2 * Xen event channels (FIFO-based ABI)
4 * Copyright (C) 2013 Citrix Systems R&D ltd.
6 * This source code is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License as
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 void free_unused_array_pages(void)
107 for (i = event_array_pages; i < MAX_EVENT_ARRAY_PAGES; i++) {
110 free_page((unsigned long)event_array[i]);
111 event_array[i] = NULL;
115 static void init_array_page(event_word_t *array_page)
119 for (i = 0; i < EVENT_WORDS_PER_PAGE; i++)
120 array_page[i] = 1 << EVTCHN_FIFO_MASKED;
123 static int evtchn_fifo_setup(struct irq_info *info)
125 unsigned port = info->evtchn;
126 unsigned new_array_pages;
129 new_array_pages = port / EVENT_WORDS_PER_PAGE + 1;
131 if (new_array_pages > MAX_EVENT_ARRAY_PAGES)
134 while (event_array_pages < new_array_pages) {
136 struct evtchn_expand_array expand_array;
138 /* Might already have a page if we've resumed. */
139 array_page = event_array[event_array_pages];
141 array_page = (void *)__get_free_page(GFP_KERNEL);
142 if (array_page == NULL) {
146 event_array[event_array_pages] = array_page;
149 /* Mask all events in this page before adding it. */
150 init_array_page(array_page);
152 expand_array.array_gfn = virt_to_mfn(array_page);
154 ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array);
163 if (event_array_pages == 0)
164 panic("xen: unable to expand event array with initial page (%d)\n", ret);
166 pr_err("unable to expand event array (%d)\n", ret);
167 free_unused_array_pages();
171 static void evtchn_fifo_bind_to_cpu(struct irq_info *info, unsigned cpu)
176 static void evtchn_fifo_clear_pending(unsigned port)
178 event_word_t *word = event_word_from_port(port);
179 sync_clear_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
182 static void evtchn_fifo_set_pending(unsigned port)
184 event_word_t *word = event_word_from_port(port);
185 sync_set_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
188 static bool evtchn_fifo_is_pending(unsigned port)
190 event_word_t *word = event_word_from_port(port);
191 return sync_test_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
194 static bool evtchn_fifo_test_and_set_mask(unsigned port)
196 event_word_t *word = event_word_from_port(port);
197 return sync_test_and_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
200 static void evtchn_fifo_mask(unsigned port)
202 event_word_t *word = event_word_from_port(port);
203 sync_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
206 static bool evtchn_fifo_is_masked(unsigned port)
208 event_word_t *word = event_word_from_port(port);
209 return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
212 * Clear MASKED, spinning if BUSY is set.
214 static void clear_masked(volatile event_word_t *word)
216 event_word_t new, old, w;
221 old = w & ~(1 << EVTCHN_FIFO_BUSY);
222 new = old & ~(1 << EVTCHN_FIFO_MASKED);
223 w = sync_cmpxchg(word, old, new);
227 static void evtchn_fifo_unmask(unsigned port)
229 event_word_t *word = event_word_from_port(port);
231 BUG_ON(!irqs_disabled());
234 if (evtchn_fifo_is_pending(port)) {
235 struct evtchn_unmask unmask = { .port = port };
236 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
240 static uint32_t clear_linked(volatile event_word_t *word)
242 event_word_t new, old, w;
248 new = (w & ~((1 << EVTCHN_FIFO_LINKED)
249 | EVTCHN_FIFO_LINK_MASK));
250 } while ((w = sync_cmpxchg(word, old, new)) != old);
252 return w & EVTCHN_FIFO_LINK_MASK;
255 static void handle_irq_for_port(unsigned port)
259 irq = get_evtchn_to_irq(port);
261 generic_handle_irq(irq);
264 static void consume_one_event(unsigned cpu,
265 struct evtchn_fifo_control_block *control_block,
266 unsigned priority, unsigned long *ready)
268 struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
273 head = q->head[priority];
276 * Reached the tail last time? Read the new HEAD from the
280 rmb(); /* Ensure word is up-to-date before reading head. */
281 head = control_block->head[priority];
285 word = event_word_from_port(port);
286 head = clear_linked(word);
289 * If the link is non-zero, there are more events in the
290 * queue, otherwise the queue is empty.
292 * If the queue is empty, clear this priority from our local
293 * copy of the ready word.
296 clear_bit(priority, ready);
298 if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port))
299 handle_irq_for_port(port);
301 q->head[priority] = head;
304 static void evtchn_fifo_handle_events(unsigned cpu)
306 struct evtchn_fifo_control_block *control_block;
310 control_block = per_cpu(cpu_control_block, cpu);
312 ready = xchg(&control_block->ready, 0);
315 q = find_first_bit(BM(&ready), EVTCHN_FIFO_MAX_QUEUES);
316 consume_one_event(cpu, control_block, q, &ready);
317 ready |= xchg(&control_block->ready, 0);
321 static void evtchn_fifo_resume(void)
325 for_each_possible_cpu(cpu) {
326 void *control_block = per_cpu(cpu_control_block, cpu);
327 struct evtchn_init_control init_control;
334 * If this CPU is offline, take the opportunity to
335 * free the control block while it is not being
338 if (!cpu_online(cpu)) {
339 free_page((unsigned long)control_block);
340 per_cpu(cpu_control_block, cpu) = NULL;
344 init_control.control_gfn = virt_to_mfn(control_block);
345 init_control.offset = 0;
346 init_control.vcpu = cpu;
348 ret = HYPERVISOR_event_channel_op(EVTCHNOP_init_control,
355 * The event array starts out as empty again and is extended
356 * as normal when events are bound. The existing pages will
359 event_array_pages = 0;
362 static const struct evtchn_ops evtchn_ops_fifo = {
363 .max_channels = evtchn_fifo_max_channels,
364 .nr_channels = evtchn_fifo_nr_channels,
365 .setup = evtchn_fifo_setup,
366 .bind_to_cpu = evtchn_fifo_bind_to_cpu,
367 .clear_pending = evtchn_fifo_clear_pending,
368 .set_pending = evtchn_fifo_set_pending,
369 .is_pending = evtchn_fifo_is_pending,
370 .test_and_set_mask = evtchn_fifo_test_and_set_mask,
371 .mask = evtchn_fifo_mask,
372 .unmask = evtchn_fifo_unmask,
373 .handle_events = evtchn_fifo_handle_events,
374 .resume = evtchn_fifo_resume,
377 static int evtchn_fifo_init_control_block(unsigned cpu)
379 struct page *control_block = NULL;
380 struct evtchn_init_control init_control;
383 control_block = alloc_page(GFP_KERNEL|__GFP_ZERO);
384 if (control_block == NULL)
387 init_control.control_gfn = virt_to_mfn(page_address(control_block));
388 init_control.offset = 0;
389 init_control.vcpu = cpu;
391 ret = HYPERVISOR_event_channel_op(EVTCHNOP_init_control, &init_control);
395 per_cpu(cpu_control_block, cpu) = page_address(control_block);
400 __free_page(control_block);
404 static int evtchn_fifo_cpu_notification(struct notifier_block *self,
405 unsigned long action,
408 int cpu = (long)hcpu;
413 if (!per_cpu(cpu_control_block, cpu))
414 ret = evtchn_fifo_init_control_block(cpu);
419 return ret < 0 ? NOTIFY_BAD : NOTIFY_OK;
422 static struct notifier_block evtchn_fifo_cpu_notifier = {
423 .notifier_call = evtchn_fifo_cpu_notification,
426 int __init xen_evtchn_fifo_init(void)
431 ret = evtchn_fifo_init_control_block(cpu);
435 pr_info("Using FIFO-based ABI\n");
437 evtchn_ops = &evtchn_ops_fifo;
439 register_cpu_notifier(&evtchn_fifo_cpu_notifier);