2 * Xen event channels (FIFO-based ABI)
4 * Copyright (C) 2013 Citrix Systems R&D ltd.
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8 * published by the Free Software Foundation; either version 2 of the
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11 * Or, when distributed separately from the Linux kernel or
12 * incorporated into other software packages, subject to the following
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34 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
36 #include <linux/linkage.h>
37 #include <linux/interrupt.h>
38 #include <linux/irq.h>
39 #include <linux/module.h>
40 #include <linux/smp.h>
41 #include <linux/percpu.h>
42 #include <linux/cpu.h>
44 #include <asm/sync_bitops.h>
45 #include <asm/xen/hypercall.h>
46 #include <asm/xen/hypervisor.h>
47 #include <asm/xen/page.h>
50 #include <xen/xen-ops.h>
51 #include <xen/events.h>
52 #include <xen/interface/xen.h>
53 #include <xen/interface/event_channel.h>
55 #include "events_internal.h"
57 #define EVENT_WORDS_PER_PAGE (PAGE_SIZE / sizeof(event_word_t))
58 #define MAX_EVENT_ARRAY_PAGES (EVTCHN_FIFO_NR_CHANNELS / EVENT_WORDS_PER_PAGE)
60 struct evtchn_fifo_queue {
61 uint32_t head[EVTCHN_FIFO_MAX_QUEUES];
64 static DEFINE_PER_CPU(struct evtchn_fifo_control_block *, cpu_control_block);
65 static DEFINE_PER_CPU(struct evtchn_fifo_queue, cpu_queue);
66 static event_word_t *event_array[MAX_EVENT_ARRAY_PAGES] __read_mostly;
67 static unsigned event_array_pages __read_mostly;
70 * sync_set_bit() and friends must be unsigned long aligned on non-x86
73 #if !defined(CONFIG_X86) && BITS_PER_LONG > 32
75 #define BM(w) (unsigned long *)((unsigned long)w & ~0x7UL)
76 #define EVTCHN_FIFO_BIT(b, w) \
77 (((unsigned long)w & 0x4UL) ? (EVTCHN_FIFO_ ##b + 32) : EVTCHN_FIFO_ ##b)
81 #define BM(w) ((unsigned long *)(w))
82 #define EVTCHN_FIFO_BIT(b, w) EVTCHN_FIFO_ ##b
86 static inline event_word_t *event_word_from_port(unsigned port)
88 unsigned i = port / EVENT_WORDS_PER_PAGE;
90 return event_array[i] + port % EVENT_WORDS_PER_PAGE;
93 static unsigned evtchn_fifo_max_channels(void)
95 return EVTCHN_FIFO_NR_CHANNELS;
98 static unsigned evtchn_fifo_nr_channels(void)
100 return event_array_pages * EVENT_WORDS_PER_PAGE;
103 static int init_control_block(int cpu,
104 struct evtchn_fifo_control_block *control_block)
106 struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
107 struct evtchn_init_control init_control;
110 /* Reset the control block and the local HEADs. */
111 clear_page(control_block);
112 for (i = 0; i < EVTCHN_FIFO_MAX_QUEUES; i++)
115 init_control.control_gfn = virt_to_mfn(control_block);
116 init_control.offset = 0;
117 init_control.vcpu = cpu;
119 return HYPERVISOR_event_channel_op(EVTCHNOP_init_control, &init_control);
122 static void free_unused_array_pages(void)
126 for (i = event_array_pages; i < MAX_EVENT_ARRAY_PAGES; i++) {
129 free_page((unsigned long)event_array[i]);
130 event_array[i] = NULL;
134 static void init_array_page(event_word_t *array_page)
138 for (i = 0; i < EVENT_WORDS_PER_PAGE; i++)
139 array_page[i] = 1 << EVTCHN_FIFO_MASKED;
142 static int evtchn_fifo_setup(struct irq_info *info)
144 unsigned port = info->evtchn;
145 unsigned new_array_pages;
148 new_array_pages = port / EVENT_WORDS_PER_PAGE + 1;
150 if (new_array_pages > MAX_EVENT_ARRAY_PAGES)
153 while (event_array_pages < new_array_pages) {
155 struct evtchn_expand_array expand_array;
157 /* Might already have a page if we've resumed. */
158 array_page = event_array[event_array_pages];
160 array_page = (void *)__get_free_page(GFP_KERNEL);
161 if (array_page == NULL) {
165 event_array[event_array_pages] = array_page;
168 /* Mask all events in this page before adding it. */
169 init_array_page(array_page);
171 expand_array.array_gfn = virt_to_mfn(array_page);
173 ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array);
182 if (event_array_pages == 0)
183 panic("xen: unable to expand event array with initial page (%d)\n", ret);
185 pr_err("unable to expand event array (%d)\n", ret);
186 free_unused_array_pages();
190 static void evtchn_fifo_bind_to_cpu(struct irq_info *info, unsigned cpu)
195 static void evtchn_fifo_clear_pending(unsigned port)
197 event_word_t *word = event_word_from_port(port);
198 sync_clear_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
201 static void evtchn_fifo_set_pending(unsigned port)
203 event_word_t *word = event_word_from_port(port);
204 sync_set_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
207 static bool evtchn_fifo_is_pending(unsigned port)
209 event_word_t *word = event_word_from_port(port);
210 return sync_test_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
213 static bool evtchn_fifo_test_and_set_mask(unsigned port)
215 event_word_t *word = event_word_from_port(port);
216 return sync_test_and_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
219 static void evtchn_fifo_mask(unsigned port)
221 event_word_t *word = event_word_from_port(port);
222 sync_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
225 static bool evtchn_fifo_is_masked(unsigned port)
227 event_word_t *word = event_word_from_port(port);
228 return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
231 * Clear MASKED, spinning if BUSY is set.
233 static void clear_masked(volatile event_word_t *word)
235 event_word_t new, old, w;
240 old = w & ~(1 << EVTCHN_FIFO_BUSY);
241 new = old & ~(1 << EVTCHN_FIFO_MASKED);
242 w = sync_cmpxchg(word, old, new);
246 static void evtchn_fifo_unmask(unsigned port)
248 event_word_t *word = event_word_from_port(port);
250 BUG_ON(!irqs_disabled());
253 if (evtchn_fifo_is_pending(port)) {
254 struct evtchn_unmask unmask = { .port = port };
255 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
259 static uint32_t clear_linked(volatile event_word_t *word)
261 event_word_t new, old, w;
267 new = (w & ~((1 << EVTCHN_FIFO_LINKED)
268 | EVTCHN_FIFO_LINK_MASK));
269 } while ((w = sync_cmpxchg(word, old, new)) != old);
271 return w & EVTCHN_FIFO_LINK_MASK;
274 static void handle_irq_for_port(unsigned port)
278 irq = get_evtchn_to_irq(port);
280 generic_handle_irq(irq);
283 static void consume_one_event(unsigned cpu,
284 struct evtchn_fifo_control_block *control_block,
285 unsigned priority, unsigned long *ready)
287 struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
292 head = q->head[priority];
295 * Reached the tail last time? Read the new HEAD from the
299 rmb(); /* Ensure word is up-to-date before reading head. */
300 head = control_block->head[priority];
304 word = event_word_from_port(port);
305 head = clear_linked(word);
308 * If the link is non-zero, there are more events in the
309 * queue, otherwise the queue is empty.
311 * If the queue is empty, clear this priority from our local
312 * copy of the ready word.
315 clear_bit(priority, ready);
317 if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port))
318 handle_irq_for_port(port);
320 q->head[priority] = head;
323 static void evtchn_fifo_handle_events(unsigned cpu)
325 struct evtchn_fifo_control_block *control_block;
329 control_block = per_cpu(cpu_control_block, cpu);
331 ready = xchg(&control_block->ready, 0);
334 q = find_first_bit(BM(&ready), EVTCHN_FIFO_MAX_QUEUES);
335 consume_one_event(cpu, control_block, q, &ready);
336 ready |= xchg(&control_block->ready, 0);
340 static void evtchn_fifo_resume(void)
344 for_each_possible_cpu(cpu) {
345 void *control_block = per_cpu(cpu_control_block, cpu);
352 * If this CPU is offline, take the opportunity to
353 * free the control block while it is not being
356 if (!cpu_online(cpu)) {
357 free_page((unsigned long)control_block);
358 per_cpu(cpu_control_block, cpu) = NULL;
362 ret = init_control_block(cpu, control_block);
368 * The event array starts out as empty again and is extended
369 * as normal when events are bound. The existing pages will
372 event_array_pages = 0;
375 static const struct evtchn_ops evtchn_ops_fifo = {
376 .max_channels = evtchn_fifo_max_channels,
377 .nr_channels = evtchn_fifo_nr_channels,
378 .setup = evtchn_fifo_setup,
379 .bind_to_cpu = evtchn_fifo_bind_to_cpu,
380 .clear_pending = evtchn_fifo_clear_pending,
381 .set_pending = evtchn_fifo_set_pending,
382 .is_pending = evtchn_fifo_is_pending,
383 .test_and_set_mask = evtchn_fifo_test_and_set_mask,
384 .mask = evtchn_fifo_mask,
385 .unmask = evtchn_fifo_unmask,
386 .handle_events = evtchn_fifo_handle_events,
387 .resume = evtchn_fifo_resume,
390 static int evtchn_fifo_alloc_control_block(unsigned cpu)
392 void *control_block = NULL;
395 control_block = (void *)__get_free_page(GFP_KERNEL);
396 if (control_block == NULL)
399 ret = init_control_block(cpu, control_block);
403 per_cpu(cpu_control_block, cpu) = control_block;
408 free_page((unsigned long)control_block);
412 static int evtchn_fifo_cpu_notification(struct notifier_block *self,
413 unsigned long action,
416 int cpu = (long)hcpu;
421 if (!per_cpu(cpu_control_block, cpu))
422 ret = evtchn_fifo_alloc_control_block(cpu);
427 return ret < 0 ? NOTIFY_BAD : NOTIFY_OK;
430 static struct notifier_block evtchn_fifo_cpu_notifier = {
431 .notifier_call = evtchn_fifo_cpu_notification,
434 int __init xen_evtchn_fifo_init(void)
439 ret = evtchn_fifo_alloc_control_block(cpu);
443 pr_info("Using FIFO-based ABI\n");
445 evtchn_ops = &evtchn_ops_fifo;
447 register_cpu_notifier(&evtchn_fifo_cpu_notifier);