diff options
Diffstat (limited to 'drivers/xen/events/events_fifo.c')
| -rw-r--r-- | drivers/xen/events/events_fifo.c | 442 |
1 files changed, 442 insertions, 0 deletions
diff --git a/drivers/xen/events/events_fifo.c b/drivers/xen/events/events_fifo.c new file mode 100644 index 000000000..ad9fe51d3 --- /dev/null +++ b/drivers/xen/events/events_fifo.c @@ -0,0 +1,442 @@ +/* + * 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(evtchn_port_t 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(evtchn_port_t port) +{ + 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(evtchn_port_t evtchn, unsigned int cpu, + unsigned int old_cpu) +{ + /* no-op */ +} + +static void evtchn_fifo_clear_pending(evtchn_port_t 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(evtchn_port_t 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(evtchn_port_t port) +{ + event_word_t *word = event_word_from_port(port); + return sync_test_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word)); +} + +static void evtchn_fifo_mask(evtchn_port_t 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(evtchn_port_t port) +{ + event_word_t *word = event_word_from_port(port); + return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word)); +} +/* + * Clear MASKED if not PENDING, spinning if BUSY is set. + * Return true if mask was cleared. + */ +static bool clear_masked_cond(volatile event_word_t *word) +{ + event_word_t new, old, w; + + w = *word; + + do { + if (!(w & (1 << EVTCHN_FIFO_MASKED))) + return true; + + if (w & (1 << EVTCHN_FIFO_PENDING)) + return false; + + old = w & ~(1 << EVTCHN_FIFO_BUSY); + new = old & ~(1 << EVTCHN_FIFO_MASKED); + w = sync_cmpxchg(word, old, new); + } while (w != old); + + return true; +} + +static void evtchn_fifo_unmask(evtchn_port_t port) +{ + event_word_t *word = event_word_from_port(port); + + BUG_ON(!irqs_disabled()); + + if (!clear_masked_cond(word)) { + 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 consume_one_event(unsigned cpu, struct evtchn_loop_ctrl *ctrl, + struct evtchn_fifo_control_block *control_block, + unsigned priority, unsigned long *ready) +{ + struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu); + uint32_t head; + evtchn_port_t 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(!ctrl)) + pr_warn("Dropping pending event for port %u\n", port); + else + handle_irq_for_port(port, ctrl); + } + + q->head[priority] = head; +} + +static void __evtchn_fifo_handle_events(unsigned cpu, + struct evtchn_loop_ctrl *ctrl) +{ + 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, ctrl, control_block, q, &ready); + ready |= xchg(&control_block->ready, 0); + } +} + +static void evtchn_fifo_handle_events(unsigned cpu, + struct evtchn_loop_ctrl *ctrl) +{ + __evtchn_fifo_handle_events(cpu, ctrl); +} + +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 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 evtchn_fifo_percpu_init(unsigned int cpu) +{ + if (!per_cpu(cpu_control_block, cpu)) + return evtchn_fifo_alloc_control_block(cpu); + return 0; +} + +static int evtchn_fifo_percpu_deinit(unsigned int cpu) +{ + __evtchn_fifo_handle_events(cpu, NULL); + return 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, + .mask = evtchn_fifo_mask, + .unmask = evtchn_fifo_unmask, + .handle_events = evtchn_fifo_handle_events, + .resume = evtchn_fifo_resume, + .percpu_init = evtchn_fifo_percpu_init, + .percpu_deinit = evtchn_fifo_percpu_deinit, +}; + +int __init xen_evtchn_fifo_init(void) +{ + int cpu = smp_processor_id(); + int ret; + + ret = evtchn_fifo_alloc_control_block(cpu); + if (ret < 0) + return ret; + + pr_info("Using FIFO-based ABI\n"); + + evtchn_ops = &evtchn_ops_fifo; + + return ret; +} |