1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * VFIO generic eventfd code for IRQFD support. 4 * Derived from drivers/vfio/pci/vfio_pci_intrs.c 5 * 6 * Copyright (C) 2012 Red Hat, Inc. All rights reserved. 7 * Author: Alex Williamson <alex.williamson@redhat.com> 8 */ 9 10 #include <linux/vfio.h> 11 #include <linux/eventfd.h> 12 #include <linux/file.h> 13 #include <linux/module.h> 14 #include <linux/slab.h> 15 16 #define DRIVER_VERSION "0.1" 17 #define DRIVER_AUTHOR "Alex Williamson <alex.williamson@redhat.com>" 18 #define DRIVER_DESC "IRQFD support for VFIO bus drivers" 19 20 static struct workqueue_struct *vfio_irqfd_cleanup_wq; 21 static DEFINE_SPINLOCK(virqfd_lock); 22 23 static int __init vfio_virqfd_init(void) 24 { 25 vfio_irqfd_cleanup_wq = 26 create_singlethread_workqueue("vfio-irqfd-cleanup"); 27 if (!vfio_irqfd_cleanup_wq) 28 return -ENOMEM; 29 30 return 0; 31 } 32 33 static void __exit vfio_virqfd_exit(void) 34 { 35 destroy_workqueue(vfio_irqfd_cleanup_wq); 36 } 37 38 static void virqfd_deactivate(struct virqfd *virqfd) 39 { 40 queue_work(vfio_irqfd_cleanup_wq, &virqfd->shutdown); 41 } 42 43 static int virqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) 44 { 45 struct virqfd *virqfd = container_of(wait, struct virqfd, wait); 46 __poll_t flags = key_to_poll(key); 47 48 if (flags & EPOLLIN) { 49 /* An event has been signaled, call function */ 50 if ((!virqfd->handler || 51 virqfd->handler(virqfd->opaque, virqfd->data)) && 52 virqfd->thread) 53 schedule_work(&virqfd->inject); 54 } 55 56 if (flags & EPOLLHUP) { 57 unsigned long flags; 58 spin_lock_irqsave(&virqfd_lock, flags); 59 60 /* 61 * The eventfd is closing, if the virqfd has not yet been 62 * queued for release, as determined by testing whether the 63 * virqfd pointer to it is still valid, queue it now. As 64 * with kvm irqfds, we know we won't race against the virqfd 65 * going away because we hold the lock to get here. 66 */ 67 if (*(virqfd->pvirqfd) == virqfd) { 68 *(virqfd->pvirqfd) = NULL; 69 virqfd_deactivate(virqfd); 70 } 71 72 spin_unlock_irqrestore(&virqfd_lock, flags); 73 } 74 75 return 0; 76 } 77 78 static void virqfd_ptable_queue_proc(struct file *file, 79 wait_queue_head_t *wqh, poll_table *pt) 80 { 81 struct virqfd *virqfd = container_of(pt, struct virqfd, pt); 82 add_wait_queue(wqh, &virqfd->wait); 83 } 84 85 static void virqfd_shutdown(struct work_struct *work) 86 { 87 struct virqfd *virqfd = container_of(work, struct virqfd, shutdown); 88 u64 cnt; 89 90 eventfd_ctx_remove_wait_queue(virqfd->eventfd, &virqfd->wait, &cnt); 91 flush_work(&virqfd->inject); 92 eventfd_ctx_put(virqfd->eventfd); 93 94 kfree(virqfd); 95 } 96 97 static void virqfd_inject(struct work_struct *work) 98 { 99 struct virqfd *virqfd = container_of(work, struct virqfd, inject); 100 if (virqfd->thread) 101 virqfd->thread(virqfd->opaque, virqfd->data); 102 } 103 104 int vfio_virqfd_enable(void *opaque, 105 int (*handler)(void *, void *), 106 void (*thread)(void *, void *), 107 void *data, struct virqfd **pvirqfd, int fd) 108 { 109 struct fd irqfd; 110 struct eventfd_ctx *ctx; 111 struct virqfd *virqfd; 112 int ret = 0; 113 __poll_t events; 114 115 virqfd = kzalloc(sizeof(*virqfd), GFP_KERNEL); 116 if (!virqfd) 117 return -ENOMEM; 118 119 virqfd->pvirqfd = pvirqfd; 120 virqfd->opaque = opaque; 121 virqfd->handler = handler; 122 virqfd->thread = thread; 123 virqfd->data = data; 124 125 INIT_WORK(&virqfd->shutdown, virqfd_shutdown); 126 INIT_WORK(&virqfd->inject, virqfd_inject); 127 128 irqfd = fdget(fd); 129 if (!irqfd.file) { 130 ret = -EBADF; 131 goto err_fd; 132 } 133 134 ctx = eventfd_ctx_fileget(irqfd.file); 135 if (IS_ERR(ctx)) { 136 ret = PTR_ERR(ctx); 137 goto err_ctx; 138 } 139 140 virqfd->eventfd = ctx; 141 142 /* 143 * virqfds can be released by closing the eventfd or directly 144 * through ioctl. These are both done through a workqueue, so 145 * we update the pointer to the virqfd under lock to avoid 146 * pushing multiple jobs to release the same virqfd. 147 */ 148 spin_lock_irq(&virqfd_lock); 149 150 if (*pvirqfd) { 151 spin_unlock_irq(&virqfd_lock); 152 ret = -EBUSY; 153 goto err_busy; 154 } 155 *pvirqfd = virqfd; 156 157 spin_unlock_irq(&virqfd_lock); 158 159 /* 160 * Install our own custom wake-up handling so we are notified via 161 * a callback whenever someone signals the underlying eventfd. 162 */ 163 init_waitqueue_func_entry(&virqfd->wait, virqfd_wakeup); 164 init_poll_funcptr(&virqfd->pt, virqfd_ptable_queue_proc); 165 166 events = vfs_poll(irqfd.file, &virqfd->pt); 167 168 /* 169 * Check if there was an event already pending on the eventfd 170 * before we registered and trigger it as if we didn't miss it. 171 */ 172 if (events & EPOLLIN) { 173 if ((!handler || handler(opaque, data)) && thread) 174 schedule_work(&virqfd->inject); 175 } 176 177 /* 178 * Do not drop the file until the irqfd is fully initialized, 179 * otherwise we might race against the EPOLLHUP. 180 */ 181 fdput(irqfd); 182 183 return 0; 184 err_busy: 185 eventfd_ctx_put(ctx); 186 err_ctx: 187 fdput(irqfd); 188 err_fd: 189 kfree(virqfd); 190 191 return ret; 192 } 193 EXPORT_SYMBOL_GPL(vfio_virqfd_enable); 194 195 void vfio_virqfd_disable(struct virqfd **pvirqfd) 196 { 197 unsigned long flags; 198 199 spin_lock_irqsave(&virqfd_lock, flags); 200 201 if (*pvirqfd) { 202 virqfd_deactivate(*pvirqfd); 203 *pvirqfd = NULL; 204 } 205 206 spin_unlock_irqrestore(&virqfd_lock, flags); 207 208 /* 209 * Block until we know all outstanding shutdown jobs have completed. 210 * Even if we don't queue the job, flush the wq to be sure it's 211 * been released. 212 */ 213 flush_workqueue(vfio_irqfd_cleanup_wq); 214 } 215 EXPORT_SYMBOL_GPL(vfio_virqfd_disable); 216 217 module_init(vfio_virqfd_init); 218 module_exit(vfio_virqfd_exit); 219 220 MODULE_VERSION(DRIVER_VERSION); 221 MODULE_LICENSE("GPL v2"); 222 MODULE_AUTHOR(DRIVER_AUTHOR); 223 MODULE_DESCRIPTION(DRIVER_DESC); 224