/* * Xen event channels (FIFO-based ABI) * * Copyright (C) 2013 Citrix Systems R&D ltd. * * This source code is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation; either version 2 of the * License, or (at your option) any later version. * * Or, when distributed separately from the Linux kernel or * incorporated into other software packages, subject to the following * license: * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this source file (the "Software"), to deal in the Software without * restriction, including without limitation the rights to use, copy, modify, * merge, publish, distribute, sublicense, and/or sell copies of the Software, * and to permit persons to whom the Software is furnished to do so, subject to * the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS * IN THE SOFTWARE. */ #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt #include <linux/linkage.h> #include <linux/interrupt.h> #include <linux/irq.h> #include <linux/smp.h> #include <linux/percpu.h> #include <linux/cpu.h> #include <asm/barrier.h> #include <asm/sync_bitops.h> #include <asm/xen/hypercall.h> #include <asm/xen/hypervisor.h> #include <xen/xen.h> #include <xen/xen-ops.h> #include <xen/events.h> #include <xen/interface/xen.h> #include <xen/interface/event_channel.h> #include <xen/page.h> #include "events_internal.h" #define EVENT_WORDS_PER_PAGE (XEN_PAGE_SIZE / sizeof(event_word_t)) #define MAX_EVENT_ARRAY_PAGES (EVTCHN_FIFO_NR_CHANNELS / EVENT_WORDS_PER_PAGE) struct evtchn_fifo_queue { uint32_t head[EVTCHN_FIFO_MAX_QUEUES]; }; static DEFINE_PER_CPU(struct evtchn_fifo_control_block *, cpu_control_block); static DEFINE_PER_CPU(struct evtchn_fifo_queue, cpu_queue); static event_word_t *event_array[MAX_EVENT_ARRAY_PAGES] __read_mostly; static unsigned event_array_pages __read_mostly; /* * sync_set_bit() and friends must be unsigned long aligned. */ #if BITS_PER_LONG > 32 #define BM(w) (unsigned long *)((unsigned long)w & ~0x7UL) #define EVTCHN_FIFO_BIT(b, w) \ (((unsigned long)w & 0x4UL) ? (EVTCHN_FIFO_ ##b + 32) : EVTCHN_FIFO_ ##b) #else #define BM(w) ((unsigned long *)(w)) #define EVTCHN_FIFO_BIT(b, w) EVTCHN_FIFO_ ##b #endif static inline event_word_t *event_word_from_port(unsigned port) { unsigned i = port / EVENT_WORDS_PER_PAGE; return event_array[i] + port % EVENT_WORDS_PER_PAGE; } static unsigned evtchn_fifo_max_channels(void) { return EVTCHN_FIFO_NR_CHANNELS; } static unsigned evtchn_fifo_nr_channels(void) { return event_array_pages * EVENT_WORDS_PER_PAGE; } static int init_control_block(int cpu, struct evtchn_fifo_control_block *control_block) { struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu); struct evtchn_init_control init_control; unsigned int i; /* Reset the control block and the local HEADs. */ clear_page(control_block); for (i = 0; i < EVTCHN_FIFO_MAX_QUEUES; i++) q->head[i] = 0; init_control.control_gfn = virt_to_gfn(control_block); init_control.offset = 0; init_control.vcpu = xen_vcpu_nr(cpu); return HYPERVISOR_event_channel_op(EVTCHNOP_init_control, &init_control); } static void free_unused_array_pages(void) { unsigned i; for (i = event_array_pages; i < MAX_EVENT_ARRAY_PAGES; i++) { if (!event_array[i]) break; free_page((unsigned long)event_array[i]); event_array[i] = NULL; } } static void init_array_page(event_word_t *array_page) { unsigned i; for (i = 0; i < EVENT_WORDS_PER_PAGE; i++) array_page[i] = 1 << EVTCHN_FIFO_MASKED; } static int evtchn_fifo_setup(struct irq_info *info) { unsigned port = info->evtchn; unsigned new_array_pages; int ret; new_array_pages = port / EVENT_WORDS_PER_PAGE + 1; if (new_array_pages > MAX_EVENT_ARRAY_PAGES) return -EINVAL; while (event_array_pages < new_array_pages) { void *array_page; struct evtchn_expand_array expand_array; /* Might already have a page if we've resumed. */ array_page = event_array[event_array_pages]; if (!array_page) { array_page = (void *)__get_free_page(GFP_KERNEL); if (array_page == NULL) { ret = -ENOMEM; goto error; } event_array[event_array_pages] = array_page; } /* Mask all events in this page before adding it. */ init_array_page(array_page); expand_array.array_gfn = virt_to_gfn(array_page); ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array); if (ret < 0) goto error; event_array_pages++; } return 0; error: if (event_array_pages == 0) panic("xen: unable to expand event array with initial page (%d)\n", ret); else pr_err("unable to expand event array (%d)\n", ret); free_unused_array_pages(); return ret; } static void evtchn_fifo_bind_to_cpu(struct irq_info *info, unsigned cpu) { /* no-op */ } static void evtchn_fifo_clear_pending(unsigned port) { event_word_t *word = event_word_from_port(port); sync_clear_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word)); } static void evtchn_fifo_set_pending(unsigned port) { event_word_t *word = event_word_from_port(port); sync_set_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word)); } static bool evtchn_fifo_is_pending(unsigned port) { event_word_t *word = event_word_from_port(port); return sync_test_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word)); } static bool evtchn_fifo_test_and_set_mask(unsigned port) { event_word_t *word = event_word_from_port(port); return sync_test_and_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word)); } static void evtchn_fifo_mask(unsigned port) { event_word_t *word = event_word_from_port(port); sync_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word)); } static bool evtchn_fifo_is_masked(unsigned port) { event_word_t *word = event_word_from_port(port); return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word)); } /* * Clear MASKED, spinning if BUSY is set. */ static void clear_masked(volatile event_word_t *word) { event_word_t new, old, w; w = *word; do { old = w & ~(1 << EVTCHN_FIFO_BUSY); new = old & ~(1 << EVTCHN_FIFO_MASKED); w = sync_cmpxchg(word, old, new); } while (w != old); } static void evtchn_fifo_unmask(unsigned port) { event_word_t *word = event_word_from_port(port); BUG_ON(!irqs_disabled()); clear_masked(word); if (evtchn_fifo_is_pending(port)) { struct evtchn_unmask unmask = { .port = port }; (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask); } } static uint32_t clear_linked(volatile event_word_t *word) { event_word_t new, old, w; w = *word; do { old = w; new = (w & ~((1 << EVTCHN_FIFO_LINKED) | EVTCHN_FIFO_LINK_MASK)); } while ((w = sync_cmpxchg(word, old, new)) != old); return w & EVTCHN_FIFO_LINK_MASK; } static void handle_irq_for_port(unsigned port) { int irq; irq = get_evtchn_to_irq(port); if (irq != -1) generic_handle_irq(irq); } static void consume_one_event(unsigned cpu, struct evtchn_fifo_control_block *control_block, unsigned priority, unsigned long *ready, bool drop) { struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu); uint32_t head; unsigned port; event_word_t *word; head = q->head[priority]; /* * Reached the tail last time? Read the new HEAD from the * control block. */ if (head == 0) { virt_rmb(); /* Ensure word is up-to-date before reading head. */ head = control_block->head[priority]; } port = head; word = event_word_from_port(port); head = clear_linked(word); /* * If the link is non-zero, there are more events in the * queue, otherwise the queue is empty. * * If the queue is empty, clear this priority from our local * copy of the ready word. */ if (head == 0) clear_bit(priority, ready); if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port)) { if (unlikely(drop)) pr_warn("Dropping pending event for port %u\n", port); else handle_irq_for_port(port); } q->head[priority] = head; } static void __evtchn_fifo_handle_events(unsigned cpu, bool drop) { struct evtchn_fifo_control_block *control_block; unsigned long ready; unsigned q; control_block = per_cpu(cpu_control_block, cpu); ready = xchg(&control_block->ready, 0); while (ready) { q = find_first_bit(&ready, EVTCHN_FIFO_MAX_QUEUES); consume_one_event(cpu, control_block, q, &ready, drop); ready |= xchg(&control_block->ready, 0); } } static void evtchn_fifo_handle_events(unsigned cpu) { __evtchn_fifo_handle_events(cpu, false); } static void evtchn_fifo_resume(void) { unsigned cpu; for_each_possible_cpu(cpu) { void *control_block = per_cpu(cpu_control_block, cpu); int ret; if (!control_block) continue; /* * If this CPU is offline, take the opportunity to * free the control block while it is not being * used. */ if (!cpu_online(cpu)) { free_page((unsigned long)control_block); per_cpu(cpu_control_block, cpu) = NULL; continue; } ret = init_control_block(cpu, control_block); BUG_ON(ret < 0); } /* * The event array starts out as empty again and is extended * as normal when events are bound. The existing pages will * be reused. */ event_array_pages = 0; } static const struct evtchn_ops evtchn_ops_fifo = { .max_channels = evtchn_fifo_max_channels, .nr_channels = evtchn_fifo_nr_channels, .setup = evtchn_fifo_setup, .bind_to_cpu = evtchn_fifo_bind_to_cpu, .clear_pending = evtchn_fifo_clear_pending, .set_pending = evtchn_fifo_set_pending, .is_pending = evtchn_fifo_is_pending, .test_and_set_mask = evtchn_fifo_test_and_set_mask, .mask = evtchn_fifo_mask, .unmask = evtchn_fifo_unmask, .handle_events = evtchn_fifo_handle_events, .resume = evtchn_fifo_resume, }; static int evtchn_fifo_alloc_control_block(unsigned cpu) { void *control_block = NULL; int ret = -ENOMEM; control_block = (void *)__get_free_page(GFP_KERNEL); if (control_block == NULL) goto error; ret = init_control_block(cpu, control_block); if (ret < 0) goto error; per_cpu(cpu_control_block, cpu) = control_block; return 0; error: free_page((unsigned long)control_block); return ret; } static int xen_evtchn_cpu_prepare(unsigned int cpu) { if (!per_cpu(cpu_control_block, cpu)) return evtchn_fifo_alloc_control_block(cpu); return 0; } static int xen_evtchn_cpu_dead(unsigned int cpu) { __evtchn_fifo_handle_events(cpu, true); return 0; } int __init xen_evtchn_fifo_init(void) { int cpu = get_cpu(); int ret; ret = evtchn_fifo_alloc_control_block(cpu); if (ret < 0) goto out; pr_info("Using FIFO-based ABI\n"); evtchn_ops = &evtchn_ops_fifo; cpuhp_setup_state_nocalls(CPUHP_XEN_EVTCHN_PREPARE, "xen/evtchn:prepare", xen_evtchn_cpu_prepare, xen_evtchn_cpu_dead); out: put_cpu(); return ret; }