1 | #ifndef _LINUX_VIRTIO_RING_H |
2 | #define _LINUX_VIRTIO_RING_H |
3 | /* An interface for efficient virtio implementation, currently for use by KVM, |
4 | * but hopefully others soon. Do NOT change this since it will |
5 | * break existing servers and clients. |
6 | * |
7 | * This header is BSD licensed so anyone can use the definitions to implement |
8 | * compatible drivers/servers. |
9 | * |
10 | * Redistribution and use in source and binary forms, with or without |
11 | * modification, are permitted provided that the following conditions |
12 | * are met: |
13 | * 1. Redistributions of source code must retain the above copyright |
14 | * notice, this list of conditions and the following disclaimer. |
15 | * 2. Redistributions in binary form must reproduce the above copyright |
16 | * notice, this list of conditions and the following disclaimer in the |
17 | * documentation and/or other materials provided with the distribution. |
18 | * 3. Neither the name of IBM nor the names of its contributors |
19 | * may be used to endorse or promote products derived from this software |
20 | * without specific prior written permission. |
21 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND |
22 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
24 | * ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE |
25 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
26 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
27 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
28 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
29 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
30 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
31 | * SUCH DAMAGE. |
32 | * |
33 | * Copyright Rusty Russell IBM Corporation 2007. */ |
34 | #include <stdint.h> |
35 | #include "standard-headers/linux/types.h" |
36 | #include "standard-headers/linux/virtio_types.h" |
37 | |
38 | /* This marks a buffer as continuing via the next field. */ |
39 | #define VRING_DESC_F_NEXT 1 |
40 | /* This marks a buffer as write-only (otherwise read-only). */ |
41 | #define VRING_DESC_F_WRITE 2 |
42 | /* This means the buffer contains a list of buffer descriptors. */ |
43 | #define VRING_DESC_F_INDIRECT 4 |
44 | |
45 | /* |
46 | * Mark a descriptor as available or used in packed ring. |
47 | * Notice: they are defined as shifts instead of shifted values. |
48 | */ |
49 | #define VRING_PACKED_DESC_F_AVAIL 7 |
50 | #define VRING_PACKED_DESC_F_USED 15 |
51 | |
52 | /* The Host uses this in used->flags to advise the Guest: don't kick me when |
53 | * you add a buffer. It's unreliable, so it's simply an optimization. Guest |
54 | * will still kick if it's out of buffers. */ |
55 | #define VRING_USED_F_NO_NOTIFY 1 |
56 | /* The Guest uses this in avail->flags to advise the Host: don't interrupt me |
57 | * when you consume a buffer. It's unreliable, so it's simply an |
58 | * optimization. */ |
59 | #define VRING_AVAIL_F_NO_INTERRUPT 1 |
60 | |
61 | /* Enable events in packed ring. */ |
62 | #define VRING_PACKED_EVENT_FLAG_ENABLE 0x0 |
63 | /* Disable events in packed ring. */ |
64 | #define VRING_PACKED_EVENT_FLAG_DISABLE 0x1 |
65 | /* |
66 | * Enable events for a specific descriptor in packed ring. |
67 | * (as specified by Descriptor Ring Change Event Offset/Wrap Counter). |
68 | * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated. |
69 | */ |
70 | #define VRING_PACKED_EVENT_FLAG_DESC 0x2 |
71 | |
72 | /* |
73 | * Wrap counter bit shift in event suppression structure |
74 | * of packed ring. |
75 | */ |
76 | #define VRING_PACKED_EVENT_F_WRAP_CTR 15 |
77 | |
78 | /* We support indirect buffer descriptors */ |
79 | #define VIRTIO_RING_F_INDIRECT_DESC 28 |
80 | |
81 | /* The Guest publishes the used index for which it expects an interrupt |
82 | * at the end of the avail ring. Host should ignore the avail->flags field. */ |
83 | /* The Host publishes the avail index for which it expects a kick |
84 | * at the end of the used ring. Guest should ignore the used->flags field. */ |
85 | #define VIRTIO_RING_F_EVENT_IDX 29 |
86 | |
87 | /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ |
88 | struct vring_desc { |
89 | /* Address (guest-physical). */ |
90 | __virtio64 addr; |
91 | /* Length. */ |
92 | __virtio32 len; |
93 | /* The flags as indicated above. */ |
94 | __virtio16 flags; |
95 | /* We chain unused descriptors via this, too */ |
96 | __virtio16 next; |
97 | }; |
98 | |
99 | struct vring_avail { |
100 | __virtio16 flags; |
101 | __virtio16 idx; |
102 | __virtio16 ring[]; |
103 | }; |
104 | |
105 | /* uint32_t is used here for ids for padding reasons. */ |
106 | struct vring_used_elem { |
107 | /* Index of start of used descriptor chain. */ |
108 | __virtio32 id; |
109 | /* Total length of the descriptor chain which was used (written to) */ |
110 | __virtio32 len; |
111 | }; |
112 | |
113 | struct vring_used { |
114 | __virtio16 flags; |
115 | __virtio16 idx; |
116 | struct vring_used_elem ring[]; |
117 | }; |
118 | |
119 | struct vring { |
120 | unsigned int num; |
121 | |
122 | struct vring_desc *desc; |
123 | |
124 | struct vring_avail *avail; |
125 | |
126 | struct vring_used *used; |
127 | }; |
128 | |
129 | /* Alignment requirements for vring elements. |
130 | * When using pre-virtio 1.0 layout, these fall out naturally. |
131 | */ |
132 | #define VRING_AVAIL_ALIGN_SIZE 2 |
133 | #define VRING_USED_ALIGN_SIZE 4 |
134 | #define VRING_DESC_ALIGN_SIZE 16 |
135 | |
136 | /* The standard layout for the ring is a continuous chunk of memory which looks |
137 | * like this. We assume num is a power of 2. |
138 | * |
139 | * struct vring |
140 | * { |
141 | * // The actual descriptors (16 bytes each) |
142 | * struct vring_desc desc[num]; |
143 | * |
144 | * // A ring of available descriptor heads with free-running index. |
145 | * __virtio16 avail_flags; |
146 | * __virtio16 avail_idx; |
147 | * __virtio16 available[num]; |
148 | * __virtio16 used_event_idx; |
149 | * |
150 | * // Padding to the next align boundary. |
151 | * char pad[]; |
152 | * |
153 | * // A ring of used descriptor heads with free-running index. |
154 | * __virtio16 used_flags; |
155 | * __virtio16 used_idx; |
156 | * struct vring_used_elem used[num]; |
157 | * __virtio16 avail_event_idx; |
158 | * }; |
159 | */ |
160 | /* We publish the used event index at the end of the available ring, and vice |
161 | * versa. They are at the end for backwards compatibility. */ |
162 | #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) |
163 | #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num]) |
164 | |
165 | static inline void vring_init(struct vring *vr, unsigned int num, void *p, |
166 | unsigned long align) |
167 | { |
168 | vr->num = num; |
169 | vr->desc = p; |
170 | vr->avail = p + num*sizeof(struct vring_desc); |
171 | vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16) |
172 | + align-1) & ~(align - 1)); |
173 | } |
174 | |
175 | static inline unsigned vring_size(unsigned int num, unsigned long align) |
176 | { |
177 | return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num) |
178 | + align - 1) & ~(align - 1)) |
179 | + sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num; |
180 | } |
181 | |
182 | /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */ |
183 | /* Assuming a given event_idx value from the other side, if |
184 | * we have just incremented index from old to new_idx, |
185 | * should we trigger an event? */ |
186 | static inline int vring_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old) |
187 | { |
188 | /* Note: Xen has similar logic for notification hold-off |
189 | * in include/xen/interface/io/ring.h with req_event and req_prod |
190 | * corresponding to event_idx + 1 and new_idx respectively. |
191 | * Note also that req_event and req_prod in Xen start at 1, |
192 | * event indexes in virtio start at 0. */ |
193 | return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx - old); |
194 | } |
195 | |
196 | struct vring_packed_desc_event { |
197 | /* Descriptor Ring Change Event Offset/Wrap Counter. */ |
198 | uint16_t off_wrap; |
199 | /* Descriptor Ring Change Event Flags. */ |
200 | uint16_t flags; |
201 | }; |
202 | |
203 | struct vring_packed_desc { |
204 | /* Buffer Address. */ |
205 | uint64_t addr; |
206 | /* Buffer Length. */ |
207 | uint32_t len; |
208 | /* Buffer ID. */ |
209 | uint16_t id; |
210 | /* The flags depending on descriptor type. */ |
211 | uint16_t flags; |
212 | }; |
213 | |
214 | #endif /* _LINUX_VIRTIO_RING_H */ |
215 | |