1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Virtio balloon implementation, inspired by Dor Laor and Marcelo
4 * Tosatti's implementations.
6 * Copyright 2008 Rusty Russell IBM Corporation
9 #include <linux/virtio.h>
10 #include <linux/virtio_balloon.h>
11 #include <linux/swap.h>
12 #include <linux/workqueue.h>
13 #include <linux/delay.h>
14 #include <linux/slab.h>
15 #include <linux/module.h>
16 #include <linux/balloon_compaction.h>
17 #include <linux/oom.h>
18 #include <linux/wait.h>
20 #include <linux/mount.h>
21 #include <linux/magic.h>
22 #include <linux/pseudo_fs.h>
23 #include <linux/page_reporting.h>
26 * Balloon device works in 4K page units. So each page is pointed to by
27 * multiple balloon pages. All memory counters in this driver are in balloon
30 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
31 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
32 /* Maximum number of (4k) pages to deflate on OOM notifications. */
33 #define VIRTIO_BALLOON_OOM_NR_PAGES 256
34 #define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80
36 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
38 /* The order of free page blocks to report to host */
39 #define VIRTIO_BALLOON_HINT_BLOCK_ORDER (MAX_ORDER - 1)
40 /* The size of a free page block in bytes */
41 #define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
42 (1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
43 #define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
45 #ifdef CONFIG_BALLOON_COMPACTION
46 static struct vfsmount
*balloon_mnt
;
49 enum virtio_balloon_vq
{
50 VIRTIO_BALLOON_VQ_INFLATE
,
51 VIRTIO_BALLOON_VQ_DEFLATE
,
52 VIRTIO_BALLOON_VQ_STATS
,
53 VIRTIO_BALLOON_VQ_FREE_PAGE
,
54 VIRTIO_BALLOON_VQ_REPORTING
,
58 enum virtio_balloon_config_read
{
59 VIRTIO_BALLOON_CONFIG_READ_CMD_ID
= 0,
62 struct virtio_balloon
{
63 struct virtio_device
*vdev
;
64 struct virtqueue
*inflate_vq
, *deflate_vq
, *stats_vq
, *free_page_vq
;
66 /* Balloon's own wq for cpu-intensive work items */
67 struct workqueue_struct
*balloon_wq
;
68 /* The free page reporting work item submitted to the balloon wq */
69 struct work_struct report_free_page_work
;
71 /* The balloon servicing is delegated to a freezable workqueue. */
72 struct work_struct update_balloon_stats_work
;
73 struct work_struct update_balloon_size_work
;
75 /* Prevent updating balloon when it is being canceled. */
76 spinlock_t stop_update_lock
;
78 /* Bitmap to indicate if reading the related config fields are needed */
79 unsigned long config_read_bitmap
;
81 /* The list of allocated free pages, waiting to be given back to mm */
82 struct list_head free_page_list
;
83 spinlock_t free_page_list_lock
;
84 /* The number of free page blocks on the above list */
85 unsigned long num_free_page_blocks
;
87 * The cmd id received from host.
88 * Read it via virtio_balloon_cmd_id_received to get the latest value
91 u32 cmd_id_received_cache
;
92 /* The cmd id that is actively in use */
93 __virtio32 cmd_id_active
;
94 /* Buffer to store the stop sign */
95 __virtio32 cmd_id_stop
;
97 /* Waiting for host to ack the pages we released. */
98 wait_queue_head_t acked
;
100 /* Number of balloon pages we've told the Host we're not using. */
101 unsigned int num_pages
;
103 * The pages we've told the Host we're not using are enqueued
104 * at vb_dev_info->pages list.
105 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
106 * to num_pages above.
108 struct balloon_dev_info vb_dev_info
;
110 /* Synchronize access/update to this struct virtio_balloon elements */
111 struct mutex balloon_lock
;
113 /* The array of pfns we tell the Host about. */
114 unsigned int num_pfns
;
115 __virtio32 pfns
[VIRTIO_BALLOON_ARRAY_PFNS_MAX
];
117 /* Memory statistics */
118 struct virtio_balloon_stat stats
[VIRTIO_BALLOON_S_NR
];
120 /* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */
121 struct shrinker shrinker
;
123 /* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */
124 struct notifier_block oom_nb
;
126 /* Free page reporting device */
127 struct virtqueue
*reporting_vq
;
128 struct page_reporting_dev_info pr_dev_info
;
131 static const struct virtio_device_id id_table
[] = {
132 { VIRTIO_ID_BALLOON
, VIRTIO_DEV_ANY_ID
},
136 static u32
page_to_balloon_pfn(struct page
*page
)
138 unsigned long pfn
= page_to_pfn(page
);
140 BUILD_BUG_ON(PAGE_SHIFT
< VIRTIO_BALLOON_PFN_SHIFT
);
141 /* Convert pfn from Linux page size to balloon page size. */
142 return pfn
* VIRTIO_BALLOON_PAGES_PER_PAGE
;
145 static void balloon_ack(struct virtqueue
*vq
)
147 struct virtio_balloon
*vb
= vq
->vdev
->priv
;
152 static void tell_host(struct virtio_balloon
*vb
, struct virtqueue
*vq
)
154 struct scatterlist sg
;
157 sg_init_one(&sg
, vb
->pfns
, sizeof(vb
->pfns
[0]) * vb
->num_pfns
);
159 /* We should always be able to add one buffer to an empty queue. */
160 virtqueue_add_outbuf(vq
, &sg
, 1, vb
, GFP_KERNEL
);
163 /* When host has read buffer, this completes via balloon_ack */
164 wait_event(vb
->acked
, virtqueue_get_buf(vq
, &len
));
168 static int virtballoon_free_page_report(struct page_reporting_dev_info
*pr_dev_info
,
169 struct scatterlist
*sg
, unsigned int nents
)
171 struct virtio_balloon
*vb
=
172 container_of(pr_dev_info
, struct virtio_balloon
, pr_dev_info
);
173 struct virtqueue
*vq
= vb
->reporting_vq
;
174 unsigned int unused
, err
;
176 /* We should always be able to add these buffers to an empty queue. */
177 err
= virtqueue_add_inbuf(vq
, sg
, nents
, vb
, GFP_NOWAIT
| __GFP_NOWARN
);
180 * In the extremely unlikely case that something has occurred and we
181 * are able to trigger an error we will simply display a warning
182 * and exit without actually processing the pages.
184 if (WARN_ON_ONCE(err
))
189 /* When host has read buffer, this completes via balloon_ack */
190 wait_event(vb
->acked
, virtqueue_get_buf(vq
, &unused
));
195 static void set_page_pfns(struct virtio_balloon
*vb
,
196 __virtio32 pfns
[], struct page
*page
)
200 BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE
> VIRTIO_BALLOON_ARRAY_PFNS_MAX
);
203 * Set balloon pfns pointing at this page.
204 * Note that the first pfn points at start of the page.
206 for (i
= 0; i
< VIRTIO_BALLOON_PAGES_PER_PAGE
; i
++)
207 pfns
[i
] = cpu_to_virtio32(vb
->vdev
,
208 page_to_balloon_pfn(page
) + i
);
211 static unsigned fill_balloon(struct virtio_balloon
*vb
, size_t num
)
213 unsigned num_allocated_pages
;
218 /* We can only do one array worth at a time. */
219 num
= min(num
, ARRAY_SIZE(vb
->pfns
));
221 for (num_pfns
= 0; num_pfns
< num
;
222 num_pfns
+= VIRTIO_BALLOON_PAGES_PER_PAGE
) {
223 struct page
*page
= balloon_page_alloc();
226 dev_info_ratelimited(&vb
->vdev
->dev
,
227 "Out of puff! Can't get %u pages\n",
228 VIRTIO_BALLOON_PAGES_PER_PAGE
);
229 /* Sleep for at least 1/5 of a second before retry. */
234 balloon_page_push(&pages
, page
);
237 mutex_lock(&vb
->balloon_lock
);
241 while ((page
= balloon_page_pop(&pages
))) {
242 balloon_page_enqueue(&vb
->vb_dev_info
, page
);
244 set_page_pfns(vb
, vb
->pfns
+ vb
->num_pfns
, page
);
245 vb
->num_pages
+= VIRTIO_BALLOON_PAGES_PER_PAGE
;
246 if (!virtio_has_feature(vb
->vdev
,
247 VIRTIO_BALLOON_F_DEFLATE_ON_OOM
))
248 adjust_managed_page_count(page
, -1);
249 vb
->num_pfns
+= VIRTIO_BALLOON_PAGES_PER_PAGE
;
252 num_allocated_pages
= vb
->num_pfns
;
253 /* Did we get any? */
254 if (vb
->num_pfns
!= 0)
255 tell_host(vb
, vb
->inflate_vq
);
256 mutex_unlock(&vb
->balloon_lock
);
258 return num_allocated_pages
;
261 static void release_pages_balloon(struct virtio_balloon
*vb
,
262 struct list_head
*pages
)
264 struct page
*page
, *next
;
266 list_for_each_entry_safe(page
, next
, pages
, lru
) {
267 if (!virtio_has_feature(vb
->vdev
,
268 VIRTIO_BALLOON_F_DEFLATE_ON_OOM
))
269 adjust_managed_page_count(page
, 1);
270 list_del(&page
->lru
);
271 put_page(page
); /* balloon reference */
275 static unsigned leak_balloon(struct virtio_balloon
*vb
, size_t num
)
277 unsigned num_freed_pages
;
279 struct balloon_dev_info
*vb_dev_info
= &vb
->vb_dev_info
;
282 /* We can only do one array worth at a time. */
283 num
= min(num
, ARRAY_SIZE(vb
->pfns
));
285 mutex_lock(&vb
->balloon_lock
);
286 /* We can't release more pages than taken */
287 num
= min(num
, (size_t)vb
->num_pages
);
288 for (vb
->num_pfns
= 0; vb
->num_pfns
< num
;
289 vb
->num_pfns
+= VIRTIO_BALLOON_PAGES_PER_PAGE
) {
290 page
= balloon_page_dequeue(vb_dev_info
);
293 set_page_pfns(vb
, vb
->pfns
+ vb
->num_pfns
, page
);
294 list_add(&page
->lru
, &pages
);
295 vb
->num_pages
-= VIRTIO_BALLOON_PAGES_PER_PAGE
;
298 num_freed_pages
= vb
->num_pfns
;
301 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
302 * is true, we *have* to do it in this order
304 if (vb
->num_pfns
!= 0)
305 tell_host(vb
, vb
->deflate_vq
);
306 release_pages_balloon(vb
, &pages
);
307 mutex_unlock(&vb
->balloon_lock
);
308 return num_freed_pages
;
311 static inline void update_stat(struct virtio_balloon
*vb
, int idx
,
314 BUG_ON(idx
>= VIRTIO_BALLOON_S_NR
);
315 vb
->stats
[idx
].tag
= cpu_to_virtio16(vb
->vdev
, tag
);
316 vb
->stats
[idx
].val
= cpu_to_virtio64(vb
->vdev
, val
);
319 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
321 static unsigned int update_balloon_stats(struct virtio_balloon
*vb
)
323 unsigned long events
[NR_VM_EVENT_ITEMS
];
325 unsigned int idx
= 0;
327 unsigned long caches
;
329 all_vm_events(events
);
332 available
= si_mem_available();
333 caches
= global_node_page_state(NR_FILE_PAGES
);
335 #ifdef CONFIG_VM_EVENT_COUNTERS
336 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_SWAP_IN
,
337 pages_to_bytes(events
[PSWPIN
]));
338 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_SWAP_OUT
,
339 pages_to_bytes(events
[PSWPOUT
]));
340 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_MAJFLT
, events
[PGMAJFAULT
]);
341 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_MINFLT
, events
[PGFAULT
]);
342 #ifdef CONFIG_HUGETLB_PAGE
343 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_HTLB_PGALLOC
,
344 events
[HTLB_BUDDY_PGALLOC
]);
345 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_HTLB_PGFAIL
,
346 events
[HTLB_BUDDY_PGALLOC_FAIL
]);
349 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_MEMFREE
,
350 pages_to_bytes(i
.freeram
));
351 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_MEMTOT
,
352 pages_to_bytes(i
.totalram
));
353 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_AVAIL
,
354 pages_to_bytes(available
));
355 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_CACHES
,
356 pages_to_bytes(caches
));
362 * While most virtqueues communicate guest-initiated requests to the hypervisor,
363 * the stats queue operates in reverse. The driver initializes the virtqueue
364 * with a single buffer. From that point forward, all conversations consist of
365 * a hypervisor request (a call to this function) which directs us to refill
366 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
367 * we delegate the job to a freezable workqueue that will do the actual work via
368 * stats_handle_request().
370 static void stats_request(struct virtqueue
*vq
)
372 struct virtio_balloon
*vb
= vq
->vdev
->priv
;
374 spin_lock(&vb
->stop_update_lock
);
375 if (!vb
->stop_update
)
376 queue_work(system_freezable_wq
, &vb
->update_balloon_stats_work
);
377 spin_unlock(&vb
->stop_update_lock
);
380 static void stats_handle_request(struct virtio_balloon
*vb
)
382 struct virtqueue
*vq
;
383 struct scatterlist sg
;
384 unsigned int len
, num_stats
;
386 num_stats
= update_balloon_stats(vb
);
389 if (!virtqueue_get_buf(vq
, &len
))
391 sg_init_one(&sg
, vb
->stats
, sizeof(vb
->stats
[0]) * num_stats
);
392 virtqueue_add_outbuf(vq
, &sg
, 1, vb
, GFP_KERNEL
);
396 static inline s64
towards_target(struct virtio_balloon
*vb
)
401 /* Legacy balloon config space is LE, unlike all other devices. */
402 virtio_cread_le(vb
->vdev
, struct virtio_balloon_config
, num_pages
,
406 return target
- vb
->num_pages
;
409 /* Gives back @num_to_return blocks of free pages to mm. */
410 static unsigned long return_free_pages_to_mm(struct virtio_balloon
*vb
,
411 unsigned long num_to_return
)
414 unsigned long num_returned
;
416 spin_lock_irq(&vb
->free_page_list_lock
);
417 for (num_returned
= 0; num_returned
< num_to_return
; num_returned
++) {
418 page
= balloon_page_pop(&vb
->free_page_list
);
421 free_pages((unsigned long)page_address(page
),
422 VIRTIO_BALLOON_HINT_BLOCK_ORDER
);
424 vb
->num_free_page_blocks
-= num_returned
;
425 spin_unlock_irq(&vb
->free_page_list_lock
);
430 static void virtio_balloon_queue_free_page_work(struct virtio_balloon
*vb
)
432 if (!virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_FREE_PAGE_HINT
))
435 /* No need to queue the work if the bit was already set. */
436 if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID
,
437 &vb
->config_read_bitmap
))
440 queue_work(vb
->balloon_wq
, &vb
->report_free_page_work
);
443 static void virtballoon_changed(struct virtio_device
*vdev
)
445 struct virtio_balloon
*vb
= vdev
->priv
;
448 spin_lock_irqsave(&vb
->stop_update_lock
, flags
);
449 if (!vb
->stop_update
) {
450 queue_work(system_freezable_wq
,
451 &vb
->update_balloon_size_work
);
452 virtio_balloon_queue_free_page_work(vb
);
454 spin_unlock_irqrestore(&vb
->stop_update_lock
, flags
);
457 static void update_balloon_size(struct virtio_balloon
*vb
)
459 u32 actual
= vb
->num_pages
;
461 /* Legacy balloon config space is LE, unlike all other devices. */
462 virtio_cwrite_le(vb
->vdev
, struct virtio_balloon_config
, actual
,
466 static void update_balloon_stats_func(struct work_struct
*work
)
468 struct virtio_balloon
*vb
;
470 vb
= container_of(work
, struct virtio_balloon
,
471 update_balloon_stats_work
);
472 stats_handle_request(vb
);
475 static void update_balloon_size_func(struct work_struct
*work
)
477 struct virtio_balloon
*vb
;
480 vb
= container_of(work
, struct virtio_balloon
,
481 update_balloon_size_work
);
482 diff
= towards_target(vb
);
488 diff
-= fill_balloon(vb
, diff
);
490 diff
+= leak_balloon(vb
, -diff
);
491 update_balloon_size(vb
);
494 queue_work(system_freezable_wq
, work
);
497 static int init_vqs(struct virtio_balloon
*vb
)
499 struct virtqueue
*vqs
[VIRTIO_BALLOON_VQ_MAX
];
500 vq_callback_t
*callbacks
[VIRTIO_BALLOON_VQ_MAX
];
501 const char *names
[VIRTIO_BALLOON_VQ_MAX
];
505 * Inflateq and deflateq are used unconditionally. The names[]
506 * will be NULL if the related feature is not enabled, which will
507 * cause no allocation for the corresponding virtqueue in find_vqs.
509 callbacks
[VIRTIO_BALLOON_VQ_INFLATE
] = balloon_ack
;
510 names
[VIRTIO_BALLOON_VQ_INFLATE
] = "inflate";
511 callbacks
[VIRTIO_BALLOON_VQ_DEFLATE
] = balloon_ack
;
512 names
[VIRTIO_BALLOON_VQ_DEFLATE
] = "deflate";
513 callbacks
[VIRTIO_BALLOON_VQ_STATS
] = NULL
;
514 names
[VIRTIO_BALLOON_VQ_STATS
] = NULL
;
515 callbacks
[VIRTIO_BALLOON_VQ_FREE_PAGE
] = NULL
;
516 names
[VIRTIO_BALLOON_VQ_FREE_PAGE
] = NULL
;
517 names
[VIRTIO_BALLOON_VQ_REPORTING
] = NULL
;
519 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_STATS_VQ
)) {
520 names
[VIRTIO_BALLOON_VQ_STATS
] = "stats";
521 callbacks
[VIRTIO_BALLOON_VQ_STATS
] = stats_request
;
524 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_FREE_PAGE_HINT
)) {
525 names
[VIRTIO_BALLOON_VQ_FREE_PAGE
] = "free_page_vq";
526 callbacks
[VIRTIO_BALLOON_VQ_FREE_PAGE
] = NULL
;
529 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_REPORTING
)) {
530 names
[VIRTIO_BALLOON_VQ_REPORTING
] = "reporting_vq";
531 callbacks
[VIRTIO_BALLOON_VQ_REPORTING
] = balloon_ack
;
534 err
= vb
->vdev
->config
->find_vqs(vb
->vdev
, VIRTIO_BALLOON_VQ_MAX
,
535 vqs
, callbacks
, names
, NULL
, NULL
);
539 vb
->inflate_vq
= vqs
[VIRTIO_BALLOON_VQ_INFLATE
];
540 vb
->deflate_vq
= vqs
[VIRTIO_BALLOON_VQ_DEFLATE
];
541 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_STATS_VQ
)) {
542 struct scatterlist sg
;
543 unsigned int num_stats
;
544 vb
->stats_vq
= vqs
[VIRTIO_BALLOON_VQ_STATS
];
547 * Prime this virtqueue with one buffer so the hypervisor can
548 * use it to signal us later (it can't be broken yet!).
550 num_stats
= update_balloon_stats(vb
);
552 sg_init_one(&sg
, vb
->stats
, sizeof(vb
->stats
[0]) * num_stats
);
553 err
= virtqueue_add_outbuf(vb
->stats_vq
, &sg
, 1, vb
,
556 dev_warn(&vb
->vdev
->dev
, "%s: add stat_vq failed\n",
560 virtqueue_kick(vb
->stats_vq
);
563 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_FREE_PAGE_HINT
))
564 vb
->free_page_vq
= vqs
[VIRTIO_BALLOON_VQ_FREE_PAGE
];
566 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_REPORTING
))
567 vb
->reporting_vq
= vqs
[VIRTIO_BALLOON_VQ_REPORTING
];
572 static u32
virtio_balloon_cmd_id_received(struct virtio_balloon
*vb
)
574 if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID
,
575 &vb
->config_read_bitmap
)) {
576 /* Legacy balloon config space is LE, unlike all other devices. */
577 virtio_cread_le(vb
->vdev
, struct virtio_balloon_config
,
578 free_page_hint_cmd_id
,
579 &vb
->cmd_id_received_cache
);
582 return vb
->cmd_id_received_cache
;
585 static int send_cmd_id_start(struct virtio_balloon
*vb
)
587 struct scatterlist sg
;
588 struct virtqueue
*vq
= vb
->free_page_vq
;
591 /* Detach all the used buffers from the vq */
592 while (virtqueue_get_buf(vq
, &unused
))
595 vb
->cmd_id_active
= cpu_to_virtio32(vb
->vdev
,
596 virtio_balloon_cmd_id_received(vb
));
597 sg_init_one(&sg
, &vb
->cmd_id_active
, sizeof(vb
->cmd_id_active
));
598 err
= virtqueue_add_outbuf(vq
, &sg
, 1, &vb
->cmd_id_active
, GFP_KERNEL
);
604 static int send_cmd_id_stop(struct virtio_balloon
*vb
)
606 struct scatterlist sg
;
607 struct virtqueue
*vq
= vb
->free_page_vq
;
610 /* Detach all the used buffers from the vq */
611 while (virtqueue_get_buf(vq
, &unused
))
614 sg_init_one(&sg
, &vb
->cmd_id_stop
, sizeof(vb
->cmd_id_stop
));
615 err
= virtqueue_add_outbuf(vq
, &sg
, 1, &vb
->cmd_id_stop
, GFP_KERNEL
);
621 static int get_free_page_and_send(struct virtio_balloon
*vb
)
623 struct virtqueue
*vq
= vb
->free_page_vq
;
625 struct scatterlist sg
;
629 /* Detach all the used buffers from the vq */
630 while (virtqueue_get_buf(vq
, &unused
))
633 page
= alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG
,
634 VIRTIO_BALLOON_HINT_BLOCK_ORDER
);
636 * When the allocation returns NULL, it indicates that we have got all
637 * the possible free pages, so return -EINTR to stop.
642 p
= page_address(page
);
643 sg_init_one(&sg
, p
, VIRTIO_BALLOON_HINT_BLOCK_BYTES
);
644 /* There is always 1 entry reserved for the cmd id to use. */
645 if (vq
->num_free
> 1) {
646 err
= virtqueue_add_inbuf(vq
, &sg
, 1, p
, GFP_KERNEL
);
648 free_pages((unsigned long)p
,
649 VIRTIO_BALLOON_HINT_BLOCK_ORDER
);
653 spin_lock_irq(&vb
->free_page_list_lock
);
654 balloon_page_push(&vb
->free_page_list
, page
);
655 vb
->num_free_page_blocks
++;
656 spin_unlock_irq(&vb
->free_page_list_lock
);
659 * The vq has no available entry to add this page block, so
662 free_pages((unsigned long)p
, VIRTIO_BALLOON_HINT_BLOCK_ORDER
);
668 static int send_free_pages(struct virtio_balloon
*vb
)
675 * If a stop id or a new cmd id was just received from host,
676 * stop the reporting.
678 cmd_id_active
= virtio32_to_cpu(vb
->vdev
, vb
->cmd_id_active
);
679 if (unlikely(cmd_id_active
!=
680 virtio_balloon_cmd_id_received(vb
)))
684 * The free page blocks are allocated and sent to host one by
687 err
= get_free_page_and_send(vb
);
690 else if (unlikely(err
))
697 static void virtio_balloon_report_free_page(struct virtio_balloon
*vb
)
700 struct device
*dev
= &vb
->vdev
->dev
;
702 /* Start by sending the received cmd id to host with an outbuf. */
703 err
= send_cmd_id_start(vb
);
705 dev_err(dev
, "Failed to send a start id, err = %d\n", err
);
707 err
= send_free_pages(vb
);
709 dev_err(dev
, "Failed to send a free page, err = %d\n", err
);
711 /* End by sending a stop id to host with an outbuf. */
712 err
= send_cmd_id_stop(vb
);
714 dev_err(dev
, "Failed to send a stop id, err = %d\n", err
);
717 static void report_free_page_func(struct work_struct
*work
)
719 struct virtio_balloon
*vb
= container_of(work
, struct virtio_balloon
,
720 report_free_page_work
);
723 cmd_id_received
= virtio_balloon_cmd_id_received(vb
);
724 if (cmd_id_received
== VIRTIO_BALLOON_CMD_ID_DONE
) {
725 /* Pass ULONG_MAX to give back all the free pages */
726 return_free_pages_to_mm(vb
, ULONG_MAX
);
727 } else if (cmd_id_received
!= VIRTIO_BALLOON_CMD_ID_STOP
&&
729 virtio32_to_cpu(vb
->vdev
, vb
->cmd_id_active
)) {
730 virtio_balloon_report_free_page(vb
);
734 #ifdef CONFIG_BALLOON_COMPACTION
736 * virtballoon_migratepage - perform the balloon page migration on behalf of
737 * a compation thread. (called under page lock)
738 * @vb_dev_info: the balloon device
739 * @newpage: page that will replace the isolated page after migration finishes.
740 * @page : the isolated (old) page that is about to be migrated to newpage.
741 * @mode : compaction mode -- not used for balloon page migration.
743 * After a ballooned page gets isolated by compaction procedures, this is the
744 * function that performs the page migration on behalf of a compaction thread
745 * The page migration for virtio balloon is done in a simple swap fashion which
746 * follows these two macro steps:
747 * 1) insert newpage into vb->pages list and update the host about it;
748 * 2) update the host about the old page removed from vb->pages list;
750 * This function preforms the balloon page migration task.
751 * Called through balloon_mapping->a_ops->migratepage
753 static int virtballoon_migratepage(struct balloon_dev_info
*vb_dev_info
,
754 struct page
*newpage
, struct page
*page
, enum migrate_mode mode
)
756 struct virtio_balloon
*vb
= container_of(vb_dev_info
,
757 struct virtio_balloon
, vb_dev_info
);
761 * In order to avoid lock contention while migrating pages concurrently
762 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
763 * this turn, as it is easier to retry the page migration later.
764 * This also prevents fill_balloon() getting stuck into a mutex
765 * recursion in the case it ends up triggering memory compaction
766 * while it is attempting to inflate the ballon.
768 if (!mutex_trylock(&vb
->balloon_lock
))
771 get_page(newpage
); /* balloon reference */
774 * When we migrate a page to a different zone and adjusted the
775 * managed page count when inflating, we have to fixup the count of
776 * both involved zones.
778 if (!virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_DEFLATE_ON_OOM
) &&
779 page_zone(page
) != page_zone(newpage
)) {
780 adjust_managed_page_count(page
, 1);
781 adjust_managed_page_count(newpage
, -1);
784 /* balloon's page migration 1st step -- inflate "newpage" */
785 spin_lock_irqsave(&vb_dev_info
->pages_lock
, flags
);
786 balloon_page_insert(vb_dev_info
, newpage
);
787 vb_dev_info
->isolated_pages
--;
788 __count_vm_event(BALLOON_MIGRATE
);
789 spin_unlock_irqrestore(&vb_dev_info
->pages_lock
, flags
);
790 vb
->num_pfns
= VIRTIO_BALLOON_PAGES_PER_PAGE
;
791 set_page_pfns(vb
, vb
->pfns
, newpage
);
792 tell_host(vb
, vb
->inflate_vq
);
794 /* balloon's page migration 2nd step -- deflate "page" */
795 spin_lock_irqsave(&vb_dev_info
->pages_lock
, flags
);
796 balloon_page_delete(page
);
797 spin_unlock_irqrestore(&vb_dev_info
->pages_lock
, flags
);
798 vb
->num_pfns
= VIRTIO_BALLOON_PAGES_PER_PAGE
;
799 set_page_pfns(vb
, vb
->pfns
, page
);
800 tell_host(vb
, vb
->deflate_vq
);
802 mutex_unlock(&vb
->balloon_lock
);
804 put_page(page
); /* balloon reference */
806 return MIGRATEPAGE_SUCCESS
;
809 static int balloon_init_fs_context(struct fs_context
*fc
)
811 return init_pseudo(fc
, BALLOON_KVM_MAGIC
) ? 0 : -ENOMEM
;
814 static struct file_system_type balloon_fs
= {
815 .name
= "balloon-kvm",
816 .init_fs_context
= balloon_init_fs_context
,
817 .kill_sb
= kill_anon_super
,
820 #endif /* CONFIG_BALLOON_COMPACTION */
822 static unsigned long shrink_free_pages(struct virtio_balloon
*vb
,
823 unsigned long pages_to_free
)
825 unsigned long blocks_to_free
, blocks_freed
;
827 pages_to_free
= round_up(pages_to_free
,
828 VIRTIO_BALLOON_HINT_BLOCK_PAGES
);
829 blocks_to_free
= pages_to_free
/ VIRTIO_BALLOON_HINT_BLOCK_PAGES
;
830 blocks_freed
= return_free_pages_to_mm(vb
, blocks_to_free
);
832 return blocks_freed
* VIRTIO_BALLOON_HINT_BLOCK_PAGES
;
835 static unsigned long virtio_balloon_shrinker_scan(struct shrinker
*shrinker
,
836 struct shrink_control
*sc
)
838 struct virtio_balloon
*vb
= container_of(shrinker
,
839 struct virtio_balloon
, shrinker
);
841 return shrink_free_pages(vb
, sc
->nr_to_scan
);
844 static unsigned long virtio_balloon_shrinker_count(struct shrinker
*shrinker
,
845 struct shrink_control
*sc
)
847 struct virtio_balloon
*vb
= container_of(shrinker
,
848 struct virtio_balloon
, shrinker
);
850 return vb
->num_free_page_blocks
* VIRTIO_BALLOON_HINT_BLOCK_PAGES
;
853 static int virtio_balloon_oom_notify(struct notifier_block
*nb
,
854 unsigned long dummy
, void *parm
)
856 struct virtio_balloon
*vb
= container_of(nb
,
857 struct virtio_balloon
, oom_nb
);
858 unsigned long *freed
= parm
;
860 *freed
+= leak_balloon(vb
, VIRTIO_BALLOON_OOM_NR_PAGES
) /
861 VIRTIO_BALLOON_PAGES_PER_PAGE
;
862 update_balloon_size(vb
);
867 static void virtio_balloon_unregister_shrinker(struct virtio_balloon
*vb
)
869 unregister_shrinker(&vb
->shrinker
);
872 static int virtio_balloon_register_shrinker(struct virtio_balloon
*vb
)
874 vb
->shrinker
.scan_objects
= virtio_balloon_shrinker_scan
;
875 vb
->shrinker
.count_objects
= virtio_balloon_shrinker_count
;
876 vb
->shrinker
.seeks
= DEFAULT_SEEKS
;
878 return register_shrinker(&vb
->shrinker
);
881 static int virtballoon_probe(struct virtio_device
*vdev
)
883 struct virtio_balloon
*vb
;
886 if (!vdev
->config
->get
) {
887 dev_err(&vdev
->dev
, "%s failure: config access disabled\n",
892 vdev
->priv
= vb
= kzalloc(sizeof(*vb
), GFP_KERNEL
);
898 INIT_WORK(&vb
->update_balloon_stats_work
, update_balloon_stats_func
);
899 INIT_WORK(&vb
->update_balloon_size_work
, update_balloon_size_func
);
900 spin_lock_init(&vb
->stop_update_lock
);
901 mutex_init(&vb
->balloon_lock
);
902 init_waitqueue_head(&vb
->acked
);
905 balloon_devinfo_init(&vb
->vb_dev_info
);
911 #ifdef CONFIG_BALLOON_COMPACTION
912 balloon_mnt
= kern_mount(&balloon_fs
);
913 if (IS_ERR(balloon_mnt
)) {
914 err
= PTR_ERR(balloon_mnt
);
918 vb
->vb_dev_info
.migratepage
= virtballoon_migratepage
;
919 vb
->vb_dev_info
.inode
= alloc_anon_inode(balloon_mnt
->mnt_sb
);
920 if (IS_ERR(vb
->vb_dev_info
.inode
)) {
921 err
= PTR_ERR(vb
->vb_dev_info
.inode
);
922 goto out_kern_unmount
;
924 vb
->vb_dev_info
.inode
->i_mapping
->a_ops
= &balloon_aops
;
926 if (virtio_has_feature(vdev
, VIRTIO_BALLOON_F_FREE_PAGE_HINT
)) {
928 * There is always one entry reserved for cmd id, so the ring
929 * size needs to be at least two to report free page hints.
931 if (virtqueue_get_vring_size(vb
->free_page_vq
) < 2) {
935 vb
->balloon_wq
= alloc_workqueue("balloon-wq",
936 WQ_FREEZABLE
| WQ_CPU_INTENSIVE
, 0);
937 if (!vb
->balloon_wq
) {
941 INIT_WORK(&vb
->report_free_page_work
, report_free_page_func
);
942 vb
->cmd_id_received_cache
= VIRTIO_BALLOON_CMD_ID_STOP
;
943 vb
->cmd_id_active
= cpu_to_virtio32(vb
->vdev
,
944 VIRTIO_BALLOON_CMD_ID_STOP
);
945 vb
->cmd_id_stop
= cpu_to_virtio32(vb
->vdev
,
946 VIRTIO_BALLOON_CMD_ID_STOP
);
947 spin_lock_init(&vb
->free_page_list_lock
);
948 INIT_LIST_HEAD(&vb
->free_page_list
);
950 * We're allowed to reuse any free pages, even if they are
951 * still to be processed by the host.
953 err
= virtio_balloon_register_shrinker(vb
);
955 goto out_del_balloon_wq
;
958 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_DEFLATE_ON_OOM
)) {
959 vb
->oom_nb
.notifier_call
= virtio_balloon_oom_notify
;
960 vb
->oom_nb
.priority
= VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY
;
961 err
= register_oom_notifier(&vb
->oom_nb
);
963 goto out_unregister_shrinker
;
966 if (virtio_has_feature(vdev
, VIRTIO_BALLOON_F_PAGE_POISON
)) {
967 /* Start with poison val of 0 representing general init */
968 __u32 poison_val
= 0;
971 * Let the hypervisor know that we are expecting a
972 * specific value to be written back in balloon pages.
974 * If the PAGE_POISON value was larger than a byte we would
975 * need to byte swap poison_val here to guarantee it is
976 * little-endian. However for now it is a single byte so we
979 if (!want_init_on_free())
980 memset(&poison_val
, PAGE_POISON
, sizeof(poison_val
));
982 virtio_cwrite_le(vb
->vdev
, struct virtio_balloon_config
,
983 poison_val
, &poison_val
);
986 vb
->pr_dev_info
.report
= virtballoon_free_page_report
;
987 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_REPORTING
)) {
988 unsigned int capacity
;
990 capacity
= virtqueue_get_vring_size(vb
->reporting_vq
);
991 if (capacity
< PAGE_REPORTING_CAPACITY
) {
993 goto out_unregister_oom
;
996 err
= page_reporting_register(&vb
->pr_dev_info
);
998 goto out_unregister_oom
;
1001 virtio_device_ready(vdev
);
1003 if (towards_target(vb
))
1004 virtballoon_changed(vdev
);
1008 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_DEFLATE_ON_OOM
))
1009 unregister_oom_notifier(&vb
->oom_nb
);
1010 out_unregister_shrinker
:
1011 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_FREE_PAGE_HINT
))
1012 virtio_balloon_unregister_shrinker(vb
);
1014 if (virtio_has_feature(vdev
, VIRTIO_BALLOON_F_FREE_PAGE_HINT
))
1015 destroy_workqueue(vb
->balloon_wq
);
1017 #ifdef CONFIG_BALLOON_COMPACTION
1018 iput(vb
->vb_dev_info
.inode
);
1020 kern_unmount(balloon_mnt
);
1023 vdev
->config
->del_vqs(vdev
);
1030 static void remove_common(struct virtio_balloon
*vb
)
1032 /* There might be pages left in the balloon: free them. */
1033 while (vb
->num_pages
)
1034 leak_balloon(vb
, vb
->num_pages
);
1035 update_balloon_size(vb
);
1037 /* There might be free pages that are being reported: release them. */
1038 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_FREE_PAGE_HINT
))
1039 return_free_pages_to_mm(vb
, ULONG_MAX
);
1041 /* Now we reset the device so we can clean up the queues. */
1042 vb
->vdev
->config
->reset(vb
->vdev
);
1044 vb
->vdev
->config
->del_vqs(vb
->vdev
);
1047 static void virtballoon_remove(struct virtio_device
*vdev
)
1049 struct virtio_balloon
*vb
= vdev
->priv
;
1051 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_REPORTING
))
1052 page_reporting_unregister(&vb
->pr_dev_info
);
1053 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_DEFLATE_ON_OOM
))
1054 unregister_oom_notifier(&vb
->oom_nb
);
1055 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_FREE_PAGE_HINT
))
1056 virtio_balloon_unregister_shrinker(vb
);
1057 spin_lock_irq(&vb
->stop_update_lock
);
1058 vb
->stop_update
= true;
1059 spin_unlock_irq(&vb
->stop_update_lock
);
1060 cancel_work_sync(&vb
->update_balloon_size_work
);
1061 cancel_work_sync(&vb
->update_balloon_stats_work
);
1063 if (virtio_has_feature(vdev
, VIRTIO_BALLOON_F_FREE_PAGE_HINT
)) {
1064 cancel_work_sync(&vb
->report_free_page_work
);
1065 destroy_workqueue(vb
->balloon_wq
);
1069 #ifdef CONFIG_BALLOON_COMPACTION
1070 if (vb
->vb_dev_info
.inode
)
1071 iput(vb
->vb_dev_info
.inode
);
1073 kern_unmount(balloon_mnt
);
1078 #ifdef CONFIG_PM_SLEEP
1079 static int virtballoon_freeze(struct virtio_device
*vdev
)
1081 struct virtio_balloon
*vb
= vdev
->priv
;
1084 * The workqueue is already frozen by the PM core before this
1085 * function is called.
1091 static int virtballoon_restore(struct virtio_device
*vdev
)
1093 struct virtio_balloon
*vb
= vdev
->priv
;
1096 ret
= init_vqs(vdev
->priv
);
1100 virtio_device_ready(vdev
);
1102 if (towards_target(vb
))
1103 virtballoon_changed(vdev
);
1104 update_balloon_size(vb
);
1109 static int virtballoon_validate(struct virtio_device
*vdev
)
1112 * Inform the hypervisor that our pages are poisoned or
1113 * initialized. If we cannot do that then we should disable
1114 * page reporting as it could potentially change the contents
1115 * of our free pages.
1117 if (!want_init_on_free() && !page_poisoning_enabled_static())
1118 __virtio_clear_bit(vdev
, VIRTIO_BALLOON_F_PAGE_POISON
);
1119 else if (!virtio_has_feature(vdev
, VIRTIO_BALLOON_F_PAGE_POISON
))
1120 __virtio_clear_bit(vdev
, VIRTIO_BALLOON_F_REPORTING
);
1122 __virtio_clear_bit(vdev
, VIRTIO_F_ACCESS_PLATFORM
);
1126 static unsigned int features
[] = {
1127 VIRTIO_BALLOON_F_MUST_TELL_HOST
,
1128 VIRTIO_BALLOON_F_STATS_VQ
,
1129 VIRTIO_BALLOON_F_DEFLATE_ON_OOM
,
1130 VIRTIO_BALLOON_F_FREE_PAGE_HINT
,
1131 VIRTIO_BALLOON_F_PAGE_POISON
,
1132 VIRTIO_BALLOON_F_REPORTING
,
1135 static struct virtio_driver virtio_balloon_driver
= {
1136 .feature_table
= features
,
1137 .feature_table_size
= ARRAY_SIZE(features
),
1138 .driver
.name
= KBUILD_MODNAME
,
1139 .driver
.owner
= THIS_MODULE
,
1140 .id_table
= id_table
,
1141 .validate
= virtballoon_validate
,
1142 .probe
= virtballoon_probe
,
1143 .remove
= virtballoon_remove
,
1144 .config_changed
= virtballoon_changed
,
1145 #ifdef CONFIG_PM_SLEEP
1146 .freeze
= virtballoon_freeze
,
1147 .restore
= virtballoon_restore
,
1151 module_virtio_driver(virtio_balloon_driver
);
1152 MODULE_DEVICE_TABLE(virtio
, id_table
);
1153 MODULE_DESCRIPTION("Virtio balloon driver");
1154 MODULE_LICENSE("GPL");