1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Xen event channels (2-level ABI)
4 *
5 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
6 */
7
8 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
9
10 #include <linux/linkage.h>
11 #include <linux/interrupt.h>
12 #include <linux/irq.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 #define EVTCHN_MASK_SIZE (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)
42
43 static DEFINE_PER_CPU(xen_ulong_t [EVTCHN_MASK_SIZE], cpu_evtchn_mask);
44
evtchn_2l_max_channels(void)45 static unsigned evtchn_2l_max_channels(void)
46 {
47 return EVTCHN_2L_NR_CHANNELS;
48 }
49
evtchn_2l_bind_to_cpu(struct irq_info * info,unsigned cpu)50 static void evtchn_2l_bind_to_cpu(struct irq_info *info, unsigned cpu)
51 {
52 clear_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, info->cpu)));
53 set_bit(info->evtchn, BM(per_cpu(cpu_evtchn_mask, cpu)));
54 }
55
evtchn_2l_clear_pending(unsigned port)56 static void evtchn_2l_clear_pending(unsigned port)
57 {
58 struct shared_info *s = HYPERVISOR_shared_info;
59 sync_clear_bit(port, BM(&s->evtchn_pending[0]));
60 }
61
evtchn_2l_set_pending(unsigned port)62 static void evtchn_2l_set_pending(unsigned port)
63 {
64 struct shared_info *s = HYPERVISOR_shared_info;
65 sync_set_bit(port, BM(&s->evtchn_pending[0]));
66 }
67
evtchn_2l_is_pending(unsigned port)68 static bool evtchn_2l_is_pending(unsigned port)
69 {
70 struct shared_info *s = HYPERVISOR_shared_info;
71 return sync_test_bit(port, BM(&s->evtchn_pending[0]));
72 }
73
evtchn_2l_test_and_set_mask(unsigned port)74 static bool evtchn_2l_test_and_set_mask(unsigned port)
75 {
76 struct shared_info *s = HYPERVISOR_shared_info;
77 return sync_test_and_set_bit(port, BM(&s->evtchn_mask[0]));
78 }
79
evtchn_2l_mask(unsigned port)80 static void evtchn_2l_mask(unsigned port)
81 {
82 struct shared_info *s = HYPERVISOR_shared_info;
83 sync_set_bit(port, BM(&s->evtchn_mask[0]));
84 }
85
evtchn_2l_unmask(unsigned port)86 static void evtchn_2l_unmask(unsigned port)
87 {
88 struct shared_info *s = HYPERVISOR_shared_info;
89 unsigned int cpu = get_cpu();
90 int do_hypercall = 0, evtchn_pending = 0;
91
92 BUG_ON(!irqs_disabled());
93
94 if (unlikely((cpu != cpu_from_evtchn(port))))
95 do_hypercall = 1;
96 else {
97 /*
98 * Need to clear the mask before checking pending to
99 * avoid a race with an event becoming pending.
100 *
101 * EVTCHNOP_unmask will only trigger an upcall if the
102 * mask bit was set, so if a hypercall is needed
103 * remask the event.
104 */
105 sync_clear_bit(port, BM(&s->evtchn_mask[0]));
106 evtchn_pending = sync_test_bit(port, BM(&s->evtchn_pending[0]));
107
108 if (unlikely(evtchn_pending && xen_hvm_domain())) {
109 sync_set_bit(port, BM(&s->evtchn_mask[0]));
110 do_hypercall = 1;
111 }
112 }
113
114 /* Slow path (hypercall) if this is a non-local port or if this is
115 * an hvm domain and an event is pending (hvm domains don't have
116 * their own implementation of irq_enable). */
117 if (do_hypercall) {
118 struct evtchn_unmask unmask = { .port = port };
119 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
120 } else {
121 struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
122
123 /*
124 * The following is basically the equivalent of
125 * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
126 * the interrupt edge' if the channel is masked.
127 */
128 if (evtchn_pending &&
129 !sync_test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
130 BM(&vcpu_info->evtchn_pending_sel)))
131 vcpu_info->evtchn_upcall_pending = 1;
132 }
133
134 put_cpu();
135 }
136
137 static DEFINE_PER_CPU(unsigned int, current_word_idx);
138 static DEFINE_PER_CPU(unsigned int, current_bit_idx);
139
140 /*
141 * Mask out the i least significant bits of w
142 */
143 #define MASK_LSBS(w, i) (w & ((~((xen_ulong_t)0UL)) << i))
144
active_evtchns(unsigned int cpu,struct shared_info * sh,unsigned int idx)145 static inline xen_ulong_t active_evtchns(unsigned int cpu,
146 struct shared_info *sh,
147 unsigned int idx)
148 {
149 return sh->evtchn_pending[idx] &
150 per_cpu(cpu_evtchn_mask, cpu)[idx] &
151 ~sh->evtchn_mask[idx];
152 }
153
154 /*
155 * Search the CPU's pending events bitmasks. For each one found, map
156 * the event number to an irq, and feed it into do_IRQ() for handling.
157 *
158 * Xen uses a two-level bitmap to speed searching. The first level is
159 * a bitset of words which contain pending event bits. The second
160 * level is a bitset of pending events themselves.
161 */
evtchn_2l_handle_events(unsigned cpu)162 static void evtchn_2l_handle_events(unsigned cpu)
163 {
164 int irq;
165 xen_ulong_t pending_words;
166 xen_ulong_t pending_bits;
167 int start_word_idx, start_bit_idx;
168 int word_idx, bit_idx;
169 int i;
170 struct shared_info *s = HYPERVISOR_shared_info;
171 struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
172
173 /* Timer interrupt has highest priority. */
174 irq = irq_from_virq(cpu, VIRQ_TIMER);
175 if (irq != -1) {
176 unsigned int evtchn = evtchn_from_irq(irq);
177 word_idx = evtchn / BITS_PER_LONG;
178 bit_idx = evtchn % BITS_PER_LONG;
179 if (active_evtchns(cpu, s, word_idx) & (1ULL << bit_idx))
180 generic_handle_irq(irq);
181 }
182
183 /*
184 * Master flag must be cleared /before/ clearing
185 * selector flag. xchg_xen_ulong must contain an
186 * appropriate barrier.
187 */
188 pending_words = xchg_xen_ulong(&vcpu_info->evtchn_pending_sel, 0);
189
190 start_word_idx = __this_cpu_read(current_word_idx);
191 start_bit_idx = __this_cpu_read(current_bit_idx);
192
193 word_idx = start_word_idx;
194
195 for (i = 0; pending_words != 0; i++) {
196 xen_ulong_t words;
197
198 words = MASK_LSBS(pending_words, word_idx);
199
200 /*
201 * If we masked out all events, wrap to beginning.
202 */
203 if (words == 0) {
204 word_idx = 0;
205 bit_idx = 0;
206 continue;
207 }
208 word_idx = EVTCHN_FIRST_BIT(words);
209
210 pending_bits = active_evtchns(cpu, s, word_idx);
211 bit_idx = 0; /* usually scan entire word from start */
212 /*
213 * We scan the starting word in two parts.
214 *
215 * 1st time: start in the middle, scanning the
216 * upper bits.
217 *
218 * 2nd time: scan the whole word (not just the
219 * parts skipped in the first pass) -- if an
220 * event in the previously scanned bits is
221 * pending again it would just be scanned on
222 * the next loop anyway.
223 */
224 if (word_idx == start_word_idx) {
225 if (i == 0)
226 bit_idx = start_bit_idx;
227 }
228
229 do {
230 xen_ulong_t bits;
231 int port;
232
233 bits = MASK_LSBS(pending_bits, bit_idx);
234
235 /* If we masked out all events, move on. */
236 if (bits == 0)
237 break;
238
239 bit_idx = EVTCHN_FIRST_BIT(bits);
240
241 /* Process port. */
242 port = (word_idx * BITS_PER_EVTCHN_WORD) + bit_idx;
243 irq = get_evtchn_to_irq(port);
244
245 if (irq != -1)
246 generic_handle_irq(irq);
247
248 bit_idx = (bit_idx + 1) % BITS_PER_EVTCHN_WORD;
249
250 /* Next caller starts at last processed + 1 */
251 __this_cpu_write(current_word_idx,
252 bit_idx ? word_idx :
253 (word_idx+1) % BITS_PER_EVTCHN_WORD);
254 __this_cpu_write(current_bit_idx, bit_idx);
255 } while (bit_idx != 0);
256
257 /* Scan start_l1i twice; all others once. */
258 if ((word_idx != start_word_idx) || (i != 0))
259 pending_words &= ~(1UL << word_idx);
260
261 word_idx = (word_idx + 1) % BITS_PER_EVTCHN_WORD;
262 }
263 }
264
xen_debug_interrupt(int irq,void * dev_id)265 irqreturn_t xen_debug_interrupt(int irq, void *dev_id)
266 {
267 struct shared_info *sh = HYPERVISOR_shared_info;
268 int cpu = smp_processor_id();
269 xen_ulong_t *cpu_evtchn = per_cpu(cpu_evtchn_mask, cpu);
270 int i;
271 unsigned long flags;
272 static DEFINE_SPINLOCK(debug_lock);
273 struct vcpu_info *v;
274
275 spin_lock_irqsave(&debug_lock, flags);
276
277 printk("\nvcpu %d\n ", cpu);
278
279 for_each_online_cpu(i) {
280 int pending;
281 v = per_cpu(xen_vcpu, i);
282 pending = (get_irq_regs() && i == cpu)
283 ? xen_irqs_disabled(get_irq_regs())
284 : v->evtchn_upcall_mask;
285 printk("%d: masked=%d pending=%d event_sel %0*"PRI_xen_ulong"\n ", i,
286 pending, v->evtchn_upcall_pending,
287 (int)(sizeof(v->evtchn_pending_sel)*2),
288 v->evtchn_pending_sel);
289 }
290 v = per_cpu(xen_vcpu, cpu);
291
292 printk("\npending:\n ");
293 for (i = ARRAY_SIZE(sh->evtchn_pending)-1; i >= 0; i--)
294 printk("%0*"PRI_xen_ulong"%s",
295 (int)sizeof(sh->evtchn_pending[0])*2,
296 sh->evtchn_pending[i],
297 i % 8 == 0 ? "\n " : " ");
298 printk("\nglobal mask:\n ");
299 for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
300 printk("%0*"PRI_xen_ulong"%s",
301 (int)(sizeof(sh->evtchn_mask[0])*2),
302 sh->evtchn_mask[i],
303 i % 8 == 0 ? "\n " : " ");
304
305 printk("\nglobally unmasked:\n ");
306 for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--)
307 printk("%0*"PRI_xen_ulong"%s",
308 (int)(sizeof(sh->evtchn_mask[0])*2),
309 sh->evtchn_pending[i] & ~sh->evtchn_mask[i],
310 i % 8 == 0 ? "\n " : " ");
311
312 printk("\nlocal cpu%d mask:\n ", cpu);
313 for (i = (EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD)-1; i >= 0; i--)
314 printk("%0*"PRI_xen_ulong"%s", (int)(sizeof(cpu_evtchn[0])*2),
315 cpu_evtchn[i],
316 i % 8 == 0 ? "\n " : " ");
317
318 printk("\nlocally unmasked:\n ");
319 for (i = ARRAY_SIZE(sh->evtchn_mask)-1; i >= 0; i--) {
320 xen_ulong_t pending = sh->evtchn_pending[i]
321 & ~sh->evtchn_mask[i]
322 & cpu_evtchn[i];
323 printk("%0*"PRI_xen_ulong"%s",
324 (int)(sizeof(sh->evtchn_mask[0])*2),
325 pending, i % 8 == 0 ? "\n " : " ");
326 }
327
328 printk("\npending list:\n");
329 for (i = 0; i < EVTCHN_2L_NR_CHANNELS; i++) {
330 if (sync_test_bit(i, BM(sh->evtchn_pending))) {
331 int word_idx = i / BITS_PER_EVTCHN_WORD;
332 printk(" %d: event %d -> irq %d%s%s%s\n",
333 cpu_from_evtchn(i), i,
334 get_evtchn_to_irq(i),
335 sync_test_bit(word_idx, BM(&v->evtchn_pending_sel))
336 ? "" : " l2-clear",
337 !sync_test_bit(i, BM(sh->evtchn_mask))
338 ? "" : " globally-masked",
339 sync_test_bit(i, BM(cpu_evtchn))
340 ? "" : " locally-masked");
341 }
342 }
343
344 spin_unlock_irqrestore(&debug_lock, flags);
345
346 return IRQ_HANDLED;
347 }
348
evtchn_2l_resume(void)349 static void evtchn_2l_resume(void)
350 {
351 int i;
352
353 for_each_online_cpu(i)
354 memset(per_cpu(cpu_evtchn_mask, i), 0, sizeof(xen_ulong_t) *
355 EVTCHN_2L_NR_CHANNELS/BITS_PER_EVTCHN_WORD);
356 }
357
358 static const struct evtchn_ops evtchn_ops_2l = {
359 .max_channels = evtchn_2l_max_channels,
360 .nr_channels = evtchn_2l_max_channels,
361 .bind_to_cpu = evtchn_2l_bind_to_cpu,
362 .clear_pending = evtchn_2l_clear_pending,
363 .set_pending = evtchn_2l_set_pending,
364 .is_pending = evtchn_2l_is_pending,
365 .test_and_set_mask = evtchn_2l_test_and_set_mask,
366 .mask = evtchn_2l_mask,
367 .unmask = evtchn_2l_unmask,
368 .handle_events = evtchn_2l_handle_events,
369 .resume = evtchn_2l_resume,
370 };
371
xen_evtchn_2l_init(void)372 void __init xen_evtchn_2l_init(void)
373 {
374 pr_info("Using 2-level ABI\n");
375 evtchn_ops = &evtchn_ops_2l;
376 }
377
