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 * $FreeBSD$
31 */
32
33#ifndef _VIRTIO_BALLOON_H
34#define _VIRTIO_BALLOON_H
35
36/* Feature bits. */
37#define VIRTIO_BALLOON_F_MUST_TELL_HOST	0x1 /* Tell before reclaiming pages */
38#define VIRTIO_BALLOON_F_STATS_VQ	0x2 /* Memory stats virtqueue */
39#define VIRTIO_BALLOON_F_DEFLATE_ON_OOM	0x4 /* Deflate balloon on OOM */
40
41/* Size of a PFN in the balloon interface. */
42#define VIRTIO_BALLOON_PFN_SHIFT 12
43
44struct virtio_balloon_config {
45	/* Number of pages host wants Guest to give up. */
46	uint32_t num_pages;
47
48	/* Number of pages we've actually got in balloon. */
49	uint32_t actual;
50};
51
52#define VIRTIO_BALLOON_S_SWAP_IN  0   /* Amount of memory swapped in */
53#define VIRTIO_BALLOON_S_SWAP_OUT 1   /* Amount of memory swapped out */
54#define VIRTIO_BALLOON_S_MAJFLT   2   /* Number of major faults */
55#define VIRTIO_BALLOON_S_MINFLT   3   /* Number of minor faults */
56#define VIRTIO_BALLOON_S_MEMFREE  4   /* Total amount of free memory */
57#define VIRTIO_BALLOON_S_MEMTOT   5   /* Total amount of memory */
58#define VIRTIO_BALLOON_S_AVAIL    6   /* Available memory as in /proc */
59#define VIRTIO_BALLOON_S_CACHES   7   /* Disk caches */
60#define VIRTIO_BALLOON_S_NR       8
61
62/*
63 * Memory statistics structure.
64 * Driver fills an array of these structures and passes to device.
65 *
66 * NOTE: fields are laid out in a way that would make compiler add padding
67 * between and after fields, so we have to use compiler-specific attributes to
68 * pack it, to disable this padding. This also often causes compiler to
69 * generate suboptimal code.
70 *
71 * We maintain this statistics structure format for backwards compatibility,
72 * but don't follow this example.
73 *
74 * If implementing a similar structure, do something like the below instead:
75 *     struct virtio_balloon_stat {
76 *         __virtio16 tag;
77 *         __u8 reserved[6];
78 *         __virtio64 val;
79 *     };
80 *
81 * In other words, add explicit reserved fields to align field and
82 * structure boundaries at field size, avoiding compiler padding
83 * without the packed attribute.
84 */
85struct virtio_balloon_stat {
86	uint16_t tag;
87	uint64_t val;
88} __packed;
89
90#endif /* _VIRTIO_BALLOON_H */
91