1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Collaborative memory management interface.
4  *
5  * Copyright (C) 2008 IBM Corporation
6  * Author(s): Brian King (brking@linux.vnet.ibm.com),
7  */
8 
9 #include <linux/ctype.h>
10 #include <linux/delay.h>
11 #include <linux/errno.h>
12 #include <linux/fs.h>
13 #include <linux/gfp.h>
14 #include <linux/kthread.h>
15 #include <linux/module.h>
16 #include <linux/oom.h>
17 #include <linux/reboot.h>
18 #include <linux/sched.h>
19 #include <linux/stringify.h>
20 #include <linux/swap.h>
21 #include <linux/device.h>
22 #include <linux/balloon_compaction.h>
23 #include <asm/firmware.h>
24 #include <asm/hvcall.h>
25 #include <asm/mmu.h>
26 #include <linux/uaccess.h>
27 #include <linux/memory.h>
28 #include <asm/plpar_wrappers.h>
29 
30 #include "pseries.h"
31 
32 #define CMM_DRIVER_VERSION	"1.0.0"
33 #define CMM_DEFAULT_DELAY	1
34 #define CMM_HOTPLUG_DELAY	5
35 #define CMM_DEBUG			0
36 #define CMM_DISABLE		0
37 #define CMM_OOM_KB		1024
38 #define CMM_MIN_MEM_MB		256
39 #define KB2PAGES(_p)		((_p)>>(PAGE_SHIFT-10))
40 #define PAGES2KB(_p)		((_p)<<(PAGE_SHIFT-10))
41 
42 #define CMM_MEM_HOTPLUG_PRI	1
43 
44 static unsigned int delay = CMM_DEFAULT_DELAY;
45 static unsigned int hotplug_delay = CMM_HOTPLUG_DELAY;
46 static unsigned int oom_kb = CMM_OOM_KB;
47 static unsigned int cmm_debug = CMM_DEBUG;
48 static unsigned int cmm_disabled = CMM_DISABLE;
49 static unsigned long min_mem_mb = CMM_MIN_MEM_MB;
50 static bool __read_mostly simulate;
51 static unsigned long simulate_loan_target_kb;
52 static struct device cmm_dev;
53 
54 MODULE_AUTHOR("Brian King <brking@linux.vnet.ibm.com>");
55 MODULE_DESCRIPTION("IBM System p Collaborative Memory Manager");
56 MODULE_LICENSE("GPL");
57 MODULE_VERSION(CMM_DRIVER_VERSION);
58 
59 module_param_named(delay, delay, uint, 0644);
60 MODULE_PARM_DESC(delay, "Delay (in seconds) between polls to query hypervisor paging requests. "
61 		 "[Default=" __stringify(CMM_DEFAULT_DELAY) "]");
62 module_param_named(hotplug_delay, hotplug_delay, uint, 0644);
63 MODULE_PARM_DESC(hotplug_delay, "Delay (in seconds) after memory hotplug remove "
64 		 "before loaning resumes. "
65 		 "[Default=" __stringify(CMM_HOTPLUG_DELAY) "]");
66 module_param_named(oom_kb, oom_kb, uint, 0644);
67 MODULE_PARM_DESC(oom_kb, "Amount of memory in kb to free on OOM. "
68 		 "[Default=" __stringify(CMM_OOM_KB) "]");
69 module_param_named(min_mem_mb, min_mem_mb, ulong, 0644);
70 MODULE_PARM_DESC(min_mem_mb, "Minimum amount of memory (in MB) to not balloon. "
71 		 "[Default=" __stringify(CMM_MIN_MEM_MB) "]");
72 module_param_named(debug, cmm_debug, uint, 0644);
73 MODULE_PARM_DESC(debug, "Enable module debugging logging. Set to 1 to enable. "
74 		 "[Default=" __stringify(CMM_DEBUG) "]");
75 module_param_named(simulate, simulate, bool, 0444);
76 MODULE_PARM_DESC(simulate, "Enable simulation mode (no communication with hw).");
77 
78 #define cmm_dbg(...) if (cmm_debug) { printk(KERN_INFO "cmm: "__VA_ARGS__); }
79 
80 static atomic_long_t loaned_pages;
81 static unsigned long loaned_pages_target;
82 static unsigned long oom_freed_pages;
83 
84 static DEFINE_MUTEX(hotplug_mutex);
85 static int hotplug_occurred; /* protected by the hotplug mutex */
86 
87 static struct task_struct *cmm_thread_ptr;
88 static struct balloon_dev_info b_dev_info;
89 
90 static long plpar_page_set_loaned(struct page *page)
91 {
92 	const unsigned long vpa = page_to_phys(page);
93 	unsigned long cmo_page_sz = cmo_get_page_size();
94 	long rc = 0;
95 	int i;
96 
97 	if (unlikely(simulate))
98 		return 0;
99 
100 	for (i = 0; !rc && i < PAGE_SIZE; i += cmo_page_sz)
101 		rc = plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_LOANED, vpa + i, 0);
102 
103 	for (i -= cmo_page_sz; rc && i != 0; i -= cmo_page_sz)
104 		plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_ACTIVE,
105 				   vpa + i - cmo_page_sz, 0);
106 
107 	return rc;
108 }
109 
110 static long plpar_page_set_active(struct page *page)
111 {
112 	const unsigned long vpa = page_to_phys(page);
113 	unsigned long cmo_page_sz = cmo_get_page_size();
114 	long rc = 0;
115 	int i;
116 
117 	if (unlikely(simulate))
118 		return 0;
119 
120 	for (i = 0; !rc && i < PAGE_SIZE; i += cmo_page_sz)
121 		rc = plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_ACTIVE, vpa + i, 0);
122 
123 	for (i -= cmo_page_sz; rc && i != 0; i -= cmo_page_sz)
124 		plpar_hcall_norets(H_PAGE_INIT, H_PAGE_SET_LOANED,
125 				   vpa + i - cmo_page_sz, 0);
126 
127 	return rc;
128 }
129 
130 /**
131  * cmm_alloc_pages - Allocate pages and mark them as loaned
132  * @nr:	number of pages to allocate
133  *
134  * Return value:
135  * 	number of pages requested to be allocated which were not
136  **/
137 static long cmm_alloc_pages(long nr)
138 {
139 	struct page *page;
140 	long rc;
141 
142 	cmm_dbg("Begin request for %ld pages\n", nr);
143 
144 	while (nr) {
145 		/* Exit if a hotplug operation is in progress or occurred */
146 		if (mutex_trylock(&hotplug_mutex)) {
147 			if (hotplug_occurred) {
148 				mutex_unlock(&hotplug_mutex);
149 				break;
150 			}
151 			mutex_unlock(&hotplug_mutex);
152 		} else {
153 			break;
154 		}
155 
156 		page = balloon_page_alloc();
157 		if (!page)
158 			break;
159 		rc = plpar_page_set_loaned(page);
160 		if (rc) {
161 			pr_err("%s: Can not set page to loaned. rc=%ld\n", __func__, rc);
162 			__free_page(page);
163 			break;
164 		}
165 
166 		balloon_page_enqueue(&b_dev_info, page);
167 		atomic_long_inc(&loaned_pages);
168 		adjust_managed_page_count(page, -1);
169 		nr--;
170 	}
171 
172 	cmm_dbg("End request with %ld pages unfulfilled\n", nr);
173 	return nr;
174 }
175 
176 /**
177  * cmm_free_pages - Free pages and mark them as active
178  * @nr:	number of pages to free
179  *
180  * Return value:
181  * 	number of pages requested to be freed which were not
182  **/
183 static long cmm_free_pages(long nr)
184 {
185 	struct page *page;
186 
187 	cmm_dbg("Begin free of %ld pages.\n", nr);
188 	while (nr) {
189 		page = balloon_page_dequeue(&b_dev_info);
190 		if (!page)
191 			break;
192 		plpar_page_set_active(page);
193 		adjust_managed_page_count(page, 1);
194 		__free_page(page);
195 		atomic_long_dec(&loaned_pages);
196 		nr--;
197 	}
198 	cmm_dbg("End request with %ld pages unfulfilled\n", nr);
199 	return nr;
200 }
201 
202 /**
203  * cmm_oom_notify - OOM notifier
204  * @self:	notifier block struct
205  * @dummy:	not used
206  * @parm:	returned - number of pages freed
207  *
208  * Return value:
209  * 	NOTIFY_OK
210  **/
211 static int cmm_oom_notify(struct notifier_block *self,
212 			  unsigned long dummy, void *parm)
213 {
214 	unsigned long *freed = parm;
215 	long nr = KB2PAGES(oom_kb);
216 
217 	cmm_dbg("OOM processing started\n");
218 	nr = cmm_free_pages(nr);
219 	loaned_pages_target = atomic_long_read(&loaned_pages);
220 	*freed += KB2PAGES(oom_kb) - nr;
221 	oom_freed_pages += KB2PAGES(oom_kb) - nr;
222 	cmm_dbg("OOM processing complete\n");
223 	return NOTIFY_OK;
224 }
225 
226 /**
227  * cmm_get_mpp - Read memory performance parameters
228  *
229  * Makes hcall to query the current page loan request from the hypervisor.
230  *
231  * Return value:
232  * 	nothing
233  **/
234 static void cmm_get_mpp(void)
235 {
236 	const long __loaned_pages = atomic_long_read(&loaned_pages);
237 	const long total_pages = totalram_pages() + __loaned_pages;
238 	int rc;
239 	struct hvcall_mpp_data mpp_data;
240 	signed long active_pages_target, page_loan_request, target;
241 	signed long min_mem_pages = (min_mem_mb * 1024 * 1024) / PAGE_SIZE;
242 
243 	if (likely(!simulate)) {
244 		rc = h_get_mpp(&mpp_data);
245 		if (rc != H_SUCCESS)
246 			return;
247 		page_loan_request = div_s64((s64)mpp_data.loan_request,
248 					    PAGE_SIZE);
249 		target = page_loan_request + __loaned_pages;
250 	} else {
251 		target = KB2PAGES(simulate_loan_target_kb);
252 		page_loan_request = target - __loaned_pages;
253 	}
254 
255 	if (target < 0 || total_pages < min_mem_pages)
256 		target = 0;
257 
258 	if (target > oom_freed_pages)
259 		target -= oom_freed_pages;
260 	else
261 		target = 0;
262 
263 	active_pages_target = total_pages - target;
264 
265 	if (min_mem_pages > active_pages_target)
266 		target = total_pages - min_mem_pages;
267 
268 	if (target < 0)
269 		target = 0;
270 
271 	loaned_pages_target = target;
272 
273 	cmm_dbg("delta = %ld, loaned = %lu, target = %lu, oom = %lu, totalram = %lu\n",
274 		page_loan_request, __loaned_pages, loaned_pages_target,
275 		oom_freed_pages, totalram_pages());
276 }
277 
278 static struct notifier_block cmm_oom_nb = {
279 	.notifier_call = cmm_oom_notify
280 };
281 
282 /**
283  * cmm_thread - CMM task thread
284  * @dummy:	not used
285  *
286  * Return value:
287  * 	0
288  **/
289 static int cmm_thread(void *dummy)
290 {
291 	unsigned long timeleft;
292 	long __loaned_pages;
293 
294 	while (1) {
295 		timeleft = msleep_interruptible(delay * 1000);
296 
297 		if (kthread_should_stop() || timeleft)
298 			break;
299 
300 		if (mutex_trylock(&hotplug_mutex)) {
301 			if (hotplug_occurred) {
302 				hotplug_occurred = 0;
303 				mutex_unlock(&hotplug_mutex);
304 				cmm_dbg("Hotplug operation has occurred, "
305 						"loaning activity suspended "
306 						"for %d seconds.\n",
307 						hotplug_delay);
308 				timeleft = msleep_interruptible(hotplug_delay *
309 						1000);
310 				if (kthread_should_stop() || timeleft)
311 					break;
312 				continue;
313 			}
314 			mutex_unlock(&hotplug_mutex);
315 		} else {
316 			cmm_dbg("Hotplug operation in progress, activity "
317 					"suspended\n");
318 			continue;
319 		}
320 
321 		cmm_get_mpp();
322 
323 		__loaned_pages = atomic_long_read(&loaned_pages);
324 		if (loaned_pages_target > __loaned_pages) {
325 			if (cmm_alloc_pages(loaned_pages_target - __loaned_pages))
326 				loaned_pages_target = __loaned_pages;
327 		} else if (loaned_pages_target < __loaned_pages)
328 			cmm_free_pages(__loaned_pages - loaned_pages_target);
329 	}
330 	return 0;
331 }
332 
333 #define CMM_SHOW(name, format, args...)			\
334 	static ssize_t show_##name(struct device *dev,	\
335 				   struct device_attribute *attr,	\
336 				   char *buf)			\
337 	{							\
338 		return sprintf(buf, format, ##args);		\
339 	}							\
340 	static DEVICE_ATTR(name, 0444, show_##name, NULL)
341 
342 CMM_SHOW(loaned_kb, "%lu\n", PAGES2KB(atomic_long_read(&loaned_pages)));
343 CMM_SHOW(loaned_target_kb, "%lu\n", PAGES2KB(loaned_pages_target));
344 
345 static ssize_t show_oom_pages(struct device *dev,
346 			      struct device_attribute *attr, char *buf)
347 {
348 	return sprintf(buf, "%lu\n", PAGES2KB(oom_freed_pages));
349 }
350 
351 static ssize_t store_oom_pages(struct device *dev,
352 			       struct device_attribute *attr,
353 			       const char *buf, size_t count)
354 {
355 	unsigned long val = simple_strtoul (buf, NULL, 10);
356 
357 	if (!capable(CAP_SYS_ADMIN))
358 		return -EPERM;
359 	if (val != 0)
360 		return -EBADMSG;
361 
362 	oom_freed_pages = 0;
363 	return count;
364 }
365 
366 static DEVICE_ATTR(oom_freed_kb, 0644,
367 		   show_oom_pages, store_oom_pages);
368 
369 static struct device_attribute *cmm_attrs[] = {
370 	&dev_attr_loaned_kb,
371 	&dev_attr_loaned_target_kb,
372 	&dev_attr_oom_freed_kb,
373 };
374 
375 static DEVICE_ULONG_ATTR(simulate_loan_target_kb, 0644,
376 			 simulate_loan_target_kb);
377 
378 static struct bus_type cmm_subsys = {
379 	.name = "cmm",
380 	.dev_name = "cmm",
381 };
382 
383 static void cmm_release_device(struct device *dev)
384 {
385 }
386 
387 /**
388  * cmm_sysfs_register - Register with sysfs
389  *
390  * Return value:
391  * 	0 on success / other on failure
392  **/
393 static int cmm_sysfs_register(struct device *dev)
394 {
395 	int i, rc;
396 
397 	if ((rc = subsys_system_register(&cmm_subsys, NULL)))
398 		return rc;
399 
400 	dev->id = 0;
401 	dev->bus = &cmm_subsys;
402 	dev->release = cmm_release_device;
403 
404 	if ((rc = device_register(dev)))
405 		goto subsys_unregister;
406 
407 	for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) {
408 		if ((rc = device_create_file(dev, cmm_attrs[i])))
409 			goto fail;
410 	}
411 
412 	if (!simulate)
413 		return 0;
414 	rc = device_create_file(dev, &dev_attr_simulate_loan_target_kb.attr);
415 	if (rc)
416 		goto fail;
417 	return 0;
418 
419 fail:
420 	while (--i >= 0)
421 		device_remove_file(dev, cmm_attrs[i]);
422 	device_unregister(dev);
423 subsys_unregister:
424 	bus_unregister(&cmm_subsys);
425 	return rc;
426 }
427 
428 /**
429  * cmm_unregister_sysfs - Unregister from sysfs
430  *
431  **/
432 static void cmm_unregister_sysfs(struct device *dev)
433 {
434 	int i;
435 
436 	for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++)
437 		device_remove_file(dev, cmm_attrs[i]);
438 	device_unregister(dev);
439 	bus_unregister(&cmm_subsys);
440 }
441 
442 /**
443  * cmm_reboot_notifier - Make sure pages are not still marked as "loaned"
444  *
445  **/
446 static int cmm_reboot_notifier(struct notifier_block *nb,
447 			       unsigned long action, void *unused)
448 {
449 	if (action == SYS_RESTART) {
450 		if (cmm_thread_ptr)
451 			kthread_stop(cmm_thread_ptr);
452 		cmm_thread_ptr = NULL;
453 		cmm_free_pages(atomic_long_read(&loaned_pages));
454 	}
455 	return NOTIFY_DONE;
456 }
457 
458 static struct notifier_block cmm_reboot_nb = {
459 	.notifier_call = cmm_reboot_notifier,
460 };
461 
462 /**
463  * cmm_memory_cb - Handle memory hotplug notifier calls
464  * @self:	notifier block struct
465  * @action:	action to take
466  * @arg:	struct memory_notify data for handler
467  *
468  * Return value:
469  *	NOTIFY_OK or notifier error based on subfunction return value
470  *
471  **/
472 static int cmm_memory_cb(struct notifier_block *self,
473 			unsigned long action, void *arg)
474 {
475 	switch (action) {
476 	case MEM_GOING_OFFLINE:
477 		mutex_lock(&hotplug_mutex);
478 		hotplug_occurred = 1;
479 		break;
480 	case MEM_OFFLINE:
481 	case MEM_CANCEL_OFFLINE:
482 		mutex_unlock(&hotplug_mutex);
483 		cmm_dbg("Memory offline operation complete.\n");
484 		break;
485 	case MEM_GOING_ONLINE:
486 	case MEM_ONLINE:
487 	case MEM_CANCEL_ONLINE:
488 		break;
489 	}
490 
491 	return NOTIFY_OK;
492 }
493 
494 static struct notifier_block cmm_mem_nb = {
495 	.notifier_call = cmm_memory_cb,
496 	.priority = CMM_MEM_HOTPLUG_PRI
497 };
498 
499 #ifdef CONFIG_BALLOON_COMPACTION
500 static int cmm_migratepage(struct balloon_dev_info *b_dev_info,
501 			   struct page *newpage, struct page *page,
502 			   enum migrate_mode mode)
503 {
504 	unsigned long flags;
505 
506 	/*
507 	 * loan/"inflate" the newpage first.
508 	 *
509 	 * We might race against the cmm_thread who might discover after our
510 	 * loan request that another page is to be unloaned. However, once
511 	 * the cmm_thread runs again later, this error will automatically
512 	 * be corrected.
513 	 */
514 	if (plpar_page_set_loaned(newpage)) {
515 		/* Unlikely, but possible. Tell the caller not to retry now. */
516 		pr_err_ratelimited("%s: Cannot set page to loaned.", __func__);
517 		return -EBUSY;
518 	}
519 
520 	/* balloon page list reference */
521 	get_page(newpage);
522 
523 	/*
524 	 * When we migrate a page to a different zone, we have to fixup the
525 	 * count of both involved zones as we adjusted the managed page count
526 	 * when inflating.
527 	 */
528 	if (page_zone(page) != page_zone(newpage)) {
529 		adjust_managed_page_count(page, 1);
530 		adjust_managed_page_count(newpage, -1);
531 	}
532 
533 	spin_lock_irqsave(&b_dev_info->pages_lock, flags);
534 	balloon_page_insert(b_dev_info, newpage);
535 	balloon_page_delete(page);
536 	b_dev_info->isolated_pages--;
537 	spin_unlock_irqrestore(&b_dev_info->pages_lock, flags);
538 
539 	/*
540 	 * activate/"deflate" the old page. We ignore any errors just like the
541 	 * other callers.
542 	 */
543 	plpar_page_set_active(page);
544 
545 	/* balloon page list reference */
546 	put_page(page);
547 
548 	return MIGRATEPAGE_SUCCESS;
549 }
550 
551 static void cmm_balloon_compaction_init(void)
552 {
553 	balloon_devinfo_init(&b_dev_info);
554 	b_dev_info.migratepage = cmm_migratepage;
555 }
556 #else /* CONFIG_BALLOON_COMPACTION */
557 static void cmm_balloon_compaction_init(void)
558 {
559 }
560 #endif /* CONFIG_BALLOON_COMPACTION */
561 
562 /**
563  * cmm_init - Module initialization
564  *
565  * Return value:
566  * 	0 on success / other on failure
567  **/
568 static int cmm_init(void)
569 {
570 	int rc;
571 
572 	if (!firmware_has_feature(FW_FEATURE_CMO) && !simulate)
573 		return -EOPNOTSUPP;
574 
575 	cmm_balloon_compaction_init();
576 
577 	rc = register_oom_notifier(&cmm_oom_nb);
578 	if (rc < 0)
579 		goto out_balloon_compaction;
580 
581 	if ((rc = register_reboot_notifier(&cmm_reboot_nb)))
582 		goto out_oom_notifier;
583 
584 	if ((rc = cmm_sysfs_register(&cmm_dev)))
585 		goto out_reboot_notifier;
586 
587 	rc = register_memory_notifier(&cmm_mem_nb);
588 	if (rc)
589 		goto out_unregister_notifier;
590 
591 	if (cmm_disabled)
592 		return 0;
593 
594 	cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
595 	if (IS_ERR(cmm_thread_ptr)) {
596 		rc = PTR_ERR(cmm_thread_ptr);
597 		goto out_unregister_notifier;
598 	}
599 
600 	return 0;
601 out_unregister_notifier:
602 	unregister_memory_notifier(&cmm_mem_nb);
603 	cmm_unregister_sysfs(&cmm_dev);
604 out_reboot_notifier:
605 	unregister_reboot_notifier(&cmm_reboot_nb);
606 out_oom_notifier:
607 	unregister_oom_notifier(&cmm_oom_nb);
608 out_balloon_compaction:
609 	return rc;
610 }
611 
612 /**
613  * cmm_exit - Module exit
614  *
615  * Return value:
616  * 	nothing
617  **/
618 static void cmm_exit(void)
619 {
620 	if (cmm_thread_ptr)
621 		kthread_stop(cmm_thread_ptr);
622 	unregister_oom_notifier(&cmm_oom_nb);
623 	unregister_reboot_notifier(&cmm_reboot_nb);
624 	unregister_memory_notifier(&cmm_mem_nb);
625 	cmm_free_pages(atomic_long_read(&loaned_pages));
626 	cmm_unregister_sysfs(&cmm_dev);
627 }
628 
629 /**
630  * cmm_set_disable - Disable/Enable CMM
631  *
632  * Return value:
633  * 	0 on success / other on failure
634  **/
635 static int cmm_set_disable(const char *val, const struct kernel_param *kp)
636 {
637 	int disable = simple_strtoul(val, NULL, 10);
638 
639 	if (disable != 0 && disable != 1)
640 		return -EINVAL;
641 
642 	if (disable && !cmm_disabled) {
643 		if (cmm_thread_ptr)
644 			kthread_stop(cmm_thread_ptr);
645 		cmm_thread_ptr = NULL;
646 		cmm_free_pages(atomic_long_read(&loaned_pages));
647 	} else if (!disable && cmm_disabled) {
648 		cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
649 		if (IS_ERR(cmm_thread_ptr))
650 			return PTR_ERR(cmm_thread_ptr);
651 	}
652 
653 	cmm_disabled = disable;
654 	return 0;
655 }
656 
657 module_param_call(disable, cmm_set_disable, param_get_uint,
658 		  &cmm_disabled, 0644);
659 MODULE_PARM_DESC(disable, "Disable CMM. Set to 1 to disable. "
660 		 "[Default=" __stringify(CMM_DISABLE) "]");
661 
662 module_init(cmm_init);
663 module_exit(cmm_exit);
664