xref: /openbmc/linux/drivers/xen/events/events_2l.c (revision e8f6f3b4)
1 /*
2  * Xen event channels (2-level ABI)
3  *
4  * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
5  */
6 
7 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
8 
9 #include <linux/linkage.h>
10 #include <linux/interrupt.h>
11 #include <linux/irq.h>
12 #include <linux/module.h>
13 
14 #include <asm/sync_bitops.h>
15 #include <asm/xen/hypercall.h>
16 #include <asm/xen/hypervisor.h>
17 
18 #include <xen/xen.h>
19 #include <xen/xen-ops.h>
20 #include <xen/events.h>
21 #include <xen/interface/xen.h>
22 #include <xen/interface/event_channel.h>
23 
24 #include "events_internal.h"
25 
26 /*
27  * Note sizeof(xen_ulong_t) can be more than sizeof(unsigned long). Be
28  * careful to only use bitops which allow for this (e.g
29  * test_bit/find_first_bit and friends but not __ffs) and to pass
30  * BITS_PER_EVTCHN_WORD as the bitmask length.
31  */
32 #define BITS_PER_EVTCHN_WORD (sizeof(xen_ulong_t)*8)
33 /*
34  * Make a bitmask (i.e. unsigned long *) of a xen_ulong_t
35  * array. Primarily to avoid long lines (hence the terse name).
36  */
37 #define BM(x) (unsigned long *)(x)
38 /* Find the first set bit in a evtchn mask */
39 #define EVTCHN_FIRST_BIT(w) find_first_bit(BM(&(w)), BITS_PER_EVTCHN_WORD)
40 
41 static DEFINE_PER_CPU(xen_ulong_t [EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD],
42 		      cpu_evtchn_mask);
43 
44 static unsigned evtchn_2l_max_channels(void)
45 {
46 	return EVTCHN_2L_NR_CHANNELS;
47 }
48 
49 static void evtchn_2l_bind_to_cpu(struct irq_info *info, unsigned cpu)
50 {
51 	clear_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, info->cpu)));
52 	set_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
53 }
54 
55 static void evtchn_2l_clear_pending(unsigned port)
56 {
57 	struct shared_info *s = HYPERVISOR_shared_info;
58 	sync_clear_bit(port, BM(&s->evtchn_pending[0]));
59 }
60 
61 static void evtchn_2l_set_pending(unsigned port)
62 {
63 	struct shared_info *s = HYPERVISOR_shared_info;
64 	sync_set_bit(port, BM(&s->evtchn_pending[0]));
65 }
66 
67 static bool evtchn_2l_is_pending(unsigned port)
68 {
69 	struct shared_info *s = HYPERVISOR_shared_info;
70 	return sync_test_bit(port, BM(&s->evtchn_pending[0]));
71 }
72 
73 static bool evtchn_2l_test_and_set_mask(unsigned port)
74 {
75 	struct shared_info *s = HYPERVISOR_shared_info;
76 	return sync_test_and_set_bit(port, BM(&s->evtchn_mask[0]));
77 }
78 
79 static void evtchn_2l_mask(unsigned port)
80 {
81 	struct shared_info *s = HYPERVISOR_shared_info;
82 	sync_set_bit(port, BM(&s->evtchn_mask[0]));
83 }
84 
85 static void evtchn_2l_unmask(unsigned port)
86 {
87 	struct shared_info *s = HYPERVISOR_shared_info;
88 	unsigned int cpu = get_cpu();
89 	int do_hypercall = 0, evtchn_pending = 0;
90 
91 	BUG_ON(!irqs_disabled());
92 
93 	if (unlikely((cpu != cpu_from_evtchn(port))))
94 		do_hypercall = 1;
95 	else {
96 		/*
97 		 * Need to clear the mask before checking pending to
98 		 * avoid a race with an event becoming pending.
99 		 *
100 		 * EVTCHNOP_unmask will only trigger an upcall if the
101 		 * mask bit was set, so if a hypercall is needed
102 		 * remask the event.
103 		 */
104 		sync_clear_bit(port, BM(&s->evtchn_mask[0]));
105 		evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));
106 
107 		if (unlikely(evtchn_pending && xen_hvm_domain())) {
108 			sync_set_bit(port, BM(&s->evtchn_mask[0]));
109 			do_hypercall = 1;
110 		}
111 	}
112 
113 	/* Slow path (hypercall) if this is a non-local port or if this is
114 	 * an hvm domain and an event is pending (hvm domains don't have
115 	 * their own implementation of irq_enable). */
116 	if (do_hypercall) {
117 		struct evtchn_unmask unmask = { .port = port };
118 		(void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
119 	} else {
120 		struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
121 
122 		/*
123 		 * The following is basically the equivalent of
124 		 * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
125 		 * the interrupt edge' if the channel is masked.
126 		 */
127 		if (evtchn_pending &&
128 		    !sync_test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
129 					   BM(&vcpu_info->evtchn_pending_sel)))
130 			vcpu_info->evtchn_upcall_pending = 1;
131 	}
132 
133 	put_cpu();
134 }
135 
136 static DEFINE_PER_CPU(unsigned int, current_word_idx);
137 static DEFINE_PER_CPU(unsigned int, current_bit_idx);
138 
139 /*
140  * Mask out the i least significant bits of w
141  */
142 #define MASK_LSBS(w, i) (w & ((~((xen_ulong_t)0UL)) << i))
143 
144 static inline xen_ulong_t active_evtchns(unsigned int cpu,
145 					 struct shared_info *sh,
146 					 unsigned int idx)
147 {
148 	return sh->evtchn_pending[idx] &
149 		per_cpu(cpu_evtchn_mask, cpu)[idx] &
150 		~sh->evtchn_mask[idx];
151 }
152 
153 /*
154  * Search the CPU's pending events bitmasks.  For each one found, map
155  * the event number to an irq, and feed it into do_IRQ() for handling.
156  *
157  * Xen uses a two-level bitmap to speed searching.  The first level is
158  * a bitset of words which contain pending event bits.  The second
159  * level is a bitset of pending events themselves.
160  */
161 static void evtchn_2l_handle_events(unsigned cpu)
162 {
163 	int irq;
164 	xen_ulong_t pending_words;
165 	xen_ulong_t pending_bits;
166 	int start_word_idx, start_bit_idx;
167 	int word_idx, bit_idx;
168 	int i;
169 	struct shared_info *s = HYPERVISOR_shared_info;
170 	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
171 
172 	/* Timer interrupt has highest priority. */
173 	irq = irq_from_virq(cpu, VIRQ_TIMER);
174 	if (irq != -1) {
175 		unsigned int evtchn = evtchn_from_irq(irq);
176 		word_idx = evtchn / BITS_PER_LONG;
177 		bit_idx = evtchn % BITS_PER_LONG;
178 		if (active_evtchns(cpu, s, word_idx) & (1ULL << bit_idx))
179 			generic_handle_irq(irq);
180 	}
181 
182 	/*
183 	 * Master flag must be cleared /before/ clearing
184 	 * selector flag. xchg_xen_ulong must contain an
185 	 * appropriate barrier.
186 	 */
187 	pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);
188 
189 	start_word_idx = __this_cpu_read(current_word_idx);
190 	start_bit_idx = __this_cpu_read(current_bit_idx);
191 
192 	word_idx = start_word_idx;
193 
194 	for (i = 0; pending_words != 0; i++) {
195 		xen_ulong_t words;
196 
197 		words = MASK_LSBS(pending_words, word_idx);
198 
199 		/*
200 		 * If we masked out all events, wrap to beginning.
201 		 */
202 		if (words == 0) {
203 			word_idx = 0;
204 			bit_idx = 0;
205 			continue;
206 		}
207 		word_idx = EVTCHN_FIRST_BIT(words);
208 
209 		pending_bits = active_evtchns(cpu, s, word_idx);
210 		bit_idx = 0; /* usually scan entire word from start */
211 		/*
212 		 * We scan the starting word in two parts.
213 		 *
214 		 * 1st time: start in the middle, scanning the
215 		 * upper bits.
216 		 *
217 		 * 2nd time: scan the whole word (not just the
218 		 * parts skipped in the first pass) -- if an
219 		 * event in the previously scanned bits is
220 		 * pending again it would just be scanned on
221 		 * the next loop anyway.
222 		 */
223 		if (word_idx == start_word_idx) {
224 			if (i == 0)
225 				bit_idx = start_bit_idx;
226 		}
227 
228 		do {
229 			xen_ulong_t bits;
230 			int port;
231 
232 			bits = MASK_LSBS(pending_bits, bit_idx);
233 
234 			/* If we masked out all events, move on. */
235 			if (bits == 0)
236 				break;
237 
238 			bit_idx = EVTCHN_FIRST_BIT(bits);
239 
240 			/* Process port. */
241 			port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
242 			irq = get_evtchn_to_irq(port);
243 
244 			if (irq != -1)
245 				generic_handle_irq(irq);
246 
247 			bit_idx = (bit_idx + 1) % BITS_PER_EVTCHN_WORD;
248 
249 			/* Next caller starts at last processed + 1 */
250 			__this_cpu_write(current_word_idx,
251 					 bit_idx ? word_idx :
252 					 (word_idx+1) % BITS_PER_EVTCHN_WORD);
253 			__this_cpu_write(current_bit_idx, bit_idx);
254 		} while (bit_idx != 0);
255 
256 		/* Scan start_l1i twice; all others once. */
257 		if ((word_idx != start_word_idx) || (i != 0))
258 			pending_words &= ~(1UL << word_idx);
259 
260 		word_idx = (word_idx + 1) % BITS_PER_EVTCHN_WORD;
261 	}
262 }
263 
264 irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
265 {
266 	struct shared_info *sh = HYPERVISOR_shared_info;
267 	int cpu = smp_processor_id();
268 	xen_ulong_t *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
269 	int i;
270 	unsigned long flags;
271 	static DEFINE_SPINLOCK(debug_lock);
272 	struct vcpu_info *v;
273 
274 	spin_lock_irqsave(&debug_lock, flags);
275 
276 	printk("\nvcpu %d\n  ", cpu);
277 
278 	for_each_online_cpu(i) {
279 		int pending;
280 		v = per_cpu(xen_vcpu, i);
281 		pending = (get_irq_regs() && i == cpu)
282 			? xen_irqs_disabled(get_irq_regs())
283 			: v->evtchn_upcall_mask;
284 		printk("%d: masked=%d pending=%d event_sel %0*"PRI_xen_ulong"\n  ", i,
285 		       pending, v->evtchn_upcall_pending,
286 		       (int)(sizeof(v->evtchn_pending_sel)*2),
287 		       v->evtchn_pending_sel);
288 	}
289 	v = per_cpu(xen_vcpu, cpu);
290 
291 	printk("\npending:\n   ");
292 	for (i = ARRAY_SIZE(sh->evtchn_pending)-1; i >= 0; i--)
293 		printk("%0*"PRI_xen_ulong"%s",
294 		       (int)sizeof(sh->evtchn_pending[0])*2,
295 		       sh->evtchn_pending[i],
296 		       i % 8 == 0 ? "\n   " : " ");
297 	printk("\nglobal mask:\n   ");
298 	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
299 		printk("%0*"PRI_xen_ulong"%s",
300 		       (int)(sizeof(sh->evtchn_mask[0])*2),
301 		       sh->evtchn_mask[i],
302 		       i % 8 == 0 ? "\n   " : " ");
303 
304 	printk("\nglobally unmasked:\n   ");
305 	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
306 		printk("%0*"PRI_xen_ulong"%s",
307 		       (int)(sizeof(sh->evtchn_mask[0])*2),
308 		       sh->evtchn_pending[i] & ~sh->evtchn_mask[i],
309 		       i % 8 == 0 ? "\n   " : " ");
310 
311 	printk("\nlocal cpu%d mask:\n   ", cpu);
312 	for (i = (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
313 		printk("%0*"PRI_xen_ulong"%s", (int)(sizeof(cpu_evtchn[0])*2),
314 		       cpu_evtchn[i],
315 		       i % 8 == 0 ? "\n   " : " ");
316 
317 	printk("\nlocally unmasked:\n   ");
318 	for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--) {
319 		xen_ulong_t pending = sh->evtchn_pending[i]
320 			& ~sh->evtchn_mask[i]
321 			& cpu_evtchn[i];
322 		printk("%0*"PRI_xen_ulong"%s",
323 		       (int)(sizeof(sh->evtchn_mask[0])*2),
324 		       pending, i % 8 == 0 ? "\n   " : " ");
325 	}
326 
327 	printk("\npending list:\n");
328 	for (i = 0; i < EVTCHN_2L_NR_CHANNELS; i++) {
329 		if (sync_test_bit(i, BM(sh->evtchn_pending))) {
330 			int word_idx = i / BITS_PER_EVTCHN_WORD;
331 			printk("  %d: event %d -> irq %d%s%s%s\n",
332 			       cpu_from_evtchn(i), i,
333 			       get_evtchn_to_irq(i),
334 			       sync_test_bit(word_idx, BM(&v->evtchn_pending_sel))
335 			       ? "" : " l2-clear",
336 			       !sync_test_bit(i, BM(sh->evtchn_mask))
337 			       ? "" : " globally-masked",
338 			       sync_test_bit(i, BM(cpu_evtchn))
339 			       ? "" : " locally-masked");
340 		}
341 	}
342 
343 	spin_unlock_irqrestore(&debug_lock, flags);
344 
345 	return IRQ_HANDLED;
346 }
347 
348 static const struct evtchn_ops evtchn_ops_2l = {
349 	.max_channels      = evtchn_2l_max_channels,
350 	.nr_channels       = evtchn_2l_max_channels,
351 	.bind_to_cpu       = evtchn_2l_bind_to_cpu,
352 	.clear_pending     = evtchn_2l_clear_pending,
353 	.set_pending       = evtchn_2l_set_pending,
354 	.is_pending        = evtchn_2l_is_pending,
355 	.test_and_set_mask = evtchn_2l_test_and_set_mask,
356 	.mask              = evtchn_2l_mask,
357 	.unmask            = evtchn_2l_unmask,
358 	.handle_events     = evtchn_2l_handle_events,
359 };
360 
361 void __init xen_evtchn_2l_init(void)
362 {
363 	pr_info("Using 2-level ABI\n");
364 	evtchn_ops = &evtchn_ops_2l;
365 }
366