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authorJeremy Fitzhardinge <jeremy@xensource.com>2007-07-17 21:37:05 -0400
committerJeremy Fitzhardinge <jeremy@goop.org>2007-07-18 11:47:42 -0400
commite46cdb66c8fc1c8d61cfae0f219ff47ac4b9d531 (patch)
tree7d9cdfef91e69fcfcba762a5a70cd58900308a5b /arch/i386/xen/events.c
parent3b827c1b3aadf3adb4c602d19863f2d24e7cbc18 (diff)
xen: event channels
Xen implements interrupts in terms of event channels. Each guest domain gets 1024 event channels which can be used for a variety of purposes, such as Xen timer events, inter-domain events, inter-processor events (IPI) or for real hardware IRQs. Within the kernel, we map the event channels to IRQs, and implement the whole interrupt handling using a Xen irq_chip. Rather than setting NR_IRQ to 1024 under PARAVIRT in order to accomodate Xen, we create a dynamic mapping between event channels and IRQs. Ideally, Linux will eventually move towards dynamically allocating per-irq structures, and we can use a 1:1 mapping between event channels and irqs. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Eric W. Biederman <ebiederm@xmission.com>
Diffstat (limited to 'arch/i386/xen/events.c')
-rw-r--r--arch/i386/xen/events.c511
1 files changed, 511 insertions, 0 deletions
diff --git a/arch/i386/xen/events.c b/arch/i386/xen/events.c
new file mode 100644
index 000000000000..e7c5d00ab4fe
--- /dev/null
+++ b/arch/i386/xen/events.c
@@ -0,0 +1,511 @@
1/*
2 * Xen event channels
3 *
4 * Xen models interrupts with abstract event channels. Because each
5 * domain gets 1024 event channels, but NR_IRQ is not that large, we
6 * must dynamically map irqs<->event channels. The event channels
7 * interface with the rest of the kernel by defining a xen interrupt
8 * chip. When an event is recieved, it is mapped to an irq and sent
9 * through the normal interrupt processing path.
10 *
11 * There are four kinds of events which can be mapped to an event
12 * channel:
13 *
14 * 1. Inter-domain notifications. This includes all the virtual
15 * device events, since they're driven by front-ends in another domain
16 * (typically dom0).
17 * 2. VIRQs, typically used for timers. These are per-cpu events.
18 * 3. IPIs.
19 * 4. Hardware interrupts. Not supported at present.
20 *
21 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
22 */
23
24#include <linux/linkage.h>
25#include <linux/interrupt.h>
26#include <linux/irq.h>
27#include <linux/module.h>
28#include <linux/string.h>
29
30#include <asm/ptrace.h>
31#include <asm/irq.h>
32#include <asm/sync_bitops.h>
33#include <asm/xen/hypercall.h>
34
35#include <xen/events.h>
36#include <xen/interface/xen.h>
37#include <xen/interface/event_channel.h>
38
39#include "xen-ops.h"
40
41/*
42 * This lock protects updates to the following mapping and reference-count
43 * arrays. The lock does not need to be acquired to read the mapping tables.
44 */
45static DEFINE_SPINLOCK(irq_mapping_update_lock);
46
47/* IRQ <-> VIRQ mapping. */
48static DEFINE_PER_CPU(int, virq_to_irq[NR_VIRQS]) = {[0 ... NR_VIRQS-1] = -1};
49
50/* Packed IRQ information: binding type, sub-type index, and event channel. */
51struct packed_irq
52{
53 unsigned short evtchn;
54 unsigned char index;
55 unsigned char type;
56};
57
58static struct packed_irq irq_info[NR_IRQS];
59
60/* Binding types. */
61enum { IRQT_UNBOUND, IRQT_PIRQ, IRQT_VIRQ, IRQT_IPI, IRQT_EVTCHN };
62
63/* Convenient shorthand for packed representation of an unbound IRQ. */
64#define IRQ_UNBOUND mk_irq_info(IRQT_UNBOUND, 0, 0)
65
66static int evtchn_to_irq[NR_EVENT_CHANNELS] = {
67 [0 ... NR_EVENT_CHANNELS-1] = -1
68};
69static unsigned long cpu_evtchn_mask[NR_CPUS][NR_EVENT_CHANNELS/BITS_PER_LONG];
70static u8 cpu_evtchn[NR_EVENT_CHANNELS];
71
72/* Reference counts for bindings to IRQs. */
73static int irq_bindcount[NR_IRQS];
74
75/* Xen will never allocate port zero for any purpose. */
76#define VALID_EVTCHN(chn) ((chn) != 0)
77
78/*
79 * Force a proper event-channel callback from Xen after clearing the
80 * callback mask. We do this in a very simple manner, by making a call
81 * down into Xen. The pending flag will be checked by Xen on return.
82 */
83void force_evtchn_callback(void)
84{
85 (void)HYPERVISOR_xen_version(0, NULL);
86}
87EXPORT_SYMBOL_GPL(force_evtchn_callback);
88
89static struct irq_chip xen_dynamic_chip;
90
91/* Constructor for packed IRQ information. */
92static inline struct packed_irq mk_irq_info(u32 type, u32 index, u32 evtchn)
93{
94 return (struct packed_irq) { evtchn, index, type };
95}
96
97/*
98 * Accessors for packed IRQ information.
99 */
100static inline unsigned int evtchn_from_irq(int irq)
101{
102 return irq_info[irq].evtchn;
103}
104
105static inline unsigned int index_from_irq(int irq)
106{
107 return irq_info[irq].index;
108}
109
110static inline unsigned int type_from_irq(int irq)
111{
112 return irq_info[irq].type;
113}
114
115static inline unsigned long active_evtchns(unsigned int cpu,
116 struct shared_info *sh,
117 unsigned int idx)
118{
119 return (sh->evtchn_pending[idx] &
120 cpu_evtchn_mask[cpu][idx] &
121 ~sh->evtchn_mask[idx]);
122}
123
124static void bind_evtchn_to_cpu(unsigned int chn, unsigned int cpu)
125{
126 int irq = evtchn_to_irq[chn];
127
128 BUG_ON(irq == -1);
129#ifdef CONFIG_SMP
130 irq_desc[irq].affinity = cpumask_of_cpu(cpu);
131#endif
132
133 __clear_bit(chn, cpu_evtchn_mask[cpu_evtchn[chn]]);
134 __set_bit(chn, cpu_evtchn_mask[cpu]);
135
136 cpu_evtchn[chn] = cpu;
137}
138
139static void init_evtchn_cpu_bindings(void)
140{
141#ifdef CONFIG_SMP
142 int i;
143 /* By default all event channels notify CPU#0. */
144 for (i = 0; i < NR_IRQS; i++)
145 irq_desc[i].affinity = cpumask_of_cpu(0);
146#endif
147
148 memset(cpu_evtchn, 0, sizeof(cpu_evtchn));
149 memset(cpu_evtchn_mask[0], ~0, sizeof(cpu_evtchn_mask[0]));
150}
151
152static inline unsigned int cpu_from_evtchn(unsigned int evtchn)
153{
154 return cpu_evtchn[evtchn];
155}
156
157static inline void clear_evtchn(int port)
158{
159 struct shared_info *s = HYPERVISOR_shared_info;
160 sync_clear_bit(port, &s->evtchn_pending[0]);
161}
162
163static inline void set_evtchn(int port)
164{
165 struct shared_info *s = HYPERVISOR_shared_info;
166 sync_set_bit(port, &s->evtchn_pending[0]);
167}
168
169
170/**
171 * notify_remote_via_irq - send event to remote end of event channel via irq
172 * @irq: irq of event channel to send event to
173 *
174 * Unlike notify_remote_via_evtchn(), this is safe to use across
175 * save/restore. Notifications on a broken connection are silently
176 * dropped.
177 */
178void notify_remote_via_irq(int irq)
179{
180 int evtchn = evtchn_from_irq(irq);
181
182 if (VALID_EVTCHN(evtchn))
183 notify_remote_via_evtchn(evtchn);
184}
185EXPORT_SYMBOL_GPL(notify_remote_via_irq);
186
187static void mask_evtchn(int port)
188{
189 struct shared_info *s = HYPERVISOR_shared_info;
190 sync_set_bit(port, &s->evtchn_mask[0]);
191}
192
193static void unmask_evtchn(int port)
194{
195 struct shared_info *s = HYPERVISOR_shared_info;
196 unsigned int cpu = get_cpu();
197
198 BUG_ON(!irqs_disabled());
199
200 /* Slow path (hypercall) if this is a non-local port. */
201 if (unlikely(cpu != cpu_from_evtchn(port))) {
202 struct evtchn_unmask unmask = { .port = port };
203 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
204 } else {
205 struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);
206
207 sync_clear_bit(port, &s->evtchn_mask[0]);
208
209 /*
210 * The following is basically the equivalent of
211 * 'hw_resend_irq'. Just like a real IO-APIC we 'lose
212 * the interrupt edge' if the channel is masked.
213 */
214 if (sync_test_bit(port, &s->evtchn_pending[0]) &&
215 !sync_test_and_set_bit(port / BITS_PER_LONG,
216 &vcpu_info->evtchn_pending_sel))
217 vcpu_info->evtchn_upcall_pending = 1;
218 }
219
220 put_cpu();
221}
222
223static int find_unbound_irq(void)
224{
225 int irq;
226
227 /* Only allocate from dynirq range */
228 for (irq = 0; irq < NR_IRQS; irq++)
229 if (irq_bindcount[irq] == 0)
230 break;
231
232 if (irq == NR_IRQS)
233 panic("No available IRQ to bind to: increase NR_IRQS!\n");
234
235 return irq;
236}
237
238static int bind_evtchn_to_irq(unsigned int evtchn)
239{
240 int irq;
241
242 spin_lock(&irq_mapping_update_lock);
243
244 irq = evtchn_to_irq[evtchn];
245
246 if (irq == -1) {
247 irq = find_unbound_irq();
248
249 dynamic_irq_init(irq);
250 set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
251 handle_level_irq, "event");
252
253 evtchn_to_irq[evtchn] = irq;
254 irq_info[irq] = mk_irq_info(IRQT_EVTCHN, 0, evtchn);
255 }
256
257 irq_bindcount[irq]++;
258
259 spin_unlock(&irq_mapping_update_lock);
260
261 return irq;
262}
263
264static int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
265{
266 struct evtchn_bind_virq bind_virq;
267 int evtchn, irq;
268
269 spin_lock(&irq_mapping_update_lock);
270
271 irq = per_cpu(virq_to_irq, cpu)[virq];
272
273 if (irq == -1) {
274 bind_virq.virq = virq;
275 bind_virq.vcpu = cpu;
276 if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
277 &bind_virq) != 0)
278 BUG();
279 evtchn = bind_virq.port;
280
281 irq = find_unbound_irq();
282
283 dynamic_irq_init(irq);
284 set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
285 handle_level_irq, "virq");
286
287 evtchn_to_irq[evtchn] = irq;
288 irq_info[irq] = mk_irq_info(IRQT_VIRQ, virq, evtchn);
289
290 per_cpu(virq_to_irq, cpu)[virq] = irq;
291
292 bind_evtchn_to_cpu(evtchn, cpu);
293 }
294
295 irq_bindcount[irq]++;
296
297 spin_unlock(&irq_mapping_update_lock);
298
299 return irq;
300}
301
302static void unbind_from_irq(unsigned int irq)
303{
304 struct evtchn_close close;
305 int evtchn = evtchn_from_irq(irq);
306
307 spin_lock(&irq_mapping_update_lock);
308
309 if (VALID_EVTCHN(evtchn) && (--irq_bindcount[irq] == 0)) {
310 close.port = evtchn;
311 if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
312 BUG();
313
314 switch (type_from_irq(irq)) {
315 case IRQT_VIRQ:
316 per_cpu(virq_to_irq, cpu_from_evtchn(evtchn))
317 [index_from_irq(irq)] = -1;
318 break;
319 default:
320 break;
321 }
322
323 /* Closed ports are implicitly re-bound to VCPU0. */
324 bind_evtchn_to_cpu(evtchn, 0);
325
326 evtchn_to_irq[evtchn] = -1;
327 irq_info[irq] = IRQ_UNBOUND;
328
329 dynamic_irq_init(irq);
330 }
331
332 spin_unlock(&irq_mapping_update_lock);
333}
334
335int bind_evtchn_to_irqhandler(unsigned int evtchn,
336 irqreturn_t (*handler)(int, void *),
337 unsigned long irqflags,
338 const char *devname, void *dev_id)
339{
340 unsigned int irq;
341 int retval;
342
343 irq = bind_evtchn_to_irq(evtchn);
344 retval = request_irq(irq, handler, irqflags, devname, dev_id);
345 if (retval != 0) {
346 unbind_from_irq(irq);
347 return retval;
348 }
349
350 return irq;
351}
352EXPORT_SYMBOL_GPL(bind_evtchn_to_irqhandler);
353
354int bind_virq_to_irqhandler(unsigned int virq, unsigned int cpu,
355 irqreturn_t (*handler)(int, void *),
356 unsigned long irqflags, const char *devname, void *dev_id)
357{
358 unsigned int irq;
359 int retval;
360
361 irq = bind_virq_to_irq(virq, cpu);
362 retval = request_irq(irq, handler, irqflags, devname, dev_id);
363 if (retval != 0) {
364 unbind_from_irq(irq);
365 return retval;
366 }
367
368 return irq;
369}
370EXPORT_SYMBOL_GPL(bind_virq_to_irqhandler);
371
372void unbind_from_irqhandler(unsigned int irq, void *dev_id)
373{
374 free_irq(irq, dev_id);
375 unbind_from_irq(irq);
376}
377EXPORT_SYMBOL_GPL(unbind_from_irqhandler);
378
379/*
380 * Search the CPUs pending events bitmasks. For each one found, map
381 * the event number to an irq, and feed it into do_IRQ() for
382 * handling.
383 *
384 * Xen uses a two-level bitmap to speed searching. The first level is
385 * a bitset of words which contain pending event bits. The second
386 * level is a bitset of pending events themselves.
387 */
388fastcall void xen_evtchn_do_upcall(struct pt_regs *regs)
389{
390 int cpu = get_cpu();
391 struct shared_info *s = HYPERVISOR_shared_info;
392 struct vcpu_info *vcpu_info = __get_cpu_var(xen_vcpu);
393 unsigned long pending_words;
394
395 vcpu_info->evtchn_upcall_pending = 0;
396
397 /* NB. No need for a barrier here -- XCHG is a barrier on x86. */
398 pending_words = xchg(&vcpu_info->evtchn_pending_sel, 0);
399 while (pending_words != 0) {
400 unsigned long pending_bits;
401 int word_idx = __ffs(pending_words);
402 pending_words &= ~(1UL << word_idx);
403
404 while ((pending_bits = active_evtchns(cpu, s, word_idx)) != 0) {
405 int bit_idx = __ffs(pending_bits);
406 int port = (word_idx * BITS_PER_LONG) + bit_idx;
407 int irq = evtchn_to_irq[port];
408
409 if (irq != -1) {
410 regs->orig_eax = ~irq;
411 do_IRQ(regs);
412 }
413 }
414 }
415
416 put_cpu();
417}
418
419/* Rebind an evtchn so that it gets delivered to a specific cpu */
420static void rebind_irq_to_cpu(unsigned irq, unsigned tcpu)
421{
422 struct evtchn_bind_vcpu bind_vcpu;
423 int evtchn = evtchn_from_irq(irq);
424
425 if (!VALID_EVTCHN(evtchn))
426 return;
427
428 /* Send future instances of this interrupt to other vcpu. */
429 bind_vcpu.port = evtchn;
430 bind_vcpu.vcpu = tcpu;
431
432 /*
433 * If this fails, it usually just indicates that we're dealing with a
434 * virq or IPI channel, which don't actually need to be rebound. Ignore
435 * it, but don't do the xenlinux-level rebind in that case.
436 */
437 if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_vcpu, &bind_vcpu) >= 0)
438 bind_evtchn_to_cpu(evtchn, tcpu);
439}
440
441
442static void set_affinity_irq(unsigned irq, cpumask_t dest)
443{
444 unsigned tcpu = first_cpu(dest);
445 rebind_irq_to_cpu(irq, tcpu);
446}
447
448static void enable_dynirq(unsigned int irq)
449{
450 int evtchn = evtchn_from_irq(irq);
451
452 if (VALID_EVTCHN(evtchn))
453 unmask_evtchn(evtchn);
454}
455
456static void disable_dynirq(unsigned int irq)
457{
458 int evtchn = evtchn_from_irq(irq);
459
460 if (VALID_EVTCHN(evtchn))
461 mask_evtchn(evtchn);
462}
463
464static void ack_dynirq(unsigned int irq)
465{
466 int evtchn = evtchn_from_irq(irq);
467
468 move_native_irq(irq);
469
470 if (VALID_EVTCHN(evtchn))
471 clear_evtchn(evtchn);
472}
473
474static int retrigger_dynirq(unsigned int irq)
475{
476 int evtchn = evtchn_from_irq(irq);
477 int ret = 0;
478
479 if (VALID_EVTCHN(evtchn)) {
480 set_evtchn(evtchn);
481 ret = 1;
482 }
483
484 return ret;
485}
486
487static struct irq_chip xen_dynamic_chip __read_mostly = {
488 .name = "xen-dyn",
489 .mask = disable_dynirq,
490 .unmask = enable_dynirq,
491 .ack = ack_dynirq,
492 .set_affinity = set_affinity_irq,
493 .retrigger = retrigger_dynirq,
494};
495
496void __init xen_init_IRQ(void)
497{
498 int i;
499
500 init_evtchn_cpu_bindings();
501
502 /* No event channels are 'live' right now. */
503 for (i = 0; i < NR_EVENT_CHANNELS; i++)
504 mask_evtchn(i);
505
506 /* Dynamic IRQ space is currently unbound. Zero the refcnts. */
507 for (i = 0; i < NR_IRQS; i++)
508 irq_bindcount[i] = 0;
509
510 irq_ctx_init(smp_processor_id());
511}