debug_irq, cpu) >= 0)
166                 unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
167         if (per_cpu(xen_callfuncsingle_irq, cpu) >= 0)
168                 unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu),
169                                        NULL);
170         if (per_cpu(xen_irq_work, cpu) >= 0)
171                 unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);
172
173         return rc;
174 }
175
176 static void __init xen_fill_possible_map(void)
177 {
178         int i, rc;
179
180         if (xen_initial_domain())
181                 return;
182
183         for (i = 0; i < nr_cpu_ids; i++) {
184                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
185                 if (rc >= 0) {
186                         num_processors++;
187                         set_cpu_possible(i, true);
188                 }
189         }
190 }
191
192 static void __init xen_filter_cpu_maps(void)
193 {
194         int i, rc;
195         unsigned int subtract = 0;
196
197         if (!xen_initial_domain())
198                 return;
199
200         num_processors = 0;
201         disabled_cpus = 0;
202         for (i = 0; i < nr_cpu_ids; i++) {
203                 rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
204                 if (rc >= 0) {
205                         num_processors++;
206                         set_cpu_possible(i, true);
207                 } else {
208                         set_cpu_possible(i, false);
209                         set_cpu_present(i, false);
210                         subtract++;
211                 }
212         }
213 #ifdef CONFIG_HOTPLUG_CPU
214         /* This is akin to using 'nr_cpus' on the Linux command line.
215          * Which is OK as when we use 'dom0_max_vcpus=X' we can only
216          * have up to X, while nr_cpu_ids is greater than X. This
217          * normally is not a problem, except when CPU hotplugging
218          * is involved and then there might be more than X CPUs
219          * in the guest - which will not work as there is no
220          * hypercall to expand the max number of VCPUs an already
221          * running guest has. So cap it up to X. */
222         if (subtract)
223                 nr_cpu_ids = nr_cpu_ids - subtract;
224 #endif
225
226 }
227
228 static void __init xen_smp_prepare_boot_cpu(void)
229 {
230         BUG_ON(smp_processor_id() != 0);
231         native_smp_prepare_boot_cpu();
232
233         /* We've switched to the "real" per-cpu gdt, so make sure the
234            old memory can be recycled */
235         make_lowmem_page_readwrite(xen_initial_gdt);
236
237         xen_filter_cpu_maps();
238         xen_setup_vcpu_info_placement();
239 }
240
241 static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
242 {
243         unsigned cpu;
244         unsigned int i;
245
246         if (skip_ioapic_setup) {
247                 char *m = (max_cpus == 0) ?
248                         "The nosmp parameter is incompatible with Xen; " \
249                         "use Xen dom0_max_vcpus=1 parameter" :
250                         "The noapic parameter is incompatible with Xen";
251
252                 xen_raw_printk(m);
253                 panic(m);
254         }
255         xen_init_lock_cpu(0);
256
257         smp_store_boot_cpu_info();
258         cpu_data(0).x86_max_cores = 1;
259
260         for_each_possible_cpu(i) {
261                 zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
262                 zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
263                 zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
264         }
265         set_cpu_sibling_map(0);
266
267         if (xen_smp_intr_init(0))
268                 BUG();
269
270         if (!alloc_cpumask_var(&xen_cpu_initialized_map, GFP_KERNEL))
271                 panic("could not allocate xen_cpu_initialized_map\n");
272
273         cpumask_copy(xen_cpu_initialized_map, cpumask_of(0));
274
275         /* Restrict the possible_map according to max_cpus. */
276         while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
277                 for (cpu = nr_cpu_ids - 1; !cpu_possible(cpu); cpu--)
278                         continue;
279                 set_cpu_possible(cpu, false);
280         }
281
282         for_each_possible_cpu(cpu)
283                 set_cpu_present(cpu, true);
284 }
285
286 static int __cpuinit
287 cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
288 {
289         struct vcpu_guest_context *ctxt;
290         struct desc_struct *gdt;
291         unsigned long gdt_mfn;
292
293         if (cpumask_test_and_set_cpu(cpu, xen_cpu_initialized_map))
294                 return 0;
295
296         ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
297         if (ctxt == NULL)
298                 return -ENOMEM;
299
300         gdt = get_cpu_gdt_table(cpu);
301
302         ctxt->flags = VGCF_IN_KERNEL;
303         ctxt->user_regs.ds = __USER_DS;
304         ctxt->user_regs.es = __USER_DS;
305         ctxt->user_regs.ss = __KERNEL_DS;
306 #ifdef CONFIG_X86_32
307         ctxt->user_regs.fs = __KERNEL_PERCPU;
308         ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
309 #else
310         ctxt->gs_base_kernel = per_cpu_offset(cpu);
311 #endif
312         ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
313         ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */
314
315         memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
316
317         xen_copy_trap_info(ctxt->trap_ctxt);
318
319         ctxt->ldt_ents = 0;
320
321         BUG_ON((unsigned long)gdt & ~PAGE_MASK);
322
323         gdt_mfn = arbitrary_virt_to_mfn(gdt);
324         make_lowmem_page_readonly(gdt);
325         make_lowmem_page_readonly(mfn_to_virt(gdt_mfn));
326
327         ctxt->gdt_frames[0] = gdt_mfn;
328         ctxt->gdt_ents      = GDT_ENTRIES;
329
330         ctxt->user_regs.cs = __KERNEL_CS;
331         ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);
332
333         ctxt->kernel_ss = __KERNEL_DS;
334         ctxt->kernel_sp = idle->thread.sp0;
335
336 #ifdef CONFIG_X86_32
337         ctxt->event_callback_cs     = __KERNEL_CS;
338         ctxt->failsafe_callback_cs  = __KERNEL_CS;
339 #endif
340         ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
341         ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback;
342
343         per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
344         ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));
345
346         if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
347                 BUG();
348
349         kfree(ctxt);
350         return 0;
351 }
352
353 static int __cpuinit xen_cpu_up(unsigned int cpu, struct task_struct *idle)
354 {
355         int rc;
356
357         per_cpu(current_task, cpu) = idle;
358 #ifdef CONFIG_X86_32
359         irq_ctx_init(cpu);
360 #else
361         clear_tsk_thread_flag(idle, TIF_FORK);
362         per_cpu(kernel_stack, cpu) =
363                 (unsigned long)task_stack_page(idle) -
364                 KERNEL_STACK_OFFSET + THREAD_SIZE;
365 #endif
366         xen_setup_runstate_info(cpu);
367         xen_setup_timer(cpu);
368         xen_init_lock_cpu(cpu);
369
370         per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
371
372         /* make sure interrupts start blocked */
373         per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
374
375         rc = cpu_initialize_context(cpu, idle);
376         if (rc)
377                 return rc;
378
379         if (num_online_cpus() == 1)
380                 /* Just in case we booted with a single CPU. */
381                 alternatives_enable_smp();
382
383         rc = xen_smp_intr_init(cpu);
384         if (rc)
385                 return rc;
386
387         rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
388         BUG_ON(rc);
389
390         while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
391                 HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
392                 barrier();
393         }
394
395         return 0;
396 }
397
398 static void xen_smp_cpus_done(unsigned int max_cpus)
399 {
400 }
401
402 #ifdef CONFIG_HOTPLUG_CPU
403 static int xen_cpu_disable(void)
404 {
405         unsigned int cpu = smp_processor_id();
406         if (cpu == 0)
407                 return -EBUSY;
408
409         cpu_disable_common();
410
411         load_cr3(swapper_pg_dir);
412         return 0;
413 }
414
415 static void xen_cpu_die(unsigned int cpu)
416 {
417         while (HYPERVISOR_vcpu_op(VCPUOP_is_up, cpu, NULL)) {
418                 current->state = TASK_UNINTERRUPTIBLE;
419                 schedule_timeout(HZ/10);
420         }
421         unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
422         unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
423         unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
424         unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu), NULL);
425         unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);
426         xen_uninit_lock_cpu(cpu);
427         xen_teardown_timer(cpu);
428 }
429
430 static void __cpuinit xen_play_dead(void) /* used only with HOTPLUG_CPU */
431 {
432         play_dead_common();
433         HYPERVISOR_vcpu_op(VCPUOP_down, smp_processor_id(), NULL);
434         cpu_bringup();
435         /*
436          * Balance out the preempt calls - as we are running in cpu_idle
437          * loop which has been called at bootup from cpu_bringup_and_idle.
438          * The cpucpu_bringup_and_idle called cpu_bringup which made a
439          * preempt_disable() So this preempt_enable will balance it out.
440          */
441         preempt_enable();
442 }
443
444 #else /* !CONFIG_HOTPLUG_CPU */
445 static int xen_cpu_disable(void)
446 {
447         return -ENOSYS;
448 }
449
450 static void xen_cpu_die(unsigned int cpu)
451 {
452         BUG();
453 }
454
455 static void xen_play_dead(void)
456 {
457         BUG();
458 }
459
460 #endif
461 static void stop_self(void *v)
462 {
463         int cpu = smp_processor_id();
464
465         /* make sure we're not pinning something down */
466         load_cr3(swapper_pg_dir);
467         /* should set up a minimal gdt */
468
469         set_cpu_online(cpu, false);
470
471         HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
472         BUG();
473 }
474
475 static void xen_stop_other_cpus(int wait)
476 {
477         smp_call_function(stop_self, NULL, wait);
478 }
479
480 static void xen_smp_send_reschedule(int cpu)
481 {
482         xen_send_IPI_one(cpu, XEN_RESCHEDULE_VECTOR);
483 }
484
485 static void __xen_send_IPI_mask(const struct cpumask *mask,
486                               int vector)
487 {
488         unsigned cpu;
489
490         for_each_cpu_and(cpu, mask, cpu_online_mask)
491                 xen_send_IPI_one(cpu, vector);
492 }
493
494 static void xen_smp_send_call_function_ipi(const struct cpumask *mask)
495 {
496         int cpu;
497
498         __xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);
499
500         /* Make sure other vcpus get a chance to run if they need to. */
501         for_each_cpu(cpu, mask) {
502                 if (xen_vcpu_stolen(cpu)) {
503                         HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
504                         break;
505                 }
506         }
507 }
508
509 static void xen_smp_send_call_function_single_ipi(int cpu)
510 {
511         __xen_send_IPI_mask(cpumask_of(cpu),
512                           XEN_CALL_FUNCTION_SINGLE_VECTOR);
513 }
514
515 static inline int xen_map_vector(int vector)
516 {
517         int xen_vector;
518
519         switch (vector) {
520         case RESCHEDULE_VECTOR:
521                 xen_vector = XEN_RESCHEDULE_VECTOR;
522                 break;
523         case CALL_FUNCTION_VECTOR:
524                 xen_vector = XEN_CALL_FUNCTION_VECTOR;
525                 break;
526         case CALL_FUNCTION_SINGLE_VECTOR:
527                 xen_vector = XEN_CALL_FUNCTION_SINGLE_VECTOR;
528                 break;
529         case IRQ_WORK_VECTOR:
530                 xen_vector = XEN_IRQ_WORK_VECTOR;
531                 break;
532         default:
533                 xen_vector = -1;
534                 printk(KERN_ERR "xen: vector 0x%x is not implemented\n",
535                         vector);
536         }
537
538         return xen_vector;
539 }
540
541 void xen_send_IPI_mask(const struct cpumask *mask,
542                               int vector)
543 {
544         int xen_vector = xen_map_vector(vector);
545
546         if (xen_vector >= 0)
547                 __xen_send_IPI_mask(mask, xen_vector);
548 }
549
550 void xen_send_IPI_all(int vector)
551 {
552         int xen_vector = xen_map_vector(vector);
553
554         if (xen_vector >= 0)
555                 __xen_send_IPI_mask(cpu_online_mask, xen_vector);
556 }
557
558 void xen_send_IPI_self(int vector)
559 {
560         int xen_vector = xen_map_vector(vector);
561
562         if (xen_vector >= 0)
563                 xen_send_IPI_one(smp_processor_id(), xen_vector);
564 }
565
566 void xen_send_IPI_mask_allbutself(const struct cpumask *mask,
567                                 int vector)
568 {
569         unsigned cpu;
570         unsigned int this_cpu = smp_processor_id();
571
572         if (!(num_online_cpus() > 1))
573                 return;
574
575         for_each_cpu_and(cpu, mask, cpu_online_mask) {
576                 if (this_cpu == cpu)
577                         continue;
578
579                 xen_smp_send_call_function_single_ipi(cpu);
580         }
581 }
582
583 void xen_send_IPI_allbutself(int vector)
584 {
585         int xen_vector = xen_map_vector(vector);
586
587         if (xen_vector >= 0)
588                 xen_send_IPI_mask_allbutself(cpu_online_mask, xen_vector);
589 }
590
591 static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
592 {
593         irq_enter();
594         generic_smp_call_function_interrupt();
595         inc_irq_stat(irq_call_count);
596         irq_exit();
597
598         return IRQ_HANDLED;
599 }
600
601 static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id)
602 {
603         irq_enter();
604         generic_smp_call_function_single_interrupt();
605         inc_irq_stat(irq_call_count);
606         irq_exit();
607
608         return IRQ_HANDLED;
609 }
610
611 static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
612 {
613         irq_enter();
614         irq_work_run();
615         inc_irq_stat(apic_irq_work_irqs);
616         irq_exit();
617
618         return IRQ_HANDLED;
619 }
620
621 static const struct smp_ops xen_smp_ops __initconst = {
622         .smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
623         .smp_prepare_cpus = xen_smp_prepare_cpus,
624         .smp_cpus_done = xen_smp_cpus_done,
625
626         .cpu_up = xen_cpu_up,
627         .cpu_die = xen_cpu_die,
628         .cpu_disable = xen_cpu_disable,
629         .play_dead = xen_play_dead,
630
631         .stop_other_cpus = xen_stop_other_cpus,
632         .smp_send_reschedule = xen_smp_send_reschedule,
633
634         .send_call_func_ipi = xen_smp_send_call_function_ipi,
635         .send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
636 };
637
638 void __init xen_smp_init(void)
639 {
640         smp_ops = xen_smp_ops;
641         xen_fill_possible_map();
642         xen_init_spinlocks();
643 }
644
645 static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
646 {
647         native_smp_prepare_cpus(max_cpus);
648         WARN_ON(xen_smp_intr_init(0));
649
650         xen_init_lock_cpu(0);
651 }
652
653 static int __cpuinit xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
654 {
655         int rc;
656         rc = native_cpu_up(cpu, tidle);
657         WARN_ON (xen_smp_intr_init(cpu));
658         return rc;
659 }
660
661 static void xen_hvm_cpu_die(unsigned int cpu)
662 {
663         unbind_from_irqhandler(per_cpu(xen_resched_irq, cpu), NULL);
664         unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
665         unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
666         unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu), NULL);
667         unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);
668         native_cpu_die(cpu);
669 }
670
671 void __init xen_hvm_smp_init(void)
672 {
673         if (!xen_have_vector_callback)
674                 return;
675         smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
676         smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
677         smp_ops.cpu_up = xen_hvm_cpu_up;
678         smp_ops.cpu_die = xen_hvm_cpu_die;
679         smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi;
680         smp_ops.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi;
681 }