summaryrefslogtreecommitdiffstats
path: root/drivers/xen/events/events_2l.c
blob: 5db43fc100a413bf0ee55676d2b359e4db94e7ec (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
/*
 * Xen event channels (2-level ABI)
 *
 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
 */

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#include <linux/linkage.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/module.h>

#include <asm/sync_bitops.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>

#include <xen/xen.h>
#include <xen/xen-ops.h>
#include <xen/events.h>
#include <xen/interface/xen.h>
#include <xen/interface/event_channel.h>

#include "events_internal.h"

/*
 * Note sizeof(xen_ulong_t) can be more than sizeof(unsigned long). Be
 * careful to only use bitops which allow for this (e.g
 * test_bit/find_first_bit and friends but not __ffs) and to pass
 * BITS_PER_EVTCHN_WORD as the bitmask length.
 */
#define BITS_PER_EVTCHN_WORD (sizeof(xen_ulong_t)*8)
/*
 * Make a bitmask (i.e. unsigned long *) of a xen_ulong_t
 * array. Primarily to avoid long lines (hence the terse name).
 */
#define BM(x) (unsigned long *)(x)
/* Find the first set bit in a evtchn mask */
#define EVTCHN_FIRST_BIT(w) find_first_bit(BM(&(w)), BITS_PER_EVTCHN_WORD)

static DEFINE_PER_CPU(xen_ulong_t [EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD],
		      cpu_evtchn_mask);

static unsigned evtchn_2l_max_channels(void)
{
	return EVTCHN_2L_NR_CHANNELS;
}

static void evtchn_2l_bind_to_cpu(struct irq_info *info, unsigned cpu)
{
	clear_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, info->cpu)));
	set_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
}

static void evtchn_2l_clear_pending(unsigned port)
{
	struct shared_info *s = HYPERVISOR_shared_info;
	sync_clear_bit(port, BM(&s->evtchn_pending[0]));
}

static void evtchn_2l_set_pending(unsigned port)
{
	struct shared_info *s = HYPERVISOR_shared_info;
	sync_set_bit(port, BM(&s->evtchn_pending[0]));
}

static bool evtchn_2l_is_pending(unsigned port)
{
	struct shared_info *s = HYPERVISOR_shared_info;
	return sync_test_bit(port, BM(&s->evtchn_pending[0]));
}

static bool evtchn_2l_test_and_set_mask(unsigned port)
{
	struct shared_info *s = HYPERVISOR_shared_info;
	return sync_test_and_set_bit(port, BM(&s->evtchn_mask[0]));
}

static void evtchn_2l_mask(unsigned port)
{
	struct shared_info *s = HYPERVISOR_shared_info;
	sync_set_bit(port, BM(&s->evtchn_mask[0]));
}

static void evtchn_2l_unmask(unsigned port)
{
	struct shared_info *s = HYPERVISOR_shared_info;
	unsigned int cpu = get_cpu();
	int do_hypercall = 0, evtchn_pending = 0;

	BUG_ON(!irqs_disabled());

	if (unlikely((cpu != cpu_from_evtchn(port))))
		do_hypercall = 1;
	else {
		/*
		 * Need to clear the mask before checking pending to
		 * avoid a race with an event becoming pending.
		 *
		 * EVTCHNOP_unmask will only trigger an upcall if the
		 * mask bit was set, so if a hypercall is needed
		 * remask the event.
		 */
		sync_clear_bit(port, BM(&s->evtchn_mask[0]));
		evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));

		if (unlikely(evtchn_pending && xen_hvm_domain())) {
			sync_set_bit(port, BM(&s->evtchn_mask[0]));
			do_hypercall = 1;
		}
	}

	/* Slow path (hypercall) if this is a non-local port or if this is
	 * an hvm domain and an event is pending (hvm domains don't have
	 * their own implementation of irq_enable). */
	if (do_hypercall) {
		struct evtchn_unmask unmask = { .port = port };
		(void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
	} else {
		struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);

		/*
		 * The following is basically the equivalent of
		 * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
		 * the interrupt edge' if the channel is masked.
		 */
		if (evtchn_pending &&
		    !sync_test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
					   BM(&vcpu_info->evtchn_pending_sel)))
			vcpu_info->evtchn_upcall_pending = 1;
	}

	put_cpu();
}

static DEFINE_PER_CPU(unsigned int, current_word_idx);
static DEFINE_PER_CPU(unsigned int, current_bit_idx);

/*
 * Mask out the i least significant bits of w
 */
#define MASK_LSBS(w, i) (w & ((~((xen_ulong_t)0UL)) << i))

static inline xen_ulong_t active_evtchns(unsigned int cpu,
					 struct shared_info *sh,
					 unsigned int idx)
{
	return sh->evtchn_pending[idx] &
		per_cpu(cpu_evtchn_mask, cpu)[idx] &
		~sh->evtchn_mask[idx];
}

/*
 * Search the CPU's pending events bitmasks.  For each one found, map
 * the event number to an irq, and feed it into do_IRQ() for handling.
 *
 * Xen uses a two-level bitmap to speed searching.  The first level is
 * a bitset of words which contain pending event bits.  The second
 * level is a bitset of pending events themselves.
 */
static void evtchn_2l_handle_events(unsigned cpu)
{
	int irq;
	xen_ulong_t pending_words;
	xen_ulong_t pending_bits;
	int start_word_idx, start_bit_idx;
	int word_idx, bit_idx;
	int i;
	struct shared_info *s = HYPERVISOR_shared_info;
	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);

	/* Timer interrupt has highest priority. */
	irq = irq_from_virq(cpu, VIRQ_TIMER);
	if (irq != -1) {
		unsigned int evtchn = evtchn_from_irq(irq);
		word_idx = evtchn / BITS_PER_LONG;
		bit_idx = evtchn % BITS_PER_LONG;
		if (active_evtchns(cpu, s, word_idx) & (1ULL << bit_idx))
			generic_handle_irq(irq);
	}

	/*
	 * Master flag must be cleared /before/ clearing
	 * selector flag. xchg_xen_ulong must contain an
	 * appropriate barrier.
	 */
	pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);

	start_word_idx = __this_cpu_read(current_word_idx);
	start_bit_idx = __this_cpu_read(current_bit_idx);

	word_idx = start_word_idx;

	for (i = 0; pending_words != 0; i++) {
		xen_ulong_t words;

		words = MASK_LSBS(pending_words, word_idx);

		/*
		 * If we masked out all events, wrap to beginning.
		 */
		if (words == 0) {
			word_idx = 0;
			bit_idx = 0;
			continue;
		}
		word_idx = EVTCHN_FIRST_BIT(words);

		pending_bits = active_evtchns(cpu, s, word_idx);
		bit_idx = 0; /* usually scan entire word from start */
		/*
		 * We scan the starting word in two parts.
		 *
		 * 1st time: start in the middle, scanning the
		 * upper bits.
		 *
		 * 2nd time: scan the whole word (not just the
		 * parts skipped in the first pass) -- if an
		 * event in the previously scanned bits is
		 * pending again it would just be scanned on
		 * the next loop anyway.
		 */
		if (word_idx == start_word_idx) {
			if (i == 0)
				bit_idx = start_bit_idx;
		}

		do {
			xen_ulong_t bits;
			int port;

			bits = MASK_LSBS(pending_bits, bit_idx);

			/* If we masked out all events, move on. */
			if (bits == 0)
				break;

			bit_idx = EVTCHN_FIRST_BIT(bits);

			/* Process port. */
			port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
			irq = get_evtchn_to_irq(port);

			if (irq != -1)
				generic_handle_irq(irq);

			bit_idx = (bit_idx + 1) % BITS_PER_EVTCHN_WORD;

			/* Next caller starts at last processed + 1 */
			__this_cpu_write(current_word_idx,
					 bit_idx ? word_idx :
					 (word_idx+1) % BITS_PER_EVTCHN_WORD);
			__this_cpu_write(current_bit_idx, bit_idx);
		} while (bit_idx != 0);

		/* Scan start_l1i twice; all others once. */
		if ((word_idx != start_word_idx) || (i != 0))
			pending_words &= ~(1UL << word_idx);

		word_idx = (word_idx + 1) % BITS_PER_EVTCHN_WORD;
	}
}

irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
{
	struct shared_info *sh = HYPERVISOR_shared_info;
	int cpu = smp_processor_id();
	xen_ulong_t *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
	int i;
	unsigned long flags;
	static DEFINE_SPINLOCK(debug_lock);
	struct vcpu_info *v;

	spin_lock_irqsave(&debug_lock, flags);

	printk("\nvcpu %d\n  ", cpu);

	for_each_online_cpu(i) {
		int pending;
		v = per_cpu(xen_vcpu, i);
		pending = (get_irq_regs() && i == cpu)
			? xen_irqs_disabled(get_irq_regs())
			: v->evtchn_upcall_mask;
		printk("%d: masked=%d pending=%d event_sel %0*"PRI_xen_ulong"\n  ", i,
		       pending, v->evtchn_upcall_pending,
		       (int)(sizeof(v->evtchn_pending_sel)*2),
		       v->evtchn_pending_sel);
	}
	v = per_cpu(xen_vcpu, cpu);

	printk("\npending:\n   ");
	for (i = ARRAY_SIZE(sh->evtchn_pending)-1; i >= 0; i--)
		printk("%0*"PRI_xen_ulong"%s",
		       (int)sizeof(sh->evtchn_pending[0])*2,
		       sh->evtchn_pending[i],
		       i % 8 == 0 ? "\n   " : " ");
	printk("\nglobal mask:\n   ");
	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
		printk("%0*"PRI_xen_ulong"%s",
		       (int)(sizeof(sh->evtchn_mask[0])*2),
		       sh->evtchn_mask[i],
		       i % 8 == 0 ? "\n   " : " ");

	printk("\nglobally unmasked:\n   ");
	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
		printk("%0*"PRI_xen_ulong"%s",
		       (int)(sizeof(sh->evtchn_mask[0])*2),
		       sh->evtchn_pending[i] & ~sh->evtchn_mask[i],
		       i % 8 == 0 ? "\n   " : " ");

	printk("\nlocal cpu%d mask:\n   ", cpu);
	for (i = (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
		printk("%0*"PRI_xen_ulong"%s", (int)(sizeof(cpu_evtchn[0])*2),
		       cpu_evtchn[i],
		       i % 8 == 0 ? "\n   " : " ");

	printk("\nlocally unmasked:\n   ");
	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--) {
		xen_ulong_t pending = sh->evtchn_pending[i]
			& ~sh->evtchn_mask[i]
			& cpu_evtchn[i];
		printk("%0*"PRI_xen_ulong"%s",
		       (int)(sizeof(sh->evtchn_mask[0])*2),
		       pending, i % 8 == 0 ? "\n   " : " ");
	}

	printk("\npending list:\n");
	for (i = 0; i < EVTCHN_2L_NR_CHANNELS; i++) {
		if (sync_test_bit(i, BM(sh->evtchn_pending))) {
			int word_idx = i / BITS_PER_EVTCHN_WORD;
			printk("  %d: event %d -> irq %d%s%s%s\n",
			       cpu_from_evtchn(i), i,
			       get_evtchn_to_irq(i),
			       sync_test_bit(word_idx, BM(&v->evtchn_pending_sel))
			       ? "" : " l2-clear",
			       !sync_test_bit(i, BM(sh->evtchn_mask))
			       ? "" : " globally-masked",
			       sync_test_bit(i, BM(cpu_evtchn))
			       ? "" : " locally-masked");
		}
	}

	spin_unlock_irqrestore(&debug_lock, flags);

	return IRQ_HANDLED;
}

static const struct evtchn_ops evtchn_ops_2l = {
	.max_channels      = evtchn_2l_max_channels,
	.nr_channels       = evtchn_2l_max_channels,
	.bind_to_cpu       = evtchn_2l_bind_to_cpu,
	.clear_pending     = evtchn_2l_clear_pending,
	.set_pending       = evtchn_2l_set_pending,
	.is_pending        = evtchn_2l_is_pending,
	.test_and_set_mask = evtchn_2l_test_and_set_mask,
	.mask              = evtchn_2l_mask,
	.unmask            = evtchn_2l_unmask,
	.handle_events     = evtchn_2l_handle_events,
};

void __init xen_evtchn_2l_init(void)
{
	pr_info("Using 2-level ABI\n");
	evtchn_ops = &evtchn_ops_2l;
}