summaryrefslogtreecommitdiff
path: root/arch/x86/xen/smp.c
blob: d8faf79a0a1da22b57d4f39ee58abc1ca9b908d7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
/*
 * Xen SMP support
 *
 * This file implements the Xen versions of smp_ops.  SMP under Xen is
 * very straightforward.  Bringing a CPU up is simply a matter of
 * loading its initial context and setting it running.
 *
 * IPIs are handled through the Xen event mechanism.
 *
 * Because virtual CPUs can be scheduled onto any real CPU, there's no
 * useful topology information for the kernel to make use of.  As a
 * result, all CPUs are treated as if they're single-core and
 * single-threaded.
 *
 * This does not handle HOTPLUG_CPU yet.
 */
#include <linux/sched.h>
#include <linux/kernel_stat.h>
#include <linux/err.h>
#include <linux/smp.h>

#include <asm/paravirt.h>
#include <asm/desc.h>
#include <asm/pgtable.h>
#include <asm/cpu.h>

#include <xen/interface/xen.h>
#include <xen/interface/vcpu.h>

#include <asm/xen/interface.h>
#include <asm/xen/hypercall.h>

#include <xen/page.h>
#include <xen/events.h>

#include "xen-ops.h"
#include "mmu.h"

static void __cpuinit xen_init_lock_cpu(int cpu);

cpumask_t xen_cpu_initialized_map;

static DEFINE_PER_CPU(int, resched_irq);
static DEFINE_PER_CPU(int, callfunc_irq);
static DEFINE_PER_CPU(int, callfuncsingle_irq);
static DEFINE_PER_CPU(int, debug_irq) = -1;

static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);
static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id);

/*
 * Reschedule call back. Nothing to do,
 * all the work is done automatically when
 * we return from the interrupt.
 */
static irqreturn_t xen_reschedule_interrupt(int irq, void *dev_id)
{
#ifdef CONFIG_X86_32
	__get_cpu_var(irq_stat).irq_resched_count++;
#else
	add_pda(irq_resched_count, 1);
#endif

	return IRQ_HANDLED;
}

static __cpuinit void cpu_bringup_and_idle(void)
{
	int cpu = smp_processor_id();

	cpu_init();
	preempt_disable();

	xen_enable_sysenter();
	xen_enable_syscall();

	cpu = smp_processor_id();
	smp_store_cpu_info(cpu);
	cpu_data(cpu).x86_max_cores = 1;
	set_cpu_sibling_map(cpu);

	xen_setup_cpu_clockevents();

	cpu_set(cpu, cpu_online_map);
	x86_write_percpu(cpu_state, CPU_ONLINE);
	wmb();

	/* We can take interrupts now: we're officially "up". */
	local_irq_enable();

	wmb();			/* make sure everything is out */
	cpu_idle();
}

static int xen_smp_intr_init(unsigned int cpu)
{
	int rc;
	const char *resched_name, *callfunc_name, *debug_name;

	resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
	rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
				    cpu,
				    xen_reschedule_interrupt,
				    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
				    resched_name,
				    NULL);
	if (rc < 0)
		goto fail;
	per_cpu(resched_irq, cpu) = rc;

	callfunc_name = kasprintf(GFP_KERNEL, "callfunc%d", cpu);
	rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_VECTOR,
				    cpu,
				    xen_call_function_interrupt,
				    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
				    callfunc_name,
				    NULL);
	if (rc < 0)
		goto fail;
	per_cpu(callfunc_irq, cpu) = rc;

	debug_name = kasprintf(GFP_KERNEL, "debug%d", cpu);
	rc = bind_virq_to_irqhandler(VIRQ_DEBUG, cpu, xen_debug_interrupt,
				     IRQF_DISABLED | IRQF_PERCPU | IRQF_NOBALANCING,
				     debug_name, NULL);
	if (rc < 0)
		goto fail;
	per_cpu(debug_irq, cpu) = rc;

	callfunc_name = kasprintf(GFP_KERNEL, "callfuncsingle%d", cpu);
	rc = bind_ipi_to_irqhandler(XEN_CALL_FUNCTION_SINGLE_VECTOR,
				    cpu,
				    xen_call_function_single_interrupt,
				    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
				    callfunc_name,
				    NULL);
	if (rc < 0)
		goto fail;
	per_cpu(callfuncsingle_irq, cpu) = rc;

	return 0;

 fail:
	if (per_cpu(resched_irq, cpu) >= 0)
		unbind_from_irqhandler(per_cpu(resched_irq, cpu), NULL);
	if (per_cpu(callfunc_irq, cpu) >= 0)
		unbind_from_irqhandler(per_cpu(callfunc_irq, cpu), NULL);
	if (per_cpu(debug_irq, cpu) >= 0)
		unbind_from_irqhandler(per_cpu(debug_irq, cpu), NULL);
	if (per_cpu(callfuncsingle_irq, cpu) >= 0)
		unbind_from_irqhandler(per_cpu(callfuncsingle_irq, cpu), NULL);

	return rc;
}

static void __init xen_fill_possible_map(void)
{
	int i, rc;

	for (i = 0; i < NR_CPUS; i++) {
		rc = HYPERVISOR_vcpu_op(VCPUOP_is_up, i, NULL);
		if (rc >= 0) {
			num_processors++;
			cpu_set(i, cpu_possible_map);
		}
	}
}

static void __init xen_smp_prepare_boot_cpu(void)
{
	BUG_ON(smp_processor_id() != 0);
	native_smp_prepare_boot_cpu();

	/* We've switched to the "real" per-cpu gdt, so make sure the
	   old memory can be recycled */
	make_lowmem_page_readwrite(&per_cpu_var(gdt_page));

	xen_setup_vcpu_info_placement();
}

static void __init xen_smp_prepare_cpus(unsigned int max_cpus)
{
	unsigned cpu;

	xen_init_lock_cpu(0);

	smp_store_cpu_info(0);
	cpu_data(0).x86_max_cores = 1;
	set_cpu_sibling_map(0);

	if (xen_smp_intr_init(0))
		BUG();

	xen_cpu_initialized_map = cpumask_of_cpu(0);

	/* Restrict the possible_map according to max_cpus. */
	while ((num_possible_cpus() > 1) && (num_possible_cpus() > max_cpus)) {
		for (cpu = NR_CPUS - 1; !cpu_possible(cpu); cpu--)
			continue;
		cpu_clear(cpu, cpu_possible_map);
	}

	for_each_possible_cpu (cpu) {
		struct task_struct *idle;

		if (cpu == 0)
			continue;

		idle = fork_idle(cpu);
		if (IS_ERR(idle))
			panic("failed fork for CPU %d", cpu);

		cpu_set(cpu, cpu_present_map);
	}

	//init_xenbus_allowed_cpumask();
}

static __cpuinit int
cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
{
	struct vcpu_guest_context *ctxt;
	struct desc_struct *gdt;

	if (cpu_test_and_set(cpu, xen_cpu_initialized_map))
		return 0;

	ctxt = kzalloc(sizeof(*ctxt), GFP_KERNEL);
	if (ctxt == NULL)
		return -ENOMEM;

	gdt = get_cpu_gdt_table(cpu);

	ctxt->flags = VGCF_IN_KERNEL;
	ctxt->user_regs.ds = __USER_DS;
	ctxt->user_regs.es = __USER_DS;
	ctxt->user_regs.ss = __KERNEL_DS;
#ifdef CONFIG_X86_32
	ctxt->user_regs.fs = __KERNEL_PERCPU;
#endif
	ctxt->user_regs.eip = (unsigned long)cpu_bringup_and_idle;
	ctxt->user_regs.eflags = 0x1000; /* IOPL_RING1 */

	memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));

	xen_copy_trap_info(ctxt->trap_ctxt);

	ctxt->ldt_ents = 0;

	BUG_ON((unsigned long)gdt & ~PAGE_MASK);
	make_lowmem_page_readonly(gdt);

	ctxt->gdt_frames[0] = virt_to_mfn(gdt);
	ctxt->gdt_ents      = GDT_ENTRIES;

	ctxt->user_regs.cs = __KERNEL_CS;
	ctxt->user_regs.esp = idle->thread.sp0 - sizeof(struct pt_regs);

	ctxt->kernel_ss = __KERNEL_DS;
	ctxt->kernel_sp = idle->thread.sp0;

#ifdef CONFIG_X86_32
	ctxt->event_callback_cs     = __KERNEL_CS;
	ctxt->failsafe_callback_cs  = __KERNEL_CS;
#endif
	ctxt->event_callback_eip    = (unsigned long)xen_hypervisor_callback;
	ctxt->failsafe_callback_eip = (unsigned long)xen_failsafe_callback;

	per_cpu(xen_cr3, cpu) = __pa(swapper_pg_dir);
	ctxt->ctrlreg[3] = xen_pfn_to_cr3(virt_to_mfn(swapper_pg_dir));

	if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
		BUG();

	kfree(ctxt);
	return 0;
}

static int __cpuinit xen_cpu_up(unsigned int cpu)
{
	struct task_struct *idle = idle_task(cpu);
	int rc;

#if 0
	rc = cpu_up_check(cpu);
	if (rc)
		return rc;
#endif

#ifdef CONFIG_X86_64
	/* Allocate node local memory for AP pdas */
	WARN_ON(cpu == 0);
	if (cpu > 0) {
		rc = get_local_pda(cpu);
		if (rc)
			return rc;
	}
#endif

#ifdef CONFIG_X86_32
	init_gdt(cpu);
	per_cpu(current_task, cpu) = idle;
	irq_ctx_init(cpu);
#else
	cpu_pda(cpu)->pcurrent = idle;
	clear_tsk_thread_flag(idle, TIF_FORK);
#endif
	xen_setup_timer(cpu);
	xen_init_lock_cpu(cpu);

	per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;

	/* make sure interrupts start blocked */
	per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;

	rc = cpu_initialize_context(cpu, idle);
	if (rc)
		return rc;

	if (num_online_cpus() == 1)
		alternatives_smp_switch(1);

	rc = xen_smp_intr_init(cpu);
	if (rc)
		return rc;

	rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
	BUG_ON(rc);

	while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
		HYPERVISOR_sched_op(SCHEDOP_yield, 0);
		barrier();
	}

	return 0;
}

static void xen_smp_cpus_done(unsigned int max_cpus)
{
}

static void stop_self(void *v)
{
	int cpu = smp_processor_id();

	/* make sure we're not pinning something down */
	load_cr3(swapper_pg_dir);
	/* should set up a minimal gdt */

	HYPERVISOR_vcpu_op(VCPUOP_down, cpu, NULL);
	BUG();
}

static void xen_smp_send_stop(void)
{
	smp_call_function(stop_self, NULL, 0);
}

static void xen_smp_send_reschedule(int cpu)
{
	xen_send_IPI_one(cpu, XEN_RESCHEDULE_VECTOR);
}

static void xen_send_IPI_mask(cpumask_t mask, enum ipi_vector vector)
{
	unsigned cpu;

	cpus_and(mask, mask, cpu_online_map);

	for_each_cpu_mask_nr(cpu, mask)
		xen_send_IPI_one(cpu, vector);
}

static void xen_smp_send_call_function_ipi(cpumask_t mask)
{
	int cpu;

	xen_send_IPI_mask(mask, XEN_CALL_FUNCTION_VECTOR);

	/* Make sure other vcpus get a chance to run if they need to. */
	for_each_cpu_mask_nr(cpu, mask) {
		if (xen_vcpu_stolen(cpu)) {
			HYPERVISOR_sched_op(SCHEDOP_yield, 0);
			break;
		}
	}
}

static void xen_smp_send_call_function_single_ipi(int cpu)
{
	xen_send_IPI_mask(cpumask_of_cpu(cpu), XEN_CALL_FUNCTION_SINGLE_VECTOR);
}

static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id)
{
	irq_enter();
	generic_smp_call_function_interrupt();
#ifdef CONFIG_X86_32
	__get_cpu_var(irq_stat).irq_call_count++;
#else
	add_pda(irq_call_count, 1);
#endif
	irq_exit();

	return IRQ_HANDLED;
}

static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id)
{
	irq_enter();
	generic_smp_call_function_single_interrupt();
#ifdef CONFIG_X86_32
	__get_cpu_var(irq_stat).irq_call_count++;
#else
	add_pda(irq_call_count, 1);
#endif
	irq_exit();

	return IRQ_HANDLED;
}

struct xen_spinlock {
	unsigned char lock;		/* 0 -> free; 1 -> locked */
	unsigned short spinners;	/* count of waiting cpus */
};

static int xen_spin_is_locked(struct raw_spinlock *lock)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;

	return xl->lock != 0;
}

static int xen_spin_is_contended(struct raw_spinlock *lock)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;

	/* Not strictly true; this is only the count of contended
	   lock-takers entering the slow path. */
	return xl->spinners != 0;
}

static int xen_spin_trylock(struct raw_spinlock *lock)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;
	u8 old = 1;

	asm("xchgb %b0,%1"
	    : "+q" (old), "+m" (xl->lock) : : "memory");

	return old == 0;
}

static DEFINE_PER_CPU(int, lock_kicker_irq) = -1;
static DEFINE_PER_CPU(struct xen_spinlock *, lock_spinners);

static inline void spinning_lock(struct xen_spinlock *xl)
{
	__get_cpu_var(lock_spinners) = xl;
	wmb();			/* set lock of interest before count */
	asm(LOCK_PREFIX " incw %0"
	    : "+m" (xl->spinners) : : "memory");
}

static inline void unspinning_lock(struct xen_spinlock *xl)
{
	asm(LOCK_PREFIX " decw %0"
	    : "+m" (xl->spinners) : : "memory");
	wmb();			/* decrement count before clearing lock */
	__get_cpu_var(lock_spinners) = NULL;
}

static noinline int xen_spin_lock_slow(struct raw_spinlock *lock)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;
	int irq = __get_cpu_var(lock_kicker_irq);
	int ret;

	/* If kicker interrupts not initialized yet, just spin */
	if (irq == -1)
		return 0;

	/* announce we're spinning */
	spinning_lock(xl);

	/* clear pending */
	xen_clear_irq_pending(irq);

	/* check again make sure it didn't become free while
	   we weren't looking  */
	ret = xen_spin_trylock(lock);
	if (ret)
		goto out;

	/* block until irq becomes pending */
	xen_poll_irq(irq);
	kstat_this_cpu.irqs[irq]++;

out:
	unspinning_lock(xl);
	return ret;
}

static void xen_spin_lock(struct raw_spinlock *lock)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;
	int timeout;
	u8 oldval;

	do {
		timeout = 1 << 10;

		asm("1: xchgb %1,%0\n"
		    "   testb %1,%1\n"
		    "   jz 3f\n"
		    "2: rep;nop\n"
		    "   cmpb $0,%0\n"
		    "   je 1b\n"
		    "   dec %2\n"
		    "   jnz 2b\n"
		    "3:\n"
		    : "+m" (xl->lock), "=q" (oldval), "+r" (timeout)
		    : "1" (1)
		    : "memory");

	} while (unlikely(oldval != 0 && !xen_spin_lock_slow(lock)));
}

static noinline void xen_spin_unlock_slow(struct xen_spinlock *xl)
{
	int cpu;

	for_each_online_cpu(cpu) {
		/* XXX should mix up next cpu selection */
		if (per_cpu(lock_spinners, cpu) == xl) {
			xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR);
			break;
		}
	}
}

static void xen_spin_unlock(struct raw_spinlock *lock)
{
	struct xen_spinlock *xl = (struct xen_spinlock *)lock;

	smp_wmb();		/* make sure no writes get moved after unlock */
	xl->lock = 0;		/* release lock */

	/* make sure unlock happens before kick */
	barrier();

	if (unlikely(xl->spinners))
		xen_spin_unlock_slow(xl);
}

static __cpuinit void xen_init_lock_cpu(int cpu)
{
	int irq;
	const char *name;

	name = kasprintf(GFP_KERNEL, "spinlock%d", cpu);
	irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR,
				     cpu,
				     xen_reschedule_interrupt,
				     IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
				     name,
				     NULL);

	if (irq >= 0) {
		disable_irq(irq); /* make sure it's never delivered */
		per_cpu(lock_kicker_irq, cpu) = irq;
	}

	printk("cpu %d spinlock event irq %d\n", cpu, irq);
}

static void __init xen_init_spinlocks(void)
{
	pv_lock_ops.spin_is_locked = xen_spin_is_locked;
	pv_lock_ops.spin_is_contended = xen_spin_is_contended;
	pv_lock_ops.spin_lock = xen_spin_lock;
	pv_lock_ops.spin_trylock = xen_spin_trylock;
	pv_lock_ops.spin_unlock = xen_spin_unlock;
}

static const struct smp_ops xen_smp_ops __initdata = {
	.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
	.smp_prepare_cpus = xen_smp_prepare_cpus,
	.cpu_up = xen_cpu_up,
	.smp_cpus_done = xen_smp_cpus_done,

	.smp_send_stop = xen_smp_send_stop,
	.smp_send_reschedule = xen_smp_send_reschedule,

	.send_call_func_ipi = xen_smp_send_call_function_ipi,
	.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi,
};

void __init xen_smp_init(void)
{
	smp_ops = xen_smp_ops;
	xen_fill_possible_map();
	xen_init_spinlocks();
}