xref: /openbmc/linux/drivers/hv/hv_balloon.c (revision 0edbfea5)
1 /*
2  * Copyright (c) 2012, Microsoft Corporation.
3  *
4  * Author:
5  *   K. Y. Srinivasan <kys@microsoft.com>
6  *
7  * This program is free software; you can redistribute it and/or modify it
8  * under the terms of the GNU General Public License version 2 as published
9  * by the Free Software Foundation.
10  *
11  * This program is distributed in the hope that it will be useful, but
12  * WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
14  * NON INFRINGEMENT.  See the GNU General Public License for more
15  * details.
16  *
17  */
18 
19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
20 
21 #include <linux/kernel.h>
22 #include <linux/jiffies.h>
23 #include <linux/mman.h>
24 #include <linux/delay.h>
25 #include <linux/init.h>
26 #include <linux/module.h>
27 #include <linux/slab.h>
28 #include <linux/kthread.h>
29 #include <linux/completion.h>
30 #include <linux/memory_hotplug.h>
31 #include <linux/memory.h>
32 #include <linux/notifier.h>
33 #include <linux/percpu_counter.h>
34 
35 #include <linux/hyperv.h>
36 
37 /*
38  * We begin with definitions supporting the Dynamic Memory protocol
39  * with the host.
40  *
41  * Begin protocol definitions.
42  */
43 
44 
45 
46 /*
47  * Protocol versions. The low word is the minor version, the high word the major
48  * version.
49  *
50  * History:
51  * Initial version 1.0
52  * Changed to 0.1 on 2009/03/25
53  * Changes to 0.2 on 2009/05/14
54  * Changes to 0.3 on 2009/12/03
55  * Changed to 1.0 on 2011/04/05
56  */
57 
58 #define DYNMEM_MAKE_VERSION(Major, Minor) ((__u32)(((Major) << 16) | (Minor)))
59 #define DYNMEM_MAJOR_VERSION(Version) ((__u32)(Version) >> 16)
60 #define DYNMEM_MINOR_VERSION(Version) ((__u32)(Version) & 0xff)
61 
62 enum {
63 	DYNMEM_PROTOCOL_VERSION_1 = DYNMEM_MAKE_VERSION(0, 3),
64 	DYNMEM_PROTOCOL_VERSION_2 = DYNMEM_MAKE_VERSION(1, 0),
65 	DYNMEM_PROTOCOL_VERSION_3 = DYNMEM_MAKE_VERSION(2, 0),
66 
67 	DYNMEM_PROTOCOL_VERSION_WIN7 = DYNMEM_PROTOCOL_VERSION_1,
68 	DYNMEM_PROTOCOL_VERSION_WIN8 = DYNMEM_PROTOCOL_VERSION_2,
69 	DYNMEM_PROTOCOL_VERSION_WIN10 = DYNMEM_PROTOCOL_VERSION_3,
70 
71 	DYNMEM_PROTOCOL_VERSION_CURRENT = DYNMEM_PROTOCOL_VERSION_WIN10
72 };
73 
74 
75 
76 /*
77  * Message Types
78  */
79 
80 enum dm_message_type {
81 	/*
82 	 * Version 0.3
83 	 */
84 	DM_ERROR			= 0,
85 	DM_VERSION_REQUEST		= 1,
86 	DM_VERSION_RESPONSE		= 2,
87 	DM_CAPABILITIES_REPORT		= 3,
88 	DM_CAPABILITIES_RESPONSE	= 4,
89 	DM_STATUS_REPORT		= 5,
90 	DM_BALLOON_REQUEST		= 6,
91 	DM_BALLOON_RESPONSE		= 7,
92 	DM_UNBALLOON_REQUEST		= 8,
93 	DM_UNBALLOON_RESPONSE		= 9,
94 	DM_MEM_HOT_ADD_REQUEST		= 10,
95 	DM_MEM_HOT_ADD_RESPONSE		= 11,
96 	DM_VERSION_03_MAX		= 11,
97 	/*
98 	 * Version 1.0.
99 	 */
100 	DM_INFO_MESSAGE			= 12,
101 	DM_VERSION_1_MAX		= 12
102 };
103 
104 
105 /*
106  * Structures defining the dynamic memory management
107  * protocol.
108  */
109 
110 union dm_version {
111 	struct {
112 		__u16 minor_version;
113 		__u16 major_version;
114 	};
115 	__u32 version;
116 } __packed;
117 
118 
119 union dm_caps {
120 	struct {
121 		__u64 balloon:1;
122 		__u64 hot_add:1;
123 		/*
124 		 * To support guests that may have alignment
125 		 * limitations on hot-add, the guest can specify
126 		 * its alignment requirements; a value of n
127 		 * represents an alignment of 2^n in mega bytes.
128 		 */
129 		__u64 hot_add_alignment:4;
130 		__u64 reservedz:58;
131 	} cap_bits;
132 	__u64 caps;
133 } __packed;
134 
135 union dm_mem_page_range {
136 	struct  {
137 		/*
138 		 * The PFN number of the first page in the range.
139 		 * 40 bits is the architectural limit of a PFN
140 		 * number for AMD64.
141 		 */
142 		__u64 start_page:40;
143 		/*
144 		 * The number of pages in the range.
145 		 */
146 		__u64 page_cnt:24;
147 	} finfo;
148 	__u64  page_range;
149 } __packed;
150 
151 
152 
153 /*
154  * The header for all dynamic memory messages:
155  *
156  * type: Type of the message.
157  * size: Size of the message in bytes; including the header.
158  * trans_id: The guest is responsible for manufacturing this ID.
159  */
160 
161 struct dm_header {
162 	__u16 type;
163 	__u16 size;
164 	__u32 trans_id;
165 } __packed;
166 
167 /*
168  * A generic message format for dynamic memory.
169  * Specific message formats are defined later in the file.
170  */
171 
172 struct dm_message {
173 	struct dm_header hdr;
174 	__u8 data[]; /* enclosed message */
175 } __packed;
176 
177 
178 /*
179  * Specific message types supporting the dynamic memory protocol.
180  */
181 
182 /*
183  * Version negotiation message. Sent from the guest to the host.
184  * The guest is free to try different versions until the host
185  * accepts the version.
186  *
187  * dm_version: The protocol version requested.
188  * is_last_attempt: If TRUE, this is the last version guest will request.
189  * reservedz: Reserved field, set to zero.
190  */
191 
192 struct dm_version_request {
193 	struct dm_header hdr;
194 	union dm_version version;
195 	__u32 is_last_attempt:1;
196 	__u32 reservedz:31;
197 } __packed;
198 
199 /*
200  * Version response message; Host to Guest and indicates
201  * if the host has accepted the version sent by the guest.
202  *
203  * is_accepted: If TRUE, host has accepted the version and the guest
204  * should proceed to the next stage of the protocol. FALSE indicates that
205  * guest should re-try with a different version.
206  *
207  * reservedz: Reserved field, set to zero.
208  */
209 
210 struct dm_version_response {
211 	struct dm_header hdr;
212 	__u64 is_accepted:1;
213 	__u64 reservedz:63;
214 } __packed;
215 
216 /*
217  * Message reporting capabilities. This is sent from the guest to the
218  * host.
219  */
220 
221 struct dm_capabilities {
222 	struct dm_header hdr;
223 	union dm_caps caps;
224 	__u64 min_page_cnt;
225 	__u64 max_page_number;
226 } __packed;
227 
228 /*
229  * Response to the capabilities message. This is sent from the host to the
230  * guest. This message notifies if the host has accepted the guest's
231  * capabilities. If the host has not accepted, the guest must shutdown
232  * the service.
233  *
234  * is_accepted: Indicates if the host has accepted guest's capabilities.
235  * reservedz: Must be 0.
236  */
237 
238 struct dm_capabilities_resp_msg {
239 	struct dm_header hdr;
240 	__u64 is_accepted:1;
241 	__u64 reservedz:63;
242 } __packed;
243 
244 /*
245  * This message is used to report memory pressure from the guest.
246  * This message is not part of any transaction and there is no
247  * response to this message.
248  *
249  * num_avail: Available memory in pages.
250  * num_committed: Committed memory in pages.
251  * page_file_size: The accumulated size of all page files
252  *		   in the system in pages.
253  * zero_free: The nunber of zero and free pages.
254  * page_file_writes: The writes to the page file in pages.
255  * io_diff: An indicator of file cache efficiency or page file activity,
256  *	    calculated as File Cache Page Fault Count - Page Read Count.
257  *	    This value is in pages.
258  *
259  * Some of these metrics are Windows specific and fortunately
260  * the algorithm on the host side that computes the guest memory
261  * pressure only uses num_committed value.
262  */
263 
264 struct dm_status {
265 	struct dm_header hdr;
266 	__u64 num_avail;
267 	__u64 num_committed;
268 	__u64 page_file_size;
269 	__u64 zero_free;
270 	__u32 page_file_writes;
271 	__u32 io_diff;
272 } __packed;
273 
274 
275 /*
276  * Message to ask the guest to allocate memory - balloon up message.
277  * This message is sent from the host to the guest. The guest may not be
278  * able to allocate as much memory as requested.
279  *
280  * num_pages: number of pages to allocate.
281  */
282 
283 struct dm_balloon {
284 	struct dm_header hdr;
285 	__u32 num_pages;
286 	__u32 reservedz;
287 } __packed;
288 
289 
290 /*
291  * Balloon response message; this message is sent from the guest
292  * to the host in response to the balloon message.
293  *
294  * reservedz: Reserved; must be set to zero.
295  * more_pages: If FALSE, this is the last message of the transaction.
296  * if TRUE there will atleast one more message from the guest.
297  *
298  * range_count: The number of ranges in the range array.
299  *
300  * range_array: An array of page ranges returned to the host.
301  *
302  */
303 
304 struct dm_balloon_response {
305 	struct dm_header hdr;
306 	__u32 reservedz;
307 	__u32 more_pages:1;
308 	__u32 range_count:31;
309 	union dm_mem_page_range range_array[];
310 } __packed;
311 
312 /*
313  * Un-balloon message; this message is sent from the host
314  * to the guest to give guest more memory.
315  *
316  * more_pages: If FALSE, this is the last message of the transaction.
317  * if TRUE there will atleast one more message from the guest.
318  *
319  * reservedz: Reserved; must be set to zero.
320  *
321  * range_count: The number of ranges in the range array.
322  *
323  * range_array: An array of page ranges returned to the host.
324  *
325  */
326 
327 struct dm_unballoon_request {
328 	struct dm_header hdr;
329 	__u32 more_pages:1;
330 	__u32 reservedz:31;
331 	__u32 range_count;
332 	union dm_mem_page_range range_array[];
333 } __packed;
334 
335 /*
336  * Un-balloon response message; this message is sent from the guest
337  * to the host in response to an unballoon request.
338  *
339  */
340 
341 struct dm_unballoon_response {
342 	struct dm_header hdr;
343 } __packed;
344 
345 
346 /*
347  * Hot add request message. Message sent from the host to the guest.
348  *
349  * mem_range: Memory range to hot add.
350  *
351  * On Linux we currently don't support this since we cannot hot add
352  * arbitrary granularity of memory.
353  */
354 
355 struct dm_hot_add {
356 	struct dm_header hdr;
357 	union dm_mem_page_range range;
358 } __packed;
359 
360 /*
361  * Hot add response message.
362  * This message is sent by the guest to report the status of a hot add request.
363  * If page_count is less than the requested page count, then the host should
364  * assume all further hot add requests will fail, since this indicates that
365  * the guest has hit an upper physical memory barrier.
366  *
367  * Hot adds may also fail due to low resources; in this case, the guest must
368  * not complete this message until the hot add can succeed, and the host must
369  * not send a new hot add request until the response is sent.
370  * If VSC fails to hot add memory DYNMEM_NUMBER_OF_UNSUCCESSFUL_HOTADD_ATTEMPTS
371  * times it fails the request.
372  *
373  *
374  * page_count: number of pages that were successfully hot added.
375  *
376  * result: result of the operation 1: success, 0: failure.
377  *
378  */
379 
380 struct dm_hot_add_response {
381 	struct dm_header hdr;
382 	__u32 page_count;
383 	__u32 result;
384 } __packed;
385 
386 /*
387  * Types of information sent from host to the guest.
388  */
389 
390 enum dm_info_type {
391 	INFO_TYPE_MAX_PAGE_CNT = 0,
392 	MAX_INFO_TYPE
393 };
394 
395 
396 /*
397  * Header for the information message.
398  */
399 
400 struct dm_info_header {
401 	enum dm_info_type type;
402 	__u32 data_size;
403 } __packed;
404 
405 /*
406  * This message is sent from the host to the guest to pass
407  * some relevant information (win8 addition).
408  *
409  * reserved: no used.
410  * info_size: size of the information blob.
411  * info: information blob.
412  */
413 
414 struct dm_info_msg {
415 	struct dm_header hdr;
416 	__u32 reserved;
417 	__u32 info_size;
418 	__u8  info[];
419 };
420 
421 /*
422  * End protocol definitions.
423  */
424 
425 /*
426  * State to manage hot adding memory into the guest.
427  * The range start_pfn : end_pfn specifies the range
428  * that the host has asked us to hot add. The range
429  * start_pfn : ha_end_pfn specifies the range that we have
430  * currently hot added. We hot add in multiples of 128M
431  * chunks; it is possible that we may not be able to bring
432  * online all the pages in the region. The range
433  * covered_end_pfn defines the pages that can
434  * be brough online.
435  */
436 
437 struct hv_hotadd_state {
438 	struct list_head list;
439 	unsigned long start_pfn;
440 	unsigned long covered_end_pfn;
441 	unsigned long ha_end_pfn;
442 	unsigned long end_pfn;
443 };
444 
445 struct balloon_state {
446 	__u32 num_pages;
447 	struct work_struct wrk;
448 };
449 
450 struct hot_add_wrk {
451 	union dm_mem_page_range ha_page_range;
452 	union dm_mem_page_range ha_region_range;
453 	struct work_struct wrk;
454 };
455 
456 static bool hot_add = true;
457 static bool do_hot_add;
458 /*
459  * Delay reporting memory pressure by
460  * the specified number of seconds.
461  */
462 static uint pressure_report_delay = 45;
463 
464 /*
465  * The last time we posted a pressure report to host.
466  */
467 static unsigned long last_post_time;
468 
469 module_param(hot_add, bool, (S_IRUGO | S_IWUSR));
470 MODULE_PARM_DESC(hot_add, "If set attempt memory hot_add");
471 
472 module_param(pressure_report_delay, uint, (S_IRUGO | S_IWUSR));
473 MODULE_PARM_DESC(pressure_report_delay, "Delay in secs in reporting pressure");
474 static atomic_t trans_id = ATOMIC_INIT(0);
475 
476 static int dm_ring_size = (5 * PAGE_SIZE);
477 
478 /*
479  * Driver specific state.
480  */
481 
482 enum hv_dm_state {
483 	DM_INITIALIZING = 0,
484 	DM_INITIALIZED,
485 	DM_BALLOON_UP,
486 	DM_BALLOON_DOWN,
487 	DM_HOT_ADD,
488 	DM_INIT_ERROR
489 };
490 
491 
492 static __u8 recv_buffer[PAGE_SIZE];
493 static __u8 *send_buffer;
494 #define PAGES_IN_2M	512
495 #define HA_CHUNK (32 * 1024)
496 
497 struct hv_dynmem_device {
498 	struct hv_device *dev;
499 	enum hv_dm_state state;
500 	struct completion host_event;
501 	struct completion config_event;
502 
503 	/*
504 	 * Number of pages we have currently ballooned out.
505 	 */
506 	unsigned int num_pages_ballooned;
507 	unsigned int num_pages_onlined;
508 	unsigned int num_pages_added;
509 
510 	/*
511 	 * State to manage the ballooning (up) operation.
512 	 */
513 	struct balloon_state balloon_wrk;
514 
515 	/*
516 	 * State to execute the "hot-add" operation.
517 	 */
518 	struct hot_add_wrk ha_wrk;
519 
520 	/*
521 	 * This state tracks if the host has specified a hot-add
522 	 * region.
523 	 */
524 	bool host_specified_ha_region;
525 
526 	/*
527 	 * State to synchronize hot-add.
528 	 */
529 	struct completion  ol_waitevent;
530 	bool ha_waiting;
531 	/*
532 	 * This thread handles hot-add
533 	 * requests from the host as well as notifying
534 	 * the host with regards to memory pressure in
535 	 * the guest.
536 	 */
537 	struct task_struct *thread;
538 
539 	struct mutex ha_region_mutex;
540 
541 	/*
542 	 * A list of hot-add regions.
543 	 */
544 	struct list_head ha_region_list;
545 
546 	/*
547 	 * We start with the highest version we can support
548 	 * and downgrade based on the host; we save here the
549 	 * next version to try.
550 	 */
551 	__u32 next_version;
552 };
553 
554 static struct hv_dynmem_device dm_device;
555 
556 static void post_status(struct hv_dynmem_device *dm);
557 
558 #ifdef CONFIG_MEMORY_HOTPLUG
559 static int hv_memory_notifier(struct notifier_block *nb, unsigned long val,
560 			      void *v)
561 {
562 	struct memory_notify *mem = (struct memory_notify *)v;
563 
564 	switch (val) {
565 	case MEM_GOING_ONLINE:
566 		mutex_lock(&dm_device.ha_region_mutex);
567 		break;
568 
569 	case MEM_ONLINE:
570 		dm_device.num_pages_onlined += mem->nr_pages;
571 	case MEM_CANCEL_ONLINE:
572 		if (val == MEM_ONLINE ||
573 		    mutex_is_locked(&dm_device.ha_region_mutex))
574 			mutex_unlock(&dm_device.ha_region_mutex);
575 		if (dm_device.ha_waiting) {
576 			dm_device.ha_waiting = false;
577 			complete(&dm_device.ol_waitevent);
578 		}
579 		break;
580 
581 	case MEM_OFFLINE:
582 		mutex_lock(&dm_device.ha_region_mutex);
583 		dm_device.num_pages_onlined -= mem->nr_pages;
584 		mutex_unlock(&dm_device.ha_region_mutex);
585 		break;
586 	case MEM_GOING_OFFLINE:
587 	case MEM_CANCEL_OFFLINE:
588 		break;
589 	}
590 	return NOTIFY_OK;
591 }
592 
593 static struct notifier_block hv_memory_nb = {
594 	.notifier_call = hv_memory_notifier,
595 	.priority = 0
596 };
597 
598 
599 static void hv_bring_pgs_online(unsigned long start_pfn, unsigned long size)
600 {
601 	int i;
602 
603 	for (i = 0; i < size; i++) {
604 		struct page *pg;
605 		pg = pfn_to_page(start_pfn + i);
606 		__online_page_set_limits(pg);
607 		__online_page_increment_counters(pg);
608 		__online_page_free(pg);
609 	}
610 }
611 
612 static void hv_mem_hot_add(unsigned long start, unsigned long size,
613 				unsigned long pfn_count,
614 				struct hv_hotadd_state *has)
615 {
616 	int ret = 0;
617 	int i, nid;
618 	unsigned long start_pfn;
619 	unsigned long processed_pfn;
620 	unsigned long total_pfn = pfn_count;
621 
622 	for (i = 0; i < (size/HA_CHUNK); i++) {
623 		start_pfn = start + (i * HA_CHUNK);
624 		has->ha_end_pfn +=  HA_CHUNK;
625 
626 		if (total_pfn > HA_CHUNK) {
627 			processed_pfn = HA_CHUNK;
628 			total_pfn -= HA_CHUNK;
629 		} else {
630 			processed_pfn = total_pfn;
631 			total_pfn = 0;
632 		}
633 
634 		has->covered_end_pfn +=  processed_pfn;
635 
636 		init_completion(&dm_device.ol_waitevent);
637 		dm_device.ha_waiting = true;
638 
639 		mutex_unlock(&dm_device.ha_region_mutex);
640 		nid = memory_add_physaddr_to_nid(PFN_PHYS(start_pfn));
641 		ret = add_memory(nid, PFN_PHYS((start_pfn)),
642 				(HA_CHUNK << PAGE_SHIFT));
643 
644 		if (ret) {
645 			pr_info("hot_add memory failed error is %d\n", ret);
646 			if (ret == -EEXIST) {
647 				/*
648 				 * This error indicates that the error
649 				 * is not a transient failure. This is the
650 				 * case where the guest's physical address map
651 				 * precludes hot adding memory. Stop all further
652 				 * memory hot-add.
653 				 */
654 				do_hot_add = false;
655 			}
656 			has->ha_end_pfn -= HA_CHUNK;
657 			has->covered_end_pfn -=  processed_pfn;
658 			mutex_lock(&dm_device.ha_region_mutex);
659 			break;
660 		}
661 
662 		/*
663 		 * Wait for the memory block to be onlined.
664 		 * Since the hot add has succeeded, it is ok to
665 		 * proceed even if the pages in the hot added region
666 		 * have not been "onlined" within the allowed time.
667 		 */
668 		wait_for_completion_timeout(&dm_device.ol_waitevent, 5*HZ);
669 		mutex_lock(&dm_device.ha_region_mutex);
670 		post_status(&dm_device);
671 	}
672 
673 	return;
674 }
675 
676 static void hv_online_page(struct page *pg)
677 {
678 	struct list_head *cur;
679 	struct hv_hotadd_state *has;
680 	unsigned long cur_start_pgp;
681 	unsigned long cur_end_pgp;
682 
683 	list_for_each(cur, &dm_device.ha_region_list) {
684 		has = list_entry(cur, struct hv_hotadd_state, list);
685 		cur_start_pgp = (unsigned long)pfn_to_page(has->start_pfn);
686 		cur_end_pgp = (unsigned long)pfn_to_page(has->covered_end_pfn);
687 
688 		if (((unsigned long)pg >= cur_start_pgp) &&
689 			((unsigned long)pg < cur_end_pgp)) {
690 			/*
691 			 * This frame is currently backed; online the
692 			 * page.
693 			 */
694 			__online_page_set_limits(pg);
695 			__online_page_increment_counters(pg);
696 			__online_page_free(pg);
697 		}
698 	}
699 }
700 
701 static bool pfn_covered(unsigned long start_pfn, unsigned long pfn_cnt)
702 {
703 	struct list_head *cur;
704 	struct hv_hotadd_state *has;
705 	unsigned long residual, new_inc;
706 
707 	if (list_empty(&dm_device.ha_region_list))
708 		return false;
709 
710 	list_for_each(cur, &dm_device.ha_region_list) {
711 		has = list_entry(cur, struct hv_hotadd_state, list);
712 
713 		/*
714 		 * If the pfn range we are dealing with is not in the current
715 		 * "hot add block", move on.
716 		 */
717 		if (start_pfn < has->start_pfn || start_pfn >= has->end_pfn)
718 			continue;
719 		/*
720 		 * If the current hot add-request extends beyond
721 		 * our current limit; extend it.
722 		 */
723 		if ((start_pfn + pfn_cnt) > has->end_pfn) {
724 			residual = (start_pfn + pfn_cnt - has->end_pfn);
725 			/*
726 			 * Extend the region by multiples of HA_CHUNK.
727 			 */
728 			new_inc = (residual / HA_CHUNK) * HA_CHUNK;
729 			if (residual % HA_CHUNK)
730 				new_inc += HA_CHUNK;
731 
732 			has->end_pfn += new_inc;
733 		}
734 
735 		/*
736 		 * If the current start pfn is not where the covered_end
737 		 * is, update it.
738 		 */
739 
740 		if (has->covered_end_pfn != start_pfn)
741 			has->covered_end_pfn = start_pfn;
742 
743 		return true;
744 
745 	}
746 
747 	return false;
748 }
749 
750 static unsigned long handle_pg_range(unsigned long pg_start,
751 					unsigned long pg_count)
752 {
753 	unsigned long start_pfn = pg_start;
754 	unsigned long pfn_cnt = pg_count;
755 	unsigned long size;
756 	struct list_head *cur;
757 	struct hv_hotadd_state *has;
758 	unsigned long pgs_ol = 0;
759 	unsigned long old_covered_state;
760 
761 	if (list_empty(&dm_device.ha_region_list))
762 		return 0;
763 
764 	list_for_each(cur, &dm_device.ha_region_list) {
765 		has = list_entry(cur, struct hv_hotadd_state, list);
766 
767 		/*
768 		 * If the pfn range we are dealing with is not in the current
769 		 * "hot add block", move on.
770 		 */
771 		if (start_pfn < has->start_pfn || start_pfn >= has->end_pfn)
772 			continue;
773 
774 		old_covered_state = has->covered_end_pfn;
775 
776 		if (start_pfn < has->ha_end_pfn) {
777 			/*
778 			 * This is the case where we are backing pages
779 			 * in an already hot added region. Bring
780 			 * these pages online first.
781 			 */
782 			pgs_ol = has->ha_end_pfn - start_pfn;
783 			if (pgs_ol > pfn_cnt)
784 				pgs_ol = pfn_cnt;
785 
786 			/*
787 			 * Check if the corresponding memory block is already
788 			 * online by checking its last previously backed page.
789 			 * In case it is we need to bring rest (which was not
790 			 * backed previously) online too.
791 			 */
792 			if (start_pfn > has->start_pfn &&
793 			    !PageReserved(pfn_to_page(start_pfn - 1)))
794 				hv_bring_pgs_online(start_pfn, pgs_ol);
795 
796 			has->covered_end_pfn +=  pgs_ol;
797 			pfn_cnt -= pgs_ol;
798 		}
799 
800 		if ((has->ha_end_pfn < has->end_pfn) && (pfn_cnt > 0)) {
801 			/*
802 			 * We have some residual hot add range
803 			 * that needs to be hot added; hot add
804 			 * it now. Hot add a multiple of
805 			 * of HA_CHUNK that fully covers the pages
806 			 * we have.
807 			 */
808 			size = (has->end_pfn - has->ha_end_pfn);
809 			if (pfn_cnt <= size) {
810 				size = ((pfn_cnt / HA_CHUNK) * HA_CHUNK);
811 				if (pfn_cnt % HA_CHUNK)
812 					size += HA_CHUNK;
813 			} else {
814 				pfn_cnt = size;
815 			}
816 			hv_mem_hot_add(has->ha_end_pfn, size, pfn_cnt, has);
817 		}
818 		/*
819 		 * If we managed to online any pages that were given to us,
820 		 * we declare success.
821 		 */
822 		return has->covered_end_pfn - old_covered_state;
823 
824 	}
825 
826 	return 0;
827 }
828 
829 static unsigned long process_hot_add(unsigned long pg_start,
830 					unsigned long pfn_cnt,
831 					unsigned long rg_start,
832 					unsigned long rg_size)
833 {
834 	struct hv_hotadd_state *ha_region = NULL;
835 
836 	if (pfn_cnt == 0)
837 		return 0;
838 
839 	if (!dm_device.host_specified_ha_region)
840 		if (pfn_covered(pg_start, pfn_cnt))
841 			goto do_pg_range;
842 
843 	/*
844 	 * If the host has specified a hot-add range; deal with it first.
845 	 */
846 
847 	if (rg_size != 0) {
848 		ha_region = kzalloc(sizeof(struct hv_hotadd_state), GFP_KERNEL);
849 		if (!ha_region)
850 			return 0;
851 
852 		INIT_LIST_HEAD(&ha_region->list);
853 
854 		list_add_tail(&ha_region->list, &dm_device.ha_region_list);
855 		ha_region->start_pfn = rg_start;
856 		ha_region->ha_end_pfn = rg_start;
857 		ha_region->covered_end_pfn = pg_start;
858 		ha_region->end_pfn = rg_start + rg_size;
859 	}
860 
861 do_pg_range:
862 	/*
863 	 * Process the page range specified; bringing them
864 	 * online if possible.
865 	 */
866 	return handle_pg_range(pg_start, pfn_cnt);
867 }
868 
869 #endif
870 
871 static void hot_add_req(struct work_struct *dummy)
872 {
873 	struct dm_hot_add_response resp;
874 #ifdef CONFIG_MEMORY_HOTPLUG
875 	unsigned long pg_start, pfn_cnt;
876 	unsigned long rg_start, rg_sz;
877 #endif
878 	struct hv_dynmem_device *dm = &dm_device;
879 
880 	memset(&resp, 0, sizeof(struct dm_hot_add_response));
881 	resp.hdr.type = DM_MEM_HOT_ADD_RESPONSE;
882 	resp.hdr.size = sizeof(struct dm_hot_add_response);
883 
884 #ifdef CONFIG_MEMORY_HOTPLUG
885 	mutex_lock(&dm_device.ha_region_mutex);
886 	pg_start = dm->ha_wrk.ha_page_range.finfo.start_page;
887 	pfn_cnt = dm->ha_wrk.ha_page_range.finfo.page_cnt;
888 
889 	rg_start = dm->ha_wrk.ha_region_range.finfo.start_page;
890 	rg_sz = dm->ha_wrk.ha_region_range.finfo.page_cnt;
891 
892 	if ((rg_start == 0) && (!dm->host_specified_ha_region)) {
893 		unsigned long region_size;
894 		unsigned long region_start;
895 
896 		/*
897 		 * The host has not specified the hot-add region.
898 		 * Based on the hot-add page range being specified,
899 		 * compute a hot-add region that can cover the pages
900 		 * that need to be hot-added while ensuring the alignment
901 		 * and size requirements of Linux as it relates to hot-add.
902 		 */
903 		region_start = pg_start;
904 		region_size = (pfn_cnt / HA_CHUNK) * HA_CHUNK;
905 		if (pfn_cnt % HA_CHUNK)
906 			region_size += HA_CHUNK;
907 
908 		region_start = (pg_start / HA_CHUNK) * HA_CHUNK;
909 
910 		rg_start = region_start;
911 		rg_sz = region_size;
912 	}
913 
914 	if (do_hot_add)
915 		resp.page_count = process_hot_add(pg_start, pfn_cnt,
916 						rg_start, rg_sz);
917 
918 	dm->num_pages_added += resp.page_count;
919 	mutex_unlock(&dm_device.ha_region_mutex);
920 #endif
921 	/*
922 	 * The result field of the response structure has the
923 	 * following semantics:
924 	 *
925 	 * 1. If all or some pages hot-added: Guest should return success.
926 	 *
927 	 * 2. If no pages could be hot-added:
928 	 *
929 	 * If the guest returns success, then the host
930 	 * will not attempt any further hot-add operations. This
931 	 * signifies a permanent failure.
932 	 *
933 	 * If the guest returns failure, then this failure will be
934 	 * treated as a transient failure and the host may retry the
935 	 * hot-add operation after some delay.
936 	 */
937 	if (resp.page_count > 0)
938 		resp.result = 1;
939 	else if (!do_hot_add)
940 		resp.result = 1;
941 	else
942 		resp.result = 0;
943 
944 	if (!do_hot_add || (resp.page_count == 0))
945 		pr_info("Memory hot add failed\n");
946 
947 	dm->state = DM_INITIALIZED;
948 	resp.hdr.trans_id = atomic_inc_return(&trans_id);
949 	vmbus_sendpacket(dm->dev->channel, &resp,
950 			sizeof(struct dm_hot_add_response),
951 			(unsigned long)NULL,
952 			VM_PKT_DATA_INBAND, 0);
953 }
954 
955 static void process_info(struct hv_dynmem_device *dm, struct dm_info_msg *msg)
956 {
957 	struct dm_info_header *info_hdr;
958 
959 	info_hdr = (struct dm_info_header *)msg->info;
960 
961 	switch (info_hdr->type) {
962 	case INFO_TYPE_MAX_PAGE_CNT:
963 		pr_info("Received INFO_TYPE_MAX_PAGE_CNT\n");
964 		pr_info("Data Size is %d\n", info_hdr->data_size);
965 		break;
966 	default:
967 		pr_info("Received Unknown type: %d\n", info_hdr->type);
968 	}
969 }
970 
971 static unsigned long compute_balloon_floor(void)
972 {
973 	unsigned long min_pages;
974 #define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
975 	/* Simple continuous piecewiese linear function:
976 	 *  max MiB -> min MiB  gradient
977 	 *       0         0
978 	 *      16        16
979 	 *      32        24
980 	 *     128        72    (1/2)
981 	 *     512       168    (1/4)
982 	 *    2048       360    (1/8)
983 	 *    8192       744    (1/16)
984 	 *   32768      1512	(1/32)
985 	 */
986 	if (totalram_pages < MB2PAGES(128))
987 		min_pages = MB2PAGES(8) + (totalram_pages >> 1);
988 	else if (totalram_pages < MB2PAGES(512))
989 		min_pages = MB2PAGES(40) + (totalram_pages >> 2);
990 	else if (totalram_pages < MB2PAGES(2048))
991 		min_pages = MB2PAGES(104) + (totalram_pages >> 3);
992 	else if (totalram_pages < MB2PAGES(8192))
993 		min_pages = MB2PAGES(232) + (totalram_pages >> 4);
994 	else
995 		min_pages = MB2PAGES(488) + (totalram_pages >> 5);
996 #undef MB2PAGES
997 	return min_pages;
998 }
999 
1000 /*
1001  * Post our status as it relates memory pressure to the
1002  * host. Host expects the guests to post this status
1003  * periodically at 1 second intervals.
1004  *
1005  * The metrics specified in this protocol are very Windows
1006  * specific and so we cook up numbers here to convey our memory
1007  * pressure.
1008  */
1009 
1010 static void post_status(struct hv_dynmem_device *dm)
1011 {
1012 	struct dm_status status;
1013 	struct sysinfo val;
1014 	unsigned long now = jiffies;
1015 	unsigned long last_post = last_post_time;
1016 
1017 	if (pressure_report_delay > 0) {
1018 		--pressure_report_delay;
1019 		return;
1020 	}
1021 
1022 	if (!time_after(now, (last_post_time + HZ)))
1023 		return;
1024 
1025 	si_meminfo(&val);
1026 	memset(&status, 0, sizeof(struct dm_status));
1027 	status.hdr.type = DM_STATUS_REPORT;
1028 	status.hdr.size = sizeof(struct dm_status);
1029 	status.hdr.trans_id = atomic_inc_return(&trans_id);
1030 
1031 	/*
1032 	 * The host expects the guest to report free and committed memory.
1033 	 * Furthermore, the host expects the pressure information to include
1034 	 * the ballooned out pages. For a given amount of memory that we are
1035 	 * managing we need to compute a floor below which we should not
1036 	 * balloon. Compute this and add it to the pressure report.
1037 	 * We also need to report all offline pages (num_pages_added -
1038 	 * num_pages_onlined) as committed to the host, otherwise it can try
1039 	 * asking us to balloon them out.
1040 	 */
1041 	status.num_avail = val.freeram;
1042 	status.num_committed = vm_memory_committed() +
1043 		dm->num_pages_ballooned +
1044 		(dm->num_pages_added > dm->num_pages_onlined ?
1045 		 dm->num_pages_added - dm->num_pages_onlined : 0) +
1046 		compute_balloon_floor();
1047 
1048 	/*
1049 	 * If our transaction ID is no longer current, just don't
1050 	 * send the status. This can happen if we were interrupted
1051 	 * after we picked our transaction ID.
1052 	 */
1053 	if (status.hdr.trans_id != atomic_read(&trans_id))
1054 		return;
1055 
1056 	/*
1057 	 * If the last post time that we sampled has changed,
1058 	 * we have raced, don't post the status.
1059 	 */
1060 	if (last_post != last_post_time)
1061 		return;
1062 
1063 	last_post_time = jiffies;
1064 	vmbus_sendpacket(dm->dev->channel, &status,
1065 				sizeof(struct dm_status),
1066 				(unsigned long)NULL,
1067 				VM_PKT_DATA_INBAND, 0);
1068 
1069 }
1070 
1071 static void free_balloon_pages(struct hv_dynmem_device *dm,
1072 			 union dm_mem_page_range *range_array)
1073 {
1074 	int num_pages = range_array->finfo.page_cnt;
1075 	__u64 start_frame = range_array->finfo.start_page;
1076 	struct page *pg;
1077 	int i;
1078 
1079 	for (i = 0; i < num_pages; i++) {
1080 		pg = pfn_to_page(i + start_frame);
1081 		__free_page(pg);
1082 		dm->num_pages_ballooned--;
1083 	}
1084 }
1085 
1086 
1087 
1088 static unsigned int alloc_balloon_pages(struct hv_dynmem_device *dm,
1089 					unsigned int num_pages,
1090 					struct dm_balloon_response *bl_resp,
1091 					int alloc_unit)
1092 {
1093 	unsigned int i = 0;
1094 	struct page *pg;
1095 
1096 	if (num_pages < alloc_unit)
1097 		return 0;
1098 
1099 	for (i = 0; (i * alloc_unit) < num_pages; i++) {
1100 		if (bl_resp->hdr.size + sizeof(union dm_mem_page_range) >
1101 			PAGE_SIZE)
1102 			return i * alloc_unit;
1103 
1104 		/*
1105 		 * We execute this code in a thread context. Furthermore,
1106 		 * we don't want the kernel to try too hard.
1107 		 */
1108 		pg = alloc_pages(GFP_HIGHUSER | __GFP_NORETRY |
1109 				__GFP_NOMEMALLOC | __GFP_NOWARN,
1110 				get_order(alloc_unit << PAGE_SHIFT));
1111 
1112 		if (!pg)
1113 			return i * alloc_unit;
1114 
1115 		dm->num_pages_ballooned += alloc_unit;
1116 
1117 		/*
1118 		 * If we allocatted 2M pages; split them so we
1119 		 * can free them in any order we get.
1120 		 */
1121 
1122 		if (alloc_unit != 1)
1123 			split_page(pg, get_order(alloc_unit << PAGE_SHIFT));
1124 
1125 		bl_resp->range_count++;
1126 		bl_resp->range_array[i].finfo.start_page =
1127 			page_to_pfn(pg);
1128 		bl_resp->range_array[i].finfo.page_cnt = alloc_unit;
1129 		bl_resp->hdr.size += sizeof(union dm_mem_page_range);
1130 
1131 	}
1132 
1133 	return num_pages;
1134 }
1135 
1136 
1137 
1138 static void balloon_up(struct work_struct *dummy)
1139 {
1140 	unsigned int num_pages = dm_device.balloon_wrk.num_pages;
1141 	unsigned int num_ballooned = 0;
1142 	struct dm_balloon_response *bl_resp;
1143 	int alloc_unit;
1144 	int ret;
1145 	bool done = false;
1146 	int i;
1147 	struct sysinfo val;
1148 	unsigned long floor;
1149 
1150 	/* The host balloons pages in 2M granularity. */
1151 	WARN_ON_ONCE(num_pages % PAGES_IN_2M != 0);
1152 
1153 	/*
1154 	 * We will attempt 2M allocations. However, if we fail to
1155 	 * allocate 2M chunks, we will go back to 4k allocations.
1156 	 */
1157 	alloc_unit = 512;
1158 
1159 	si_meminfo(&val);
1160 	floor = compute_balloon_floor();
1161 
1162 	/* Refuse to balloon below the floor, keep the 2M granularity. */
1163 	if (val.freeram < num_pages || val.freeram - num_pages < floor) {
1164 		num_pages = val.freeram > floor ? (val.freeram - floor) : 0;
1165 		num_pages -= num_pages % PAGES_IN_2M;
1166 	}
1167 
1168 	while (!done) {
1169 		bl_resp = (struct dm_balloon_response *)send_buffer;
1170 		memset(send_buffer, 0, PAGE_SIZE);
1171 		bl_resp->hdr.type = DM_BALLOON_RESPONSE;
1172 		bl_resp->hdr.size = sizeof(struct dm_balloon_response);
1173 		bl_resp->more_pages = 1;
1174 
1175 
1176 		num_pages -= num_ballooned;
1177 		num_ballooned = alloc_balloon_pages(&dm_device, num_pages,
1178 						    bl_resp, alloc_unit);
1179 
1180 		if (alloc_unit != 1 && num_ballooned == 0) {
1181 			alloc_unit = 1;
1182 			continue;
1183 		}
1184 
1185 		if (num_ballooned == 0 || num_ballooned == num_pages) {
1186 			bl_resp->more_pages = 0;
1187 			done = true;
1188 			dm_device.state = DM_INITIALIZED;
1189 		}
1190 
1191 		/*
1192 		 * We are pushing a lot of data through the channel;
1193 		 * deal with transient failures caused because of the
1194 		 * lack of space in the ring buffer.
1195 		 */
1196 
1197 		do {
1198 			bl_resp->hdr.trans_id = atomic_inc_return(&trans_id);
1199 			ret = vmbus_sendpacket(dm_device.dev->channel,
1200 						bl_resp,
1201 						bl_resp->hdr.size,
1202 						(unsigned long)NULL,
1203 						VM_PKT_DATA_INBAND, 0);
1204 
1205 			if (ret == -EAGAIN)
1206 				msleep(20);
1207 			post_status(&dm_device);
1208 		} while (ret == -EAGAIN);
1209 
1210 		if (ret) {
1211 			/*
1212 			 * Free up the memory we allocatted.
1213 			 */
1214 			pr_info("Balloon response failed\n");
1215 
1216 			for (i = 0; i < bl_resp->range_count; i++)
1217 				free_balloon_pages(&dm_device,
1218 						 &bl_resp->range_array[i]);
1219 
1220 			done = true;
1221 		}
1222 	}
1223 
1224 }
1225 
1226 static void balloon_down(struct hv_dynmem_device *dm,
1227 			struct dm_unballoon_request *req)
1228 {
1229 	union dm_mem_page_range *range_array = req->range_array;
1230 	int range_count = req->range_count;
1231 	struct dm_unballoon_response resp;
1232 	int i;
1233 
1234 	for (i = 0; i < range_count; i++) {
1235 		free_balloon_pages(dm, &range_array[i]);
1236 		complete(&dm_device.config_event);
1237 	}
1238 
1239 	if (req->more_pages == 1)
1240 		return;
1241 
1242 	memset(&resp, 0, sizeof(struct dm_unballoon_response));
1243 	resp.hdr.type = DM_UNBALLOON_RESPONSE;
1244 	resp.hdr.trans_id = atomic_inc_return(&trans_id);
1245 	resp.hdr.size = sizeof(struct dm_unballoon_response);
1246 
1247 	vmbus_sendpacket(dm_device.dev->channel, &resp,
1248 				sizeof(struct dm_unballoon_response),
1249 				(unsigned long)NULL,
1250 				VM_PKT_DATA_INBAND, 0);
1251 
1252 	dm->state = DM_INITIALIZED;
1253 }
1254 
1255 static void balloon_onchannelcallback(void *context);
1256 
1257 static int dm_thread_func(void *dm_dev)
1258 {
1259 	struct hv_dynmem_device *dm = dm_dev;
1260 
1261 	while (!kthread_should_stop()) {
1262 		wait_for_completion_interruptible_timeout(
1263 						&dm_device.config_event, 1*HZ);
1264 		/*
1265 		 * The host expects us to post information on the memory
1266 		 * pressure every second.
1267 		 */
1268 		reinit_completion(&dm_device.config_event);
1269 		post_status(dm);
1270 	}
1271 
1272 	return 0;
1273 }
1274 
1275 
1276 static void version_resp(struct hv_dynmem_device *dm,
1277 			struct dm_version_response *vresp)
1278 {
1279 	struct dm_version_request version_req;
1280 	int ret;
1281 
1282 	if (vresp->is_accepted) {
1283 		/*
1284 		 * We are done; wakeup the
1285 		 * context waiting for version
1286 		 * negotiation.
1287 		 */
1288 		complete(&dm->host_event);
1289 		return;
1290 	}
1291 	/*
1292 	 * If there are more versions to try, continue
1293 	 * with negotiations; if not
1294 	 * shutdown the service since we are not able
1295 	 * to negotiate a suitable version number
1296 	 * with the host.
1297 	 */
1298 	if (dm->next_version == 0)
1299 		goto version_error;
1300 
1301 	memset(&version_req, 0, sizeof(struct dm_version_request));
1302 	version_req.hdr.type = DM_VERSION_REQUEST;
1303 	version_req.hdr.size = sizeof(struct dm_version_request);
1304 	version_req.hdr.trans_id = atomic_inc_return(&trans_id);
1305 	version_req.version.version = dm->next_version;
1306 
1307 	/*
1308 	 * Set the next version to try in case current version fails.
1309 	 * Win7 protocol ought to be the last one to try.
1310 	 */
1311 	switch (version_req.version.version) {
1312 	case DYNMEM_PROTOCOL_VERSION_WIN8:
1313 		dm->next_version = DYNMEM_PROTOCOL_VERSION_WIN7;
1314 		version_req.is_last_attempt = 0;
1315 		break;
1316 	default:
1317 		dm->next_version = 0;
1318 		version_req.is_last_attempt = 1;
1319 	}
1320 
1321 	ret = vmbus_sendpacket(dm->dev->channel, &version_req,
1322 				sizeof(struct dm_version_request),
1323 				(unsigned long)NULL,
1324 				VM_PKT_DATA_INBAND, 0);
1325 
1326 	if (ret)
1327 		goto version_error;
1328 
1329 	return;
1330 
1331 version_error:
1332 	dm->state = DM_INIT_ERROR;
1333 	complete(&dm->host_event);
1334 }
1335 
1336 static void cap_resp(struct hv_dynmem_device *dm,
1337 			struct dm_capabilities_resp_msg *cap_resp)
1338 {
1339 	if (!cap_resp->is_accepted) {
1340 		pr_info("Capabilities not accepted by host\n");
1341 		dm->state = DM_INIT_ERROR;
1342 	}
1343 	complete(&dm->host_event);
1344 }
1345 
1346 static void balloon_onchannelcallback(void *context)
1347 {
1348 	struct hv_device *dev = context;
1349 	u32 recvlen;
1350 	u64 requestid;
1351 	struct dm_message *dm_msg;
1352 	struct dm_header *dm_hdr;
1353 	struct hv_dynmem_device *dm = hv_get_drvdata(dev);
1354 	struct dm_balloon *bal_msg;
1355 	struct dm_hot_add *ha_msg;
1356 	union dm_mem_page_range *ha_pg_range;
1357 	union dm_mem_page_range *ha_region;
1358 
1359 	memset(recv_buffer, 0, sizeof(recv_buffer));
1360 	vmbus_recvpacket(dev->channel, recv_buffer,
1361 			 PAGE_SIZE, &recvlen, &requestid);
1362 
1363 	if (recvlen > 0) {
1364 		dm_msg = (struct dm_message *)recv_buffer;
1365 		dm_hdr = &dm_msg->hdr;
1366 
1367 		switch (dm_hdr->type) {
1368 		case DM_VERSION_RESPONSE:
1369 			version_resp(dm,
1370 				 (struct dm_version_response *)dm_msg);
1371 			break;
1372 
1373 		case DM_CAPABILITIES_RESPONSE:
1374 			cap_resp(dm,
1375 				 (struct dm_capabilities_resp_msg *)dm_msg);
1376 			break;
1377 
1378 		case DM_BALLOON_REQUEST:
1379 			if (dm->state == DM_BALLOON_UP)
1380 				pr_warn("Currently ballooning\n");
1381 			bal_msg = (struct dm_balloon *)recv_buffer;
1382 			dm->state = DM_BALLOON_UP;
1383 			dm_device.balloon_wrk.num_pages = bal_msg->num_pages;
1384 			schedule_work(&dm_device.balloon_wrk.wrk);
1385 			break;
1386 
1387 		case DM_UNBALLOON_REQUEST:
1388 			dm->state = DM_BALLOON_DOWN;
1389 			balloon_down(dm,
1390 				 (struct dm_unballoon_request *)recv_buffer);
1391 			break;
1392 
1393 		case DM_MEM_HOT_ADD_REQUEST:
1394 			if (dm->state == DM_HOT_ADD)
1395 				pr_warn("Currently hot-adding\n");
1396 			dm->state = DM_HOT_ADD;
1397 			ha_msg = (struct dm_hot_add *)recv_buffer;
1398 			if (ha_msg->hdr.size == sizeof(struct dm_hot_add)) {
1399 				/*
1400 				 * This is a normal hot-add request specifying
1401 				 * hot-add memory.
1402 				 */
1403 				dm->host_specified_ha_region = false;
1404 				ha_pg_range = &ha_msg->range;
1405 				dm->ha_wrk.ha_page_range = *ha_pg_range;
1406 				dm->ha_wrk.ha_region_range.page_range = 0;
1407 			} else {
1408 				/*
1409 				 * Host is specifying that we first hot-add
1410 				 * a region and then partially populate this
1411 				 * region.
1412 				 */
1413 				dm->host_specified_ha_region = true;
1414 				ha_pg_range = &ha_msg->range;
1415 				ha_region = &ha_pg_range[1];
1416 				dm->ha_wrk.ha_page_range = *ha_pg_range;
1417 				dm->ha_wrk.ha_region_range = *ha_region;
1418 			}
1419 			schedule_work(&dm_device.ha_wrk.wrk);
1420 			break;
1421 
1422 		case DM_INFO_MESSAGE:
1423 			process_info(dm, (struct dm_info_msg *)dm_msg);
1424 			break;
1425 
1426 		default:
1427 			pr_err("Unhandled message: type: %d\n", dm_hdr->type);
1428 
1429 		}
1430 	}
1431 
1432 }
1433 
1434 static int balloon_probe(struct hv_device *dev,
1435 			const struct hv_vmbus_device_id *dev_id)
1436 {
1437 	int ret;
1438 	unsigned long t;
1439 	struct dm_version_request version_req;
1440 	struct dm_capabilities cap_msg;
1441 
1442 	do_hot_add = hot_add;
1443 
1444 	/*
1445 	 * First allocate a send buffer.
1446 	 */
1447 
1448 	send_buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
1449 	if (!send_buffer)
1450 		return -ENOMEM;
1451 
1452 	ret = vmbus_open(dev->channel, dm_ring_size, dm_ring_size, NULL, 0,
1453 			balloon_onchannelcallback, dev);
1454 
1455 	if (ret)
1456 		goto probe_error0;
1457 
1458 	dm_device.dev = dev;
1459 	dm_device.state = DM_INITIALIZING;
1460 	dm_device.next_version = DYNMEM_PROTOCOL_VERSION_WIN8;
1461 	init_completion(&dm_device.host_event);
1462 	init_completion(&dm_device.config_event);
1463 	INIT_LIST_HEAD(&dm_device.ha_region_list);
1464 	mutex_init(&dm_device.ha_region_mutex);
1465 	INIT_WORK(&dm_device.balloon_wrk.wrk, balloon_up);
1466 	INIT_WORK(&dm_device.ha_wrk.wrk, hot_add_req);
1467 	dm_device.host_specified_ha_region = false;
1468 
1469 	dm_device.thread =
1470 		 kthread_run(dm_thread_func, &dm_device, "hv_balloon");
1471 	if (IS_ERR(dm_device.thread)) {
1472 		ret = PTR_ERR(dm_device.thread);
1473 		goto probe_error1;
1474 	}
1475 
1476 #ifdef CONFIG_MEMORY_HOTPLUG
1477 	set_online_page_callback(&hv_online_page);
1478 	register_memory_notifier(&hv_memory_nb);
1479 #endif
1480 
1481 	hv_set_drvdata(dev, &dm_device);
1482 	/*
1483 	 * Initiate the hand shake with the host and negotiate
1484 	 * a version that the host can support. We start with the
1485 	 * highest version number and go down if the host cannot
1486 	 * support it.
1487 	 */
1488 	memset(&version_req, 0, sizeof(struct dm_version_request));
1489 	version_req.hdr.type = DM_VERSION_REQUEST;
1490 	version_req.hdr.size = sizeof(struct dm_version_request);
1491 	version_req.hdr.trans_id = atomic_inc_return(&trans_id);
1492 	version_req.version.version = DYNMEM_PROTOCOL_VERSION_WIN10;
1493 	version_req.is_last_attempt = 0;
1494 
1495 	ret = vmbus_sendpacket(dev->channel, &version_req,
1496 				sizeof(struct dm_version_request),
1497 				(unsigned long)NULL,
1498 				VM_PKT_DATA_INBAND, 0);
1499 	if (ret)
1500 		goto probe_error2;
1501 
1502 	t = wait_for_completion_timeout(&dm_device.host_event, 5*HZ);
1503 	if (t == 0) {
1504 		ret = -ETIMEDOUT;
1505 		goto probe_error2;
1506 	}
1507 
1508 	/*
1509 	 * If we could not negotiate a compatible version with the host
1510 	 * fail the probe function.
1511 	 */
1512 	if (dm_device.state == DM_INIT_ERROR) {
1513 		ret = -ETIMEDOUT;
1514 		goto probe_error2;
1515 	}
1516 	/*
1517 	 * Now submit our capabilities to the host.
1518 	 */
1519 	memset(&cap_msg, 0, sizeof(struct dm_capabilities));
1520 	cap_msg.hdr.type = DM_CAPABILITIES_REPORT;
1521 	cap_msg.hdr.size = sizeof(struct dm_capabilities);
1522 	cap_msg.hdr.trans_id = atomic_inc_return(&trans_id);
1523 
1524 	cap_msg.caps.cap_bits.balloon = 1;
1525 	cap_msg.caps.cap_bits.hot_add = 1;
1526 
1527 	/*
1528 	 * Specify our alignment requirements as it relates
1529 	 * memory hot-add. Specify 128MB alignment.
1530 	 */
1531 	cap_msg.caps.cap_bits.hot_add_alignment = 7;
1532 
1533 	/*
1534 	 * Currently the host does not use these
1535 	 * values and we set them to what is done in the
1536 	 * Windows driver.
1537 	 */
1538 	cap_msg.min_page_cnt = 0;
1539 	cap_msg.max_page_number = -1;
1540 
1541 	ret = vmbus_sendpacket(dev->channel, &cap_msg,
1542 				sizeof(struct dm_capabilities),
1543 				(unsigned long)NULL,
1544 				VM_PKT_DATA_INBAND, 0);
1545 	if (ret)
1546 		goto probe_error2;
1547 
1548 	t = wait_for_completion_timeout(&dm_device.host_event, 5*HZ);
1549 	if (t == 0) {
1550 		ret = -ETIMEDOUT;
1551 		goto probe_error2;
1552 	}
1553 
1554 	/*
1555 	 * If the host does not like our capabilities,
1556 	 * fail the probe function.
1557 	 */
1558 	if (dm_device.state == DM_INIT_ERROR) {
1559 		ret = -ETIMEDOUT;
1560 		goto probe_error2;
1561 	}
1562 
1563 	dm_device.state = DM_INITIALIZED;
1564 
1565 	return 0;
1566 
1567 probe_error2:
1568 #ifdef CONFIG_MEMORY_HOTPLUG
1569 	restore_online_page_callback(&hv_online_page);
1570 #endif
1571 	kthread_stop(dm_device.thread);
1572 
1573 probe_error1:
1574 	vmbus_close(dev->channel);
1575 probe_error0:
1576 	kfree(send_buffer);
1577 	return ret;
1578 }
1579 
1580 static int balloon_remove(struct hv_device *dev)
1581 {
1582 	struct hv_dynmem_device *dm = hv_get_drvdata(dev);
1583 	struct list_head *cur, *tmp;
1584 	struct hv_hotadd_state *has;
1585 
1586 	if (dm->num_pages_ballooned != 0)
1587 		pr_warn("Ballooned pages: %d\n", dm->num_pages_ballooned);
1588 
1589 	cancel_work_sync(&dm->balloon_wrk.wrk);
1590 	cancel_work_sync(&dm->ha_wrk.wrk);
1591 
1592 	vmbus_close(dev->channel);
1593 	kthread_stop(dm->thread);
1594 	kfree(send_buffer);
1595 #ifdef CONFIG_MEMORY_HOTPLUG
1596 	restore_online_page_callback(&hv_online_page);
1597 	unregister_memory_notifier(&hv_memory_nb);
1598 #endif
1599 	list_for_each_safe(cur, tmp, &dm->ha_region_list) {
1600 		has = list_entry(cur, struct hv_hotadd_state, list);
1601 		list_del(&has->list);
1602 		kfree(has);
1603 	}
1604 
1605 	return 0;
1606 }
1607 
1608 static const struct hv_vmbus_device_id id_table[] = {
1609 	/* Dynamic Memory Class ID */
1610 	/* 525074DC-8985-46e2-8057-A307DC18A502 */
1611 	{ HV_DM_GUID, },
1612 	{ },
1613 };
1614 
1615 MODULE_DEVICE_TABLE(vmbus, id_table);
1616 
1617 static  struct hv_driver balloon_drv = {
1618 	.name = "hv_balloon",
1619 	.id_table = id_table,
1620 	.probe =  balloon_probe,
1621 	.remove =  balloon_remove,
1622 };
1623 
1624 static int __init init_balloon_drv(void)
1625 {
1626 
1627 	return vmbus_driver_register(&balloon_drv);
1628 }
1629 
1630 module_init(init_balloon_drv);
1631 
1632 MODULE_DESCRIPTION("Hyper-V Balloon");
1633 MODULE_LICENSE("GPL");
1634