1 /****************************************************************************** 2 * balloon.c 3 * 4 * Xen balloon driver - enables returning/claiming memory to/from Xen. 5 * 6 * Copyright (c) 2003, B Dragovic 7 * Copyright (c) 2003-2004, M Williamson, K Fraser 8 * Copyright (c) 2005 Dan M. Smith, IBM Corporation 9 * 10 * This file may be distributed separately from the Linux kernel, or 11 * incorporated into other software packages, subject to the following license: 12 * 13 * Permission is hereby granted, free of charge, to any person obtaining a copy 14 * of this source file (the "Software"), to deal in the Software without 15 * restriction, including without limitation the rights to use, copy, modify, 16 * merge, publish, distribute, sublicense, and/or sell copies of the Software, 17 * and to permit persons to whom the Software is furnished to do so, subject to 18 * the following conditions: 19 * 20 * The above copyright notice and this permission notice shall be included in 21 * all copies or substantial portions of the Software. 22 * 23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 24 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 25 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 26 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 27 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 28 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 29 * IN THE SOFTWARE. 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include <sys/param.h> 36 #include <sys/lock.h> 37 #include <sys/kernel.h> 38 #include <sys/kthread.h> 39 #include <sys/malloc.h> 40 #include <sys/mutex.h> 41 #include <sys/sysctl.h> 42 #include <sys/module.h> 43 44 #include <vm/vm.h> 45 #include <vm/vm_page.h> 46 47 #include <xen/xen-os.h> 48 #include <xen/hypervisor.h> 49 #include <xen/features.h> 50 #include <xen/xenstore/xenstorevar.h> 51 52 static MALLOC_DEFINE(M_BALLOON, "Balloon", "Xen Balloon Driver"); 53 54 /* Convert from KB (as fetched from xenstore) to number of PAGES */ 55 #define KB_TO_PAGE_SHIFT (PAGE_SHIFT - 10) 56 57 struct mtx balloon_mutex; 58 59 /* We increase/decrease in batches which fit in a page */ 60 static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)]; 61 62 struct balloon_stats { 63 /* We aim for 'current allocation' == 'target allocation'. */ 64 unsigned long current_pages; 65 unsigned long target_pages; 66 /* We may hit the hard limit in Xen. If we do then we remember it. */ 67 unsigned long hard_limit; 68 /* 69 * Drivers may alter the memory reservation independently, but they 70 * must inform the balloon driver so we avoid hitting the hard limit. 71 */ 72 unsigned long driver_pages; 73 /* Number of pages in high- and low-memory balloons. */ 74 unsigned long balloon_low; 75 unsigned long balloon_high; 76 }; 77 78 static struct balloon_stats balloon_stats; 79 #define bs balloon_stats 80 81 SYSCTL_DECL(_dev_xen); 82 static SYSCTL_NODE(_dev_xen, OID_AUTO, balloon, 83 CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 84 "Balloon"); 85 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, current, CTLFLAG_RD, 86 &bs.current_pages, 0, "Current allocation"); 87 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, target, CTLFLAG_RD, 88 &bs.target_pages, 0, "Target allocation"); 89 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, driver_pages, CTLFLAG_RD, 90 &bs.driver_pages, 0, "Driver pages"); 91 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, hard_limit, CTLFLAG_RD, 92 &bs.hard_limit, 0, "Xen hard limit"); 93 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, low_mem, CTLFLAG_RD, 94 &bs.balloon_low, 0, "Low-mem balloon"); 95 SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, high_mem, CTLFLAG_RD, 96 &bs.balloon_high, 0, "High-mem balloon"); 97 98 /* List of ballooned pages, threaded through the mem_map array. */ 99 static TAILQ_HEAD(,vm_page) ballooned_pages; 100 101 /* Main work function, always executed in process context. */ 102 static void balloon_process(void *unused); 103 104 #define IPRINTK(fmt, args...) \ 105 printk(KERN_INFO "xen_mem: " fmt, ##args) 106 #define WPRINTK(fmt, args...) \ 107 printk(KERN_WARNING "xen_mem: " fmt, ##args) 108 109 static unsigned long 110 current_target(void) 111 { 112 unsigned long target = min(bs.target_pages, bs.hard_limit); 113 if (target > (bs.current_pages + bs.balloon_low + bs.balloon_high)) 114 target = bs.current_pages + bs.balloon_low + bs.balloon_high; 115 return (target); 116 } 117 118 static unsigned long 119 minimum_target(void) 120 { 121 unsigned long min_pages, curr_pages = current_target(); 122 123 #define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT)) 124 /* 125 * Simple continuous piecewiese linear function: 126 * max MiB -> min MiB gradient 127 * 0 0 128 * 16 16 129 * 32 24 130 * 128 72 (1/2) 131 * 512 168 (1/4) 132 * 2048 360 (1/8) 133 * 8192 552 (1/32) 134 * 32768 1320 135 * 131072 4392 136 */ 137 if (realmem < MB2PAGES(128)) 138 min_pages = MB2PAGES(8) + (realmem >> 1); 139 else if (realmem < MB2PAGES(512)) 140 min_pages = MB2PAGES(40) + (realmem >> 2); 141 else if (realmem < MB2PAGES(2048)) 142 min_pages = MB2PAGES(104) + (realmem >> 3); 143 else 144 min_pages = MB2PAGES(296) + (realmem >> 5); 145 #undef MB2PAGES 146 147 /* Don't enforce growth */ 148 return (min(min_pages, curr_pages)); 149 } 150 151 static int 152 increase_reservation(unsigned long nr_pages) 153 { 154 unsigned long i; 155 vm_page_t page; 156 long rc; 157 struct xen_memory_reservation reservation = { 158 .extent_order = 0, 159 .domid = DOMID_SELF 160 }; 161 162 mtx_assert(&balloon_mutex, MA_OWNED); 163 164 if (nr_pages > nitems(frame_list)) 165 nr_pages = nitems(frame_list); 166 167 for (page = TAILQ_FIRST(&ballooned_pages), i = 0; 168 i < nr_pages; i++, page = TAILQ_NEXT(page, plinks.q)) { 169 KASSERT(page != NULL, ("ballooned_pages list corrupt")); 170 frame_list[i] = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); 171 } 172 173 set_xen_guest_handle(reservation.extent_start, frame_list); 174 reservation.nr_extents = nr_pages; 175 rc = HYPERVISOR_memory_op( 176 XENMEM_populate_physmap, &reservation); 177 if (rc < nr_pages) { 178 if (rc > 0) { 179 int ret __diagused; 180 181 /* We hit the Xen hard limit: reprobe. */ 182 reservation.nr_extents = rc; 183 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, 184 &reservation); 185 KASSERT(ret == rc, ("HYPERVISOR_memory_op failed")); 186 } 187 if (rc >= 0) 188 bs.hard_limit = (bs.current_pages + rc - 189 bs.driver_pages); 190 goto out; 191 } 192 193 for (i = 0; i < nr_pages; i++) { 194 page = TAILQ_FIRST(&ballooned_pages); 195 KASSERT(page != NULL, ("Unable to get ballooned page")); 196 TAILQ_REMOVE(&ballooned_pages, page, plinks.q); 197 bs.balloon_low--; 198 199 KASSERT(xen_feature(XENFEAT_auto_translated_physmap), 200 ("auto translated physmap but mapping is valid")); 201 202 vm_page_free(page); 203 } 204 205 bs.current_pages += nr_pages; 206 207 out: 208 return (0); 209 } 210 211 static int 212 decrease_reservation(unsigned long nr_pages) 213 { 214 unsigned long i; 215 vm_page_t page; 216 int need_sleep = 0; 217 int ret __diagused; 218 struct xen_memory_reservation reservation = { 219 .extent_order = 0, 220 .domid = DOMID_SELF 221 }; 222 223 mtx_assert(&balloon_mutex, MA_OWNED); 224 225 if (nr_pages > nitems(frame_list)) 226 nr_pages = nitems(frame_list); 227 228 for (i = 0; i < nr_pages; i++) { 229 /* 230 * Zero the page, or else we might be leaking important data to 231 * other domains on the same host. Xen doesn't scrub ballooned 232 * out memory pages, the guest is in charge of making sure that 233 * no information is leaked. 234 */ 235 if ((page = vm_page_alloc_noobj(VM_ALLOC_ZERO)) == NULL) { 236 nr_pages = i; 237 need_sleep = 1; 238 break; 239 } 240 241 frame_list[i] = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); 242 243 TAILQ_INSERT_HEAD(&ballooned_pages, page, plinks.q); 244 bs.balloon_low++; 245 } 246 247 set_xen_guest_handle(reservation.extent_start, frame_list); 248 reservation.nr_extents = nr_pages; 249 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); 250 KASSERT(ret == nr_pages, ("HYPERVISOR_memory_op failed")); 251 252 bs.current_pages -= nr_pages; 253 254 return (need_sleep); 255 } 256 257 /* 258 * We avoid multiple worker processes conflicting via the balloon mutex. 259 * We may of course race updates of the target counts (which are protected 260 * by the balloon lock), or with changes to the Xen hard limit, but we will 261 * recover from these in time. 262 */ 263 static void 264 balloon_process(void *unused) 265 { 266 int need_sleep = 0; 267 long credit; 268 269 mtx_lock(&balloon_mutex); 270 for (;;) { 271 int sleep_time; 272 273 do { 274 credit = current_target() - bs.current_pages; 275 if (credit > 0) 276 need_sleep = (increase_reservation(credit) != 0); 277 if (credit < 0) 278 need_sleep = (decrease_reservation(-credit) != 0); 279 280 } while ((credit != 0) && !need_sleep); 281 282 /* Schedule more work if there is some still to be done. */ 283 if (current_target() != bs.current_pages) 284 sleep_time = hz; 285 else 286 sleep_time = 0; 287 288 msleep(balloon_process, &balloon_mutex, 0, "balloon", 289 sleep_time); 290 } 291 mtx_unlock(&balloon_mutex); 292 } 293 294 /* Resets the Xen limit, sets new target, and kicks off processing. */ 295 static void 296 set_new_target(unsigned long target) 297 { 298 /* No need for lock. Not read-modify-write updates. */ 299 bs.hard_limit = ~0UL; 300 bs.target_pages = max(target, minimum_target()); 301 wakeup(balloon_process); 302 } 303 304 static struct xs_watch target_watch = 305 { 306 .node = "memory/target", 307 .max_pending = 1, 308 }; 309 310 /* React to a change in the target key */ 311 static void 312 watch_target(struct xs_watch *watch, 313 const char **vec, unsigned int len) 314 { 315 unsigned long long new_target; 316 int err; 317 318 err = xs_scanf(XST_NIL, "memory", "target", NULL, 319 "%llu", &new_target); 320 if (err) { 321 /* This is ok (for domain0 at least) - so just return */ 322 return; 323 } 324 325 /* 326 * The given memory/target value is in KiB, so it needs converting to 327 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10. 328 */ 329 set_new_target(new_target >> KB_TO_PAGE_SHIFT); 330 } 331 332 /*------------------ Private Device Attachment Functions --------------------*/ 333 /** 334 * \brief Identify instances of this device type in the system. 335 * 336 * \param driver The driver performing this identify action. 337 * \param parent The NewBus parent device for any devices this method adds. 338 */ 339 static void 340 xenballoon_identify(driver_t *driver __unused, device_t parent) 341 { 342 /* 343 * A single device instance for our driver is always present 344 * in a system operating under Xen. 345 */ 346 BUS_ADD_CHILD(parent, 0, driver->name, 0); 347 } 348 349 /** 350 * \brief Probe for the existence of the Xen Balloon device 351 * 352 * \param dev NewBus device_t for this Xen control instance. 353 * 354 * \return Always returns 0 indicating success. 355 */ 356 static int 357 xenballoon_probe(device_t dev) 358 { 359 360 device_set_desc(dev, "Xen Balloon Device"); 361 return (0); 362 } 363 364 /** 365 * \brief Attach the Xen Balloon device. 366 * 367 * \param dev NewBus device_t for this Xen control instance. 368 * 369 * \return On success, 0. Otherwise an errno value indicating the 370 * type of failure. 371 */ 372 static int 373 xenballoon_attach(device_t dev) 374 { 375 int err; 376 377 mtx_init(&balloon_mutex, "balloon_mutex", NULL, MTX_DEF); 378 379 bs.current_pages = realmem; 380 bs.target_pages = bs.current_pages; 381 bs.balloon_low = 0; 382 bs.balloon_high = 0; 383 bs.driver_pages = 0UL; 384 bs.hard_limit = ~0UL; 385 386 kproc_create(balloon_process, NULL, NULL, 0, 0, "balloon"); 387 388 target_watch.callback = watch_target; 389 390 err = xs_register_watch(&target_watch); 391 if (err) 392 device_printf(dev, 393 "xenballon: failed to set balloon watcher\n"); 394 395 return (err); 396 } 397 398 /*-------------------- Private Device Attachment Data -----------------------*/ 399 static device_method_t xenballoon_methods[] = { 400 /* Device interface */ 401 DEVMETHOD(device_identify, xenballoon_identify), 402 DEVMETHOD(device_probe, xenballoon_probe), 403 DEVMETHOD(device_attach, xenballoon_attach), 404 405 DEVMETHOD_END 406 }; 407 408 DEFINE_CLASS_0(xenballoon, xenballoon_driver, xenballoon_methods, 0); 409 410 DRIVER_MODULE(xenballoon, xenstore, xenballoon_driver, NULL, NULL); 411