1 /*-
2 * Copyright Rusty Russell IBM Corporation 2007.
3 * Copyright 2019,2022 NXP
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_RING_H
34 #define VIRTIO_RING_H
35
36 /* This marks a buffer as continuing via the next field. */
37 #define VRING_DESC_F_NEXT 1U
38 /* This marks a buffer as write-only (otherwise read-only). */
39 #define VRING_DESC_F_WRITE 2U
40 /* This means the buffer contains a list of buffer descriptors. */
41 #define VRING_DESC_F_INDIRECT 4U
42
43 /* The Host uses this in used->flags to advise the Guest: don't kick me
44 * when you add a buffer. It's unreliable, so it's simply an
45 * optimization. Guest will still kick if it's out of buffers. */
46 #define VRING_USED_F_NO_NOTIFY 1U
47 /* The Guest uses this in avail->flags to advise the Host: don't
48 * interrupt me when you consume a buffer. It's unreliable, so it's
49 * simply an optimization. */
50 #define VRING_AVAIL_F_NO_INTERRUPT 1U
51
52 /* VirtIO ring descriptors: 16 bytes.
53 * These can chain together via "next". */
54 struct vring_desc
55 {
56 /* Address (guest-physical). */
57 uint64_t addr;
58 /* Length. */
59 uint32_t len;
60 /* The flags as indicated above. */
61 uint16_t flags;
62 /* We chain unused descriptors via this, too. */
63 uint16_t next;
64 };
65
66 struct vring_avail
67 {
68 uint16_t flags;
69 uint16_t idx;
70 uint16_t ring[1];
71 };
72
73 /* uint32_t is used here for ids for padding reasons. */
74 struct vring_used_elem
75 {
76 /* Index of start of used descriptor chain. */
77 uint32_t id;
78 /* Total length of the descriptor chain which was written to. */
79 uint32_t len;
80 };
81
82 struct vring_used
83 {
84 uint16_t flags;
85 uint16_t idx;
86 struct vring_used_elem ring[1];
87 };
88
89 struct vring
90 {
91 uint32_t num;
92
93 struct vring_desc *desc;
94 struct vring_avail *avail;
95 struct vring_used *used;
96 };
97
98 /* The standard layout for the ring is a continuous chunk of memory which
99 * looks like this. We assume num is a power of 2.
100 *
101 * struct vring {
102 * # The actual descriptors (16 bytes each)
103 * struct vring_desc desc[num];
104 *
105 * # A ring of available descriptor heads with free-running index.
106 * __u16 avail_flags;
107 * __u16 avail_idx;
108 * __u16 available[num];
109 * __u16 used_event_idx;
110 *
111 * # Padding to the next align boundary.
112 * char pad[];
113 *
114 * # A ring of used descriptor heads with free-running index.
115 * __u16 used_flags;
116 * __u16 used_idx;
117 * struct vring_used_elem used[num];
118 * __u16 avail_event_idx;
119 * };
120 *
121 * NOTE: for VirtIO PCI, align is 4096.
122 */
123
124 /*
125 * We publish the used event index at the end of the available ring, and vice
126 * versa. They are at the end for backwards compatibility.
127 */
128 #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
129 #define vring_avail_event(vr) ((vr)->used->ring[(vr)->num].id)
130
vring_size(uint32_t num,uint32_t align)131 static inline int32_t vring_size(uint32_t num, uint32_t align)
132 {
133 uint32_t size;
134
135 size = num * sizeof(struct vring_desc);
136 size += sizeof(struct vring_avail) + (num * sizeof(uint16_t)) + sizeof(uint16_t);
137 size = (size + align - 1UL) & ~(align - 1UL);
138 size += sizeof(struct vring_used) + (num * sizeof(struct vring_used_elem)) + sizeof(uint16_t);
139 return ((int32_t)size);
140 }
141
vring_init(struct vring * vr,uint32_t num,uint8_t * p,uint32_t align)142 static inline void vring_init(struct vring *vr, uint32_t num, uint8_t *p, uint32_t align)
143 {
144 vr->num = num;
145 vr->desc = (struct vring_desc *)(void *)p;
146 vr->avail = (struct vring_avail *)(void *)(p + num * sizeof(struct vring_desc));
147 vr->used = (struct vring_used *)(((uintptr_t)&vr->avail->ring[num] + align - 1UL) & ~(align - 1UL));
148 }
149
150 /*
151 * The following is used with VIRTIO_RING_F_EVENT_IDX.
152 *
153 * Assuming a given event_idx value from the other size, if we have
154 * just incremented index from old to new_idx, should we trigger an
155 * event?
156 */
vring_need_event(uint16_t event_idx,uint16_t new_idx,uint16_t old)157 static inline int32_t vring_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old)
158 {
159 /* coco begin validated: This function does not need to be tested because it is not used in rpmsg_lite
160 * implementation (only called from unused part of vq_ring_must_notify_host() ). */
161 if ((uint16_t)(new_idx - event_idx - 1U) < (uint16_t)(new_idx - old))
162 {
163 return 1;
164 }
165 else
166 {
167 return 0;
168 }
169 }
170 /* coco end */
171 #endif /* VIRTIO_RING_H */
172
