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_ids.h> 23 #include <linux/virtio_balloon.h> 24 #include <linux/swap.h> 25 #include <linux/kthread.h> 26 #include <linux/freezer.h> 27 #include <linux/delay.h> 28 29 struct virtio_balloon 30 { 31 struct virtio_device *vdev; 32 struct virtqueue *inflate_vq, *deflate_vq; 33 34 /* Where the ballooning thread waits for config to change. */ 35 wait_queue_head_t config_change; 36 37 /* The thread servicing the balloon. */ 38 struct task_struct *thread; 39 40 /* Waiting for host to ack the pages we released. */ 41 struct completion acked; 42 43 /* Do we have to tell Host *before* we reuse pages? */ 44 bool tell_host_first; 45 46 /* The pages we've told the Host we're not using. */ 47 unsigned int num_pages; 48 struct list_head pages; 49 50 /* The array of pfns we tell the Host about. */ 51 unsigned int num_pfns; 52 u32 pfns[256]; 53 }; 54 55 static struct virtio_device_id id_table[] = { 56 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, 57 { 0 }, 58 }; 59 60 static u32 page_to_balloon_pfn(struct page *page) 61 { 62 unsigned long pfn = page_to_pfn(page); 63 64 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); 65 /* Convert pfn from Linux page size to balloon page size. */ 66 return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT); 67 } 68 69 static void balloon_ack(struct virtqueue *vq) 70 { 71 struct virtio_balloon *vb; 72 unsigned int len; 73 74 vb = vq->vq_ops->get_buf(vq, &len); 75 if (vb) 76 complete(&vb->acked); 77 } 78 79 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) 80 { 81 struct scatterlist sg; 82 83 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); 84 85 init_completion(&vb->acked); 86 87 /* We should always be able to add one buffer to an empty queue. */ 88 if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0) 89 BUG(); 90 vq->vq_ops->kick(vq); 91 92 /* When host has read buffer, this completes via balloon_ack */ 93 wait_for_completion(&vb->acked); 94 } 95 96 static void fill_balloon(struct virtio_balloon *vb, size_t num) 97 { 98 /* We can only do one array worth at a time. */ 99 num = min(num, ARRAY_SIZE(vb->pfns)); 100 101 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 102 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY); 103 if (!page) { 104 if (printk_ratelimit()) 105 dev_printk(KERN_INFO, &vb->vdev->dev, 106 "Out of puff! Can't get %zu pages\n", 107 num); 108 /* Sleep for at least 1/5 of a second before retry. */ 109 msleep(200); 110 break; 111 } 112 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); 113 totalram_pages--; 114 vb->num_pages++; 115 list_add(&page->lru, &vb->pages); 116 } 117 118 /* Didn't get any? Oh well. */ 119 if (vb->num_pfns == 0) 120 return; 121 122 tell_host(vb, vb->inflate_vq); 123 } 124 125 static void release_pages_by_pfn(const u32 pfns[], unsigned int num) 126 { 127 unsigned int i; 128 129 for (i = 0; i < num; i++) { 130 __free_page(pfn_to_page(pfns[i])); 131 totalram_pages++; 132 } 133 } 134 135 static void leak_balloon(struct virtio_balloon *vb, size_t num) 136 { 137 struct page *page; 138 139 /* We can only do one array worth at a time. */ 140 num = min(num, ARRAY_SIZE(vb->pfns)); 141 142 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { 143 page = list_first_entry(&vb->pages, struct page, lru); 144 list_del(&page->lru); 145 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); 146 vb->num_pages--; 147 } 148 149 if (vb->tell_host_first) { 150 tell_host(vb, vb->deflate_vq); 151 release_pages_by_pfn(vb->pfns, vb->num_pfns); 152 } else { 153 release_pages_by_pfn(vb->pfns, vb->num_pfns); 154 tell_host(vb, vb->deflate_vq); 155 } 156 } 157 158 static void virtballoon_changed(struct virtio_device *vdev) 159 { 160 struct virtio_balloon *vb = vdev->priv; 161 162 wake_up(&vb->config_change); 163 } 164 165 static inline s64 towards_target(struct virtio_balloon *vb) 166 { 167 u32 v; 168 vb->vdev->config->get(vb->vdev, 169 offsetof(struct virtio_balloon_config, num_pages), 170 &v, sizeof(v)); 171 return (s64)v - vb->num_pages; 172 } 173 174 static void update_balloon_size(struct virtio_balloon *vb) 175 { 176 __le32 actual = cpu_to_le32(vb->num_pages); 177 178 vb->vdev->config->set(vb->vdev, 179 offsetof(struct virtio_balloon_config, actual), 180 &actual, sizeof(actual)); 181 } 182 183 static int balloon(void *_vballoon) 184 { 185 struct virtio_balloon *vb = _vballoon; 186 187 set_freezable(); 188 while (!kthread_should_stop()) { 189 s64 diff; 190 191 try_to_freeze(); 192 wait_event_interruptible(vb->config_change, 193 (diff = towards_target(vb)) != 0 194 || kthread_should_stop() 195 || freezing(current)); 196 if (diff > 0) 197 fill_balloon(vb, diff); 198 else if (diff < 0) 199 leak_balloon(vb, -diff); 200 update_balloon_size(vb); 201 } 202 return 0; 203 } 204 205 static int virtballoon_probe(struct virtio_device *vdev) 206 { 207 struct virtio_balloon *vb; 208 struct virtqueue *vqs[2]; 209 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack }; 210 const char *names[] = { "inflate", "deflate" }; 211 int err; 212 213 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); 214 if (!vb) { 215 err = -ENOMEM; 216 goto out; 217 } 218 219 INIT_LIST_HEAD(&vb->pages); 220 vb->num_pages = 0; 221 init_waitqueue_head(&vb->config_change); 222 vb->vdev = vdev; 223 224 /* We expect two virtqueues. */ 225 err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names); 226 if (err) 227 goto out_free_vb; 228 229 vb->inflate_vq = vqs[0]; 230 vb->deflate_vq = vqs[1]; 231 232 vb->thread = kthread_run(balloon, vb, "vballoon"); 233 if (IS_ERR(vb->thread)) { 234 err = PTR_ERR(vb->thread); 235 goto out_del_vqs; 236 } 237 238 vb->tell_host_first 239 = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); 240 241 return 0; 242 243 out_del_vqs: 244 vdev->config->del_vqs(vdev); 245 out_free_vb: 246 kfree(vb); 247 out: 248 return err; 249 } 250 251 static void virtballoon_remove(struct virtio_device *vdev) 252 { 253 struct virtio_balloon *vb = vdev->priv; 254 255 kthread_stop(vb->thread); 256 257 /* There might be pages left in the balloon: free them. */ 258 while (vb->num_pages) 259 leak_balloon(vb, vb->num_pages); 260 261 /* Now we reset the device so we can clean up the queues. */ 262 vdev->config->reset(vdev); 263 264 vdev->config->del_vqs(vdev); 265 kfree(vb); 266 } 267 268 static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST }; 269 270 static struct virtio_driver virtio_balloon = { 271 .feature_table = features, 272 .feature_table_size = ARRAY_SIZE(features), 273 .driver.name = KBUILD_MODNAME, 274 .driver.owner = THIS_MODULE, 275 .id_table = id_table, 276 .probe = virtballoon_probe, 277 .remove = __devexit_p(virtballoon_remove), 278 .config_changed = virtballoon_changed, 279 }; 280 281 static int __init init(void) 282 { 283 return register_virtio_driver(&virtio_balloon); 284 } 285 286 static void __exit fini(void) 287 { 288 unregister_virtio_driver(&virtio_balloon); 289 } 290 module_init(init); 291 module_exit(fini); 292 293 MODULE_DEVICE_TABLE(virtio, id_table); 294 MODULE_DESCRIPTION("Virtio balloon driver"); 295 MODULE_LICENSE("GPL"); 296