1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * This header is BSD licensed so anyone can use the definitions to implement
5 * compatible drivers/servers.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of IBM nor the names of its contributors
16 *    may be used to endorse or promote products derived from this software
17 *    without specific prior written permission.
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
20 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
21 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31#ifndef _VIRTIO_BALLOON_H
32#define _VIRTIO_BALLOON_H
33
34/* Feature bits. */
35#define VIRTIO_BALLOON_F_MUST_TELL_HOST	0x1 /* Tell before reclaiming pages */
36#define VIRTIO_BALLOON_F_STATS_VQ	0x2 /* Memory stats virtqueue */
37#define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	0x4 /* Deflate balloon on OOM */
38
39/* Size of a PFN in the balloon interface. */
40#define VIRTIO_BALLOON_PFN_SHIFT 12
41
42struct virtio_balloon_config {
43	/* Number of pages host wants Guest to give up. */
44	uint32_t num_pages;
45
46	/* Number of pages we've actually got in balloon. */
47	uint32_t actual;
48};
49
50#define VIRTIO_BALLOON_S_SWAP_IN  0   /* Amount of memory swapped in */
51#define VIRTIO_BALLOON_S_SWAP_OUT 1   /* Amount of memory swapped out */
52#define VIRTIO_BALLOON_S_MAJFLT   2   /* Number of major faults */
53#define VIRTIO_BALLOON_S_MINFLT   3   /* Number of minor faults */
54#define VIRTIO_BALLOON_S_MEMFREE  4   /* Total amount of free memory */
55#define VIRTIO_BALLOON_S_MEMTOT   5   /* Total amount of memory */
56#define VIRTIO_BALLOON_S_AVAIL    6   /* Available memory as in /proc */
57#define VIRTIO_BALLOON_S_CACHES   7   /* Disk caches */
58#define VIRTIO_BALLOON_S_NR       8
59
60/*
61 * Memory statistics structure.
62 * Driver fills an array of these structures and passes to device.
63 *
64 * NOTE: fields are laid out in a way that would make compiler add padding
65 * between and after fields, so we have to use compiler-specific attributes to
66 * pack it, to disable this padding. This also often causes compiler to
67 * generate suboptimal code.
68 *
69 * We maintain this statistics structure format for backwards compatibility,
70 * but don't follow this example.
71 *
72 * If implementing a similar structure, do something like the below instead:
73 *     struct virtio_balloon_stat {
74 *         __virtio16 tag;
75 *         __u8 reserved[6];
76 *         __virtio64 val;
77 *     };
78 *
79 * In other words, add explicit reserved fields to align field and
80 * structure boundaries at field size, avoiding compiler padding
81 * without the packed attribute.
82 */
83struct virtio_balloon_stat {
84	uint16_t tag;
85	uint64_t val;
86} __packed;
87
88#endif /* _VIRTIO_BALLOON_H */
89