Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/dev/xen/balloon/balloon.c
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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 .address_bits = 0, 159 .extent_order = 0, 160 .domid = DOMID_SELF 161 }; 162 163 mtx_assert(&balloon_mutex, MA_OWNED); 164 165 if (nr_pages > nitems(frame_list)) 166 nr_pages = nitems(frame_list); 167 168 for (page = TAILQ_FIRST(&ballooned_pages), i = 0; 169 i < nr_pages; i++, page = TAILQ_NEXT(page, plinks.q)) { 170 KASSERT(page != NULL, ("ballooned_pages list corrupt")); 171 frame_list[i] = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); 172 } 173 174 set_xen_guest_handle(reservation.extent_start, frame_list); 175 reservation.nr_extents = nr_pages; 176 rc = HYPERVISOR_memory_op( 177 XENMEM_populate_physmap, &reservation); 178 if (rc < nr_pages) { 179 if (rc > 0) { 180 int ret __diagused; 181 182 /* We hit the Xen hard limit: reprobe. */ 183 reservation.nr_extents = rc; 184 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, 185 &reservation); 186 KASSERT(ret == rc, ("HYPERVISOR_memory_op failed")); 187 } 188 if (rc >= 0) 189 bs.hard_limit = (bs.current_pages + rc - 190 bs.driver_pages); 191 goto out; 192 } 193 194 for (i = 0; i < nr_pages; i++) { 195 page = TAILQ_FIRST(&ballooned_pages); 196 KASSERT(page != NULL, ("Unable to get ballooned page")); 197 TAILQ_REMOVE(&ballooned_pages, page, plinks.q); 198 bs.balloon_low--; 199 200 KASSERT(xen_feature(XENFEAT_auto_translated_physmap), 201 ("auto translated physmap but mapping is valid")); 202 203 vm_page_free(page); 204 } 205 206 bs.current_pages += nr_pages; 207 208 out: 209 return (0); 210 } 211 212 static int 213 decrease_reservation(unsigned long nr_pages) 214 { 215 unsigned long i; 216 vm_page_t page; 217 int need_sleep = 0; 218 int ret __diagused; 219 struct xen_memory_reservation reservation = { 220 .address_bits = 0, 221 .extent_order = 0, 222 .domid = DOMID_SELF 223 }; 224 225 mtx_assert(&balloon_mutex, MA_OWNED); 226 227 if (nr_pages > nitems(frame_list)) 228 nr_pages = nitems(frame_list); 229 230 for (i = 0; i < nr_pages; i++) { 231 /* 232 * Zero the page, or else we might be leaking important data to 233 * other domains on the same host. Xen doesn't scrub ballooned 234 * out memory pages, the guest is in charge of making sure that 235 * no information is leaked. 236 */ 237 if ((page = vm_page_alloc_noobj(VM_ALLOC_ZERO)) == NULL) { 238 nr_pages = i; 239 need_sleep = 1; 240 break; 241 } 242 243 frame_list[i] = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); 244 245 TAILQ_INSERT_HEAD(&ballooned_pages, page, plinks.q); 246 bs.balloon_low++; 247 } 248 249 set_xen_guest_handle(reservation.extent_start, frame_list); 250 reservation.nr_extents = nr_pages; 251 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); 252 KASSERT(ret == nr_pages, ("HYPERVISOR_memory_op failed")); 253 254 bs.current_pages -= nr_pages; 255 256 return (need_sleep); 257 } 258 259 /* 260 * We avoid multiple worker processes conflicting via the balloon mutex. 261 * We may of course race updates of the target counts (which are protected 262 * by the balloon lock), or with changes to the Xen hard limit, but we will 263 * recover from these in time. 264 */ 265 static void 266 balloon_process(void *unused) 267 { 268 int need_sleep = 0; 269 long credit; 270 271 mtx_lock(&balloon_mutex); 272 for (;;) { 273 int sleep_time; 274 275 do { 276 credit = current_target() - bs.current_pages; 277 if (credit > 0) 278 need_sleep = (increase_reservation(credit) != 0); 279 if (credit < 0) 280 need_sleep = (decrease_reservation(-credit) != 0); 281 282 } while ((credit != 0) && !need_sleep); 283 284 /* Schedule more work if there is some still to be done. */ 285 if (current_target() != bs.current_pages) 286 sleep_time = hz; 287 else 288 sleep_time = 0; 289 290 msleep(balloon_process, &balloon_mutex, 0, "balloon", 291 sleep_time); 292 } 293 mtx_unlock(&balloon_mutex); 294 } 295 296 /* Resets the Xen limit, sets new target, and kicks off processing. */ 297 static void 298 set_new_target(unsigned long target) 299 { 300 /* No need for lock. Not read-modify-write updates. */ 301 bs.hard_limit = ~0UL; 302 bs.target_pages = max(target, minimum_target()); 303 wakeup(balloon_process); 304 } 305 306 static struct xs_watch target_watch = 307 { 308 .node = "memory/target", 309 .max_pending = 1, 310 }; 311 312 /* React to a change in the target key */ 313 static void 314 watch_target(struct xs_watch *watch, 315 const char **vec, unsigned int len) 316 { 317 unsigned long long new_target; 318 int err; 319 320 err = xs_scanf(XST_NIL, "memory", "target", NULL, 321 "%llu", &new_target); 322 if (err) { 323 /* This is ok (for domain0 at least) - so just return */ 324 return; 325 } 326 327 /* 328 * The given memory/target value is in KiB, so it needs converting to 329 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10. 330 */ 331 set_new_target(new_target >> KB_TO_PAGE_SHIFT); 332 } 333 334 /*------------------ Private Device Attachment Functions --------------------*/ 335 /** 336 * \brief Identify instances of this device type in the system. 337 * 338 * \param driver The driver performing this identify action. 339 * \param parent The NewBus parent device for any devices this method adds. 340 */ 341 static void 342 xenballoon_identify(driver_t *driver __unused, device_t parent) 343 { 344 /* 345 * A single device instance for our driver is always present 346 * in a system operating under Xen. 347 */ 348 BUS_ADD_CHILD(parent, 0, driver->name, 0); 349 } 350 351 /** 352 * \brief Probe for the existence of the Xen Balloon device 353 * 354 * \param dev NewBus device_t for this Xen control instance. 355 * 356 * \return Always returns 0 indicating success. 357 */ 358 static int 359 xenballoon_probe(device_t dev) 360 { 361 362 device_set_desc(dev, "Xen Balloon Device"); 363 return (0); 364 } 365 366 /** 367 * \brief Attach the Xen Balloon device. 368 * 369 * \param dev NewBus device_t for this Xen control instance. 370 * 371 * \return On success, 0. Otherwise an errno value indicating the 372 * type of failure. 373 */ 374 static int 375 xenballoon_attach(device_t dev) 376 { 377 int err; 378 379 mtx_init(&balloon_mutex, "balloon_mutex", NULL, MTX_DEF); 380 381 bs.current_pages = realmem; 382 bs.target_pages = bs.current_pages; 383 bs.balloon_low = 0; 384 bs.balloon_high = 0; 385 bs.driver_pages = 0UL; 386 bs.hard_limit = ~0UL; 387 388 kproc_create(balloon_process, NULL, NULL, 0, 0, "balloon"); 389 390 target_watch.callback = watch_target; 391 392 err = xs_register_watch(&target_watch); 393 if (err) 394 device_printf(dev, 395 "xenballon: failed to set balloon watcher\n"); 396 397 return (err); 398 } 399 400 /*-------------------- Private Device Attachment Data -----------------------*/ 401 static device_method_t xenballoon_methods[] = { 402 /* Device interface */ 403 DEVMETHOD(device_identify, xenballoon_identify), 404 DEVMETHOD(device_probe, xenballoon_probe), 405 DEVMETHOD(device_attach, xenballoon_attach), 406 407 DEVMETHOD_END 408 }; 409 410 DEFINE_CLASS_0(xenballoon, xenballoon_driver, xenballoon_methods, 0); 411 412 DRIVER_MODULE(xenballoon, xenstore, xenballoon_driver, NULL, NULL);
Cache object: d248912e3e271378a7c89c04d991a218
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