1 /* Virtio balloon implementation, inspired by Dor Loar and Marcelo 2 * Tosatti's implementations. 3 * 4 * Copyright 2008 Rusty Russell IBM Corporation 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation; either version 2 of the License, or 9 * (at your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, write to the Free Software 18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA 19 */ 20 //#define DEBUG 21 #include <linux/virtio.h> 22 #include <linux/virtio_balloon.h> 23 #include <linux/swap.h> 24 #include <linux/kthread.h> 25 #include <linux/freezer.h> 26 27 struct virtio_balloon 28 { 29 struct virtio_device *vdev; 30 struct virtqueue *inflate_vq, *deflate_vq; 31 32 /* Where the ballooning thread waits for config to change. */ 33 wait_queue_head_t config_change; 34 35 /* The thread servicing the balloon. */ 36 struct task_struct *thread; 37 38 /* Waiting for host to ack the pages we released. */ 39 struct completion acked; 40 41 /* Do we have to tell Host *before* we reuse pages? */ 42 bool tell_host_first; 43 44 /* The pages we've told the Host we're not using. */ 45 unsigned int num_pages; 46 struct list_head pages; 47 48 /* The array of pfns we tell the Host about. */ 49 unsigned int num_pfns; 50 u32 pfns[256]; 51 }; 52 53 static struct virtio_device_id id_table[] = { 54 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 55 { 0 }, 56 }; 57 58 static void balloon_ack(struct virtqueue *vq) 59 { 60 struct virtio_balloon *vb; 61 unsigned int len; 62 63 vb = vq->vq_ops->get_buf(vq, &len); 64 if (vb) 65 complete(&vb->acked); 66 } 67 68 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 69 { 70 struct scatterlist sg; 71 72 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 73 74 init_completion(&vb->acked); 75 76 /* We should always be able to add one buffer to an empty queue. */ 77 if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0) 78 BUG(); 79 vq->vq_ops->kick(vq); 80 81 /* When host has read buffer, this completes via balloon_ack */ 82 wait_for_completion(&vb->acked); 83 } 84 85 static void fill_balloon(struct virtio_balloon *vb, size_t num) 86 { 87 /* We can only do one array worth at a time. */ 88 num = min(num, ARRAY_SIZE(vb->pfns)); 89 90 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 91 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY); 92 if (!page) { 93 if (printk_ratelimit()) 94 dev_printk(KERN_INFO, &vb->vdev->dev, 95 "Out of puff! Can't get %zu pages\n", 96 num); 97 /* Sleep for at least 1/5 of a second before retry. */ 98 msleep(200); 99 break; 100 } 101 vb->pfns[vb->num_pfns] = page_to_pfn(page); 102 totalram_pages--; 103 vb->num_pages++; 104 list_add(&page->lru, &vb->pages); 105 } 106 107 /* Didn't get any? Oh well. */ 108 if (vb->num_pfns == 0) 109 return; 110 111 tell_host(vb, vb->inflate_vq); 112 } 113 114 static void release_pages_by_pfn(const u32 pfns[], unsigned int num) 115 { 116 unsigned int i; 117 118 for (i = 0; i < num; i++) { 119 __free_page(pfn_to_page(pfns[i])); 120 totalram_pages++; 121 } 122 } 123 124 static void leak_balloon(struct virtio_balloon *vb, size_t num) 125 { 126 struct page *page; 127 128 /* We can only do one array worth at a time. */ 129 num = min(num, ARRAY_SIZE(vb->pfns)); 130 131 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 132 page = list_first_entry(&vb->pages, struct page, lru); 133 list_del(&page->lru); 134 vb->pfns[vb->num_pfns] = page_to_pfn(page); 135 vb->num_pages--; 136 } 137 138 if (vb->tell_host_first) { 139 tell_host(vb, vb->deflate_vq); 140 release_pages_by_pfn(vb->pfns, vb->num_pfns); 141 } else { 142 release_pages_by_pfn(vb->pfns, vb->num_pfns); 143 tell_host(vb, vb->deflate_vq); 144 } 145 } 146 147 static void virtballoon_changed(struct virtio_device *vdev) 148 { 149 struct virtio_balloon *vb = vdev->priv; 150 151 wake_up(&vb->config_change); 152 } 153 154 static inline int towards_target(struct virtio_balloon *vb) 155 { 156 u32 v; 157 __virtio_config_val(vb->vdev, 158 offsetof(struct virtio_balloon_config, num_pages), 159 &v); 160 return v - vb->num_pages; 161 } 162 163 static void update_balloon_size(struct virtio_balloon *vb) 164 { 165 __le32 actual = cpu_to_le32(vb->num_pages); 166 167 vb->vdev->config->set(vb->vdev, 168 offsetof(struct virtio_balloon_config, actual), 169 &actual, sizeof(actual)); 170 } 171 172 static int balloon(void *_vballoon) 173 { 174 struct virtio_balloon *vb = _vballoon; 175 176 set_freezable(); 177 while (!kthread_should_stop()) { 178 int diff; 179 180 try_to_freeze(); 181 wait_event_interruptible(vb->config_change, 182 (diff = towards_target(vb)) != 0 183 || kthread_should_stop()); 184 if (diff > 0) 185 fill_balloon(vb, diff); 186 else if (diff < 0) 187 leak_balloon(vb, -diff); 188 update_balloon_size(vb); 189 } 190 return 0; 191 } 192 193 static int virtballoon_probe(struct virtio_device *vdev) 194 { 195 struct virtio_balloon *vb; 196 int err; 197 198 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); 199 if (!vb) { 200 err = -ENOMEM; 201 goto out; 202 } 203 204 INIT_LIST_HEAD(&vb->pages); 205 vb->num_pages = 0; 206 init_waitqueue_head(&vb->config_change); 207 vb->vdev = vdev; 208 209 /* We expect two virtqueues. */ 210 vb->inflate_vq = vdev->config->find_vq(vdev, 0, balloon_ack); 211 if (IS_ERR(vb->inflate_vq)) { 212 err = PTR_ERR(vb->inflate_vq); 213 goto out_free_vb; 214 } 215 216 vb->deflate_vq = vdev->config->find_vq(vdev, 1, balloon_ack); 217 if (IS_ERR(vb->deflate_vq)) { 218 err = PTR_ERR(vb->deflate_vq); 219 goto out_del_inflate_vq; 220 } 221 222 vb->thread = kthread_run(balloon, vb, "vballoon"); 223 if (IS_ERR(vb->thread)) { 224 err = PTR_ERR(vb->thread); 225 goto out_del_deflate_vq; 226 } 227 228 vb->tell_host_first 229 = vdev->config->feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 230 231 return 0; 232 233 out_del_deflate_vq: 234 vdev->config->del_vq(vb->deflate_vq); 235 out_del_inflate_vq: 236 vdev->config->del_vq(vb->inflate_vq); 237 out_free_vb: 238 kfree(vb); 239 out: 240 return err; 241 } 242 243 static void virtballoon_remove(struct virtio_device *vdev) 244 { 245 struct virtio_balloon *vb = vdev->priv; 246 247 kthread_stop(vb->thread); 248 249 /* There might be pages left in the balloon: free them. */ 250 while (vb->num_pages) 251 leak_balloon(vb, vb->num_pages); 252 253 /* Now we reset the device so we can clean up the queues. */ 254 vdev->config->reset(vdev); 255 256 vdev->config->del_vq(vb->deflate_vq); 257 vdev->config->del_vq(vb->inflate_vq); 258 kfree(vb); 259 } 260 261 static struct virtio_driver virtio_balloon = { 262 .driver.name = KBUILD_MODNAME, 263 .driver.owner = THIS_MODULE, 264 .id_table = id_table, 265 .probe = virtballoon_probe, 266 .remove = __devexit_p(virtballoon_remove), 267 .config_changed = virtballoon_changed, 268 }; 269 270 static int __init init(void) 271 { 272 return register_virtio_driver(&virtio_balloon); 273 } 274 275 static void __exit fini(void) 276 { 277 unregister_virtio_driver(&virtio_balloon); 278 } 279 module_init(init); 280 module_exit(fini); 281 282 MODULE_DEVICE_TABLE(virtio, id_table); 283 MODULE_DESCRIPTION("Virtio balloon driver"); 284 MODULE_LICENSE("GPL"); 285